ET205 Densimeter Repair (1)

ET-205 TN Densimeter Repair

One Volume Revision 1.03 22 August 2005

BJ Services

ET-205 TN Densimeter Repair Revision 1.03



Title

Revision 1.03

Revision 1.03

BJ Services

Services

BJ Services

BJ

Introduction

Definition of Terms

Theory of Operation

Radiation Safety Review

Detector Assembly

BJ Digital Transmitter Controllers/Data Acquisition Systems Specifications and Conversions Nuclear Densimeter Calibration Nuclear Density Maintenance Appendix A

Appendix B

Nuclear Densimeter Introduction ET-205 Densimeter Repair

BJ Services’ Introduction BJ Services is an oilfield service company specializing in pressure-pumping and coiled tubing operations. A large part of the pressure pumping services include the cementing and stimulation of wells. These services require a means to measure the density of the various slurries pumped into the well during a given job. Nuclear Densimeter Introduction To this end, BJ utilizes the TN Technologies Nuclear Densimeter, which measures the density of a slurry through radiation detection. This method of measurement works well with both proppant-laden and cement-laden slurries. This device, however, is extremely sensitive, and the Electronic Technician, or ET, is usually assigned the duty of ensuring the Nuclear Densimeter works properly.

Proprietary and Confidential Property of BJ Services Company

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Scope Of This Manual • • • • • • • • • • •

Nuclear Densimeter Introduction Terminology Theory Of Operation Radiation Safety Course Review Detector Assembly Transmitters Specifications Conversion Calibration Maintenance Troubleshooting

Scope Of This Manual In order to properly maintain the Nuclear Densimeter, the ET must first understand both Operational and Standardization procedures. The scope of this course, then, can be divided into three main objectives: • Operation • Standardization • Duties Of The Electronic Technician Operation Before an Electronic Technician can perform his required duties for the Nuclear Densimeter, he must first understand its operation (bullet points 1-6), down to the electronic level. Standardization With BJ’s acquisition of various oilfield service companies through the years, the issue of standardization (bullet points 7-8) has increased in importance. The Instrumentation Engineering department has made the effort to incorporate the “plug n’ play” concept, where if a district borrows a Nuclear Gauge, or any other piece of instrumentation from another district, no modification is necessary. The device is simply hooked up and used for the job. While these various companies use the same Nuclear Technology, there are electronic differences that can make the “plug n’ play” concept difficult to implement. It is the responsibility of the ET to ensure that all Nuclear Densimeters are wired the same way, regardless of company origin. Duties Of The Electronic Technician After standardization is achieved, the ET is ready to perform his duties (Bullet Points 9-11). There are calibration and maintenance procedures that the ET must perform in order to ensure that the Densimeter works properly, and when problems occur, he must find the source of the problem and correct it in a timely fashion.


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Specifications • Dimensions (w/o Pipe) – – – –

Length, 13 in (33.0 cm) Width, 13 in (33.0 cm) Depth, 30 in (76.2 cm) Weight, 125 lbs (56 kg)

• Pipe Size – 2 to 10 in (5.1 to 25.4 cm)

• Operating Temperature – 40° to 130°F (4° to 54°C)

• Detector Output – 0 to 10VDC

• Power Requirements – ±15VDC @ 60mA minimum

Specifications From this point, the operation of the Nuclear Densimeter, or Gauge, is discussed. To begin, the specifications for this device are listed above. They include: • Dimensions • Pipe Size • Operating Temperature • Detector Output • Power Requirements Pipe Size The Nuclear Densimeter can be mounted on a wide range of pipe sizes. For BJ Services, this range is from 2 to 10 inches. If the Gauge is removed from one pipe and mounted on another, it must be recalibrated. There are however, certain gauges that cannot legally be removed from the pipe. This topic is discussed in Section 3, Nuclear Densimeter Theory of Operation. Operating Temperature Specifications list the operating temperature as 40° to 130°F (4° to 54°C). If the Nuclear Densimeter is operated outside this temperature range, it will still function but its accuracy may be compromised, and its output may become unstable, causing the density reading to fluctuate. Detector Output Depending on the density of the fluid circulating through the pipe, the Gauge outputs a 0 to 10VDC nonlinear signal. Power Requirements The Nuclear Densimeter requires ±15VDC to operate. It receives this power from some type of monitoring electronics, referred to in this course as a Transmitter.


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Nuclear Densimeter/Transmitter

0-10VDC Signal ±15VDC Power

Transmitter

TN Nuclear Densimeter

TN Nuclear Densimeter/Transmitter Relationship To receive its needed dual-polarity power, the TN Nuclear Densimeter is typically connected to a transmitter. There are additional functions of the transmitter, which are discussed in Section 3, Nuclear Densimeter Theory of Operation. The slide above shows a Gauge connected to a BJ Digital Transmitter, operating as a Stand Alone Transmitter. In addition to this type of transmitter, there are other devices that possess the capacity to power a Gauge. These include: • Data Acquisition Systems • Control Systems


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Stand Alone Transmitters

TN Analog Transmitter

TN Digital Transmitter

BJ Digital Transmitter

Stand Alone Transmitters A Stand Alone Transmitter can power the TN Nuclear Densimeter. The various transmitters used by BJS include: • TN Analog Transmitter • TN Digital Transmitter • BJ Digital Transmitter Only the BJ Digital Transmitters will be discussed in detail in this manual. Aliases Depending on the Company of Origin (i.e., BJ Services, Western, NOWSCO, Fracmaster), the District, or even the individual, these Transmitters are known by various names, including: • “Analog Head” • “Digital Head” • “BJ Density Module” • “Density Module” • “Density Display” • “Tex. Nuc. Density” Each of these names is an alias for one of those listed in the previous bullet points.


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Data Acquisition Systems

3305 Mini Monitor

3600 Well Treatment Analyzer

Data Acquisition System The primary function of a Data Acquisition System is to monitor and record the processes during a job. In addition to this function, they possess the capacity to power a Nuclear Densimeter. The data acquisition, or monitoring systems used by BJ include: • 3305 Mini Monitor • 3600 Well Treatment Analyzer • Isoplex36 Well Treatment Analyzer • Isoplex DAU Operations Manuals Each data acquisition system listed has an operations manual available which discusses the connection of a Nuclear Densimeter, therefore they are not covered in this manual. The 3305 Mini Monitor is mentioned in the Calibration section to demonstrate the calibration procedure for a Nuclear Densimeter.


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Control Systems

611C Control System Pendant Control System

Control Systems The primary function of a control system is to regulate the processes of a job. Similar to the data acquisition systems, most control systems have the ability to power a Nuclear Densimeter. These include: • Pendant Control System (shown above) • 611C Control System (shown above) • Universal Control Module II (UCM II) • Mixing Control Module Series (MCM Series) • Automatic Cement Controller II (ACC II) The Nuclear Densimeter provides the Operator with a density reading at the controller and, on blenders used in stimulation applications, this density reading from the Gauge can be compared with the density reading calculated from sand-screw rpm's for control purposes.


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Stimulation Applications

125C Blender

8” Nuclear Densimeter, Mounted on 125C Blender

Stimulation Applications When used in stimulation applications, a Nuclear Densimeter is usually mounted at the following locations: • Blender discharge line (Low Pressure) • The Treating Line (High Pressure) Nuclear Densimeter Mounted On The Blender A Gauge is mounted on the discharge side of a blender, so that the Operator knows the density of the slurry as it leaves the blender tub. At this point in the process, the slurry is pumped at low-pressure, ranging between 40-100 PSI. The advantage of the low pressure Densimeter is its rapid response to changes in concentration. Once the slurry leaves the blender, it enters the frac pump(s). The photos above show a low pressure Nuclear Densimeter mounted on a 125C blender discharge line.


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Stimulation Applications

Nuclear Densimeter, Mounted in the Treating Line

Nuclear Densimeter Mounted In The Treating Line Once the slurry exits the frac pumps, it travels to the well head under high pressure via the treating line. A Gauge is mounted on a short line (“Pup Joint”) and installed in the treating line in order to monitor the density of the slurry just before it enters into the well head. Pressure in the treating line may approach 15,000 PSI, and in some cases, 20,000 PSI. The photo above shows a Nuclear Densimeter mounted in the treating line. Because the low pressure slurry from the blender may contain some air, thus limiting the accuracy of the low pressure Nuclear Densimeter, the high pressure Densimeter is generally more accurate. Additionally, having two Nuclear Densimeters on the job provides backup insurance and a means for comparison. For these reasons, a high pressure Nuclear Densimeter is normally used on every job. Additional Application In addition to stimulation applications, the Nuclear Densimeter can be used in cementing applications.


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Cement Applications

RAM Cement Unit

Nuclear Densimeter, Mounted on RAM Cement Unit

Cementing Applications When used in cementing applications, a Nuclear Densimeter is mounted on cement units (on-shore cement applications), or cement skids (off-shore cement applications). For these applications, the Nuclear Densimeter is usually powered by one of the following: • Automatic Cement Controller II (Control System) • 3305 Mini Monitor (Data Acquisition System) • 3600 Well Treatment Analyzer (Data Acquisition System) The Automatic Cement Controller II When powered by the Automatic Cement Controller II, or ACC II, the Nuclear Densimeter can be used to provide feedback to the ACC II, in order to regulate the cement-mixing process. Additionally, it is possible to serially link the ACC II and the 3305 Mini Monitor so that the density reading can be transmitted to the 3305 for monitoring and recording purposes. The 3305 Mini Monitor In some instances, a DB-IV electronic densimeter is used to regulate the cement-mixing process. In this case, the Nuclear Densimeter is powered by a 3305 Mini Monitor and used for monitoring and recording purposes.


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Review Questions Introduction, Densimeter Repair 1. The Nuclear Densimeter can be mounted on a wide range of pipe sizes. For BJ Services, this range is from 2 to 10 in. If the Gauge is removed from one pipe and mounted on another, it must be ____________________. 2. Specifications list the Operating Temperature as __________° to __________°F (__________° to __________°C). 3. Depending on the Density of the Fluid circulating through the pipe, the Gauge outputs a ____________________ Non-Linear Signal. 4.

The Nuclear Densimeter requires ____________________ to operate.

5. When used in Stimulation Applications, a Nuclear Densimeter is usually mounted at the following locations: • _________________________ (Low Pressure) • _________________________ (High Pressure) 6. The advantage of the Low Pressure Densimeter is its ____________________ to changes in Concentration.

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Review Questions Introduction, Densimeter Repair

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Definition Of Terms Densimeter Repair

Definition Of Terms The first step an Electronic Technician, or ET, must take toward learning Nuclear Densimeter operation is to understand the associated terminology used by Operations personnel. This is important because, usually, the ET isn’t on location where job problems may occur. When the equipment arrives to the yard, the ET must repair the problem, and the Operator is usually the only person who can tell the ET exactly what happened. The Electronic Technician, however, must be capable of interpreting the necessary information from the Operator. To achieve this goal, this section discusses terminology associated with the Nuclear Densimeter that is used at the operations level.


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Definition Of Terms • Density • Types Of Density – Bulk Density – Absolute Density

• Proppant Concentration • Specific Gravity • Density Units for Various Applications – Stimulation – Cement – Sand Control

Definition Of Terms The items listed above are terminology related to density readings.


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Density

Density = ρ =

Weight Volume

Weight

Volume

Density The density of a material is defined as the ratio of a material’s weight to the volume that it occupies. For example, if a 1-gallon (volume) bucket is completely filled with water, it weighs 8.34 pounds (weight). Therefore: Density Of Water =

8.34 Pounds (Weight) 1 Gallon (Volume)

= 8.34

Pounds Gallon

= 8.34

Lbs = 8.34 PPG Gallon

Units Of Measurement For BJ Services’ US Operations, the units of measurement for density are usually expressed in pounds per gallon, or PPG. For International Operations, the units of measurement for density are expressed in kilograms per cubic meter (kg/m3), or “kilograms per cube.”


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Types Of Density

Bulk Density 14.3 PPG

Absolute Density 22.1 PPG

Example: 20/40 Sand

Types Of Density Density can be divided into 2 distinct categories: • Bulk Density • Absolute Density Bulk Density Some materials, such as sand, are granular, or powdered in nature. These materials have air pockets between the grains, or particles. The total volume that the material and the air pockets occupy is referred to as bulk volume. Bulk density can then be defined as the ratio of a material’s weight to its bulk volume. Absolute Density Other materials, such as liquids, are continuous in nature. That is to say, there is no air pockets, or voids, in the material. The volume of space that a material occupies, without any air pockets, is referred to as the absolute volume. Absolute density can then be defined as the ratio of a material’s weight to its absolute volume. Bulk Density Versus Absolute Density In its natural state, 20/40 sand is a granular material. If a 1-gallon bucket is completely filled with sand, it would weigh 14.3 Pounds, so the bulk density would be 14.3 PPG. If the sand was heated until it melted, it would occupy a smaller space because there are no air pockets present between the grains. If a 1-gallon bucket is completely filled with the melted sand, it would weigh 22.1 pounds, so the absolute density would be 22.1 PPG. The absolute density of 20/40 sand is greater than its bulk density because more of the melted sand can fit in a given volume (1 gallon), than granular sand.


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Absolute Density Material Type

Weight (Pounds)

Volume (Gals)

8.34 Pounds

1 Gallon

Density (PPG) 8.34 PPG

Base Fluid

+

1.00 Pound

.045 Gallon Absolute Volume, not Bulk

22.1 PPG Absolute Density, not Bulk

20/40 Sand 9.34 Pounds

1.045 Gallons

Slurry

9.34 Pounds 1.045 Gallons

Slurry Density = ρSlurry = 8.93 PPG

Properties Of Mixtures When a proppant, such as 20/40 sand, is mixed with a base fluid, such as water, the entire mixture may be thought of as continuous. That is to say, the space between the grains of sand is no longer filled with air, but is filled with fluid. In the case of proppant laden slurries, it is important to use the absolute volume, rather than the bulk volume of the sand when computing the total volume and density of the entire mixture.


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Proppant Concentration Material Type

Weight (Pounds)

Volume (Gals)

8.34 Pounds

1 Gallon

Density (PPG) 8.34 PPG

Base Fluid

+

1.00 Pound

.045 Gallon Absolute Volume, not Bulk

22.1 PPG Absolute Density, not Bulk

20/40 Sand 9.34 Pounds

1.045 Gallon

Slurry

9.34 Pounds 1.045 Gallons

Proppant Concentration = 1 PSA Slurry Density = 8.93 PPG Proppant Concentration Proppant concentration is a measurement of the amount of a material that is contained in a unit volume of a mixture or solution. For BJ Services applications, the amount of sand added to 1-gallon of base fluid is referred to as the proppant concentration. The units for proppant concentration are pounds of sand added, or PSA. Density/Proppant Concentration Relationship As the above diagram shows, density is not the same as proppant concentration. Density is expressed in units of pounds per gallon (PPG), while proppant concentration is expressed in units of pounds of sand added to 1 gallon of base fluid (PSA). These two items, however, are directly related. The following equation mathematically relates density to proppant concentration:

Proppant Concentration =

(Slurry Density - Base Fluid Density)

  Slurry Density    1 −       Proppant Density   Keep in mind that the proppant concentration is in units of PSA, and all density measurements are in units of PPG.


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Specific Gravity

Specific Gravity = σ =

σWater =

ρWater ρWater

=

Material’s Density Water Density

8.34 PPG 8.34 PPG

=

ρMaterial ρWater

= 1.0 (No Units)

Specific Gravity The specific gravity of a material is the ratio of the material’s density to the density of water, which is 8.34 PPG. Since the units, PPG, are both in the numerator and in the denominator, they cancel, which means that specific gravity does not have any units associated with it. Specific Gravity Of Water, σWater To obtain the specific gravity of water, σWater, take the density of water, 8.34 PPG, and ratio it with itself, to obtain a result of 1.0, as mentioned before there are no units.


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Specific Gravity Of 20/40 Sand

20/40 Sand Density = ρ20/40 Sand = 22.1 PPG

Water Density = ρWater = 8.34 PPG

ρ20/40 Sand σ20/40 Sand = ρ Water

=

22.1 PPG 8.34 PPG

= 2.65 (No Units)

Specific Gravity Of 20/40 Sand, σ20/40 Sand To calculate the specific gravity of 20/40 sand, σ20/40 Sand, take the absolute density of 20/40 sand, 22.1 PPG, and ratio it with the density of water, 8.34 PPG, to obtain a result of 2.65.


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Density Units For Various Applications • Stimulation Applications – Density • Pounds Per Gallon, or PPG

– Proppant Concentration • Pounds Sand Added to 1 Gallon of clean fluid, or PSA • Pounds Proppant Added to 1 Gallon of clean fluid, or PPA

• Cement Applications – Density • Pounds Per Gallon, or PPG

• Sand Control Applications – Proppant Concentration • Pounds Sand Added to 1 Gallon of clean fluid, or PPG

Density Units For Various Applications The items above list the units that are used to express density and proppant concentration for the various applications within BJ Services. For both stimulation and cementing applications, the units used for density and proppant concentration are consistent with the units described in this section. In Sand Control applications, however, proppant concentration is expressed in units of PPG.


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Review Questions Terminology, Densimeter Repair 1. The first step an Electronic Technician, or ET, must take toward learning Nuclear Densimeter Operation is to understand the associated ____________________ used by Operations Personnel. 2. The Density of a material is defined as the Ratio of a material’s ____________________ to the ____________________ that it occupies. 3. For BJ Services’ U.S. Operations, the Units Of Measurement for Density are usually expressed in ____________________. For International Operations, the Units Of Measurement for Density are expressed in ____________________. 4.

The ____________________ can then be defined as the Ratio of a material’s Weight to its Bulk Volume.

5. The ____________________ can then be defined as the Ratio of a material’s Weight to its Absolute Volume. 6. In the case of Proppant Laden Slurries, it is important to use the ____________________, rather than the ____________________ of the sand when computing the Total Volume and Density of the entire mixture. 7. In BJ Services, the amount of sand added to 1 unit volume of Base Fluid is referred to as the ______________________________. 8. The units for Proppant Concentration are _________________________ 9. The ____________________ of a material is the ratio of the material’s density to the density of water, which is 8.34 Pounds per Gallon.

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Nuclear Densimeter Theory Of Operation ET-205 Densimeter Repair

Theory Of Operation Now that terminology has been covered, the ET is ready to learn how a Nuclear Densimeter Gauge works. This section provides the ET a general overview of the operation of a Nuclear Gauge.


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Main Components Transmitter

process fluid pipe

radiation source holder

Radiation Energy

Detector Assembly

Main Components The drawing above shows the main components of the Nuclear Densimeter, which includes the: • Radiation Source Holder • Process Fluid Pipe • Detector Assembly • Transmitter This section discusses the components in the order listed, since the radiation energy originates at the radiation source holder and interacts with the remaining components in this sequence.


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Radiation Source Holder

Lead Filled Housing

0-10VDC

Cesium 137 finished source

Radiation Energy

Radiation Source Holder The radiation source holder consists of a protective lead-filled housing and a small Cesium-137 finished source pellet. The housing has a small “window” which serves to focus the radiation beam from the finished source. Radiation Strengths Radiation strengths are available in: • 50 mCi (millicuries) or 1.8 GBq (gigabequerels) • 100 mCi (3.7 GBq) • 200 mCi (7.5 GBq) Radiation “Window” Radiation energy is emitted from the finished source uniformly in all directions. Because the source is mounted inside the lead-filled housing, the radiation energy is unable to penetrate the lead walls, and can travel only through a cavity or “window”. The radiation energy collimates into a relatively narrow 12° 13° beam that travels through the process fluid and pipe, which is then received by the Detector Assembly.


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Radiation Source Holder Lead Filled Housing

Cesium 137 finished source

shutter

Cavity

Radiation Source Holder The photo above shows a cutout view of a radiation source holder, with a simulated radiation source installed. Notice the lead-filled housing walls. The Cesium 137 finished source is mounted in the cavity, as shown. The radiation energy can escape only through the cavity. A stainless steel disc, welded in place, protects the cavity from external contamination. Shutter Notice also that this particular radiation source holder has a slide gate, or “shutter” associated with it. When closed, the shutter places lead plates over the cavity, which blocks all radiation. This type of source allows the radiation source holder to be removed by qualified personnel. Shutters are used with radiation source holders that are mounted on process fluid pipes ranging from 5”-8”, typically low pressure applications. Some 4” applications may also use a shuttered source, but this is not common. NOTE BJ Services’ personnel DO NOT have the authorization to open the radiation source holder, or to remove a non-shuttered source from the pipe. Only TN Technologies’ personnel may do so.


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Shutter

OFF Position ON Position

REF Position

Shutter Positions The shutter, shown above, has three positions associated with it. These are: • The ON Position • The Off Position • The Reference, or REF Position There are some older shutters that only have the ON and OFF Positions. Safety Precautions The shutter must be locked in the OFF position when: • Removing the radiation source holder from the process fluid pipe • Making repairs within close range of the radiation source holder (use long handled brushes and scrapers for cleaning inside the pipe). • Transporting the Nuclear Densimeter Additionally, when the shutter is in the ON position, keep others and yourself at least three feet away from the gauge.


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Process Fluid Pipe process fluid pipe

Process Fluid

0-10VDC Radiation Energy

Process Fluid Pipe While the radiation energy travels across the process fluid pipe, its magnitude is attenuated, or weakened, by the process fluid traveling through the pipe. As the density of the process fluid increases, the magnitude of the radiation energy reaching the Detector Assembly decreases. Empty Process Fluid Pipe If the process fluid pipe is empty, the radiation energy effectively passes through unmolested (neglecting the radiation attenuated by the process fluid pipe); and reaches the Detector Assembly at what is considered to be full magnitude. Light Fluid in the Process Fluid Pipe A light fluid is a fluid with a relatively low density. Water, with a density of 8.34PPG, is a good example. If water passes through the process fluid pipe, the magnitude of the radiation energy reaching the Detector Assembly is inversely proportional to the water density. Heavy Fluid in the Process Fluid Pipe A heavy fluid is a fluid with a relatively high density. Cement and proppant laden slurries are good examples. If a slurry passes through the process fluid pipe, the magnitude of the radiation energy reaching the Detector Assembly is attenuated even further. TIP It is important to keep the inside walls of the process fluid pipe as clean as possible. Even a small buildup of sand or cement within the pipe can significantly alter the readings of the Nuclear Densimeter.


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Detector Assembly


Detector Assembly

Detector Assembly The Detector Assembly consists of the following major subassemblies: • Ion Chamber • High Voltage Board • Preamplifier Board Because there are a number of things that can be done to repair and maintain these components, both the preamplifier board and high voltage board are discussed in detail in this manual. The ion chamber is discussed, but is a sealed component that cannot be repaired by an Electronic Technician. A general overview, however, will be given on all three components. Role of the Detector Assembly When properly powered, the ion chamber converts received radiation energy into a proportional current signal that is sent to the preamplifier board; where it is converted and amplified to a proportional voltage signal of 0 to 10VDC. This non-linear 0 to 10VDC voltage signal is then sent to the Transmitter through a 10-Pin connector. Density of the Process Fluid If the process fluid pipe is empty (density = 0.00PPG), then most of the radiation energy reaches the detector assembly. This being the case, the voltage signal sent from the detector assembly is ≈10VDC. This is referred to as the Open Pipe Voltage, or VOP. If water, with a density of 8.34 PPG, is circulated through the process fluid pipe, the density increases from 0.00 to 8.34 PPG. Usually, water is used as the base fluid, but other fluids such as brine or KCL may be used as well. The voltage signal generated while water is circulating through the process fluid pipe is known as the reference voltage, or VREF. As the density increases, the magnitude of the radiation energy reaching the Detector Assembly decreases. As a result, the voltage signal sent from the Detector Assembly decreases as well.


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Ion Chamber Positrons Ion Chamber Filled with Xenon Gas

Anode + + + +

-

-

Radiation Energy

-

-

-

-

-

-

-

-

+ -

+

-

∆V

Cathode Current Signal

+ + +

R Electrons

Ion Pair

V

Ion Chamber The Ion Chamber is a cylinder that receives radiation energy and converts it into a proportional electrical signal. The assembly consists of a stainless steel cylinder filled with xenon gas and an insulated center wire. A stable +1400VDC from the high voltage board is applied to the wall (canister) of the ion chamber. The TN Technologies Densimeter is configured so that the chamber wall acts as an anode and the wire acts as a cathode. The principle is similar to that of a Geiger Counter, however most Geiger Counters use polarity which is reversed from the above example. Ion Chamber Operation Ionization is the process of an atom becoming charged due to its losing or gaining an electron. When the radiation energy enters the ion chamber, it ionizes with the xenon gas, creating ion pairs. Each ion pair consists of: • A Negative Ion (also known as an Electron) • A Positive Ion (also known as a Positron) The positrons are drawn to the wall of ion chamber, while the faster moving electrons are drawn to the wire. A charge collects on the Anode, resulting in a voltage change in the circuit. The size of this voltage change depends on the number of electrons collected from the ionizing process. This causes a proportional current signal to flow to the preamplifier board, where it is then converted to a voltage signal and amplified to 0 to 10VDC. Radiation Energy/Ionizing Relationship If the full magnitude of the radiation energy enters ion chamber, a greater number of ion pairs are created, and more charge collects on the anode, resulting in a larger current signal. This larger current signal results in a larger voltage signal sent to a transmitter, ideally 10VDC, or VOP. If the magnitude of the radiation energy entering the ion chamber is attenuated, the number of ion pairs created is less, which results in a smaller current signal, resulting in a smaller voltage signal sent to the transmitter.


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Detector Assembly Ionization Chamber

Lead Shield

high voltage board

preamplifier board

Detector Assembly The photo above shows the detector assembly. The high voltage board is mounted above the ion chamber. The lead shield, mounted on the top plate, blocks radiation from passing through the signal/power connector. This shield might not be found on new units.


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Transmitter Transmitter


±15VDC

Transmitter A transmitter provides four important functions: • Linearizes the 0-10VDC density signal • Displays the density • Supplies the Nuclear Densimeter with ±15VDC • Transmits the density signal to a remote monitor via frequency signals, analog signals or digital communication. A transmitter linearizes the voltage signal from the Detector Assembly and produces a numerical value, which is indicative of the density for the process fluid. Additionally, it provides a display of the density for the Operator. Proppant Concentration In stimulation operations, the transmitter also calculates the proppant concentration in the fluid. Proppant concentration is measured in units of PSA, or Pounds Sand Added.


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Transmitters

Analog Transmitter

3305 Mini Monitor

Digital Transmitter TN Nuclear Transmitter

3600 Well Treatment Analyzer

Pendant Control System

Transmitters There are a number of devices that may be utilized, in whole or part, as a Transmitter. • TN Analog Transmitter • TN Digital Transmitter • BJ Digital Transmitter • 3305 Mini Monitor • 3600/Isoplex36 Well Treatment Analyzer • Pendant Control System • MCM 1000 Series (Not shown)


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Nuclear Densimeter Review Transmitter

process fluid pipe

radiation source holder 0-10VDC Radiation Energy

Detector Assembly

Nuclear Densimeter Review The Nuclear Densimeter consists of four main components: • Radiation Source Holder • Process Fluid Pipe • Detector Assembly • Transmitter The radiation source holder emits radiation energy through the process fluid pipe. Depending on the density of the process fluid passing through the pipe, the proportional magnitude of the radiation energy is received by the Detector Assembly, where it is converted to a 0-10VDC non-linear signal. This signal is passed on to the transmitter, where the voltage signal is linearized, converted into a density reading, displayed for the Operator, and made available for a remote monitor.


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Review Questions Theory of Operation, Densimeter Repair 1. The Radiation Source Holder consists of a protective ______________________________ and a small ____________________ Finished Source pellet. The housing has a small ____________________ which serves to focus the radiation beam from Finished Source. 2. BJ Services Personnel ____________________ have the authorization to open the Radiation Source Holder, or to remove a non-shuttered Source from the pipe. 3. Additionally, when the Shutter is in the ON position, stay at least ____________________ away and keep others away from the gauge. 4.

As the Density of the Process Fluid ____________________, the magnitude of the radiation energy reaching the Detector Assembly ____________________.

5. It important to keep the _________________________of the Process Fluid Pipe as clean as possible. Even a small buildup of sand or cement within the pipe can significantly alter the readings of the Nuclear Densimeter. 6. When properly powered, the ____________________ converts received radiation energy into a proportional Current Signal and sends it to the Preamplifier Board 7. If the Process Fluid Pipe is empty (Density = 0.00PPG), the ____________________ of the radiation energy reaches the Detector Assembly. 8. When the radiation energy enters the Ion Chamber, it ionizes with the Xenon Gas, creating ____________________. 9. The ____________________ linearizes the Voltage Signal from the Detector Assembly and produces a numerical value, which is indicative of the Density for the Process Fluid. Additionally, it provides a display of the Density for the Operator.

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Radiation Safety Review ET-205 Densimeter Repair

Radiation Safety Review So far in this presentation, the Nuclear Densimeter has been discussed on a general level. In the sections to follow, a more in depth discussion is given, which involves opening the Detector assembly, calibration and troubleshooting. Whenever working around a device that is radioactive, safety must always be a top priority for the ET and personnel in the area. Before going forward, a review of the Radiation Safety Course is given in this section. Radiation Safety Course The purpose of the Radiation Safety Course, offered by TN Technologies, is to provide personnel with a general understanding of the possible hazards associated with Nuclear Densimeters. Additionally, the course explains how to work confidently and safely around this device. A Prerequisite This section is intended only as a supplement to the Radiation Safety Course offered by TN Technologies. Before an Electronic Technician can handle/repair a Nuclear Densimeter, he must successfully complete the Radiation Safety Course. This is necessary due to the potential hazards if the Densimeter is handled incorrectly. Topics of Discussion The following topics are discussed in this section: • What is Radiation • Using Radiation Safely • BJ Services Radiation Protection Manual • Labels


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What Is Radiation? • • • • •

Alpha Radiation Beta Radiation Gamma Radiation X-Ray Radiation Neutron Radiation

What Is Radiation? In order to work safely around Nuclear Gauges, one must first understand some basic facts about radiation. Radiation originates from atoms, which are the building blocks of all matter. Certain atoms are at excited states and release energy in the form of radiation. This energy is transferred as either particles or electromagnetic waves. Types Of Ionizing Radiation There are 5 types of Ionizing Radiation: • Alpha Radiation • Beta Radiation • Gamma Radiation • X-Ray Radiation • Neutron Radiation Each has a unique penetrating ability that needs to be considered when protecting oneself from Radiation.


2

What Is Radiation? • • • • •

Alpha Radiation Beta Radiation Gamma Radiation X-Ray Radiation Neutron Radiation

Alpha Radiation Alpha radiation occurs when the atom emits large atomic particles. These particles have very little external penetrating power, and can be shielded with something as thin as a piece of paper. When exposed externally to Alpha radiation, it poses no external hazard because it can be shielded by the dead layer of skin covering the body. Alpha radiation, however, can be internally harmful if inhaled or ingested. Beta Radiation Beta radiation occurs when the atom emits small, fast moving particles known as electrons. These particles are more penetrating than Alpha particles, but are still considered to have relatively low penetrating ability. Beta radiation can be easily shielded by materials such as cardboard or plastic. It can, however, penetrate the dead layer of skin on the body. Gamma Radiation Gamma radiation occurs when electromagnetic waves are emitted from an atom as a result of radioactive decay. This form of radiation has a high penetrating ability, and is considered an external threat. Gamma radiation can be shielded by a dense material such as concrete or lead. X-Ray Radiation X-Ray radiation is similar to Gamma radiation in that it emits electromagnetic waves. X-Ray radiation, however, is generally machine generated and is less penetrating than Gamma radiation. Neutron Radiation Neutron radiation results from the emission of a Neutron particle from the nuclei of an atom. This form of radiation is extremely penetrating and poses a significant external threat.


3

What Is Radiation?

Exposure vs. Contamination

Exposure vs. Contamination Many people have the misconception that if they become exposed to radiation, that they will glow in the dark, and become radioactive themselves. This, of course, is incorrect. A good way to explain what actually occurs is through using the fire analogy. Exposure If an extremely intense fire is a very short distance away, the heat from the fire may result in burns to the body. However, the farther the distance from the fire results in less heat exposure, which causes less damage to the body. The same concept can be related to Exposure. The more time spent around a radioactive source, and the closer the distance to the source, a greater Exposure results. Contamination After leaving the vicinity of a fire, the person does not emit heat unless he brings an amber from the fire. Similar to contamination, a person must physically come in contact with, and take a portion of the radioactive material to become contaminated, or radioactive.


4

Using Radiation Safely

As L ow As R easonably A chievable Safety Factors The different types of ionizing radiation are harmful, but there is a very little risk associated with the low levels of radiation of a Nuclear Densimeter. Nevertheless, in practice a person should keep his exposure As Low As Reasonably Achievable, or ALARA. This can be done by following 3 simple concepts: • Time • Distance • Shielding Time The more Time one remains in a radiation field, the larger the radiation dose. At times, especially during emergencies, work must be performed in a strong radiation field. In this case, the work procedure should be carefully planned outside the work area so that a minimum amount of Time is used to complete the job. If the Time required for one man to complete the job would result in an exposure beyond prescribed limits, then a team of workers should be employed. This would mean a small exposure for several people instead of a large exposure for one person. Distance Radiation is emitted from a point source uniformly in all directions. The further one is from the radiation source, the lower the exposure. Shielding A Shield is defined as a physical entity placed between the radiation source and the object to be protected in order to reduce the radiation level at the object’s location. An example would be the radiation source holder. The radiation source is mounted within a lead-filled housing that prevents the Radiation from traveling anywhere except in the specified direction. In this case, the physical entity is the lead filled-housing, and the objects to be protected are BJS personnel.


5

BJ Services Radiation Protection Manual • • • • • • • • •

Emergency Instructions Radiation Program Management Organization Radioactive Materials Records Management Radioactive Materials - Employee Notices and Instructions Use of Densimeters Having Nuclear Gauges Transportation Procedures Handling Procedures Radiation Protection Program Review Nuclear Gauge Procedures

BJ Services Radiation Protection Manual The Nuclear Regulatory Commission, and equivalent Agreement States have strict safety standards for Nuclear Densimeters. These strict regulations for radioactive material provide a high degree of worker and environmental safety when dealing with radiation. Each state, or country, operates under a specific radioactive materials license or a manufacturer’s general license. Individuals operating Nuclear Densimeters should be aware of the license conditions and follow them accordingly. There are, however, BJ specific regulations that must be followed regardless of state, or country, which are listed in the BJ Services Radiation Protection Manual. The topics in this manual include: • Emergency Instructions • Radiation Program Management Organization • Radioactive Materials Records Management • Radioactive Materials - Employee Notices and Instructions • Use of Densimeters having Nuclear Gauges • Transportation Procedures • Handling Procedures • Radiation Protection Program Review • Nuclear Gauge Procedures A copy of the BJ Services Protection Manual is found in Appendix A.


6

Labels CAUTION RADIOACTIVE MATERIAL

MODEL 5190 SERIAL NO. BXXX

ISOTOPE Cs-137 AMOUNT EMPTY DATE MEAS. 09/97 TAG NO.

BJ DEMO Texas Nuclear Products TN Technologies DO NOT REMOVE TAG MADE IN USA

Radiation Source Holder Plaque The Radiation Source Holder Plaque, which provides information about the finished source, is mounted on the end of the Radiation Source Holder. When installing or removing a Nuclear Gauge, be careful not to drag the Radiation Source Holder on the ground, as this could destroy the information on the plaque, resulting in a loss of critical information. Missing Or Illegible Plaque Missing or illegible plaques must be replaced immediately. These plaques must be ordered through the manufacturer. A missing or illegible plaque renders the device out of service until a replacement plaque is mounted.


7

Labels

R A DI C O

O

ACNTE TI NT VI S TY : :

USA DOT 7A TYPE A RADIOACTIVE MATERIAL

A C T C IV E E

O IN

7

EX D

X DE

IN

Marking Label

13 7

II

T R

T

II

R O

RAY II Label

Emergency RSO contact: (281) 351-8131 24 hour

A C T C IV E E SI U M

SP

SP

7

13 7

Notify if found: BJ SERVICES CO., USA HOUSTON, TEXAS

AN

AN

M

O

ACNTE TI NT VI S TY : : TR

TR

SI U

SPECIAL FORM, N.O.S., UN 2974 (CS-137; SEALED)

R A DI C O

RAY II Label

Labels To comply with the licensing agreement, every Nuclear Density Gauge must have two Radioactive Yellow II Labels (RAY II Labels) and one Marking Label. Radioactive Yellow II Labels (RAY II Labels) The 2 Radiation Yellow II, RAY II, Labels must be placed on the Radiation Source Holder on opposite sides. A RAY II Label displays the following information: • Contents (Always Cesium 137 for BJ Services) • Activity (In Gigabecquerels, GBq) • Transport Index This activity can be obtained from the AMOUNT reading on the Radiation Source Holder Plaque. The AMOUNT value is expressed in units of millicuries, so a unit conversion is necessary. (100mCi = 3.7GBq and 200mCi = 7.4 GBq). Transport Index When transporting the Nuclear Densimeter, the TRANSPORT INDEX must be filled in. This value is determined by taking the highest radiation survey meter reading at any point 1 meter (39 inches) from any surface of the Radiation Source Holder. The value must be less than 1.0 (no units necessary) to use the RAY II Label. The Transport Index is written to the nearest tenth (Example: use 0.3, not 0.25). Marking Label The Marking Label must be placed between the RAY II Labels. A Marking Label displays the following information: • USA DOT 7A type A Radioactive Material • Emergency phone number • Identifies BJ Services as the owner of the Nuclear Gauge


8

Review Questions Radiation Safety Review, Densimeter Repair 1. Radiation originates from ____________________, which are the building blocks of all matter. 2. When exposed externally to _________________________, it poses no external hazard because it can be shielded by the dead layer of skin covering the body. 3.

_________________________ can be easily shielded by materials such as cardboard or plastic.

4.

____________________ Radiation has a high penetrating ability, and is considered an external threat. Gamma Radiation can be shielded by a dense material such as concrete or lead.

5. The more time spent around a radioactive source, and the closer the distance to the source, a greater ____________________ results. 6. A person must physically come in contact with, and take a portion of the radioactive material to become ____________________ 7. A ____________________ is defined as a physical entity placed between the Radiation Source and the object to be protected in order to reduce the Radiation Level at the object’s location. 8. The ______________________________, which provides information about the Finished Source, is mounted on top of the Radiation Source Holder. 9. The 2 Radiation Yellow II, RAY II, Labels must be placed on the _________________________ on opposite sides. 10. When transporting the Nuclear Densimeter, the ______________________________ must be filled in. This value is determined by taking the highest radiation survey meter reading at any point 1 meter (39 inches) from any surface of the Radiation Source Holder.

Page 1 of 2

Review Questions Radiation Safety Review, Densimeter Repair This page intentionally left blank.

Page 2 of 2

Detector Assembly ET-205 Densimeter Repair

Radiation Energy

Detector Assembly

Nuclear Densimeter The “Fast Start Up” (FSU) detector is an improved version of the early SGO detector. This section of the presentation will deal with the theory of operation and maintenance of the FSU. The following will be discussed in this section: • General theory of operation review • FSU and SGO Gauge comparisons • High Voltage and Preamplifier Board circuit detail • Calibration and adjustments • Maintenance and Troubleshooting Procedures Note Only personnel who have successfully completed an approved Nuclear Safety Course are permitted to service nuclear densimeter systems.


1

Detector Assembly

Ionization Chamber

High Voltage Board

Preamplifier Board

Densimeter Detector Assembly The above photo shows a Detector Assembly, also known as an FSU Gauge. The primary subassemblies that make up the FSU Gauge are: • Ionization Chamber, or Ion Chamber • High Voltage Board • Preamplifier Board Types of Detector Assemblies BJ has used two types of TN Technologies Gauges: • TN SGO Gauge (Obsolete) • TN FSU Gauge NOTE Several activities using a Detector Assembly and simulated nuclear sources will be performed in the class. Because there may be residual high voltage present after power is removed, be careful not touch the Ion Chamber when removing it from the housing. To discharge the residual voltage, first connect a jumper to one of the grounded aluminum plates separating the boards. Next, touch the other end of the jumper to the body of the Ion Chamber.


2

Nuclear Densimeter Block Diagram

+ 1400 V

Radiation Energy

High Voltage Board

Preamplifier Board Ion Chamber

+15V GND -15V +15V GND -15V 0-10V

Gain

Power From Transmitter Density Signal To Transmitter

(For Analog Transmitter Only)

Nuclear Densimeter Block Diagram The diagram above shows how the components of the Detector Assembly connect. Ion Chamber The Ion Chamber consists of a stainless steel canister filled with Xenon gas at eight atmospheres. An insulated wire is inserted into the chamber, and high voltage potential is applied across the anode and cathode. Radiation energy received from the radiation source causes a release of free electrons from the gas. These electrons are attracted to the anode, which creates a small current flow into the preamplifier. Preamplifier Board The preamplifier board converts and amplifies this current flow into a voltage signal that is inversely proportional to the density of the material in the path of the radiation energy. High Voltage Board The high voltage board supplies a highly regulated +1400VDC, which allows sufficient voltage difference for the attraction of the free electrons. Power Source The Nuclear Densimeter is powered from an external ±15VDC, which is supplied by a transmitter or other suitable power supply.


3

Ion Chamber

Anode +

+

+ + Radiation Energy

-

Current Flow

-

-

-

-

-

-

-

-

-

Cathode

+ -

+

+ +

+

+ 1400 V

Ion Chamber Gamma particles from the nuclear source striking xenon gas ions cause ionization to occur, which results in a current flow. This extremely small current flow is converted by the preamplifier board into a representative 0 to 10VDC density signal.


4

Ion Chamber Adhesive From Heater Wrapping

Modified Gauge The adhesive residue in the above photo identifies this Ion Chamber as part of a former SGO assembly. Due to the inherent sensitivity of the obsolete SGO Gauge to changes in temperature, a heater was taped to the Ion Chamber in order to maintain a constant temperature inside the housing. Additionally, heater resistors on the top plate kept the electronics warm. Because of this temperature sensitivity, the SGO Gauge required long a “warm up” time before the density readings would stabilize, usually about an hour or more in cold climates. Upgrading an SGO unit consists of replacing the two boards and removing the heater. The FSU Gauge The improved FSU Gauge contains temperature stabilization circuitry that enables it to remain remarkably stable over a wide range of temperatures. Additionally, the “warm up” time from initial power up is dramatically reduced to 15 minutes or less. High Voltage To Ion Chamber There is a +1400VDC potential applied to the Ion Chamber. Although the actual measured voltage has a ±100V tolerance, it must be well-regulated, because any fluctuation, no matter how slight, will cause a corresponding change in the output signal voltage.


5

FSU High Voltage Board Drain Wire

Insulated Collar

High Voltage Board The high voltage board provides the potential necessary for ionization to occur. This voltage must be well regulated, as any fluctuation will result in a corresponding signal output change. The board uses ±15VDC, supplied by an external power source, for conversion to +1400VDC at approximately 20 µA. The output voltage may be within ±100V of the specified voltage, but should have no measurable fluctuation. In the photo shown, notice the Drain Wire, separated from the Ion Chamber by an Insulated Collar. This combination is used to drain any static voltage, and to act as an electrostatic shield for the signal current, thereby reducing noise pickup. The signal output current from the Ion Chamber is very small, in the order of nano amps (nA), so even minimal electrical interference can cause large errors in the output signal. High Voltage Probe A high voltage probe should ALWAYS be used to measure the potential on the Ion Chamber. Most modern digital volt meters will read only to 1000V, but this is not the only reason to use a high voltage probe. Because the high voltage board can supply only 20 µA, if a conventional digital multimeter alone were used for measurement the meter’s internal resistance (typically 10 M Ω) would drain much of the available current from the power supply, resulting in a erroneous reading. An example of a suitable probe for high voltage use is the Fluke model 80K-40 High Voltage Probe, which is useful for readings up to 40 kV, at a 1000 to 1 division ratio. Using this or a similar probe, 1400VDC will be displayed as 1.400VDC on a DVM. These high voltage measurements are made from power ground to the Ion Chamber Canister, with the aluminum plates separating the boards providing a convenient ground point. NOTE The Fluke 80K-40 is designed to work with meters that have 10MΩ input impedance.


6

High Voltage Board/Ion Chamber Connection HV Connection Screws

High Voltage Board/Ion Chamber Connection The three screws that secure the high voltage board to the Ion Chamber also provide the electrical path for the 1400VDC to the Ion Chamber canister. It is important that these screws be properly tightened and free from corrosion. Removable thread lock, such as Locktite® Green or Red, is recommended. Additionally, make sure that the star lock washers are in place.


7

FSU High Voltage Board HV Transformer T1 CA3240

U-3 -12V Regulator

From Preamplifier Board

U-2 MC-79L 12 ACP CR-1 CR-2

Q-1

3 2

2N3906

1

Blue (-15V) White/Gray Stripe (Ground) White/Purple Stripe (+15V) Oscillator

High Voltage Board Layout Some of the major components found on the high voltage board are illustrated in this drawing. They include: • High Voltage Transformer, T1 • Negative Voltage Regulator IC, U2 • Oscillator Transistor, Q1 • Control IC, U3 • Rectifier and Voltage Doubler, CR1 and CR2 Also shown is the ±15VDC hard-wired input connections from the preamplifier board.


8

High Voltage Block Diagram

±15V

Rectifier & Voltage Doubler

Oscillator

+1400V (To Ion Chamber)

Voltage Regulation & Filtering U3B

U3A

-12V Regulator

High Voltage Operational Block Diagram The high voltage circuit consists of a DC/DC converter that uses active voltage feedback for both regulation and dynamic filtering of the output voltage. Major circuits on this board include: • Free-running LC sine wave oscillator • Voltage regulator IC • Step-up power transformer • Voltage Doubler circuit • Active feedback voltage regulation These circuits will be discussed shortly. High Voltage Operation High voltage for the ion chamber is generated by a free running oscillator circuit, using a step up transformer, along with active feedback to maintain constant voltage under varying loads.


9

Fusible Resistors

High Voltage Board Power Input The high voltage board power input is protected using 10Ω, 1/4 watt resistors on the input power. If found to be open, the cause of the short should be repaired and “flame proof” resistors installed.


10

FSU High Voltage Board Oscillator

Voltage Doubler

HV Out

Active HV Regulation

-12V Regulator

Oscillator Circuit Components Q1, T1, C5, C6, R4, and R5 form an LC Hartley oscillator, utilizing positive feedback to make up a frequency-selective network running at approximately 1.5 kHz. The two primary windings of T1 act as the inductive portion of the sine wave oscillator. This loop is designed to have a gain of unity at a single frequency as determined by the frequency-selective network. In this type of oscillator, sine waves are generated essentially by a resonance phenomenon. Excitation voltage is supplied by the same ±15VDC that powers the preamplifier board. High Voltage The AC voltage produced by the oscillator circuit is stepped up by transformer, T1, to approximately 500VAC (RMS). Half-wave rectification, via CR2, gives a DC voltage of +700VDC which is increased to 1400V using a voltage doubler circuit, consisting of C7 and CR1. Filtering is provided by an RC circuit consisting of C8, R6, R7, C9 and C11. Active (dynamic) filtering is also provided in the feedback circuit. High Voltage Regulation Regulation is developed from the voltage value derived from voltage divider R8, R11 and the regulated 12V from IC, U2. Any deviation is fed back to the oscillator for correction to its output. For this voltage correction to occur, operational amplifier, U3A, must amplify any deviation between the voltage divider and ground. The non-inverting buffer, U3B, feeds the error voltage to the primary supply voltage for Q1, varying it to hold the output at a constant value. An RC circuit, consisting of R12 and C13, slows the correction slightly in order to prevent overcorrecting, which will cause “hunting”. Dynamic Filtering Similarly, any ripple voltage is treated as deviation from the referenced voltage. Amplified ripple voltage from the secondary is fed back through the low side of T1 to null the output ripple, thereby providing dynamic filtering.


11

Voltage Doubler 700V C7

-

CR2

+ CR1 Fig 1

-

700V + 700V = 1400V CR2 +

X CR1 Fig 2

Voltage Doubler Circuit Early SGO Detector Gauges used +700VDC to power the Ion Chamber. This high voltage was increased to +1400VDC on the FSU Detector Gauge in order to achieve improved sensitivity and stability. In order to achieve this higher potential with minimal component changes, a voltage doubler circuit, consisting of only two extra components (a diode and capacitor), has been added. Theory Of Operation The output from the secondary winding of the step-up transformer is an AC sine wave providing 500VRMS. During the negative-going portion of this sine wave (Fig 1), CR1 conducts and charges C7 to +700V. When the sine wave begins going positive (Fig 2), its voltage is added to the +700V already on C7 and then coupled through peak detector diode, CR2, to give an output of +1400V. This is analogous to the way batteries in series add their voltage. NOTES 1. Due to the high frequency of the oscillator circuit, when replacing the diodes in the power supply use only fast-switching replacements, not general purpose rectifiers. 2. Loose lamination plates in the transformer may result in a high-pitched audible squeal. Although the high voltage circuit may work, extra energy is used to make the laminations resonate. The transformer should be replaced.


12

FSU Preamplifier Board

Preamplifier Board The preamplifier board converts the current flow from the Ion Chamber into a proportional non linear voltage signal that represents actual density. It performs this task using a unique negative-going ramping action, the slope of which varies in accordance with the incoming current. This ramp is then converted into a DC voltage, inversely proportional to density. FSU Preamplifier Board Features Features of the FSU preamplifier board include: • Quick warm up using temperature compensation circuitry. • On-board regulation of input power supply voltage. • Output span adjustable via active gain set jumpers. • Gain fine adjust using trim pot.


13

FSU Revision D & E Board Parts Layout Signal Gnd

+15V -15V

-15V

U3

TP-8 Q5 AR6

W-3

W-2

+15 V

GND

Board notched for compression grommet

TL026 CP

W6 W4

CO4093BC P

Gain Jumpers W2 & W4 “In”

LF-13006N

TP-3 TP-4 TP-7

U2 W-1 Q6

W1/R35

Reset Reed Relay

R13 TP-1 R12

R1

Input From Ion Chamber

RELAY

Q4

R28

AR1 C13 TP-2

TP-6

Dual MOSFET Q4

FSU Board Component Layout The dotted line represents the shielded portion of the circuit. This will make a handy reference for locating component parts and test points.


14

Power Input Fusible resistors

Power Input Fusible 10Ω, 1/4 watt resistors are used on the preamplifier board for short-circuit protection. Because an open resistor may be difficult to spot visually, supply voltage measurements should be taken not at the connector, but at the test points on the board. Flame-proof resistors should be used for replacement after the cause of the short is repaired.


15

DC Differential Amplifier

Inverting Input

Non Inverting Input

Amplified Ion Chamber Signal

Reference Voltage

DC Differential Amplifier An IC operational amplifier (op amp) has two complementary inputs, inverting and non inverting. This makes it useful for application as a differential amplifier, which produces an output voltage that is proportional to the difference between two ground-referenced input voltages. Noise Rejection and Temperature Stability An advantage of this circuit is its ability to reject common-mode (noise) signals, where there may be a large picked-up interference signal. The differential amplifier rejects this interference signal, because it is common to both inputs, therefore cancelled out. An additional benefit of this circuit is temperature stability, because any voltage changes due to temperature variance will be seen on both legs, and therefore canceled out. FSU Gauge Application Because the signal from the ion chamber is coupled to the inverting input of AR4, the output will be a negative-going voltage. The non inverting input of differential amplifier, AR4, is referenced to a set voltage (The “reference” side of a dual MOSFET). When there is no current from the ion chamber, both inputs are equal and no output is seen. As current begins to flow (the result of radiation into the ion chamber), this balance becomes unequal and the voltage difference amplified.


16

FSU Integration Mode

+7.5 V

Integration Mode 0V

-10 V

Integration And Resetting During normal operation, the preamplifier will be in one of two modes: • Integration or • Resetting Integration will be discussed first, after which the reset operation will be covered. Conversion Of Signal From Ion Chamber The signal from AR4 charges an RC circuit, which creates a negative-going sawtooth ramp, the speed (slope) of which is proportional to the amount of radiation being received at the ion chamber. The above drawing shows the critical components used to control this ramp: • Dual MOSFET • Operational Amplifier IC • Feedback Resistor Network • Precision Capacitor How It Works A dual MOSFET converts the current generated from the Ion Chamber into a voltage that is then processed by an inverting differential amplifier IC. The output of this IC negatively charges a capacitor through a resistor voltage divider network, with the resulting voltage fed back to the input of the MOSFET in the form of negative feedback. In this way, a negative-going ramp is generated, the speed (slope) of which is controlled primarily by the following variables: • Current from the Ion Chamber (which is dependent upon amount of radiation received at the Ion Chamber and high voltage level) • Value of the feedback resistor • Value of the feedback capacitor Increasing the resistance or capacitance will increase the RC time constant, thus slowing the ramp, and vice versa. Proprietary and Confidential Property of BJ Services Company

17

FSU Integrator Block Diagram +12V Reg

TP 6 AR4

+15V Q4 U2 13

R28 -15V

R

C 13

14 +7.5 V

Zero Volt Potential

330 pF

Integration Mode

R

0V

W1 (X2 Mult)

15

-10 V

Converts Current Signal Into Voltage Signal Because of the extremely high input gate resistance of Q4, it is a perfect match for converting the very small current generated by the Ion Chamber into a representative voltage. Temperature Compensation Semiconductor, Q4, is actually two MOSFETs in one package. The first MOSFET connected to the Ion Chamber converts the current signal from the Ion Chamber into a representative voltage at the output source leg, while the second MOSFET (along with resistor, R28) acts as a temperature dependent voltage divider at the non-inverting leg of AR4. RC Network The slope of the ramp and resulting output signal level is a function of feedback through the electronic resistor divider network, U2 and C13, which form an RC circuit. Because of its superior temperature stability and high internal resistance, a polystyrene capacitor is used in the feedback circuit. Zeroing Reference Voltage Trim pot, R28, provides a means for zeroing, or nulling, the output from AR4 when no radiation is present at the Ion Chamber. This pot is adjusted so that the voltage on the positive input of AR4 is the same as the voltage on the negative input of AR4 when Q4 is receiving no signal from the ion chamber. NOTE Dual MOSFET, Q4, is hand-selected at the factory for matching characteristics, therefore replacements should be purchased only from TN Technologies.


18

Converting Ramp to Current Summing Point T2 TP 6

+

TP 1

C 12

AR4

+15V

C5 R7

Q4 Zero

U2 Mult

10 MΩ Ω

U2 13

T2 -15V C 13

V sig

AR1 .33 µF

Gain

R 14

330 pF R 0V Zero Volt Potential

W1

15

(X2 Mult) 150 kΩ Ω

300 kΩ Ω

-15 V

Op Amp, AR1, Converts Ramp To DC Current The negative-going ramping voltage is changed to a proportional current at the summing junction of C12 and R7. Voltage output from AR1 holds the summing point voltage at ground potential so that TP6 ramp voltage also occurs across C12. IC, U2, Sets The Overall Gain The Electronic Gain Set IC, LF13006, is similar to a resistor network, however the resistance is controlled using logic voltages.


19

Preamplifier Circuit Detail

+12V Regulator

Dual MOSFET

Signal Output

C13 Protection FET / NE2 Ramp Reset

Gain Set

Integration Review During Integration, the voltage from MOSFET, Q4, through its source leg (Pin 7) is coupled to the inverting input of AR4. The output is a negative-going signal at Pin 6 of AR4 that is coupled back to the MOSFET through a resistor network and capacitor, C13. The voltage at the input of the Preamplifier is amplified just enough to virtually cancel the change in voltage at pin 5 of Q4, so that all the current flowing into the Preamplifier from the Ion Chamber is accumulated as charge voltage on C13. The rate of voltage change, seen as a negative-going ramp at the output of AR4 (TP6), is proportional to the input current from the Ion Chamber. The reference voltage for the IC is controlled by the second portion of the dual MOSFET, thereby automatically compensating for voltage drift caused by changes in temperature. Setting Gain The slope, or gain, of the ramp is controlled by digital resistor network IC, U2, and by the value of C13. The procedure for adjusting the gain will be discussed later in this presentation. Input Protection On early version boards, an NE-2 neon lamp is used to shunt voltage spikes and protect Q4. It is connected from the junction of R12 and R13 to ground and triggers at approximately 50 V. This lamp was replaced with a solid-state FET lamp on newer version boards, thereby reducing the possibility of leakage through the neon lamp body due to impurities in glass manufacture. Voltage Regulator Because the ±15V may not be stable, a +12V regulator IC, U5, provides VCC for Q4.


20

Ramp Integration Ramp Converted to Current

Summing Point

Ramp Input From Preamp

“NULL” Adjustment Potentiometer

Overvoltage Protection

Ramp Converted To DC Voltage The “sawtooth” ramp must be converted into a proportional DC voltage for use by a suitable transmitter. This function is performed primarily via operational amplifier, AR1, which converts the ramp into a current at the summing point, C12 & R7, by feeding back its output voltage through R7. This action holds the summing point voltage at ground potential to ensure TP6 voltage change (ramp) rate also occurs across C12. At the same time, capacitor, C5, is seeing the same potential, but at this point has no ground return path. A return path will be provided for the low side of this capacitor during the reset function in order to prevent the reset pulse from being seen on the output of AR1. Its operation will be discussed later in the presentation. AR1 Protection Two back-to-back 15V zener diodes protect AR1 from external voltage spikes and prevent voltages in excess of ±15V from being seen on the signal output line, thereby protecting the external monitoring devices.


21

Reset Circuit (Part of Preamplifier Board) T2 C 12 R6 AR1

AR4 .33 uF C5 R7

U2 Mult

Q4 U2

T2

C 13 K1 330 pF

+10 V

T1 AR6

-10 V T2 Reset Circuit T2 K1

T2 T1

-15 V

Ramp Reset Circuit So far, only the ramp has been discussed. Because the signal cannot continue its negative ramp indefinitely, a reset must take place when the ramp reaches a preset voltage limit. The ramping action can then then start again. Sequence Of Events In order to reset the ramp without causing an anomaly in the output signal, several events must occur simultaneously: • The signal path from AR4 to the output, AR1, must be disabled to avoid a “spike” from being seen on the output signal. This is accomplished using an FET as an “electronic switch”, or gate, to open the ramp signal path to the output IC during reset mode. • A reed relay is activated to discharge ramping capacitor, C13, which causes the reset to occur. • Another FET gate and a capacitor (C5) are used as a version of a “sample and hold” circuit to keep the output at its last voltage level during the reset action. This entire reset activity starts at virtually the same time (the actual reset time for C13 is slowed somewhat due to inherent mechanical delay of the reed switch), and takes approximately 80 milliseconds to complete. In order to understand the dynamics of the circuit, the reset action will be looked at first, then the FET gates controlling the output will be discussed.


22

Ramp Reset Ramp Input 0V

+10V

-15 V

T1

-10V +7.5 V

Integration Mode 0V

Reset Mode

To U3C

-10 V

Voltage Limits When the ramp voltage from the preamplifier reaches a predetermined positive or negative voltage level, an action will occur to reset the ramp. Voltage divider resistors, R27, R32, and R33 are connected to ±15VDC to form the positive and negative 10V reference for voltage comparator IC, AR6A and AR6B. This dual-package op amp senses the ramp voltage limits and triggers a positive output whenever the input ramp from the preamplifier is equal to the reference voltage. In order to achieve a positive output from either ramp extreme, AR6A is configured as a non-inverting output and AR6B is an inverter. The +10VDC reference voltage limit is connected to pin 6 of AR6A, and the -10V limit is tied to AR6B, pin 3. Note Under normal operation, the ramp resets to +7.5VDC, which is set by voltage divider circuit consisting of R30 & R31 (not shown in this drawing). The +10VDC limit is not normally activated, and will only be seen in the event of an abnormal condition, such as a saturated preamplifier input signal. NAND Gates When AR6 output goes high, “NAND” gates will be activated. (NAND gates are inverting AND gates, therefore both inputs must be “high” for the output to go “low”.) An RC network makes these gates act as as Monostable Multivibrators, or “One-Shots”, meaning the output will be a single pulse when both inputs are equal. Ramp Reset When triggered, U3A & U3B develop a single positive-going square wave pulse at T1 (TP4), the duration of which is stretched by C16, R16 and R19 to about 50ms. This pulse “turns on” transistor, Q5, which in turn energizes a relay to provide a discharge path for reset feedback capacitor, C13.


23

Output Signal During Reset

T2 TP 1 V sig

AR1 C5 U2 Mult

T2

Gain

From U3B

K1 +10 V AR6

T1

-10 V T2

T2 0V -15 V

0V -15 V

Pulse Stretched

Output Must Be Stable During Reset If no provision were made to hold the output signal from AR1 at a constant value during the reset portion of the ramp, the output voltage would drop to near zero during the reset period, resulting in a large density “spike”seen at the transmitter and recorder. In order to avoid this situation, two additional pulses, T2 and /T2, are used to isolate the output during reset in an analog version of a “sample-andhold” circuit. Output Signal During Reset Function When a reset action starts, the pulse from T1 is stretched to approximately 80 milliseconds by an RC circuit on the input of NAND Gate, U3, starting at the same time as T1’s pulse. (Stretching the “hold” pulse allows time for the reed reset switch to complete its mechanical cycle.) Pulse T2 goes from -15V to 0V and can be observed at TP3. This same pulse is inverted by U3D, and seen at TP2 as a negative going pulse (/T2), from 0V to -15V. MOSFET, Q1, is used as an ultra low-resistance switch (gate), which is turned off by the action of T2, thereby isolating the ramp signal. At the same time, another MOSFET, Q2, is turned on by /T2 to provide a return (through a 10 MΩ resistor) for the voltage charge across C5, effectively holding the output at its present value until the reset action is completed. Integration FET Q6 The pulse at /T2 also turns off FET, Q6. The purpose of this semiconductor is to provide a ground return across the reed switch during integration operation to make any open switch leakage negligible, and to act as “anti-bounce” protection for the reed switch during the reset action.


24

Review of Reset and Output Circuit T2 TP 6

C 12

AR4

AR1 C5

Q4 10 Meg T2

Gain

C 13

@ 30 msec K1

330 pF

+10 V AR6

0V

T1

-15 V

T1

0V

-10 V

T2

T2

-15 V

Reset Circuit

0V T2

T2

-15 V @ 60 msec TP 6 Signal VR T2

300 K

+7.5 V Reset

K1 -15 V

0 V

Slope Determines Output Signal

Reset Start -10 V

Key Sequence Summary To summarize the sequence of events occurring during the reset mode: • T1 pulses high, turning on transistor, Q5, which activates reset relay. • T2 goes turns off Q1, to isolate the ramp signal. • /T2 turns off Q6 and turns on Q2 to provide return path for C5, effectively “holding” the output at the latest voltage. • C13 discharges through reset reed switch. • T1 then goes low, turning off Q5 and opening reed switch. • 30 ms later, T2 goes low and /T2 goes high. • The ramp starts and C13 begins to charge on its negative-going journey.


25

Key Reset and Output Components AR1, Output IC

C12, Summing Capacitor

Q1, Off During Reset

Q2, On During Reset

R7, Summing Resistor

Key Reset And Output Components MOSFET gates, Q1 and Q2, are mounted on high resistance Teflon® standoffs in order to prevent high resistance leakage which could cause erratic output signals. It is recommended that only “exact replacement” semiconductors be used to replace these components.


26

Electronic Voltage Divider IC, LF13006 C13

TP6 C8

W1

14

13

15

Resistor Array 12

DECODER LATCH

LATCH

LATCH

9

8

Digital 2

2

Digital 1

Output

Signal In W3

W2

W6 15V

AR1

W4 15V

LF13006 Digital Gain Set IC The IC, U2 is a precision laser-trimmed digital gain set IC. As part of the RC gain set in this Preamplifier circuit, it is simply an electronic version of a multiple-resistance voltage divider, the value of which is set by external jumper combinations that control internal latches. This circuit is used to set the overall gain of the preamplifier for adjustment of open pipe signal voltage to 10V. Setting The Gain of AR1 The gain of op amp, AR1, is varied by changing the voltage level of two inputs to U2: Digital 1 on pin 8 and Digital 2 on pin 9, which changes feedback resistance in the circuit. By placing a jumper in the appropriate position, Digital inputs 1 and 2 can be latched “on” (15V) or “off” (ground). When the latch is “off”, the digital resistor used for feedback is at its highest value, resulting in the lowest gain setting for the system. Conversely, when the latch is “on”, the resistance is minimal and the circuit gain increased. Digital 1 (least significant digit) function is identical to Digital 2 (middle significant digit). Ramp Gain Set Shorting pin 15 of U2 to ground puts a second precision voltage divider resistor into the ramp feedback loop, thereby increasing gain by a factor of 2. In place of a jumper, a 50 kΩ trim pot (R35) can be installed at W1 to enable a “fine adjustment” of the integration gain circuit. The gain of the circuit is inversely proportional to the resistance of the trim pot. This trim pot comes factory-installed on later boards. LF13006 Replaced Because U2 has been discontinued by the manufacturer, Revision E boards use discrete resistors for gain setting.


27

REV C, D &E Gain Jumper Settings

GAIN

W2 / W3

W4 / W6

X-1 X-2 X-4 X-8

W3 W3 W2 W2

W4 W6 W4 W6

Jumper Gain Settings The above chart gives approximate gain values for various jumper combinations, however actual gain figures may vary due to component tolerances. On Revision C boards, jumper wires must be soldered to individual components in order to set W4/W6, while Revision D & E boards have plated-through holes for easier jumper installation. Because of this, Revision C boards should be replaced with newer versions when servicing is needed.


28

R35 Gain Settings Resistance 0 (short) 2.2 kΩ 4.7 kΩ 10 kΩ 15 kΩ 22 kΩ 33 kΩ 47 kΩ Open

Gain 2.0 1.87 1.76 1.6 1.5 1.5 1.31 1.24 1.0

Variable Gain Set On earlier revision boards, installing a 50 kΩ trim pot (R35) in place of jumper W1 will provide a means for setting the integration rate. The above chart lists the approximate gain at various resistance settings. For best performance, R35 should initially be set for the lowest gain. Jumpers W2 through W6 can be configured to set open pipe voltage close to, but not exceeding 9.9V, and R35 is then used for adjustment to 9.9V. Revision D and newer boards will have this trim pot factory-installed.


29

Rev F Gain Set

R35 W1 & W2

W3

New Style Preamplifier Board Pictured is a portion of the new version Preamplifier Board, which uses discrete resistors in place of Electronic Gain Set IC, U2. The board has different locations for jumpers W1, W2, and W3. Additionally, notice that R35 is no longer in W1 position. Be careful when installing jumpers, as there is a pad (marked in red in this photo) adjacent to W3 that can be mistaken for part of the gain set circuit.


30

Rev F Jumper Location

GND

R35

-15V

+15 V

W2 W-3

W1

R35

Gain Jumpers

TP-1


31

Rev F Gain Set Components

Gain Set IC Replaced by Resistors On Revision F and higher preamplifier boards, the obsolete Digital Gain Set IC, U2, has been replaced with discrete resistors, R5, R37 and R36, which are low drift, 1% metal film components. Soldered-in jumpers continue to be used for gain setting, however the configuration of these jumpers and their effective gain values have changed. There are now three jumpers, which enable a wider range of gain settings. Additionally, jumper W1 is now part of the fixed gain set circuit. Trim pot, R35, (not pictured) is still used, but no longer in W1 position.

In addition to jumpers, trim pot R35 is Proprietary and Confidential Property of BJ Services Company

still used for fine adjustment.

32

Gain Jumpers Rev F Boards With Resistor Feedback

Gain: X-1 X-2 X-4 X-7 X-8

Jumper Positions W1 W2 W3 Out Out Out Out In Out In Out In Out Out In In Out In

New Version Preamplifier Board A fixed resistor voltage divider network replaces Gain Set IC, U2, in the Revision E Preamplifier Board (with a subsequent jumper configuration change). The above gain settings are approximate.


33

Gain Adjustment Via C13

Capacitor, C13 If the correct open pipe voltage cannot be obtained via jumper configurations, the value of feedback capacitor, C13, can be changed to raise or lower the Preamplifier gain. Raising the capacitance will decrease the gain, and vice versa. Care When Replacing C13 It is important that latex surgical gloves be worn when handling the capacitor, as any contamination deposited on the capacitor body will affect the performance of the gauge. It has been determined by TN Technologies that even thoroughly washed hands will still leave trace oil and dirt deposits on the capacitor. These contaminants can cause long term drifting and instability of the output voltage. Additionally, the capacitor must be secured to the shield plate using non-corrosive RTV silicon compound. Do not use acid-curing compound, as contamination can result, and do not let any compound make contact with the capacitor leads. If contamination is suspected, the capacitor and surrounding area can be cleaned with isopropyl alcohol. Other cleaning agents may dissolve the polystyrene body.


34

Don’t Forget! • Lower the value of C13 in Preamplifier Board to raise gain….Raise the value to lower the gain. • Use non-corrosive silicon seal to secure C13 to shield, and do not let compound touch the leads. • Nominal value of C13 is 330pF. • Dirt and oil from your hands can contaminate C13

Cleanliness Is Critical Even resistances in excess of 1x1013Ω will have a major impact upon the output signal. The Preamplifier Board must be kept clean and free from corrosion and moisture! This is especially true of polystyrene gain set capacitor, C13. Expiration Date Because polystyrene capacitors can absorb moisture, do not use any capacitors that have been sitting on the shelf for a long time (over a year in humid climates). It is a good idea to store the capacitors in a sealed container, and to keep a dated inventory list.


35

Nuclear Source Simulator

Nuclear Source Simulator An alternative to using a nuclear source for servicing and testing the FSU Gauge is a Nuclear Source Simulator, such as the one pictured, which can be constructed by an Electronic Technician, and will provide a very low adjustable current signal to the Preamplifier input, thus simulating actual operation.


36

Construction and Operation of Nuclear Source Simulator

NOTE: Keep leads short.

Circuit The Nuclear Source Simulator consists of: • 2KΩ ten-turn potentiometer • 15GΩ Resistor • 8” RG174 coaxial cable Additional components include a suitable plastic case, LED and clip leads. When building the simulator, it is important to keep the leads as short as possible, especially the coaxial cable. Operation The simulator works best with the complete assembly attached, but can be used with just the preamplifier board, connected to ±15V. To use the simulator, disconnect the ±15V connector on the preamplifier board that powers the HV board and connect the simulator power connector in its place. Connect the coaxial lead from the simulator to the junction of R12 & R13. Adjust the potentiometer fully CCW, apply power and slowly adjust the potentiometer for desired output voltage at TP1 on the preamplifier board. Note: This simulator is a troubleshooting aid only; it is not suitable for use as a calibration device.


37

Review Questions Detector Assembly, Densimeter Repair 1. The three main component parts of the Detector Assembly are: 1. ________________________________________ 2. ________________________________________ 3. _________________________________________ 2. Briefly explain why the Fluke 80K-40 High Voltage Probe is designed to work only with meters that have 10MΩ input impedance.

3. Components Q1, T1, C5, C6, R4, and R5, on the High Voltage Board, form a ____________oscillator. This oscillator uses _______________ feedback to maintain a constant voltage. 4. Other than radiation strength, the four variables which affect the overall gain of the preamplifier are: 1. __________________________ 2. __________________________ 3. __________________________ 4. __________________________ 5. The original NE-2 lamp was replaced with a solid-state FET lamp on newer version boards to reduce the possibility of _________ due to variances in glass manufacture. 6. When powered up, The preamplifier will always be in one of two modes: 1. __________________________ 2. ___________________________ 7. IC, U2, used as part of the RC gain set in the Preamplifier circuit, is simply a _____________________________________________________________.

Page 1 of 2

Review Questions Detector Assembly, Densimeter Repair 8.

Increasing the capacitance of C13 will: ( ) raise ( ) lower the output voltage from the Preamplifier. Increasing the value of the resistance in the feedback will: ( ) raise ( ) lower the output voltage from the Preamplifier.

9. When the voltage ramp applied to pins 5 and 2 of AR6 reaches the value set by ________________, one output will go ____________ and trigger the “NAND” gate U3A and U3B. 10. Temperature stability is primarily provided by component _____________________.

Page 2 of 2

Activity One - Test Points Detector Assembly, Densimeter Repair Introduction There are several Test Points on the FSU Preamplifier Board to aid the in troubleshooting and calibration. Some Test Points are labeled as such (TP followed by a number), while others are labeled as to their function, such as “GND”.

Prerequisites •

None

Objective The objective of this activity is to present a guide for locating and identifying Test Points found on the FSU Preamplifier Board

Parts and/or Tools Required FSU Densimeter Assembly Densimeter Test Stand ±15V Power Supply (May be provided by Analog or Digital Transmitter) Power /Signal Wiring Harness Digital Volt Meter High Voltage Probe Insulated Alignment Tool

Procedure 1. Mount FSU Nuclear Densimeter Assembly into Test Stand. Remove any test sticks from tube. 2. Verify power supply is turned off. Connect Power/Signal Wiring Harness from J1 on Preamplifier Board to ±15V Power Supply. 3. Locate, on the FSU Preamplifier Board, The Test Point marked “GND”. Connect common lead of DVM to this Test Point. 4. Turn on power. 5. Locate the following Test Points and measure the voltage at each: ♦ +15 ________ ♦ -15 _________ ♦ TP1 (Signal Output) _________ ♦ TP6 (Ramp Signal) __________ 6. Connect High Voltage Probe to DVM and measure voltage on the Ion Chamber, through access hole in Test Stand. Record voltage ______________. 7. While measuring High Voltage, tap on High Voltage Board with insulated tool. Did High Voltage change? ________. 8. This Activity is complete

Page 1 of 2

Activity One - Test Points Detector Assembly, Densimeter Repair Study Questions 1. What other voltage(s) can be found on the Preamplifier Board?

2. Why is it preferable to check ±15V at the Test Points, rather than on the Molex Connector?

3. Why must the High Voltage be stable and well regulated?

Page 2 of 2

Activity - Observing Ramping Action Detector Assembly, Densimeter Repair Introduction The ramping action (slope) created in the first stage of the preamplifier affects the output voltage of the Nuclear Densimeter. There are three main factors that determine the slope of the ramp: 1. Radiation at Ion Chamber 2. High Voltage level 3. Value of R-C Feedback Circuit

Prerequisites • •

Test Points Activity High Voltage Measurement Activity

Objective The objective of this Activity is to demonstrate the ramping action of the Preamplifier, and how it affects output signal voltage.

Parts and/or Tools Required FSU Densimeter Assembly Densimeter Test Stand or insulated mat Analog or Digital Transmitter, or power supply capable of providing ±15VDC at 1 amp Power /Signal Wiring Harness Nuclear Source Simulator Oscilloscope Clip lead, to discharge high voltage

Procedure 1. Place FSU Nuclear Densimeter Assembly into Test Stand 2. Connect Power/Signal Wiring Harness from J1 on Preamplifier Board to ±15V power supply. Connect the Nuclear Signal Simulator 3. Set up oscilloscope to measure voltage and display waveform (5V/Div, DC Scale, 100mS) and connect to Preamplifier Board: ♦ Probe to TP6 ♦ Ground clip to “GND” test point 4. Apply power to Densimeter 5. Adjust the Source Simulator to maximum current (fully clockwise.) 6. Observe the ramping action on TP6. 7. Observe and record the voltage at which the ramp resets: ♦ Upper voltage ramp limit_______ ♦ Lower voltage ramp limit_______ 8. Decrease the input current from the simulator. The slope of the ramp: A. Increases B. Decreases C. Stays the same

Page 1 of 2

Activity - Observing Ramping Action Detector Assembly, Densimeter Repair 9. Remove power. 10. This Activity is complete.

Study Questions 1. Why does the ramping action slow with reduced radiation exposure to the Ion Chamber?

2. Referring to the FSU schematic, what purpose(s) does Q4 serve?

3. What function does AR4 serve?

Page 2 of 2

Activity - Zeroing Preamplifier Detector Assembly, Densimeter Repair Introduction The Nuclear Densimeter will require periodic checks and adjustments to ensure that, with no received radiation, the output signal at TP1 stays near zero volts. Otherwise, accuracy of the unit may be compromised. TN Technologies recommends a slight offset voltage in order to minimize disturbance in output signal caused by the ramp reset.

Prerequisites • • •

Test Points Activity High Voltage Measurement Activity Ramp Observations Activity

Objective The objective of this Activity is to instruct the technician in the proper procedure to follow when zeroing the Nuclear Densimeter.

Parts and/or Tools Required FSU Densimeter Assembly Densimeter Test Stand or insulated mat Analog or Digital Transmitter, or power supply capable of providing ±15VDC at 1 amp Power /Signal Wiring Harness Alignment tool Digital Volt Meter Clip leads

Procedure 1. Place FSU Nuclear Densimeter Assembly into Test Stand. 2. Connect Power/Signal Wiring Harness from J1 on Preamplifier Board to ±15V Power Supply. 3. Place DVM to measure voltage at TP6 ♦ Positive lead to TP6 ♦ Negative lead to “Gnd” test point 4. Install jumper wire from resistor, R13 to TP6, to remove the effects of residual input signal. 5. Apply power to Densimeter. 6. Adjust Trim Pot R28 for 0 V at TP6. 7. Leaving jumper wire in place, move meter lead to TP1. 8. Adjust Trim Pot R1 for 0 V at TP1. 9. Recheck TP6 and re adjust if necessary. 10. Remove jumper and note that voltage at TP1 does not increase significantly. 11. Power down and discharge high voltage. 12. This Activity is complete

Page 1 of 2

Activity - Zeroing Preamplifier Detector Assembly, Densimeter Repair

Study Questions 1. Can the zeroing procedure be performed without the Ion Chamber or High Voltage Board attached? ________. Explain:

2. Why is the voltage at TP6 re-checked after adjusting TP1?

3. What will be the slope of the ramp at TP6 with a properly zeroed system.

Page 2 of 2

Activity - Setting Preamplifier Gain Detector Assembly, Densimeter Repair Introduction The Detector should be set for an “open pipe” signal output between 9.5 – 9.9VDC. This is referred to as “setting the gain”, and a trim pot adjustment and several soldered-in jumpers are provided on the preamplifier board for setting this voltage. This activity will be similar to actual field practices, however a nuclear source simulator will be used and the training preamplifier unit will have plug-in jumpers instead of soldered –in jumpers for setting the gain.

Prerequisites • • • •

Test Points Activity High Voltage Measurement Activity Ramp Observations Activity Zeroing Preamplifier Activity

Objective The objective of this activity is to familiarize the ET with gain-set adjustments and jumpers on the FSU preamplifier board.

Parts and/or Tools Required FSU Densimeter Assembly Densimeter Test Stand or insulated mat Analog or Digital Transmitter, or power supply capable of providing ±15VDC at 1 amp Power /Signal Wiring Harness Nuclear Source Simulator Digital Volt Meter Alignment tool Clip lead, to discharge high voltage

Page 1 of 3

Activity - Setting Preamplifier Gain Detector Assembly, Densimeter Repair Procedure 1. Place FSU Nuclear Densimeter assembly into test stand 2. Connect power/signal wiring harness from J1 on preamplifier board to ±15V. Connect the source simulator to the connector next to J1. Adjust the simulator knob fully counterclockwise. 3. Connect DVM to measure DC voltage between TP1 and GND. 4. Adjust trim pot, R35, to mid scale (it is a 20-turn pot).

GAIN

W2 / W3

W4 / W6

X-1 X-2 X-4 X-8

W3 W3 W2 W2

W4 W6 W4 W6

Refer to the above gain-set chart for the next steps. 5. Configure the preamplifier for a gain of “X1”. 6. Apply power to Densimeter. 7. Turn the simulator knob clockwise just enough to give approximately 1 VDC at TP1. Record X1 voltage: _________. 8. Do not change the setting of the simulator for steps 9 - 11. 9. Configure jumpers for a gain of “X2”. Record X2 Voltage: _________. 10. Configure jumpers for a gain of “X4”. Record X4 Voltage: ________. 11. Configure jumpers for a gain of “X8”. Record X8 Voltage: ________. 12. Return to “X1” setting and adjust the simulator to give approximately 8V at TP1. 13. Adjust trim pot, R35, at W1 to give approximately 9.9V “open pipe voltage” at TP1. 14. Remove power. 15. This Activity is complete.

Study Questions 1. In the above Activity, it is seen that the gain of the preamplifier can be adjusted by a combination of jumper settings. What parameter is being changed with these jumpers?

Page 2 of 3

Activity - Setting Preamplifier Gain Detector Assembly, Densimeter Repair 2. What are your observations concerning the actual gain values set by the various jumper configurations?

3. What other component value can be changed to vary the gain of the Preamplifier?

Page 3 of 3

Activity - Observing and Comparing Reset Pulses Detector Assembly, Densimeter Repair Introduction Because the ramp cannot continue indefinitely, a voltage pulse is used to reset the ramp when it reaches a predetermined level. Additional pulses prevent the reset action from being seen on the output signal.

Prerequisites • • • • •

Test Points Activity High Voltage Measurement Activity Ramp Observations Activity Zeroing Preamplifier Activity Gain Setting Activity

Objective The objective of this activity is to observe and compare the operation of the three reset pulses. By observing the time relationship between these pulses, an understanding of their purpose should become apparent.

Parts and/or Tools Required FSU Densimeter Assembly Densimeter Test Stand or insulated mat Analog or Digital Transmitter, or power supply capable of providing ±15VDC at 1 amp Power /Signal Wiring Harness Nuclear Source Simulator Oscilloscope Clip lead, to discharge high voltage

Procedure 1. Place FSU Nuclear Densimeter Assembly into Test Stand 2. Connect Power/Signal Wiring Harness from J1 on Preamplifier Board to ±15V. Connect the Nuclear Signal Simulator. 3. Connect Oscilloscope to Reset Test Points: • Channel A to TP6 • Channel B to TP4 • Ground lead to “GND” 4. Set up Scopemeter for waveform measurements as follows • Sensitivity: 5V/Div • Sweep: 50 mS/Div (may vary with source strength and ramp speed) • DC Volts 5. Apply power to Densimeter 6. Adjust the Nuclear Source Simulator fully clockwise.

Page 1 of 3

Activity - Observing and Comparing Reset Pulses Detector Assembly, Densimeter Repair 7. Observe and compare the two waveforms. • Voltage range of TP6 (Ramp) from _________ to __________ V • Voltage range of TP4 (Reset Pulse) from ________ to _______V 8. Sketch the two wave forms atTP6 and TP4. Overlay the two signals to show their time (period) relationship.

9. Leaving Channel B probe on TP4, move Channel A probe to TP3 and compare these two pulses. For ease of observation, move the base line (zero point) of one channel, thereby separating the two waveforms. Performing a “waveform capture” using single sweep function will help in this effort. Sketch these two waveforms, again showing the period relationship:

10. Move TP4 probe to TP2. Compare and sketch these two waveforms.

11. Remove power from Densimeter. 12. This Activity is complete.

Page 2 of 3

Activity - Observing and Comparing Reset Pulses Detector Assembly, Densimeter Repair Study Questions 1. Identify the function of each reset pulse: T1 (TP4) __________________________________________________________ T2 (TP3) __________________________________________________________ /T2 (TP2) _________________________________________________________ 2. What would be the observed result if pulse T1 was not present?

3. What would be the observed result of a failure of pulse T2 or /T2?

Page 3 of 3


BJ Digital Transmitter ET-205 Densimeter Repair

The BJ Digital Transmitter Originally designed to interface with the 611C Computer Controlled Blender and provide Proppant information, the BJ Digital Transmitter is an alternative to the TN Analog and Digital Transmitters. Modified UCM-II The BJ Digital Transmitter is a slightly-modified version of the popular Universal Control Module II, or UCM-II. The differences are discussed later in the presentation.


1

BJ Digital Transmitter Features

Features Of BJ Digital Transmitter The features of the BJ Digital Transmitter include: • Stand Alone or System (611C Blender) Applications • Easy To Program via Function Keypad Entry • Firmware Easily Upgraded • Operational Voltage Range 10.5 to 15 VDC • Frequency, LAN and Local Bus Outputs • Built in ±15 V Supply for Nuclear Densimeter • Supported by the Instrumentation Department Stand Alone Or System (611C Blender) The BJ Digital Transmitter is water and dust resistant. Although the BJ Digital Transmitter is water resistant, it should not be exposed to high pressure water. Additionally, the photo above shows an example of a custom enclosure that can be used for Stand Alone application. Easy To Program Via Function Keypad Entry Menu driven commands make the Transmitter user friendly. Wide Operational Voltage Range (10.5 to 15 VDC) The Transmitter requires approximately 10.5 to 15VDC @ 1 amp to operate. Frequency And LAN Outputs The Transmitter is fully compatible with the BJ LAN system. A self-powered high level frequency output is also available for non-LAN monitors (i.e., 3305 Mini Monitor). When used with the 611C Controller, a local serial bus line transmits serial data .


2

Inputs/Outputs 12VDC Power

0-10VDC Signal ±15VDC Power

LAN Output

Local Frequency Output Bus (611C)

Inputs The BJ Digital Transmitter requires 10.5 - 15VDC power to operate. It receives a 0-10V signal from the Nuclear Densimeter. Outputs The BJ Digital Transmitter has three data outputs available: • 1 - Frequency Output • 1 - LAN Output • 1 - Local Bus Frequency Output The frequency output is self powered, which means it does not require external excitation voltage for its high level (approx 10VP-P) output signal. It is scaled so that 1000 Hz = 10 Pounds Proppant Added (PPA), which equates to a PPU = 6000. LAN Communication The BJ Digital Transmitter can communicate over the BJ Local Area Network via RS-422 communication. By assigning unique ID numbers, up to three BJ Digital Transmitters can send data to a 3600, Isoplex36 or Isoplex monitor. To view this data at the 3600 and Isoplex36 Monitoring Systems, select >TEXAS NUCLEAR DETECTOR MODULES, reached by pressing the following sequence from the Main Menu Screen of either the 3600 or Isoplex36: • >SELECT PARAMETERS • Choose the appropriate Parameter Number • >SELECT INPUT • >LAN SYSTEM • >TEXAS NUCLEAR DETECTOR MODULES Local Bus The two-wire Local Bus line is designed to transmit data only to the 611C Controller. Proprietary and Confidential Property of BJ Services Company

3

611C Control Console

BJ Density Transmitter

611C Installation The above photos show a BJ Digital Transmitter in a typical 611C installation. Notice the location of the transmitter. It is usually mounted in the lower, right hand, slot.


4

Rear View

Power/Signal Connector

Contrast Control

Contrast Control The contrast control is a 10-turn potentiometer, located on the rear of the BJ Digital Transmitter. This potentiometer adjusts the contrast of the display, which changes with the angle of view. If power for the BJ Digital Transmitter is turned on, but nothing appears on the screen, check to insure that the contrast control is properly adjusted. Power/Signal Connector Power and signals are routed through this single multi-pin connector.


5

Keypads Main Screen

Numerical Keypads

BJ Digital Transmitter Keypads Now that a general overview of the BJ Transmitter has been given, it is appropriate to take a closer look at its software. Upon power up, a Firmware Revision screen briefly appears, then the Main Screen displays operator-selected density information. The transmitter is programmed through menu driven functions, which involve use of the keypads. The available keys are: • Numeric Keypads • Reference Key (REF) • Apparent Specific Gravity Key (ASG) • Fluid Weight Key (WT) • Corrected Specific Gravity Key (CSG) • Span Key (SPN) • Volts In Key (VIN) • Arrow Keys (↑ ↑ and ↓) • Test Key (TST) • Exit Key (EXT) • Clear Key (CLR) • Enter Key (ENT) Numerical Keypads The right side of the keypad is for entering numbers into the system. Depending upon the screen, the BJ Digital Transmitter may prompt the Operator for numerical information. To respond, the Operator presses the number keys on the right half of the keypad. Important Points About The Numerical Keypads It is important to note that if a minus sign is used, it should be pressed after the number is entered. For example, to enter the number -100, the Operator would press 1, 0, 0 and then ±.


6

Reference (REF) Key

Reference Key

Reference (REF) Key The Reference key is used to zero the Nuclear Densimeter when base fluid is circulating through the system. Pressing REF present two options: 1> Auto Reference 2> Manual Reference Auto Reference To automatically set the Reference Voltage, completely fill the pipe with fresh water or pad fluid and press the REF key and select 1, for Automatic. From this screen, when the ENT key is pressed, the current value of the Voltage Input, VTS IN, is “copied” and “pasted” as the Reference Voltage, VTS REF. Manual Reference The VTS REF can be manually used to input a Reference Voltage, but is more typically used to simulate a density signal and send it to a remote monitor for test purposes.


7

Apparent Specific Gravity (ASG) Key

Specific Gravity Key

Apparent Specific Gravity (ASG) Key The Apparent Specific Gravity of the base fluid is set by this key. The following list shows some common base fluids and their Apparent Specific Gravity: • Fresh Water 1.00 • KCL 1.01 • Salt Water 1.02 To set the Base ASG, type in the desired value and press the ENT key to enter the value into the BJ Digital Transmitter memory. Calculating Specific Gravity If the weight of the base fluid is known in pounds per gallon, divide the weight by 8.34 to obtain the ASG. If the weight of the base fluid is in kilograms per cubic meter, divide the weight by 1000 to obtain the ASG.


8

Base Weight (WT) Key

Fluid Weight Key

Base Weight (WT) Key This key allows the Operator to input the base weight of the base fluid, in Pounds Per Gallon, or PPG. This parameter should be set to 8.34 and left there. To set the Base Weight, type in the desired value and press the ENT key to enter the value into the BJ Digital Transmitter memory.


9

Carrier Specific Gravity (CSG) Key

Carrier Specific Gravity Key

Corrected Specific Gravity (CSG) Key The Corrected Specific Gravity is the specific gravity of the proppant used. This value enables the BJ Digital Transmitter firmware to determine how much sand is in a given volume of slurry. The values for three commonly used proppants are: • 20/40 Sand CSG = 2.65 • Interprop CSG = 3.15 • Bauxite CSG = 3.55 To set the Carrier Specific Gravity, type in the desired value and press the ENT key to enter the value into the BJ Digital Transmitter memory.


10

Span (SPN) Key

Span Key

Span (SPN) Key The Span Number is a value that defines the response of a Nuclear Densimeter to changes in density. This number is usually written on the side of the Nuclear Gauge. The Span is a scalar that “marries” the Nuclear Densimeter Gauge to the pipe on which it is mounted. Any modification to the Gauge will require that a new calibration procedure be performed by a qualified Electronic Technician. The Span Number For A Densimeter Is Not Known If the Span Number for a densimeter is not known, the densimeter should not be used. A calibration procedure must be performed prior to its use by a qualified Electronic Technician. If the densimeter must be used, the following nominal values provide an approximate value: • 2” Pipe Span = 34.0 • 3” Pipe Span = 25.0 • 4” Pipe Span = 15.5 • 6” Pipe Span = 10.0 • 8” Pipe Span = 7.3 Set The Span Number To set the Span Number, press the SPN key, enter the numerical value and press the ENT key to enter the value into memory. TIP It is important to keep the inside of the pipe as clean as possible. Buildup of cement or proppant significantly affects the Span Number.


11

Volts In (VIN) Key

Volts In Key

Volts In (VIN) Key This key monitors the “raw” signal voltage from the Detector Gauge and is very useful as a troubleshooting tool. TIP Without any fluid circulating through the Nuclear Densimeter, check to ensure that the Voltage Input into the 3305 reads between 9.5VDC and 10VDC. This is referred to as the “Open Pipe Voltage”. If the voltage is below this range, check to see if the Nuclear Densimeter has a “shutter” and, if so, that it is open. Also, check that the Nuclear Densimeter cables are connected and not damaged. If these items pass inspection and the Nuclear Densimeter is still not working properly, the Electronic Technician should be notified.


12

Arrow Up/Down Keys

Arrow Keys

Arrow Key(s) The Arrow Keys are used for two purposes: • Change Viewing Options on the Main Screen • Choose a Selection when in Test Mode Change Viewing Options On The Main Screen From the Main Screen, the two arrow keys allow the Operator to view the following parameters: • Density, in PPG • Proppant Concentration, in PPA • Both Density in PPG, and Proppant Concentration in PPA • Both Density in kg/m3, and Proppant Concentration in kgPA (Metric Units) • Density, in kg/m3 (Metric Units) • Proppant Concentration, in kgPA (Metric Units) Choose a Selection When In Test Mode In the Test Mode, the arrow keys scroll through various test choices.


13

Test (TST) Key

Self Test

Test (TST) Key The TST key enables the Electronic Technician to check the functionality of the entire module, and to perform serial communication tests. Additionally, the ID number, used for LAN communication, is located here. The tests are done by pressing the TST key and then stepping through the various menu selections (using the ↓ and ↑ keys). The available tests are: • Fixed DAC Test (Not used with the BJ Digital Transmitter) • Ramp DAC Test (Not used with the BJ Digital Transmitter) • Frequency Test, tests the input voltage-to-frequency converter. • Display Test, automatically scrolls through all available characters on the screen. To exit this test, press the EXT key. • Keypad Test, tests both keypads by displaying the selected key. To exit this test, press the EXT key. • Serial Transmit Test • Serial Loop Test enables a LAN “loop back” test to be performed. • Unit ID ( The Unit ID must be between 1 and 3)


14

Exit (EXT) Key

Exit Key

Exit (EXT) Key The Exit Key is used to return the Operator to the Main Screen.


15

Clear (CLR) Key

Clear

Clear (CLR) Key If the Operator makes a mistake while entering a numerical value, he can press the CLR key can be pressed to “erase” the value and start over. This key clears only the the data on the screen being viewed, it does not clear system memory. TIP If the BJ Digital Transmitter locks up as soon as it is powered on, chances are that the memory needs to be reset. The Memory Clear function may be performed as soon as the BJ Digital Transmitter is powered on. To do so, press the ± key four times as soon as the title screen appears. When this action is taken, all default values are restored and the transmitter must then be re-configured, including ID number.


16

Enter (ENT) Key

Data Entry

Data Entry (ENT) Key When the Operator is required to input a value, he must press the ENT key to save the value to memory. If he enters the value and presses the EXT key, the value will not be saved.


17

Calibrate The BJ Digital Transmitter

Calibrate The BJ Digital Transmitter Below is the procedure for calibration of the BJ Digital Transmitter with a Nuclear Densimeter attached: • Connect the Power/Signal Cable from the Nuclear Densimeter to the BJ Digital Transmitter. • If applicable, make sure the shutter is in the ON position and that the Process Fluid Pipe is empty. • Turn power on, and allow 15 minutes for the electronics to warm up. • Press the VIN key and observe the Open Pipe Voltage, which should be between 9 and 10V. If correct, press the EXT key. • From the Main Screen, press the ↓ key until only the Proppant Concentration, in PPA is displayed on the screen. • Press the SPN key and enter the Span Number, found on the Nuclear Densimeter. • Press the ASG key and enter the Specific Gravity of the base fluid. • Press the WT key and enter 8.34. • Press the CSG key and enter the Specific Gravity of the proppant. • Press the VIN key. Circulate, or fill the Process Fluid Pipe with the base fluid and verify that the voltage drops. • Press the REF key, select the 1 key. From this screen, when the ENT key is pressed, the current value of the Voltage Input, VTS IN, is “copied” and “pasted” as the Reference Voltage, VTS REF. Remember, the Process Fluid Pipe must be completely filled with the base fluid. • Calibration of the BJ Digital Transmitter is complete.


18

Universal Control Module II Conversion

Universal Control Module II

BJ Digital Module

Universal Control Module II Conversion The material covered to this point is applicable to both an Operator and an ET. For the remainder of this section, the electronics of the BJ Digital Transmitter will be covered, and is useful for only the ET. Before the Universal Control Module II, or UCM II, can be used as a BJ Digital Transmitter, some modifications are necessary. These modifications are: • Remove Manual/Automatic Switch • Remove Manual Control Potentiometer • Install On/Off Switch • Change Keypad nomenclature • Change Firmware • Convert Current Output to Frequency Output • Add Voltage Divider on Input • Install ± 15V Power Supply for Nuclear Densimeter power • Modify circuit board wiring Switches & Potentiometer The photo on the left shows a standard UCM II, while on the right is one that has been converted to a BJ Digital Transmitter. Notice that the Manual/Automatic Switch has been replaced with a power on/off switch, and the Control Potentiometer has been removed. Additionally, the Keypad configuration and the firmware has changed to reflect the different commands available from the keypad. Wiring changes and component additions will now be discussed.


19

Frequency Output Modification Install 2kΩ Ω Resistor Install Jumper

REFDWG: 41696

Frequency Output Modification The UCM-II current output was designed so that a current signal controls a servo valve. When used as a BJ Digital Transmitter, firmware modifications convert this current output into a self-powered frequency output. Modifications to the current output have been done, by adding a 2 kΩ resistor in series with the “collector” (drain) of output “transistor” (FET), Q2. This load resistor develops the voltage necessary to output a high level pulse. A jumper is placed across what was the load resistor for Q2, and another jumper run from the 2 kΩ resistor to VCC, which provides the voltage needed to make the output “self powered”, meaning no external power source is required for the frequency output. Finally, the EPROM (not shown) has been programmed to deliver a frequency proportional to density, rather than the formerly required current signal. This frequency is programmed for a PPU of 6000 Pulses per PPA.


20

Voltage Divider Addition

Change to 1kΩ Ω

9.09kΩ Ω Resistor Added

REFDWG: 41696

Voltage Divider Added To Input The basic UCM-II inputs were designed for two pulsed and one 4 to 20 mA current signal. Because the Nuclear Densimeter signal output is 0 to 10VDC, the current input was modified by changing resistor, R9, from 49.9Ω to 1kΩ. Additionally, a 9.09kΩ resistor in installed in series with R9, making up a voltage divider to lower the signal voltage by a factor of 10. This 0 - 1VDC signal is fed to voltage-to-frequency converter IC, U6. The output frequency signal from this converter is then sent to Three-Channel Timer IC, U14, where it is converted to a digital signal for delivery to the Microprocessor.


21

±15V Supply

REFDWG: 41709

± 15V Power Supply A ±15VDC Power Supply is added to the BJ Digital Transmitter in order to supply power to the Nuclear Densimeter. A regulated DC-DC converter operating on 12VDC input is used for this application. This converter is mounted on a separate PC board, which electrically connects to the Main Board via connector, J1.


22

Key Power Components

±15V Power Supply Board

+5V Regulator (Behind Panel)

8V Power Supply

REFDWG: 41692

BJ Density Transmitter Key Power Components The drawing above shows the locations of the major power components of the BJ Transmitter. They include: • ±15V Power Supply • +8V Power Supply • +5V Regulator • Power & Signal Connector The power supply components and system interconnect will now be discussed.


23

Power Block Diagram

12V IN

12V Vicor Power Supply Trimmed To 8V

8V Out

LM7805 5V Regulator

LM7805 5V Regulator

12V IN

±15V DC/DC Converter

5V Logic

5V

To 68VAC Inverter LCD Back Light

±15V Power To Nuclear Densimeter

Power Block Diagram Nominal +12VDC unregulated power is trimmed to 8VDC by a Vicor DC-DC Converter and sent to two 5VDC regulator IC’s. The first regulator supplies 5V power to the logic circuit and the second operates a 68VAC Inverter used to power the back light. The ±15VDC Converter, runs on unregulated power and supplies voltage to the Density Gauge.


24

Power Diagram

Vicor Converter (PS1)

Connector J1

REFDWG: 41697

Input Power Primary +12VDC power is supplied through Connector J1. The power input portion of multi-function connector J1 is: • Pin A = +12VDC • Pin B = +12VDC • Pin C = Ground • Pin D = Ground UCM II Power Supply Requirements Because the logic and backlight input circuits operate at 5VDC, and there are no other voltage requirements, the UCM-II module is designed to operate more efficiently with +8VDC input to the regulators. This voltage is typically supplied by a Vicor power supply (+12VDC supply, trimmed to +8VDC), and is found externally mounted on multiple-module setups such as the Hydration Unit. BJ Density Transmitter Power Requirements Because the ±15VDC Converter in the BJ Density Transmitter requires +12V input and the unit is designed to be functional in a stand alone mode, the +8VDC power supply is installed inside the Transmitter housing, and identified as PS1. This converter supplies power to the two 5V regulators which operate the following: • Logic and main PC board circuits • 68VAC Inverter for Backlight power Because the 5VDC regulators only have to “drop” 3 Volts, power lost to heat is lowered. In addition to power, the converter provides isolation for the circuit. 12V Vicor Converter Set To 8V The nominal +12V DC-DC Converter is set to 8VDC via trim resistor R3. The Vicor Converter input also sends +12VDC to the ±15V DC/DC Converter on PC2 through Connector, P1, Pins 1 (+12V) and 2 (GND). Proprietary and Confidential Property of BJ Services Company

25

Display Power Components -5V Converter (U8)

+5V Regulator (VR1)

To Contrast Control

68VAC Inverter (VR2)

REFDWG: 41696

Display Contrast Control In order to make the display visible, a small negative voltage is required. The voltage conversion circuit, consisting of ICL7660 (U8) and capacitor, C21, develops -5V for one side of the contrast control. The voltage “swing” goes from +5V to -5V. Loss of the -5V side will cause the screen to appear blank. Back Light Immediately behind the display is an Electro-Luminescent panel, used for low ambient light viewing. A 5VDC regulator, VR1, provides regulated voltage for a 68VAC inverter, VR2. Resistor, R2, provides current limiting and reduces the voltage to 4.2VDC at the input of VR2.


26

Serial Communication

Standard 3600 LAN Connection

Tx

Rx

/Rx /Tx GND

B

D

C

Rx Tx

/Tx

A

E

Standard LAN Node Connection

/Rx GND

B

D

C

A

E

T

R

S

U

P

M

N

Local Bus Line to 611C

JP5 TX

1

/TX

2

GND

3

RX

4

/RX

5 JP4 1

REFDWG: 41697

2

Serial Communication Serial communication over the Local Area Network (LAN) is possible with the BJ Digital Transmitter. To enable communication to occur, an ID number must be entered at the Transmitter and that same ID entered at the 3600/Isolplex36. Additionally, a Local Bus line provides one-way serial communication to a 611C Blender Console. An ID number is not necessary for communication with the Local Bus line. TIP When wiring or servicing the LAN system, keep in mind that it is a null modem configuration. TX from 3600 is sent to the RX at the Module.


27

Review Questions BJ Digital Transmitter, Densimeter Repair 1. The nominal +12V DC-DC Converter used to power the BJ Digital Transmitter is set to ___V via trim resistor _____. 2. The power supply voltages found in the BJ Digital Transmitter are: _________________________________ _________________________________ _________________________________ 3. The BJ Digital Transmitter has ______ Serial Ports. State the purpose of each.

4. What would be the observed symptom if +5V to the contrast were lost?

5. Describe the function of each of the 5V regulators, VR1 on the PC board and VR1 on the front panel.

6. The analog output is a ( ) Pulse, ( ) Voltage, ( ) mA. The span is _______________, which represents ___________ PSA.

Page 1 of 1

Controllers/Data Acquisition Systems ET-205 Densimeter Repair

Controllers & Data Acquisition Systems The next type of Transmitters to be discussed are Data Acquisition Systems and Controllers. The BJ Digital Transmitter is of the “stand alone” type, meaning that its only responsibility is to interface with the Nuclear Densimeter. The transmitters in this section not only interface with the Nuclear Densimeter, but also perform a number of other critical functions.


1

Density System With 3305 Mini Monitor

Sensor Cable Lead Filled Housing Containing Cesium-137 Source NUC DENSITY

Energy Beam

Ion Chamber Detector And Preamplifier 3305 J-Box

Interfacing Densimeter With 3305 The 3305 Mini Monitor supplies ±15 VDC for the operation of the Nuclear Densimeter, and contains an algorithm formula within its firmware that performs the slope correction necessary for linear density readings. Because of these factors, the 3305 Min Monitor is designed to connect directly to the TN Densimeter via its J-box and reads input voltages to 10VDC.


2

3305 J-Box Density Input Pin Configuration • • • • •

Pin B… Signal In Pin C… -15V Pin D… Common Pin E… +15 V Pin G… Shield

J

H

A

G

B

F K

C E

D Bulkhead Connector Front View

An interface between Preamplifier and the 3305 J-box isn’t needed

Densimeter Wiring The J-box Nuclear Density Connector uses the standard BJS-specified connector PT02E-18-11P.


3

Density System With 3600 WTA

Nuclear Density Interface J-Box

Lead Filled Housing Containing Cesium-137 Source

Energy Beam

Ion Chamber Detector And Preamplifier

3600 Interface The 3600 can accept up to two Density Inputs, but each input can only read a maximum voltage of ±5VDC. Because of this limitation, a Nuclear Density Interface J-box, consisting of an adjustable voltage divider network, is required in order to keep the input voltage below its limit.


4

Nuclear Density Inputs

Density Inputs 1 and 2

Density Input Two inputs are specific to Nuclear Densimeter. Even though the density connectors are different, the input circuitry is identical to the six Analog Inputs. The 3600 program firmware corrects the non-linear characteristics of the Nuclear Densimeter.


5

Density Input Pin Configuration • • • • •


A

G H

B C

F E D

PTO7E-12-8S (BJ P/N 22964) Bulkhead Connector Front View

Densimeter Wiring Shown above is the 3600 WTA pin configuration for Density #1 and #2 Inputs. In addition to slope correction, these two inputs provide the ±15VDC required to operate the densimeter. NOTE The 3600 density input connector is different from the connector used on the Nuclear Densimeter. It is adapted to the standard BJ connector via the dDensity Interface J-box.


6

3600 Density Interface J-box Schematic

13.3kΩ

5kΩ

J2-B

J1-B J1-C J1-D J1-E

10kΩ

-15V COM +15 V

To Densimeter

J2-C J2-D J2-E To 3600 Density Input

Nuclear Density Interface J-Box The Nuclear Density Interface J-box is used to lower the 10V open pipe voltage from the Nuclear Densimeter. It consists of a voltage divider network with potentiometer which adjusts the open pipe voltage to 4.85V. Additionally, the J-box adapts the standard Nuclear Densimeter connector to the smaller 3600 connector. Resistors in series with the upper and lower limits of the potentiometer reduce the range of adjustment, therefore it is important that the open pipe voltage be as close to 10V as possible in order that 4.85V can be set. NOTE The 3600 cannot read voltages above ± 5 Volts.


7

Pendant System Density Input

Pendant System Density Inputs Two density inputs are provided in the Pendant System, for high and low pressure densimeter inputs. The primary densimeter choice is made from the Utility screen.


8

Select Utility Routine, Densimeter Source SELECT NUCLEAR PSA SOURCE

<1>

HIGH PRESSURE PSA

<2>

LOW PRESSURE PSA

USING

(EXIT)

F1

F2

F3

F4

Select Source The Pendant has two Nuclear Densimeter input choices: • High Pressure • Low Pressure. To make the selection, use the numeric keypad to select <1> or <2>.


9

Calibrate Low Pressure PSA CALIBRATE LOW PRESSURE PSA

<1> REFERNCE

= 0.00

<2> BASE ASG

= 0.00

<3> PROP CSG

= 0.00

<4> SPAN

= 0.00

LOW PRESSURE PSA = 0.00 SENSOR VOLTAGE

= 0.00 (EXIT)

F1

F2

F3

F4

Calibration Procedure The Nuclear Densimeter setup on the Pendant consists of the following operator entries: • Reference, “zeroing” on base fluid. • Base ASG, specific gravity of the base fluid (water is 1.00). • Prop CSG, specific gravity of the proppant (20/40 sand is 2.65). • Span, the calibration number found on the Gauge housing. The raw voltage input from the densimeter is displayed on this screen, and is a handy test point to ensure voltage data is being sent from the Nuclear Densimeter. With current firmware, the value displayed will be one-half of actual input voltage.


10

Calibrate Base ASG CALIBRATE LOW PRESSURE PSA

BASE ASG

= 0.00

NEW VALUE

=


Fresh Water 1.00

= 0.00

(EXIT)

F1

F2

F3

F4

Base Absolute Specific Gravity A numerical value, representing the specific gravity of the base fluid is entered here via the numeric keypad.


11

Setting Proppant CSG CALIBRATE LOW PRESSURE SPAN

PROPPANT CSG

= 0.0

NEW VALUE

=


Sand Typically 2.65

= 0.00

(EXIT)

F1

F2

F3

F4

Proppant Corrected Specific Gravity The Proppant CSG is entered here via the numeric keypad.


12

Setting Span CALIBRATE LOW PRESSURE PSA

SPAN

= 0.0

NEW VALUE

=


Enter Span Number Found On Detector Assembly

= 0.00

(EXIT)

F1

F2

F3

F4

Span The Span number for the densimeter to be used is entered via the numeric keypad. This span number is generally found on the Nuclear Densimeter housing. If unknown, a calibration procedure should be performed by the Electronic Technician.


13

Setting The Reference Voltage CALIBRATE LOW PRESSURE PSA

REFERENCE

= 0.0

NEW VALUE

=


= 0.00

Enters Detector Voltage as “Zero” PSA

(AUTO)

F1

F2

F3

(EXIT)

F4

Reference Entry Auto (F1) key is pressed to automatically enter the current Gauge voltage as Zero PSA. This key should only be pressed while on pad fluid (ie. No proppant).


14

DENSITY1

Pendant Density Input OPTO ISOLATED I/O

DENSITY2

CLOCK

ENABLE DATA OUT

DATA IN HIGH SPEED ANALOG-TODIGITAL CONVERTER

REFDWG: 56298 1/4

Pendant Density Inputs Each Pendant density input has a separate internal ±15VDC power supply, used exclusively to power the Densimeter. These supplies isolate the signal and power ground of the Nuclear Densimeter from the Pendant logic ground, which eliminates the possibility of ground loops and reduces the chance of processor errors caused by Densimeter or cable failures. The density inputs utilize separate connectors which go to connector JP5 on the Brain Board. Density 1, on JP5 is: • Pin 1, Sig High • Pin 2, -15VDC • Pin 3, Sig/Pwr Common • Pin 4, +15VDC Density 2 pin assignment is: • Pin 6, Sig High • Pin 7, -15VDC • Pin 8, Sig/Pwr Common • Pin 9, +15VDC Both 0-10VDC density voltage inputs are reduced to 0-5VDC by a pair of 10kΩ divider resistors. These voltages are sent to high speed analog-to-digital converter, U86. The digital output from this IC is sent in serial form to Opto-Coupler, U84, which provides isolation from dirty power ground. The resulting isolated data is then sent directly to the processor. NOTE With the current firmware, the raw signal voltage on the display will read one-half of actual input. If in doubt, measure actual voltage with a DVM.


15

MCM-1000/ACC Series Controller Density Input

MCM-1000 Series Controller There are several versions of the MCM Series of Controllers, with each module EPROM determining the controllers’ specific function. Regardless of the version, each has one density input, and includes a DCDC converter for powering the Detector Assembly. The various models include: • MCM-1000, used for Cyclone Blender • MCM-1002, used for Conventional Blender • MCM-1004, used for Titan 60 Blender • MCM-1006, used for W125 Blender • ACC-II Automatic Cement Control Module


16

MCM Density Input Frequency to Voltage Converter

Voltage Divider

REFDWG: 47569 3/3

MCM Density Input Notated “DB-IV” input on the schematic the MCM-1000 series may accept either a DB-IV or Nuclear Densimeter as its density input, depending upon its configuration. The MCM Density input pin assignment on JP8 is: • Pin 10, +15VDC • Pin 11, Signal High • Pin 12, Signal Low/Power Common • Pin 16, -15VDC NOTE The -15VDC section of the power supply is not used with the DB-IV. Input Detail The 0-10VDC density input signal is reduced to approximately 0-1VDC via a resistor divider network consisting of R6 & R36. This voltage is then converted to a frequency pulse by precision V-F Converter IC, U10. The representative pulse is sent to the input of one section of Dual Opto-Coupler, U20. This Opto-Coupler performs three important functions: • Isolation of logic common from dirty power ground • Common-Mode noise rejection • Pulse shaping via “one-shot” output The isolated output is then sent directly to the processor where the firmware program performs slope correction.


17

Review Questions Monitors & Controllers, Densimeter Repair 1. Using dedicated ±15V supplies in the Pendant Controller isolates the signal and power ground of the Nuclear Density Gauge from the Pendant _______ ground, to eliminate the possibility of _____________and reduce the chance of processor errors caused by Gauge or cable failures. 2. The 3600 WTA density interface J-box is used to lower the _____________voltage from the Nuclear Density Gauge. 3. Discuss the two main differences between the 3305 and 3600 Density Inputs:

4. Nuclear Densimeter input isolation in the Pendant is provided by ________________. 5. Identify the function of each of the following MCM Controllers: • MCM-1000 ______________________ • MCM-1002 ______________________ • MCM-1004 ______________________ • MCM-1006 ______________________

Page 1 of 1

Specifications & Conversions ET-205 Densimeter Repair

Introduction With BJ Services’ acquisition of various Oilfield Service Companies throughout the years, the problem of Standardization has become a major concern. The Instrumentation Engineering Department has made an effort to incorporate the “Plug N’ Play” concept, so that if a district borrows a Nuclear Densimeter or any other piece of instrumentation, re-wiring and re-scaling will not be necessary in order to make it to work with their equipment. Standardization Is The Goal In an effort to implement the “Plug N’ Play” concept with each Nuclear Densimeter, regardless of company origin, the ET should become familiar with the differences that may be found in Nuclear Densimeters, and make it a point to convert any densimeter that does not meet BJ specifications. This section provides the information necessary to convert nonstandard Nuclear Densimeter to BJ Specifications, thus ensuring uniformity within the Company.


1

Specifications

Nuclear Densimeter Specifications - Generic The following specifications are for a generic Nuclear Densimeter ordered from TN Technologies: • Cs-137 isotope, 200 millicurie (7.5 GBq) source • Shutter comes with ON-OFF-CAL positions • CAL position is 15.1 PPG (1809 kg/m3) • Connector mounted on the Nuclear Densimeter is MS3102E-18-1P (WIN P/N 174140) • Open pipe voltage varies, depending on size of pipe and Transmitter used Nuclear Densimeter Specifications - BJ Services The following specifications are for a BJ Services-configured Nuclear Densimeter ordered from TN Technologies: • Cs-137 isotope, 200 millicurie (7.5 GBq) source • Shutter comes with ON-OFF-CAL position for five inch and larger low pressure applications • High pressure applications, for pipe diameters of four inches and smaller, have the source and detector mounted directly on the pup joint. Mounting bolts are welded. • CAL position is 12.0 PSA (1.44 kg Sand Added per cubic meter) with water in pipe • Connector on gauge is PT02E-18-11P (P/N 43291X) • Gauge output voltage is set to +10VDC with empty pipe The main difference between the the two specifications is the type of connector used on the Nuclear Densimeter. NOTE Slide gate CAL positions for either specifications are approximate and are to be used for test purposes only.


2

Conversion Connector Specifications Generic Detector Assy MS3102E-18-1P P/N 174140

BJS Detector PT02E-18-11P BJS P/N 43291X

Generic Bulkhead Conn MS3102E-18-1S

BJS Bulkhead Connector PT07E-18-11P BJS P/N 35817X

Generic Cable Connectors MS3106E-18-1P MS3106E-18-1S

Cable Connector, each end PT06E-18-11S BJS P/N 35818X

Generic Wiring Assignment Pin A +15V Pin B - 15V Pin C Neg 10V (Analog Only) Pin D Signal & Power Ground Pin E Signal Pin F Gain

BJS Wiring Assignment Pin A N/A Pin B Signal Pin C - 15V Pin D Signal & Power Ground Pin E + 15V Pin F Shield

Conversion When converting a generic Nuclear Densimeter to BJ Specification, the following steps should be taken: • Replace the connector mounted on the Detector Assembly with the BJ Connector, P/N 43291X. • Verify that the connector at the Transmitter is P/N 35817X, using the pin configuration listed on the next page. • Replace the cable with P/N 35818X. • On Detector Assembly, install potentiometer on Preamplifier Board @ W1 for gain adjustment.. • Adjust the Preamplifier Gain between the range of +9 to +10 Volts with Open Pipe, using procedure found in the Maintenance section of this manual. • Obtain a Span Number using the calibration procedure found in the Calibration section of this manual. • Using indelible marker, write the Span Number on Nuclear Densimeter housing. A water proof tag may also be used to attach the Span Number.


3

Nuclear Density Gauge Pin Assignment • • • • •


J

H

A

G

B

F K

C E

D Bulkhead Connector Front View

Transmitter Pin Assignment For BJ Services, the above connector and pin assignment should be used for the Nuclear Densimeter and transmitters. As seen on the next slide, the 3600 input uses a different connector, but the pin assignment is the same.


4

3600 Density Input Pin Assignment • • • • •


A

G H

B C

F D

E

PTO7-12-8S (BJ P/N 22964) Bulkhead Connector Front View

3600 Connector & Pin Assignment An exception to the standard listed on the previous pages is the 3600 Well Treatment Analyzer which uses a BJ PN 22964 connector on the Density 1 & 2 channels. The pin assignment, however, is the same as the standard connector. This connector is converted back to the standard at the Density Interface J-Box.


5



6

Nuclear Densimeter Calibration ET-205 Densimeter Repair

Nuclear Densimeter Calibration At this point, the Operation and Standardization of the Nuclear Densimeter have been discussed. Once the ET fully understands these topics, he is now ready to perform the required Calibration and Maintenance for a Nuclear Densimeter. Densimeter Calibration The Nuclear Densimeter should be calibrated every 6 months, or as needed. If a Nuclear Densimeter is taken off one pipe and mounted on another, it should be re-calibrated as well. Within BJ Services, there are two methods acceptable for calibration of Nuclear Densimeters: • Air/Water/Simulation Calibration • Water/Calcium Bromide Calibration Air/Water/Simulation Calibration This method is used primarily for low pressure densimeters (5” and larger), and is discussed in the TN Analog Transmitter Repair Manual and the TN Digital Transmitter Repair Manual. Water/Calcium Bromide Calibration The Water/Calcium Bromide Calibration Method is used for high pressure densimeters (4” and smaller). The remainder of this section discusses this method of calibration when the Nuclear Densimeter is connected to a: • 3305 Mini Monitor • 3600 Well Treatment Analyzer


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BJ SERVICES COMPANY TECHNICAL SERVICES Subject:

Densimeter Calibration Using Chemical Method with 3305 Mini Monitor

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Introduction Portions of the following procedure were reprinted from Procedure Number 10006-tp, Rev N/C. It outlines the calibration procedure using Calcium Bromide and a 3305 Mini Monitor. Substituting a 3600 Well Treatment Analyzer for the 3305 will yield similar results.

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Material Requirements

3.

Calcium Bromide Kit P/N 37536 (with 5 gal.) Additional Calcium Bromide P/N 37539 (5 gal.) Density cable assembly P/N 35160-XX or equivalent Thick rubber mat or plug if available 3305 Mini Monitor with J-Box Sensor cable P/N 42214-XX (2) Power cables P/N 39532-XX or equivalent 12 VDC, 10 amp power supply

Prerequisite This procedure should only be performed by personnel that have been certified in use and handling, safety and servicing of the nuclear gauges or under the supervision of someone who has been certified by TN Technologies. Perform an in-process inspection of the assembly and verify that a lock and a set of keys were included with the unit. Inspect the pipe saddles to insure that the detector/source assembly is secure and that the nuts are welded. Following is a procedure that is recommended to establish a Cal Factor (SPAN Number) for the nuclear gauge. After calibration, the Calibration Record Form is to be completed by the Electronic Technician who performed the calibration. The Densimeter should be completely checked out after calibration to verify that it is fully operational. If any difficulties are encountered during calibration, the problems should be recorded on the Calibration Record Form and Technical Services should be contacted for assistance. The completed form should be retained by the Electronic Technician, for future reference.



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Procedure 1. Plug the down end of the pipe of the gauge with a pipe plug or use a smooth rubber mat in a container to capture the Calcium Bromide after use. 2. Connect cables to the 3305 monitor, J-Box, power, and the gauge. 3. Apply power to the 3305 monitor and J-Box. Allow 15 minutes for electronics to thermally stabilize. 4. Go to the Calibration menu for “Nuclear Density”. Select option 1 for Reference Voltage. The lower right hand portion of screen will display volts input. With the shutter closed (if so equipped) Volts Input should read near zero. 5. Unlock the shutter and slide it to the “On” position. Monitor the voltage displayed on the 3305. With the pipe open to air it should read approx. 9.95 ± 0.15 VDC. If the assembly reads in excess of 10.55 VDC, the gain on the preamp of the gauge may need to be adjusted. Record this voltage on the Calibration Record Form. 6. Fill the pipe with water just above the top clamp where the detector and source are mounted. Monitor the voltage and verify that it drops to approximately the voltage noted, based on pipe size. Record this voltage on the Calibration Record Form. • 8” 2.55 VDC • 6” 3.4 VDC • 5" 4.3 VDC • 4” 5.4 VDC • 3” 6.6 VDC • 2” 7.9 VDC 7. Verify that the Base ASG has a value of 1.00. Reference the water voltage by pressing the F3 key (AUTO).



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8. Select 3 (SPAN) and enter size. • 8” • 6” • 5" • 4” • 3” • 2” 9.

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one of the approximate SPAN values, based on pipe 7.3 9.0 11.5 15.5 23.0 39.0

to to to to to to

7.5 9.5 12.0 16.0 25.0 45.0

Empty the pipe and dry it out as much as possible. Using the hydrometer from the kit, float it in the Calcium Bromide solution. After it settles, obtain a density reading, then remove the hydrometer. On the side of the hydrometer is a scale in SGU readings. Multiply the density reading by 8.34 to obtain a PPG value and record this value on the Calibration Record Form. After obtaining the PPG number, fill the pipe with the Calcium Bromide solution just above the top mounting brackets then, go to option 3 (SPAN) and adjust the initial reading up or down until the correct PPG is displayed on the 3305. Document the final SPAN number on the Calibration Record Form and on the gauge.

10. Drain and capture the Calcium Bromide for future use. 11. Rinse the pipe thoroughly and dry it out. 12. Add water again and verify that the PPG reading on the 3305 monitor comes up to 8.34 ± 0.1 PPG. 13. Empty the pipe. Slide the shutter to the “OFF” position and use the lock to secure the device. 14. Document all the information on the Calibration Record Form.

Nuclear Densimeter Maintenance ET-205 Densimeter Repair

Nuclear Densimeter Maintenance Troubleshooting of the Nuclear Densimeter FSU Gauge should be attempted only after the theory and operation of the Nuclear Densimeter is fully understood. General Inspection The radiation source holder should be free from cement or proppant build-up. Additionally, the shutter should be inspected to make sure that it slides easily, and that the lock for the shutter is in good condition. Under no circumstances, however, should the ET attempt to open the Radiation Source Holder; only qualified TN personnel may do so. Process Fluid Pipe If possible, the inside walls of the process fluid pipe should be inspected for cement or proppant buildup. Even a small buildup of material in the process fluid pipe can affect the density reading. Safety Tip It is advisable that a DOSIMETER (Radiation Absorption Detector) be worn when working with Nuclear Densimeters.


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Detector Assembly

Detector Assembly Some of the more common problems related to the Nuclear Densimeter include: • No density reading (The Nuclear Densimeter is “locked up”) • Erratic and unstable density readings • Density “spikes” • Density consistently high or low from actual The possible causes of these problems are explained in this section, as well as suggested solutions. Detector Assembly Calibration Many of the problems mentioned above may be avoided if the Detector assembly is calibrated at routine intervals. The calibration procedure is discussed in this section as well.


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Calibration/Repair Materials

Materials List A primary list of items needed to service the Detector Assembly includes: • 3/16” Allen Socket Wrench, to remove lid • 7/16” Deep Socket w/ Ratchet Wrench, to loosen the rubber grommet • 2 Large 90° Allen Wrenches, for prying out electronics • 4” Adjustable Wrench • Small Phillips Head Screwdriver and Small Flat Head Screwdriver • Clean White Eraser, to clean contacts • Trichlorethane 1,1,1 or Commercial Grade Everclear (95% ethyl alcohol) • Silicon Dielectric Grease, to lubricate the O-ring • Digital Voltmeter with 4 digit display (Fluke Model 8050-01 or equivalent) • High Voltage Probe • Test Clip Leads • Rubber Mallet • DC Power Supply (12V @1A) • Small Adjustment Screwdriver (“tweaker”) • Insulated mat • IDET Densimeter Training Video, TV-201 If repairs are to be made to boards, or if the open pipe voltage (gain) is to be set, additional tools include: • Soldering Iron and rosin-core Solder • Desoldering tool or Solder Wick • Assortment of polystyrene capacitors • Hemostats or needle nose pliers • Non-corrosive, non-flowing Silicon Seal • Latex surgical gloves


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General Visual Examination

General Visual Examination When servicing a nuclear gauge, remember that “clean and dry” is critical to proper operation. Therefore, always look for general signs of moisture, corrosion and lead dust contamination inside the detector housing. Inspect the foam inserts for dampness and deterioration. Corrosion, caused from moisture and acid fumes entering the housing, generally leaves a white or rusty red deposit, while lead dust is seen as a gray dust (actually, the epoxy paint coating the lead shield). Here are a few other specific items to check out: • Inspect all screws and mounting spacers for tightness, and ensure lock washers are in place. • Check condition of connectors on each board. • Inspect each component on boards for evidence of corrosion. • Check all components held in place with silicon seal, especially capacitors on the High Voltage Board. Re-seal any loose components or wires. • Check condition of component contacts for solid leads and good solder connections. • Inspect preamplifier coax cable that plugs into the Ion Chamber (use cotton swab and alcohol to wipe out the socket and examine swab for signs of contamination). • Check both ends and jacket of the coax cable closely for evidence of damage. • Inspect foam inserts for clean and dry condition, and for deterioration. The foam should feel firm and return to shape quickly. There should be no flaking of the material. Regardless of condition, the foam inserts should be replaced each time the unit is serviced. • Inspect the rubber compression grommet, that secures the assembly in the housing, for signs of deterioration or over tightening. • Inspect the three desiccant bags for integrity and dryness. Dry bags will have a loose, granular feel. • Inspect the nylon insulator for security and wear. • Inspect the lid, O-ring, and connector for signs of damage. Replace the O-ring, regardless of condition.


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Foam Insert Kit

Foam Insert Kit Because they deteriorate over time and may become contaminated without any outward appearance, the foam inserts should be replaced each time the FSU gauge is removed for servicing. In an effort to simplify the replacement procedure, a foam insert replacement kit (PN 79257) is now available from Instrumentation department. The very reasonable cost of this kit makes it economically feasible to replace all foam inserts each time the FSU gauge is removed. Also included in the kit is a replacement o-ring seal for the lid, desiccant packs, compression grommet and locking nut, all of which should also be replaced. Technicians are encouraged to keep several of these kits in stock at their district, as well as one in their vehicle for field repairs. Instrumentation Bulletin 81 Refer to Instrumentation Bulletin 00081 for more information and drawings.


5

High Voltage Test Points

Oscillator, Q1

C7

Voltage Regulation

Fusible Resistors

-12V Regulator

High Voltage Checks Measure the high voltage on Ion Chamber with a high voltage probe. It should read a steady +1400VDC, ±100VDC. Tap on the high voltage board with an insulated tool and use the same probe on individual components. Any voltage fluctuation indicates a problem. Likewise, heating or cooling the circuit boards should have no affect on the high voltage. TIP When measuring for the +1400VDC, be sure not to touch the body of the Ion Chamber. Also, some voltage may remain for a period of time after power is removed. High Voltage Not Present If high voltage is missing, ±15VDC or -12VDC may be missing, or the oscillator may not be running. Measure ±15VDC on both sides of fusible resistors, R3 and R1. Look for loose wiring to the high voltage transformer, T1, and for a broken leg on disc capacitor, C7. Poor regulation may indicate bad IC, U3, or -12VDC regulator IC, U2. An oscilloscope is handy for troubleshooting the oscillator circuit. Check transistor, Q1, and the primary windings of T1 for a 1.5 kHz sine wave.


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Preamplifier Test Points Ramp Test Point, TP6

Output, TP1

Preamplifier Test Points Using a DVM, look for ramping action on TP6 with a radioactive source or source simulator. It should ramp from about +8VDC to -10VDC, increasing in negative slope as radiation increases. If good ramping action is found on TP6, look at the DC output voltage on TP1. It should be close to 0VDC with no radioactive source, and increase proportionally to the radioactive strength, to a saturated level of approximately 10.5VDC.


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Ramp Reset TP5

Reset Circuit Test Points

Ramp Sense Trigger

Ramp Reset/Hold TP

Reset Circuit Test Points The negative ramp reset trigger pulse is seen on TP7, and the positive reset pulse is seen on TP8. Either trigger will result in a positive voltage at the junction of CR3, CR4 and R21. Failure of a trigger voltage at this point is indicative of defective AR6, CR3 or CR4. When either limit is reached, transistor, Q5, should trigger and energize relay, K1. This action can be observed on TP5. The same ramp found on TP6 should occur at Pin 2 & 5 of AR6. The reset pulses from U3 can be observed, with an oscilloscope, on TP2, TP3 and TP4. Refer to Section 5, TN Detector Assembly for the correct waveforms.


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Ion Chamber Insulator/Guide Ion Chamber

Nylon Insulator

Nylon Guide/Insulator A nylon guide is used in the housing assembly to properly align the Ion Chamber with the radiation beam, and to help prevent movement. The guide also provides electrical insulation of the Ion Chamber’s high voltage. The guide is pressed into a bracket in the housing of the Gauge and has an indention on one end that will mate with a pin welded onto the center of the Ion Chamber. When servicing the assembly, care must be taken to prevent the guide from becoming dislodged. It should fit tightly in its holder, as any “play” will allow the Ion Chamber to move and cause an erratic signal output when vibration is present. Inspect the guide for wear and damage. If it is slightly loose, a small amount of silicon seal applied to the base of the guide may prevent movement. Greater movement will usually require replacement of the guide. Also, inspect the Ion Chamber tip for integrity. If the tip is damaged or has fallen off, the guide may no longer prevent movement of the can. The tip can be replaced by TN Technologies.


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FSU Connectors ±15V To High Voltage Board

Connector J1 ±15V Input & Signal Output

Connector J1 And High Voltage Connector Because these connectors are gold-plated, they should not be cleaned with any abrasive material. Use only approved contact cleaner and use care when plugging in the mating connector, so that the pins are correctly aligned.


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Density Spikes 20.0 PPA

20.0 PPA

20.0 PPA

20.0 PPA

Density Spikes Often Caused By Loose Components Randomly-occurring density spikes are often caused by components on the high voltage board that have broken or are loose. This is often a result of the stressful “hammering effect” experienced on the treating line and equipment. Common vibration-related failures include: • Broken legs on High Voltage Disc capacitors • Broken wires from high voltage power transformer, T1 • Internal windings of T1 breaking down • Lead dust on components • Loose or corroded coax connection plug on Ion Chamber • Corrosion or moisture on the high voltage board or preamplifier board • Loose screws, especially those connecting high voltage board to the Ion Chamber Reset Reed Switch Another possibility of intermittent density spikes may be a weak reset reed switch on the preamplifier board. After thousands of cycles, the tensile strength of the reed switch can weaken and, under stress from vibration, let the contacts “make”when they shouldn’t, resulting in an errant reset condition occurring during the ramp (integration) function. This situation can generate a ramp reset, without engaging the “hold” action that occurs during a normal reset condition. This results in density spikes randomly occurring. Gently tapping on the reed switch with an insulated tool will often expose a weak switch. Finding The Cause Probing around suspect components with an insulated tool will often find intermittent fault conditions caused by loose or broken components. Problems relating to the high voltage board are best traced by measuring the high voltage while tapping on associated components. Preamplifier board intermittent problems are best found by exposing the gauge to low radiation or simulated signals. Then, the signal output is monitored while tapping on suspected components. Proprietary and Confidential Property of BJ Services Company

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Uniformly Occurring Density Spikes 20.0 PPA

20.0 PPA

20.0 PPA

20.0 PPA

Uniform Density Spikes Density spikes occurring at regular time intervals are often the result of a component failure in the reset portion of the the preamplifier board. During ramp reset, a defective component may continuously fail to switch the signal voltage into its “hold”condition, resulting in a ramp reset being seen on the signal output. Common causes of this type of problem include: • Multivibrator, U3 • FET, Q1 or Q2 • Transistor, Q6 • R7 or C5 The spikes can be negative or positive, depending upon which component fails, and how it fails.


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Density High/Low From Calculated 8 PPA 6 PPA

2 PPA

Density High/Low From Calculated Inaccuracies in density measurement are often attributed to the Densimeter although, in fact, other factors may have caused the error. When the problem cannot be determined by a thorough electrical test of the Densimeter, other steps can be taken. A good check to determine that the Densimeter is within operating specifications is to compare past air and water voltages with present readings. This is where good record-keeping is important, because having accurate calibration records allows the ET to track changes in voltage readings over time. For instance, if a water voltage reading recorded six weeks ago of 2.35VDC were compared with the current verified reading of 2.31VDC, the Densimeter is probably accurate and working correctly. Other Causes Of Inaccuracies There are many factors to be considered when dealing with Densimeter accuracy problems. For example, some specific variables, other than the gauge, which could effect sand totals are: • Inaccuracies in base fluid measurement • Failure to properly reference (zero) the gauge • Wrong setup (span, ASG, CSG, etc) or programming error • Sand spillage • Inaccurate sand weight ticket If the signal output of a recently calibrated Densimeter is found to have changed, a through bench test should be performed to locate and repair any weak or intermittent components. Some causes of drifting over a short period of time may be: • Moisture entry into the Detector Assembly • Contamination of Preamplifier Board by lead dust • Loose component or component failure • Bolts loose on pipe, allowing movement of densimeter • Buildup of material in pipe


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Errors in Proppant Totals

Fluid Volume If the flow meters are not accurately measuring base fluid, proppant totals will not be correct. Therefore, the first step that should be taken when discrepancies in proppant volume are reported should be to verify that the flow meter pulses per barrel (ppu’s) are correctly set. This can be done by taking strap volume measurements of the fluid tanks before and after the job, and comparing the results with clean flow meter totals. If volumes don’t match, the next step should be to verify that the correct ppu’s are programmed into the system and that no problem exists with the flow meter itself. If no problems are found, and the error is small, a change in ppu’s can be made in order to correct the problem. Increasing ppu’s will increase volume and vice versa. This holds true for Mass, Magnetic, Turbine, Encoders and 60-Tooth Gear assemblies. Proppant Volume from Encoders Unlike flow meters, encoders do not give a direct volumetric measurement, therefore other factors, such as auger wear and the resulting loss of product delivery must also be considered. Because there is no delay, the density calculated from the encoders is called “instant density”. Span Number The low-pressure densimeter on a blender is typically used as a reference for the instant density calculated from the sand augers. This procedure verifies that the screws are delivering the correct proppant volume. Because adjustments to the sand auger ppu’s are made to keep instant density in line with the nuclear densimeter, the Operator should keep in mind that theTransmitter’s span number has an inverse effect on proppant delivery. For example, increasing the span number will give a higher nuclear density reading, therefore the auger ppu’s (instant density) will have to be lowered so as to bring the density reading down.


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Zeroing The Preamplifier

Preamplifier Zeroing For best accuracy, no voltage should be seen at the output of the preamplifier with no received radiation at the Ion Chamber. A zeroing adjustment of the preamplifier board can be performed with or without the Ion Chamber or high voltage board connected. Background Radiation Must Be Negated Because it is constantly exposed to natural background radiation while out of its shielded enclosure, the preamplifier input must be disabled prior to zeroing the unit. Even if the Ion Chamber is not connected, stray noise pickup at the input will often prevent an accurate zeroing of the board. For this reason, the input must be “shorted” to the output of the ramp generator. Zeroing Procedure Now that the necessary precautions have been taken, the zeroing procedure for the preamplifier board can now performed: • Place a jumper from TP6 to input resistor R13 (or the junction of R12 and R13). • Adjust R28 for 0 V volts at TP6. TN Technologies now recommends this voltage be set slightly negative in order to ensure no reset pulse is seen at the output, TP1. • Leaving the jumper in place, adjust the NULL potentiometer, R1, for 0 V volts at TP1. • Recheck the voltage at TP6 and repeat the above procedure if necessary. NOTE A Zeroing procedure must be performed whenever a board or component is replaced on the Gauge.


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High Pressure Gauge Mounting and Handling

Proper Nuclear Densimeter Handling procedure It is important for the Electronic Technician to emphasize to field personnel that the Nuclear Densimeter is sensitive electronic equipment and not be handled like “a piece or iron”. If necessary, enlist the support of the Service Supervisors in this effort. Nuclear Densimeters should be mounted on a Line Truck or any other appropriate vehicle. Don’t allow the Gauges to remain loose during transport. A densimeter should have its own secured storage area on the truck such as a saddle, box, or threaded union. Rig Up/Rig Down Guidelines The following guidelines should be followed when installing a Nuclear Densimeter during rig-up or rigdown: • To reduce shock during line assembly, Nuclear Densimeters and Pressure Transducers should be the last items rigged up on line and the first to be rigged down. • Personnel handling Nuclear Densimeters must successfully complete a Certified Radiation Safety Course or be monitored by someone who has. • The densimeter should be mounted such that vibration on the densimeter electronics is minimized. • Avoid mounting the densimeter on Chicksan Swings, and do not let the Densimeter contact the ground. If contact with the ground is unavoidable, use shock absorbing material, such as tires or rubber mud flaps underneath. • The densimeter should be mounted on the line so that the connector cannot come in contact with the ground. • The power/signal cable going to the Treating Van should be routed so that it is not tripped over or pinched.


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Test Sticks

Test Sticks BJ Services has test sticks available for simulating various proppant and slurry weights. These sticks display the approximate weight marked on the end, but are not designed to be used as a calibration tool. They are ideal as a quick check to determine if the system is functioning, and to look for intermittent problems. To use the sticks, calibrate the Gauge in the usual manner, ensuring it is zeroed on water. Remove fluid from the pipe and install the acrylic test stick. Observe the marked density (nominal 1.6 PSA). Remove the acrylic stick and install the magnesium stick. Note that the density increases to the value marked (nominal 13.2 PSA). The density reading should remain constant unless the stick is disturbed. The part numbers and costs are as follows: • 35172-1 2” Acrylic……. $106.00 • 35172-2 2” Aluminum….$106.00 • 35172-3 2” Magnesium...$150.00 • 34955-1 3” Acrylic……..$205.00 • 34955-3 3” Magnesium...$298.00 • 39721-1 4” Acrylic……..$395.00 • 39721-3 4” Magnesium...$420.00 TIP When servicing a high pressure Nuclear Densimeter not having a shutter, a magnesium test stick can be inserted in the pup joint to reduce exposure to radiation from the source.


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Preventive Maintenance

Preventive Maintenance Tips The following provides the ET with a list of tips that, if followed, will reduce the chances of a job problem caused by a Nuclear Densimeter: • Burn-in all new and repaired boards received from TN Technologies. • Inspect all cables and connectors on a quarterly basis. All older or non-standard cables should be replaced. • Replace any damaged or missing dust caps. • Verify the Nuclear Densimeter is fitted tightly on the pipe, and that the bolts are secure and, on units without a shutter, are welded. • Examine the pipe for internal wear • Institute a scheduled preventive maintenance program to include inspections of the system for: – Tight fit of Detector assembly – Moisture, lead dust and corrosion inspection – O-ring seal – Cable and connector condition • Install two Nuclear Densimeters on each job • Train field personnel on proper handling of the Gauge: – Store and Transport properly – First on and last off the line – Mount for minimal vibration • Keep records of inspections and voltages. TIP To help the Electronic Technician institute a regular Preventative Maintenance Schedule for Nuclear Densimeters, a Nuclear Densimeter Inspection Report is given at the end of this section.


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Nuclear Densimeter Inspection Report District: _______________ Source Number: ____________________

Pipe Size: _____________ Source Strength: ____________

Date of Inspection/Calibration: _____________ Date of last Inspection: _____________ Check List: _____ Assembly securely affixed to pipe _____ Connector clean and undamaged, cables good _____ Shutter (if available) is undamaged and operates freely _____ Housing undamaged, no bolts damaged, loose or missing _____ O-ring undamaged _____ Compression grommet undamaged _____ Foam inserts clean and dry. There is no evidence of corrosion or moisture _____ Nylon Insulator in the Ion Chamber is in place _____ No corrosion is present on any circuit board _____ All capacitors on high voltage board secure, with no broken legs _____ Connectors clean and in place, no damage to wires (including Ion Chamber signal cable) _____ High voltage on Ion Chamber = 1400VDC, +/-100V _____ High voltage remains steady while tapping on circuit boards _____ Perform the following procedure: 1. Place a jumper between TP6 and junction R12 & R13 2. Adjust R23 for 0V at TP6 to GND 3. With jumper in place, adjust R1 for 0V at TP1 to GND _____ Perform Water and Calcium Bromide calibration 1. Span Number =______ 2. Write the Span Number on the Nuclear Densimeter Date completed____________ Technician Signature_________________________________

Review Questions Densimeter Gauge Maintenance, Densimeter Repair 1.

The purpose of the nylon guide in the Densimeter Housing is _______________________________ and _________________________________.

2.

List some causes, other than the Densimeter, that could cause inaccurate sand totals

3.

A zeoring procedure should always be performed with the Ion Chamber and High Voltage connected. A. True B. False 4.

Test Sticks are suitable for use in calibration of the Nuclear Densimeter. A. True B. False

5. A jumper is placed between R13 and TP6 in order to _____________________ _________________________________________________.

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Tables Densimeter Repair

Sand Densities and Volumes Proppant Name AcFrac Black AcFrac CR AcFrac CR-5000 AcFrac PR AcFrac PR-5000 AcFrac SB Arizona Silica Bauxite Bauxite HC Brady Sand Carbo Econolite Carbolite Carboprop Colorado Silica Interprop 1 Interprop Plus ISP-1 LWP Ottawa Sand Super 100 Super DC Super HS Super LC Tempered DC Tempered LC Ultraprop Plus Z-Prop

Specific Gravity Proppant Coefficient 2.55 .04950 2.55 .04695 2.55 .04705 2.50 .04780 2.56 .04687 2.55 .04630 2.65 .04529 3.55 .03380 3.65 .03284 2.65 .04529 2.65 .04560 2.73 .04390 3.25 .03692 2.65 .04529 3.15 .03780 3.15 .03780 3.16 .03770 2.60 .04660 2.65 .04529 2.53 .04745 2.57 .04663 2.53 .04745 2.60 .04609 2.60 .04609 2.57 .04663 3.49 .03440 3.17 .03785

Density (lbs/gal) 21.08 21.25 21.25 20.84 21.33 21.25 22.08 29.58 30.45 22.08 22.08 22.75 27.08 22.08 26.25 26.25 26.33 21.67 22.08 21.08 21.42 21.08 21.67 21.67 21.42 29.08 26.42

Sand Sizes The sizes of the particles are often expressed as a number, which corresponds to the mesh screen size of a sieve. The screen size indicates the number of openings in the mesh screen per inch. For example, a # 40 sieve has 40 openings per inch in the screen mesh. Particles that can sift through that mesh are said to be "40 mesh" size. Below is a list of mesh sizes and the size of the mesh opening in millimeters (1/1000 of a meter) or microns (1/1,000,000) of a meter. Of coarse there is a correlation between the size of the mesh opening and the particle size of the sifted powder. As the opening becomes smaller, so will be resulting particle size. Most of the particles of a sifted powder will have approximately the size as the mesh opening. Mesh Opening Size Mesh Size Number 10 20 30 40 50 60 70 80 100

millimeters 2.00 0.84 0.59 0.42 0.297 0.250 0.210 0.177 0.149

microns 2000 840 590 420 297 250 210 177 149

The USP 24/NF19 uses descriptive terms to define granular fineness. The table below shows the correlation their classification. Description Term Very Coarse Coarse Moderately Coarse Fine Very Fine

Mesh Opening Size (microns) > 1000 355 -1000 180 – 355 125 – 180 90 - 125

Mesh Size Number 2 – 10 20 – 40 40 – 80 80 – 120 120 - 200

Sieve Distribution API specifications place the following limitations on sieve distribution for proppants suitable for use in a fracture: • at least 90% of material must fall between the two mesh sizes • no more than 10% of the material may be coarser than the largest mesh size • no more than 0.1% of the material may be coarser than the next largest mesh size (e.g. for 20/40, up to 10% of the proppant may be between 16 and 20 mesh, but no more than 0.1% can exceed 16 mesh) • no more than 1% of material is permitted to fall onto the pan For gravel pack media, the suggested distribution is more tightly constrained: • at least 96% of material must fall between the two mesh sizes • no more than 2% of material is permitted to be finer than the specified size • no more than 0.1% of the material may be coarser than the next largest mesh size (e.g. for 20/40 media, no more than 0.1% can exceed 16 mesh, and no more than 2 percent may pass through the 40 mesh screen, and no more than 4% can be outside the range of 20/40.)


Appendix B Electrical Drawings

Density System Electrical Drawings The following drawing is from TN Technologies: • D866709 Rev B (1 sheet) - Schematic, Detector, SGO, FSU • D866709 Rev E1 (1 sheet) - Schematic, Detector, SGO, FSU The following are drawings for the BJ Density Module: • 41692 (1 sheet) – Module Assy, U.C. Module II, Density • 41697 (1 sheet) – Wiring Diagram, Univ. Controller II/Density • 41696 (1 sheet) – Schematic, U.C. II Module/Density Board • 41709 (1 sheet) – Schematic, Density Interface U.C. II


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ET205 Densimeter Repair (1)

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