SABP-A-007

Best Practice SABP-A-007 SABP-A-00 7

11 April 2006

Steam Trap Management for Energy Efficiency Document Responsibility: Responsibility: CSD/ESD/Energy Systems Unit

Steam Trap Management for Energy Efficiency

Developed by: Energy Systems Unit Consulting Services Department Issue Date: 11 April 2006

Previous issue: None Next Planned Update: 11 April 2009 Primary Contact: [email protected], [email protected], phone +966 (3) 874-6157 874-6157

Document Responsibility: CSD/ESD/Energy CSD/ESD/Energy Systems Unit Issue Date: Date: 11 April 2006 Next Planned Update: Update: 11 April 2009

SABP-A-007 Steam Trap Management Management for Energy Efficiency

Table of Contents

1.0

Introduction 1.1 Purpose and Scope 1.2 Intended Users 1.3 Conflicts with Mandatory Standards 1.4 References and Related Documents

2.0

General 2.1 Steam System Basics 2.2 Function of Steam Traps 2.3 Estimating Steam Loss 2.4 Cost of Steam & Condensate

5 5 6 8 9

3.0

Steam Traps 3.1 Classification 3.2 Selection and Sizing 3.3 Trap Installation 3.4 Failure Modes and Rates 3.5 Safety Issues

14 14 18 22 22 23

4.0

Recommended Management Practices 4.1 Inspection Frequency 4.2 Inspection Techniques and Tools 4.3 Record-keeping and Reporting 4.4 Organizational and Management Issues

25 26 27 35 37

APPENDICES A Armstrong Steam Trap Handbook (TOC) B Spirax-Sarco Steam Trap Handbook (TOC) C Armstrong Steam Trap Testing Guide D Internet Resource Directory

Page 4 4 4 4

39 40 41 45

Page 2 of 45



List of Exhibits Exh. No 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9

Title Steam System Schematic Condensation in Heat Transfer Equipment Water Hammer in Distribution Piping Temperature Reduction Caused by Air Steam Loss Rates from New Traps Leakage Rates from Defective Traps Steam Cost Calculation Template CHP Simulation Model Savings Achieved from Steam Trap Management

Page 5 6 7 7 8 8 9 11 13

3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-11

Thermostatic Traps Thermodynamic Traps Disc-type Thermodynamic Trap with Integral Strainer Mechanical Traps Steam Trap Features and Characteristics Steam Trap Service Applicability Steam Trap Performance Characteristics Steam Trap Selection Guide Operating Limits Chart for Ball-Float Steam Traps Sample Capacity Chart for Inverted Bucket Traps Typical Trap Failure Positions

14 15 16 17 18 18 19 20 19 21 22

4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12 4-13 4-14 4-15 4-16 4-17 4-18

Historical Approach to Steam Trap Management Pro-active Approach to Steam Trap Management Steam Trap Discharge Characteristics Flash Steam versus Live Steam Pipe Surface Temperatures versus Steam Pressure Using a Contact Pyrometer for Closed Condensate Return Systems Typical Operating Sounds of Various Types of Traps Situation Where Acoustic Testing Cannot be Used Conductivity-based Trap Sensors Automatic Automatic Conductivity-based Trap Monitoring System SpiratecTM R16C Trap Monitor SteamEye® Sensor/Transmitter and SteamStar TM System Sample Transmitter/Repeater/Receiver Layout for Typical Plant Sample Reports from SteamStar TM Software Condensate Line Sizing Chart Sample Steam Trap Status Report Sample Steam Trap Inspection Report Recommended Steam Trap Management Strategies

25 26 27 28 28 29 30 31 32 32 33 34 34 35 36 37 38 38

Page 3 of 45


1.0

Introduction

1.1

Purpose and Scope


All major industrial facilities use steam as the principal source of thermal energy to drive the process. Once the steam has delivered its latent heat content to the process, it condenses back into a liquid, which must be recovered recovered for recycle to the boilers. The device used to recover steam condensate is called a steam trap. Steam traps have a notoriously high failure rate, typically 20% per year. A trap that has failed open will leak steam and cost money; a trap that has failed closed will prevent the steam from delivering the required amount of heat to the process. Proper working of traps is critical critical to efficient management of the plant steam system. The purpose of this Best Practice manual is to describe the current recommend procedures for monitoring and managing steam traps towards this end. The focus of this manual manual is on managing the existing steam traps. It does not address the steam and condensate piping system, nor whether the steam trap type and size have been correctly specified for the intended application. It is assumed assumed that these have all been done correctly.

1.2

Intended Users

This Best Practice manual is intended for use by plant engineers working in Saudi Aramco plants, who are responsible for safe and efficient operation of their steam condensate recovery system.

1.3

Conflicts with Mandatory Standards

There are no conflicts with existing Saudi Aramco mandatory standards, or with any other standard operating practices with respect to reliability, safety, etc.

1.4

References and Related Documents

PEDD course ChE107: Plant Utilities, Chapter 6 – Steam Distribution Improving Steam System Performance – a Sourcebook , US Dept of Energy, Washington, DC. Steam Trap Handbook , James F. McCauley, Fairmont Press, Lilburn, Ga. Steam Distribution Systems Deskbook , James F McCauley, Fairmont Press, Lilburn, Ga. Design of Fluid Systems: Steam Utilization, Spirax-Sarco Inc, Allentown, Pa (2004). Design of Fluid Systems: Hook-Up Designs, Spirax-Sarco Inc, Blythewood, SC (2004). Steam Conservation Guidelines for Condensate Drainage, Bulletin N-101, Armstrong

International Inc, Three Rivers, Mich (1997). Industrial Steam Trapping Handbook , Yarway Corp, Blue Bell, Pa.

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2.0


General

A Best Practice is defined as a process or method that, when correctly executed, leads to enhanced system performance. The focus of this Best Practice Practice manual is on the management of the steam traps in large industrial plants, recognizing that they are only a part of the condensate recovery system, which in turn is only a part of the overall steam generation and distribution system. system. Proper trap performance also depends upon the following corollary issues: • Trap selection and sizing • Trap installation (piping and controls) • Steam distribution piping and controls • Condensate collection vessels, piping, and controls These corollary issues are not addressed in detail in this manual, as it is assumed that the systems have been designed correctly and are already being managed in the optimal fashion.

Steam System Basics

2.1

A steam system consists consists of five principal sub-systems: sub-systems:

• • • • •

Generation (boilers) Distribution End Users (process applications) Condensate recovery Boiler feedwater treatment Exhibit 2-1: Steam System System Schematic Schematic

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Physically, steam traps are a component of the condensate recovery system, but they also affect the ability of the distribution system to effectively deliver the required thermal energy to process applications. Also, in some cases, improper improper design or operation of the steam distribution piping and controls could affect affect steam trap performance. It is important therefore to distinguish between the functioning of the trap itself and the effects of poor po or design/operation of other interrelated sub-systems.

2.2

Function of Steam Traps

Steam traps have three principal functions: (a) safely and quickly drain steam condensate while while maintaining thermal efficiency. efficiency. (b) maintain the steam back-pressure back-pressure in the pipe or heat transfer process equipment. (c) vent air and other non-condensable gases from the equipment after startup. startup. Condensate forms in the steam distribution piping system because of unavoidable heat losses due to radiation, convection, and conduction. It also forms in process equipment equipment that is being heated with steam, steam, such as heat exchangers, vessel jackets, etc. etc. Once the steam steam has condensed, the hot condensate must be removed at once for two reasons:

• •

to maintain the heat transfer capacity of the exchanger or process heating vessel, and to prevent water hammer (a safety issue) Transfer Equipment Exhibit 2-2 : Condensation in Heat Transfer

Source: Armstrong Steam & Condensate Guide (1997)

Condensate in the heat transfer equipment (eg. the coil shown in Exhibit 2-2) takes up space and in effect reduces the surface surface area available for for process heat transfer. The drainage problem involves more than just condensate removal, as non-condensable gases must be cleared from the system as well. Another reason for minimizing the amount of condensate in the equipment is that if steam comes into contact with cold condensate (ie. below the temperature of steam), it can produce a kind of water hammer known as thermal shock , which can collapse the equipment shell.

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Condensate accumulating at the bottom of steam distribution lines can cause another type of water hammer. As high-speed steam flows flows over condensate at velocities of up to 100 miles per hour, it will cause waves that could form a dangerous slug when the crest of the wave reaches the top of the pipe (point A in Exhibit 2-3), growing increasingly larger as it picks up liquid in front of it (area B). Anything obstructions in the flow path – pipe fittings, valves, tees, elbows, blind flanges – will be destroyed. Water hammer is a serious safety issue, as it can damage the piping, even ripping it off its anchors, and ultimately leading to a steam explosion if left unattended. Exhibit 2-3: Water Hammer Hammer in Distribution Piping Piping


When air and other gases infiltrate the steam system, they reduce the partial pressure of steam and therefore its effective condensing temperature (see Exhibit 2-4), which in turn reduces available temperature driving forces for heat transfer. Worse still, non-condensable non-condensable gases reduce the film heat transfer coefficient coefficient dramatically. As little as 0.5 - 1% air by volume volume can reduce heat transfer rates by as much as 50%, effectively causing a production capacity bottleneck. Reduction Caused by Air Exhibit 2-4: Temperature Reduction


In addition to their primary function, steam traps should meet the following criteria: (a) (b) (c) (d)

wear-resistant parts, to minimize downtime for repair low steam blow-by (leakage) rates for good energy efficiency ability to operate against back-pressure in the condensate return system tolerance to dirt and scale carried over from the boiler and steam piping (alternatively, they should be protected by upstream strainers).

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2.3


Estimating Steam Loss

There are two ways that steam loss can occur – one is through the trap (ie. leakage) and the other is from the trap due to radiation and convection. A properly manufactured and installed installed steam trap will have little or no steam loss due to leakage under normal operation. However some blow-by will occur if the trap is operating at no-load conditions, eg. when the heat exchanger to which it is connected is down, down, but steam is on. Extensive testing by the National Engineering Laboratory in the UK led to the publication of international standards for trap leakage rates, as shown in Exhibit 2-5 [Ref. Spirax-Sarco bulletin TI-F01-27] . Exhibit 2-5 : Steam Loss Rates from New Traps in lb/h (∆P = 5 bar = 71 psi)

Pressure Thermostatic, BM = Bimetallic Bimetallic , Legend: BPT = Balanced Pressure FT = Float and Thermostatic, IB = Inverted Bucket, TD = thermodynamic

If the actual ∆P is higher, the “through” rates have to be adjusted as follows:

 Actual ∆ P , psi  Correct leakage rate (through) = Tabulated leakage rate x   71  

5/ 9

Strictly speaking the “from” rates should also be adjusted, based on the radiant and convective loss correction factors due to operation at different temperatures, but typically they are not. When the trap is worn or damaged, steam leakage rates can increase dramatically, as seen from the table below. Defective Traps Exhibit 2-6 : Leakage Rates from Defective

The problem with Exhibit 2-6, of course, is that one does not know (indeed, cannot possibly know) the “size” of the hole, especially since it is never a conveniently circular orifice as assumed. Therefore these figures must be treated as indicative only.

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In addition to saving boiler fuel, steam traps reduce other system costs as well. well. For example, higher condensate recovery levels directly translate into lower requirement for boiler feedwater makeup, with consequent savings in both raw water and BFW treatment treatment chemicals. Also, the boiler can be operated at a lower capacity, thus reducing maintenance costs and extending it’s useful life.

2.4

Cost of Steam and Condensate

In addition to knowing the steam loss rates, it is necessary to know the cost of steam and condensate at different pressures. This can be conveniently conveniently done according to the procedure developed by Energy Systems Unit of CSD, using the spreadsheet templates available from the CSD web-site on the intranet. Sample input and output tables tables from this spreadsheet spreadsheet are displayed in Exhibits 2-7a and b. The cost of steam is displayed in bold numbers. The cost of condensate is shown under the heading “condensate loss penalty”; note that this is the cost per 1000 lb of condensate, condensate, not 1000 lb of steam. The cost of demineralized water used as as BFW makeup must be supplied as input data, which can vary significantly from site to site. Exhibit 2-7a: Steam Cost Calculation Calculation Template – Input Data

The economic benefits of increasing condensate recovery can be calculated by using the plant CHP model, as illustrated in Exhibits 2-8a and b.

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Exhibit 2-7b: Steam Cost Calculation Calculation Template – Calcs & Output

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Document Responsibility: Responsibility: CSD/ESD/Energy CSD/ESD/Energy Systems Unit Issue Date: Date: 11 April 2006 Next Planned Update: Update: 11 April 2009

SABP-A-007 Steam Trap Management Management for Energy Energy Efficiency

Exhibit 2-8a: CHP Simulation Model – without Steam Trap Management Management Program

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Exhibit 2-8b: CHP Simulation Model – with Steam Steam Trap Management Program



Exhibit 2-8b: CHP Simulation Model – with Steam Steam Trap Management Program

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Exhibit 2-9: Savings Achieved from Steam Trap Management



Exhibit 2-9: Savings Achieved from Steam Trap Management

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3.0


Steam Traps

There is no universal steam trap technology that is ideal for for all applications. Rather, several technologies and design options are available to accommodate the various different situations. Each trap design has different strengths and weaknesses, and must be carefully selected for the intended application (see section 3-2).

3.1

Classification

Steam Traps are generally classified first according to their operating principle and second by their mechanical design: 1. 2. 3.

Thermostatic – balanced pressure (bellows), bimetallic Thermodynamic – disc, orifice Mechanical – float & thermostatic, inverted bucket

There are innumerable variations in design offered by the trap manufacturers, each targeted at a specific type of application or solving a particular operating problem, but the basic principles are the same. 3.1.1

Thermostatic Traps

Thermostatic traps use temperature differential to distinguish between condensate and live steam. This differential is used to open or close close a valve, which which means that the the condensate must cool down to below the steam condensing temperature before the valve will open. Balanced-Pressure (Bellows) Traps include a valve element that expands and contracts in

response to temperature changes. Often a volatile chemical such as ethanol or water is inside the element. Evaporation provides the necessary force to change the position position of the valve. At start up, the bellows trap is open due to the relative cold condition. This operating condition allows air to escape and provides maximum condensate removal when the load is the highest. Bellows traps can fail either open or closed. Exhibit 3-1: Thermostatic Traps (a) Bellows type (b) Bimetallic type

Source: Improving Steam System Performance: A Sourcebook for Industry , US Dept of Energy (2003)

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Bimetallic Traps rely on the bending of a composite strip of two dissimilar metals to open and

close a valve. Air and condensate pass freely through the valve until the temperature of the bimetallic strip approaches the steam steam temperature. After steam or relatively hot condensate heats the bimetallic strip and causes it to close the valve, the trap remains shut until the temperature of the condensate cools sufficiently to allow the bimetallic strip to return to its original shape and thereby open the valve. Bimetallic traps can fail in either the open or closed position. 3.1.2

Thermodynamic Traps

Thermodynamic traps use the difference in kinetic energy (velocity) between condensate and live steam to operate a valve. They are small in size, relatively relatively inexpensive, and resistant to water hammer. There are three basic types – disc, piston (or impulse), impulse), and orifice – and many variations. The disc type with an integral strainer is the most common, although orifice types types are gaining in popularity. Thermodynamic traps are not suitable suitable for applications that pass pass a lot of dirt, air, or are frequently in and out of service. Exhibit 3-2 : Thermodynamic Traps (a) Disc type (b) Orifice type

Source: C B Oland, Oland, Review of Orifice Plate Steam Traps , US Dept of Energy publication # ORNL/TM-2000/353/R1 (Jan 2001)

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Disc Traps use the position position of a flat disc to control steam and condensate flow.

When condensate flows through the trap, it forces the disc to rise inside the control chamber until it is discharged. As the last of the the condensate flows out, it flashes across the narrow gap between the raised disc and the seat, causing the pressure beneath the disc to fall, and the trap to close. Orifice Traps come in either plate or “short tube” designs, both of which operate on exactly

the same principles. Condensate that accumulates accumulates on the upstream side side of the orifice or tube is continuously removed due to pressure gradient. Once all condensate has been passed, a limited amount of steam continues to flow through the orifice. The main advantage is that they they are extremely cheap. The disadvantage is higher steam loss loss under variable load conditions. Thermodynamic Trap with Integral Strainer Exhibit 3-3: Disc-type Thermodynamic

3.1.3

Mechanical Traps

Mechanical traps use the difference in density between condensate and live steam to produce a change in the position of a hinged float or bucket. This movement causes a valve to open or close. There are a number of mechanical mechanical trap designs that are based on this principle. Although there are many different designs – e.g. inverted bucket, open bucket, ball float, float and lever, and float & thermostatic, etc – the F&T and IV designs are the most popular. Ball Float Traps rely on the movement of a spherical ball to open and close the outlet opening

in the trap body. When no condensate is present, the ball covers the outlet opening, thereby keeping air and steam steam from escaping. As condensate accumulates accumulates inside the trap, the ball floats and uncovers the outlet opening. This movement allows the condensate to flow continuously from the trap. Unless they are equipped with a separate air vent, ball float traps cannot vent air on start up. Float and Lever Traps are similar in operation to ball float traps except the ball in connected to a lever. When the ball floats upward upward due to accumulation of condensate inside the the trap body, the attached lever moves and causes a valve valve to open. This action allows condensate to continuously flow from the trap. If the condensate load decreases and steam reaches the trap, Page 16 of 45



down-ward ball movement causes the valve to close thereby keeping steam from escaping. Unless they are equipped with a separate air vent, float and lever traps cannot vent air on start up. (See the discussion on float and thermostatic traps) Float and Thermostatic (F&T) Traps combine a thermostatic bellows type air vent with a hinged –float mechanism. The thermostatic thermostatic air vent senses changes in temperature. Upon startup it vents air from the trap. Once operating temperature is reached, the bellows close, at which point the float takes over. F&T traps are best suited for applications that are frequently in and out of service and require immediate discharge of varying condensate loads. Exhibit 3-4: Mechanical Traps (a) Float & Thermostatic (b) Inverted Bucket

Inverted Bucket Traps are somewhat more complicated than float and lever traps. At start

up, the inverted bucket inside the trap is resting on the bottom of the trap body and valve to which the bucket is linked is wide open. The trap is initially filled with condensate. As steam enters the trap and is captured inside the bucket, it causes the bucket bucket to move upward. This upward movement closes the valve and keeps steam from escaping. When the condensate collects and cools the steam, the bucket moves downward. This movement causes the valve to open thereby allowing the condensate to escape (intermittent discharge). Inverted Bucket traps are well suited for applications containing high dissolved or suspended solids, as they are resistant to pipe-line scale, rust, and dirt. Inverted bucket traps must be “primed” (ie. filled with water) before they are put into service. Otherwise, the float mechanism will not function, and the trap will pass live steam (fail open). If this happens, the moving moving parts could break, requiring trap trap replacement. If these traps are applied in superheated steam service their “condensate seal” can be depleted, and the trap will continuously discharge live steam. Therefore they are not recommended for superheated steam service, unless special installation conditions are met.

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Open Bucket Traps consist of an upright bucket that is attached to a valve. valve. At start up, the

bucket rests on the bottom of the trap body. In this position the trap is wide open. As condensate accumulates in the trap outside of the bucket, the bucket floats upward causing the valve to close. close. When sufficient condensate has accumulated outside the bucket, it spills over the top and fills the the inside of the bucket, causing it to sink and the valve to open. This design is not suitable for superheated steam service because of the loss of condensate seal. Like inverted bucket traps, open bucket b ucket traps have intermittent discharge.

3.2

Selection and Sizing

No single steam trap technology is ideal for all applications. applications. Rather, the trap type must be selected by matching its performance characteristics against process requirements for each individual application. Trap Features and Characteristics Characteristics Exhibit 3-5 : Steam Trap

Source: G. Page, “Steam Traps”, Chem Eng Prog (Jan 2006), p16

Exhibit 3-6 : Steam Trap Trap Service Applicability

Source: G. Page, “Steam Traps”, Chem Eng Prog (Jan 2006), p16

Performance characteristics of the common steam trap designs are summarized in Exhibit 3-7. Trap selection guidelines are provided in Exhibit 3-8, which indicates which type of trap has been found to be most effective in different applications under typical field conditions.

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Exhibit 3-7 : Steam Trap Performance Characteristics Characteristics


Trap manufacturers generally publish the operating ranges over which a particular trap will operate properly, as illustrated illustrated in Exhibit 3-9. If the actual operating conditions subsequently exceed the specified limits, this could lead to trap failure. Exhibit 3-9: Operating Limits Chart for Ball-Float Steam Traps

Source: Spirax-Sarco bulletin SB-P145-03, issue 2

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Exhibit 3-8: Steam Trap Selection Guide

Source: Steam Utilization – Design of Fluid Systems , Spirax-Sarco (2004)

Trap sizing is a complex function of condensate load, available differential pressure across the trap, and operating temperature. All reputable manufacturers will supply “capacity charts” as illustrated in Exhibit Exhibit 3-10. It is critically important to ascertain whether whether the trap trap will be operating under “hot” or “cold” conditions conditions when selecting trap type and size. If the condensate upstream of the trap orifice is a superheated liquid at discharge side pressure, then it will flash as it passes through the orifice, resulting in two-phase flow. flow. Trap capacities are significantly lower under such hot conditions as opposed to non-flashing cold conditions. Page 20 of 45



Exhibit 3-10: Sample Capacity Chart for Inverted Bucket Traps

Source: Spirax-Sarco bulletin TI-S03-04 ST issue 3

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Trap Installation

3.3

Steam traps do not function function in isolation. To a very large extent, their effectiveness depends upon proper installation, which varies from from application to application. Installation guidelines are available in manufacturers’ literature (see Appendices A and B).

Failure Modes and Rates

3.4

Trap failure modes are generally classified into four categories:

• • • •

Blocked Low-temperature Leaking Blowing

The difference between leaking and blowing is one of degree. Blowing is the term used used when the trap has failed in a fully open position, whereas leaking implies that the trap is passing some steam even when it is supposedly closed closed and should be passing no steam. Leaking and blowing traps cost money because of steam loss. Blocked and “low temperature” conditions, on the other hand indicate that condensate is not being properly drained. There is no steam steam loss, but rather production capacity is lost in the the equipment, such as a heat exchanger, that is being “trapped”. Excluding design problems, the two most common causes of trap failure are over-sizing and dirt. Over-sizing invariably leads to premature erosion and and leakage. Dirt is always being generated in a steam system. system. Excessive build-up can cause plugging or prevent a valve from closing. Dirt is generally produced from pipe scale or from over-treating of chemicals in a boiler. Understanding what will happen to the steam steam system when a trap fails is very important. A trap can fail either open (ie. passing steam) or closed (ie. blocking condensate condensate drainage). The failure position depends on the operating principle and mechanical design of the trap. However, sometimes traps designed to fail closed may actually fail open due to abnormal conditions such as dirt, back-pressure, or operator action. For example, although F&T traps usually fail closed, they could also fail in the open position if the ball float becomes damaged and sinks or if the thermostatic element fails. Exhibit 3-11: Typical Trap Trap Failure Positions

Trap type Thermostatic – bellows Thermostatic – bimetal Thermodynamic (all) Float & Thermostatic Inverted Bucket Ball float

Failure Position Open or closed depending on bellows failure mode Open or closed depending on strip Open Closed Open closed

Source: Applications Newsletter, www.nicholsonsteamtrap.com

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The longevity of a trap is affected by a variety of factors including operating conditions (pressure, temperature, load), suspended solids (rust, dirt, scale), system dynamics, and neglect. A much under-appreciated cause of premature trap failure is improper sizing for the actual load. Both under-sized and over-sized traps will will begin leaking well before a correctly sized trap [Ref. F A Hooper and R D Gillette, “Comparison of Three Preventive Maintenance Strategies For Steam Trap Systems”, www.trapo.com]. The US Dept of Energy has reported [Ref. Steam Tip Sheet #1 – January 2006] that modern steam traps have an aggregate failure rate of around 5-7% per year in their first five years of service, down significantly from 15-25% for older designs. Published data in the literature indicate that without an active steam trap management program, about 17% of generated generated steam is lost on average due to defective traps. Thus a facility consuming 100 Klb/h of steam steam in the process will lose lose 17 Klb/h. Assuming a marginal cost of $2.50/Klb for steam, and 8400 equivalent hours per year of full rate operation, this is worth $357,000 per year. Typically, steam trap failure rates increase dramatically after 3-4 years.

3.5

Safety Issues

It is also important to be cognizant of safety issues associated with trap failure. When steam traps are either blocked or undersized, they can cause a backup of condensate in the steam steam mains. This has two negative consequences – (a) steam will become desuperheated, and (b) the potential for water hammer increases as high speed steam comes into contact with and picks up slugs of water (Ref. section section 2-2). When the slug of condensate being carried along the steam line reaches an obstruction, such as a bend or a valve, it can cause tremendous damage such as blowing out a valve or a strainer. Condensate in a steam system can also cause valves to become wiredrawn and unable to hold temperatures as required. Little beads of water water in a steam line can eventually cut any small orifices the steam normally passes through. Wiredrawing will eventually cut enough of the metal in a valve seat that it prevents adequate closure, producing leakage in the system. On October 10, 1986, a condensate-induced water hammer at a major US government research facility injured four steamfitters steamfitters — two of them fatally. One of the steamfitters attempted to activate an 8-inch steam line located in a manhole. manhole. He noticed that there was no steam in either the steam line or the steam trap assembly and concluded that the steam trap had failed. Steam traps are devices designed to automatically remove condensate condensate (liquid) from steam piping while the steam system is operating in a steady state. Without shutting off the steam supply, he and another steamfitter replaced the trap and left. Later the first steamfitter, his supervisor, and two other steamfitters returned and found the line held a large amount of condensate. They cracked open a gate valve valve to drain the condensate into an 8-inch main, but this was too far open to control the sudden onrush of steam into the main after all the condensate condensate had been removed. A series of powerful water water hammer surges caused the gaskets on two blind flanges in the manhole to fail, releasing hot condensate and Page 23 of 45



steam into the the manhole. All four steamfitters steamfitters suffered external burns and steam inhalation. Two of them died. A Type A Accident Investigation Board determined that the probable cause of the event was a lack of procedures and training, resulting in operational error. Operators had used an in-line gate valve to remove condensate from a steam line under pressure instead of drains installed for that purpose. The board also cited cited several management problems. There had been no Operational Readiness Review prior to system activation. Laboratory personnel had not witnessed witnessed all the hydrostatic and pressure testing, nor had all test results been submitted, as required by the contract. Documentation Documentation for design changes was inadequate. The board also determined determined that management had not been significantly involved in i n the activities of the steam shop. In June 1991, a valve gasket gasket blew out in a steam steam system at a Georgia hospital. Operators isolated that section of the the line and replaced the gasket. The section was closed for 2 weeks, allowing condensate to accumulate in the line. After the repair was completed, an operator opened the steam valve at the upstream upstream end of the section. He drove to the other end and started to open the downstream downstream steam valve. He did not open the blow-off valve to remove condensate before he opened the steam valve. Water hammer ruptured the valve before it was 20% open, releasing steam and condensate and killing the operator. Investigators determined that about 1,900 pounds of water had accumulated at the low point in the line adjacent to the the repaired valve, where a steam trap had been disconnected. disconnected. Because the line was cold, the incoming steam condensed quickly, lowering the system pressure and accelerating the steam steam flow into the section. This swept the accumulated water toward the downstream valve and may have produced a relatively small steam-propelled water slug impact before the operator arrived. About 600 pounds of steam condensed in the cold section of the pipe before equilibrium was reached. When the downstream valve was opened, the steam on the downstream side rapidly condensed into water on the upstream side. This flow picked up a 75 cubic foot slug of water about 400 feet downstream of the valve. The slug sealed off a steam pocket and accelerated until it hit the valve, causing it to rupture. The accident could have been prevented if the operator had followed accepted Best Practices, allowing the pipe to warm up first, and using the blow-off valve to remove condensate before opening the downstream valve.

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4.0


Recommended Best Practices

Despite the fact that most companies recognize poor steam trap management as a cause of significant energy losses, very few are able to sustain a systematic and effective management program. Key features of typical current practice are as follows: follows: (a) Trap survey is performed once a year (b) Evaluation of survey survey data and necessary replacements take place over over the next 3-6 months (c) Trap replacement replacement is completed completed in between other facility facility priorities (d) During the 1-year span between surveys, additional traps fail and lose steam for an average of six months (e) Traps are replaced “in-kind”, ie. like for like, without without root cause failure analysis or evaluation of changed process conditions (f) Management receives feedback on steam losses only once a year Exhibit 4-1: Historical Approach to Steam Trap Management

Predictably, the results are not satisfactory. satisfactory. With a reactive approach, failure rates and steam losses are doomed to be high. As an example, a steam trap trap survey conducted by CSD at Juaymah Gas Plant in June 2003 [ESA# NGO-042] showed that 53% of the 336 traps evaluated were malfunctioning. malfunctioning. The full range range of failure modes was encountered – low temperature, leakage, blow-through, and blocked. blocked. The report recommended that all traps should be inspected every six months using a portable device known as TrapManTM. The fundamental flaw in the historical approach is that steam trap management is treated as a series of projects, projects, not as a continuing program. A project has a beginning and an end; a program is on-going. The recommended best practice is to take a pro-active approach towards managing the trap population to provide: Page 25 of 45


• • •


Instant detection of steam trap failures with minimal labor allocation Quick diagnosis (based on root cause analysis) and action plan for trap repair or replacement based on ROI A reporting system that provides performance measurement, tracking, and easy company-wide communication Exhibit 4-2 : Pro-active Approach to Steam Trap Management

Ref: L. Schavey and J. Stout, “Achieving Operational Excellence in Gas Plants”, Hydrocarbon Processing (Jan 2005)

Industry is currently at the beginning of a transition phase from the manual mode to the automatic mode. Fortunately, the technology technology for early detection detection and systematic systematic reporting is now available through at least two reputable vendors (see section 4-2).

4.1

Inspection Frequency

The US Dept of Energy [Ref. Steam Tip Sheet #1 – January 2006] recommends steam trap testing intervals based on the operating pressure: Steam pressure, psig > 150 psig 30-150 psig < 30 psig

Testing frequency weekly – monthly monthly-quarterly annually

In reality traps fail every day, but it is not economically feasible to inspect traps on a daily basis. The above table balances the the cost of steam steam loss and equipment damage against the cost of manpower, taking into account that steam losses and water hammer from LP steam applications are considerably less than those from HP applications.

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Inspection Techniques and Tools

4.2

If the steam system is extensive, as in most Saudi Aramco plants, it is usually preferable to do the surveys section by section rather than all at once. There are two fundamental approaches to trap monitoring: (a) manual inspection and testing testing (see Appendix C) (b) automatic electronic surveillance Characteristics Exhibit 4-3: Steam Trap Discharge Characteristics

Source: Steam Utilization – Design of Fluid Systems, Spirax-Sarco (2004)

Before testing a steam trap, inspectors should first understand the specific function of the trap in that particular application, and review the actual versus design operating conditions to help avoid misdiagnosis and properly interpret interpret trap performance. There are four basic ways to test steam traps – visual, thermal, acoustic, and electrical conductivity. All will be described. 4.2.1

Visual Method

Visual observation of condensate discharging from a trap is the simplest, though not the most reliable, indication of its performance, as it depends heavily on the knowledge and experience of the inspector. In Exhibit 4-4, the the picture on the left shows lazy vapor flashing off from discharged condensate. This is natural, natural, and does not imply waste waste or trap failure. On the other hand, the picture on the right shows steam emanating from the trap discharge as a highvelocity high-temperature steam plume, which indicates the trap has failed open. A rough estimate of steam loss rate can be made from the length of the steam plume: Steam Loss, lb/h = 2 x (length, ft) 2.35 If the trap does not discharge to the atmosphere, but into a closed condensate return system, a test valve valve should be installed downstream of the trap. To check trap performance, the isolation valve is closed to shut off the condensate return line, and the test valve is opened to the atmosphere. If it discharges condensate instead instead of live steam, the trap is working. 4.2.2

Thermal Method

Thermal inspection relies on upstream/downstream temperature variations in a trap. It includes pyrometers, infrared guns, heat bands (wrapped around a trap, they change color as temperature increases), and heat sticks (which melt at various temperatures). Page 27 of 45



Exhibit 4-4: Flash Steam versus Live Steam

Source: “Simple Techniques for Surveying Steam Traps”, Yarway Corp (1996)

To use this method, one requires either a contact pyrometer or an infrared radiation pyrometer (infrared “gun”) to measure pipe surface temperature, and a knowledge of the line pressures upstream and downstream of the trap. Exhibit 4-5 shows typical pipe surface temperature readings (un-insulated) corresponding to several operating pressures. Exhibit 4-5 : Pipe Surface Temperatures Temperatures versus Steam Steam Pressure


The procedure is to first measure the pipe surface temperatures about 12 inches upstream and 12” downstream of the trap. If using a pyrometer, the pipe surfaces surfaces should be cleaned by filing or wire-brushing to provide provide good contact for the pyrometer tip. If using a non-contact non-contact radiation pyrometer, it is important to point it accurately, without obstructions in the line of sight. Let’s say the values are 335° and 270°F. Suppose the steam pressure is 150 psig, and the condensate return line pressure downstream of the trap is 50 psig. Since the measured Page 28 of 45



temperatures are within the ranges specified in Exhibit 4-5, we can conclude that the trap is operating properly. Now let’s consider a scenario with the same line pressures, but pyrometer readings of 335° and 300°F respectively. The elevated downstream temperature would suggest that that steam is blowing through. Finally, suppose that the upstream and downstream temperatures were 250°F on both sides on the trap. This is too low for steam at 150 psig, indicating that some sort sort of restriction (such a clogged strainer) in the line that is causing a very high pressure drop. If the upstream upstream strainers had already been blown down before conducting the test, per good practice, it means that condensate has probably backed up into the upstream side of the trap (a safety hazard) due to a piece of metal or dirt stuck in the trap, which would require it to be isolated, dismantled, and cleaned. Exhibit 4-6 : Using a Contact Pyrometer for Closed Condensate Return Systems Systems


Radiation pyrometers are more convenient for evaluating traps that are either dangerous (due to high pressure) or difficult to access (due to location). A wide variety of devices are available, some of which are neither neither rugged nor accurate. A good pyrometer should have an accuracy of within 2°F over the temperature range 100-800°F under field conditions. 4.2.3

Acoustic Method

Steam traps emit very distinct sound patterns; each trap type having a particular signature. These sounds are not audible to the unaided ear. Using an ultrasonic detector, the analyst is able to isolate the frequency of sound being emitted by the steam trap, compare it to trended sound signatures, and make an assessment. Changes in these ultrasonic wave wave emissions are indicative of changes in steam trap function.

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Although various listening devices ranging from screwdrivers to mechanical stethoscopes have been used in the past, ultrasonic detection instruments are best, especially for closed condensate return systems, as they enable users to listen to the sounds of steam trap operations (high-frequency short-wave signals) while screening out most ambient and stray pipe sounds. Also, ultrasonic sensors sensors are highly directional in their pick-up, enabling users to hear and see on meters the exact operations of steam traps. Ultrasonic detectors usually include a stethoscope module, which contains an ultrasonic transducer attached to a metal rod that that acts as a "wave guide". The wave guide is touched on the downstream side of a trap to determine trap condition such as mechanical movements or steam and condensate flow. Most ultrasonic detectors detectors amplify the signals signals and translate them into the audible range where they are heard through headphones or seen as intensity increments on a meter. Some also feature frequency tuning to allow users to tune into desired trap sounds. Exhibit 4-7 : Typical Operating Sounds of Various Types of Traps


The most popular device used for acoustic testing in Saudi Aramco is the TrapmanTM. For those plants using the manual method, it is recommended to have at least two such working devices, with at least three engineers from the Utilities Division Division trained in its proper use. As an alternative to having in-house steam trap inspection and testing capability, it is possible to outsource this function. Both trap manufacturers and independent consulting firms offer offer a trap survey and reporting service. service. Although using an independent consulting consulting firm may cost cost more, it is the preferred option because their recommendations are more likely to be free of bias. If a number of traps are installed in close proximity (see Exhibit 4-8), acoustic testing is not reliable because the sonic signature of each trap cannot be easily isolated. In such cases, the thermal method should be used. 4.2.4

Conductivity Method

Conductivity-based diagnostics are based on the difference in electrical conductivity between steam and water. A conductivity probe could be integrated with the steam trap or inserted just upstream of the trap into a sensing chamber. Under normal operation, the tip of the probe is immersed in condensate. If the trap is either blowing or leaking excessively excessively steam will sweep sweep the condensate away and the measurement will show the value corresponding to water. Page 30 of 45



Exhibit 4-8 : Situation Where Acoustic Acoustic Testing Cannot be Used


Conductivity measurement must be accompanied by temperature measurement to ensure a correct diagnosis. For example, a false indication of trap failure could occur if the trap has not not been used recently and has filled with air. A low temperature measurement combined with low conductivity would therefore indicate air (requiring venting, at best), while a high temperature combined with low conductivity would indicate steam (and therefore trap failure). failure). Similarly high conductivity combined with high temperature would indicate the trap is working properly, but high conductivity combined with low temperature would indicate that the trap has waterlogged because (a) it has failed closed, (b) something has blocked the line, (c) it is undersized. Internal switches for various parameters must be set properly for each application to indicate failure accurately, eg.

A major advantage of conductivity method is that it puts out an unambiguous signal that can be interpreted without resorting to to experience or personal judgment. Also, it lends itself very easily to continuous remote monitoring, as described in the next section. Page 31 of 45



Exhibit 4-9: Conductivity-based Trap Sensors

Source: Spirax-Sarco bulletin SB-S34-01 MI issue 8 (2006)

4.2.5

Automatic Continuous Surveillance

Round-the-clock electronic surveillance based on conductivity measurement is the latest and most sophisticated approach to steam steam trap performance performance monitoring. It is recommended as Best Practice for large industrial plants with trap pop ulations of 500 or more. Automatic electronic surveillance systems are currently being offered by only two vendors – Armstrong, and Spirax-Sarco. Each takes a slightly different technical approach, but the basic concept is the same, as in Exhibit 4-10. The appropriate solution in terms of system selection depends on the application. Exhibit 4-10 : Automatic Conductivity-based Conductivity-based Trap Monitoring System


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The SpiratecTM R16C from Spirax-Sarco is a remotely mounted electronic scanner that can continuously monitor up to 16 steam traps fitted fitted with Spiratec R1C sensors. When all traps are working correctly, a single single green light will be illuminated. If one or more traps has failed, then the corresponding red or orange lights come come on, and the green light goes out. The unit can be interfaced with most plant DCS systems. Exhibit 4-11: SpiratecTM R16C Trap Monitor

Source: Spirax-Sarco bulletin SB-S34-01 MI issue 8 (2006)

Armstrong International has a similar system that can remotely monitor a virtually unlimited number of traps. It consists of transmitting data data via a radio-frequency signal from individual traps fitted with their SteamEye® (conductivity + ultrasonic+ temperature measurement) sensor to a receiving station that logs the information into a computer program (SteamStar TM). The software instantly generates the following reports through a web-based platform that makes it easily accessible to all authorized au thorized company personnel:

• • • • •

Executive summary Steam Loss report Defective Trap report Trap Evaluation by application Prioritized Maintenance Work Order

See Exhibits 4-12 through 4-14.

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Exhibit 4-12 : SteamEye® Sensor/Transmitter Sensor/Transmitter and SteamStar TM System

Source: Armstrong bulletin 300 (2005)

Within line-of-sight, the transmitter range is 400 yards, but when the signal must travel through walls or vessels, a more typical range is 100 yards. If the receiver is out of range of the transmitter, up to seven “repeating” stations can be used. Exhibit 4-13: Sample Transmitter/Repeater/Receiver Transmitter/Repeater/Receiver Layout for for Typical Plant

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Exhibit 4-14: Sample Reports from SteamStar SteamStar TM Software

4.2.6

Troubleshooting

Troubleshooting guidelines are provided in the literature available from trap manufacturers (see Appendices A & B). Occasionally, a non-performing trap that has been pulled out of service will be found to be fully operable upon mechanical examination. In such a case, case, the most likely cause of malfunction is misapplication, of which the following examples are the most common:

• • • • • • • •

4.3

Over-sizing. Match condensate load to trap size, and use a smaller trap. Freeze-proof Installation. Thermostatic and thermodynamic (disc-type) traps should be

installed in a self-draining configuration, thus making them freeze-proof in case of cold weather. Use a vacuum breaker if necessary necessary to ensure gravity flow. flow. Proper Direction. Sometimes traps may be installed backwards. Look for the arrow or in/out markings on the body of the trap, and install accordingly. Condensate Piping. Condensate discharge piping should be properly sized (Exhibit 4-15) and connected, to prevent submergence of heating surfaces. Gravity Flow. Slope the drainage line away from the equipment downwards to ensure gravity flow towards the trap. Short Drainage Legs. The shorter the length, the fewer the problems. of equipment with a single trap, Individual Traps. Do not try to drain more than one piece of as it is likely to short-circuit (one of the equipment will over-whelm the others). type and size is properly matched to the Incorrect trap type and size. Make sure the trap type actual condensate load profile, which may not be the same as the design assumptions.

Record Keeping and Reporting

Good record-keeping is essential. It is one thing to just inspect inspect traps, another to be able to determine costs, efficiencies, efficiencies, inefficiencies and trouble spots. spots. To begin with, traps should should be tagged, inventoried, and mapped with respect to geographical location. All too often, many Page 35 of 45



traps in a system are forgotten. A mapping and tagging system will assure that these traps are maintained. Exhibit 4-15 : Condensate Line Sizing Chart


There are many ways to systematize data and to keep records. The result should be useful records such as cost analysis of the work performed. Also, analytic ability is needed to determine the status of all the traps within a system including those failed, blocked, leaking, out of service or operating well. Rather than trying to "reinvent the wheel," wheel," take advantage of

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commercially available software packages that can help successfully implement a good steam management system. At a minimum every facility facility should maintain the following records: • List of Traps, with basic data • Inspection History Sample reports (in spreadsheet format) are presented in Exhibits 4-16 and 4-17. Commercial Steam Trap Management software basically shows the same information in alternative formats. Exhibit 4-16: Sample Steam Trap Status Report

4.4

Organizational and Management Issues

Steam trap management should be an integral part of the energy management function in all large industrial facilities with steam consumption of more more than 100 Klb/h. The recommended approach to trap management depends upon the trap population and geographical distribution (see Exhibit 4-18). The system consists not only of hardware (traps, instruments) but also software (computer programs, trained personnel, and management practices). practices). Management must fully support the program by committing adequate resources, including proper training for the responsible plant staff, and keeping an adequate inventory of spare parts and emergency replacement valves at the plant site. Otherwise the program will fail. The cost of trap inspection will obviously vary depending on trap type and method employed. Published figures for the USA indicate a range of $15-25 per test per trap [Ref. F. A Hooper and R. D Gillette, “Comparison of Three Preventive Maintenance Strategies for Steam Trap Systems” (1997), www.trapo.com www.trapo.com]. ].

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Exhibit 4-17: Sample Steam Trap Inspection Report

Exhibit 4-18: Recommended Steam Trap Management Strategies

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APPENDIX A Table of Contents “Steam Conservation Guidelines for Condensate Drainage”, Armstrong Intl Inc (1997) Available as free download from from www.armstrong.be/prod/traps/hb

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APPENDIX B Table of Contents “Design of Fluid Systems: Steam Utilization”, Spirax-Sarco Inc, (2004) Available as free download from www.spiraxsarco/us/navigation/register.asp

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APPENDIX C Steam Trap Testing Guide Excerpted from Armstrong Bulletin 310-C (2002)

Steam Trap Testing Procedure

CAUTION: Valves in steam lines should be opened or closed by authorized personnel only, following the correct procedure for specific system conditions. Always isolate steam trap from pressurized supply and return lines before opening for ins pection or repair. Isolate Isolat e strainer from pressurized system before opening to clean. Failure to follow correct procedures can result in system damage and possible bodily injury.

Tips on Listening (Acoustic method) –

1. Some flow noises are best picked up with high frequency electronic listening devices, but these devices are not sensitive to mechanical sounds. 2. Low frequency meters, stethoscopes or even screwdrivers can be used to detect mechanical sounds, for example: bucket dance, or the bubbling through the bucket vent. 3. Before purchasing a listening device, check it out on known conditions to see that it serves your purpose. 4. When checking traps on a manifold, be sure to check them all. A good trap can telegraph a bad trap’s signal. Check to see at which trap the signal is the loudest. That’s probably the faulty trap.

I. Inverted Bucket

1. If trap is cold, then: a. Is steam shut off? Yes, Yes, then turn on steam to check check trap. If still cold cold after allowing sufficient time for purging of initial air, shut off steam. b. Is there a plugged strainer up stream stream of trap? Yes, then clean strainer. If no plugged strainer, open trap. c. Is it over-pressured, orifice too large for applied differential? Yes, then replace mechanism with one for right pressure. d. Is bucket vent plugged? Yes, clean it. e. Is inlet or outlet plugged or mechanism mechanism jammed with dirt? Yes, then clean it. f. Is bucket bucket unhooked (worn mechanism) mechanism) ? Yes, then replace mechanism. 2. If trap is hot, then listen to it. a. Is it discharging discharging intermittently? Yes, then it is OK. b. Is it relatively quiet, so you can hear the steady “bubbling” through the bucket vent? Yes, then it is OK, light load.

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c. Does bubbling sound increase and decrease in a kind of “rolling” sound? Yes, then it is handling air. Check trap in an hour. If it is still handling air, replace the standard bucket with a thermic bucket. If air problem persists, replace inverted bucket trap with a float and thermostatic trap. d. Is it discharging steadily with with no bucket sound? Yes, then it is too small. Replace trap with larger one. e. Is it discharging steadily with with bucket dancing up and down? Yes, then then it has lost its prime. Close a valve upstream or downstream of trap for a few minutes and then re-open. If trap does not catch its prime, mechanism is worn (replace), or guide assembly is misaligned (align. See instructions.) Internal check valve on tube and coupling may be necessary to cure chronic prime loss. 3. If trap is capsule construction, construction, non-repairable, remove it from the line in case of any malfunction, and apply compressed air or a water stream to its outlet and then its inlet. If this does not correct the problem replace the trap. II. Float & Thermostatic Trap

1. If trap is cold, then: a. Is steam shut off? Yes, Yes, then turn on steam to check check trap. If still cold cold after allowing sufficient time for purging of initial air shut off steam. b. Is there a plugged strainer up stream stream of trap? Yes, then clean strainer. strainer. c. If no plugged plugged strainer, open trap. d. Is it over-pressured, orifice too large for applied differential? Yes, then replace mechanism with one for right pressure. e. Has thermostatic element failed shut? (Open trap at room temperature, thermostatic valve should be open.) Yes, then replace. f. Is float collapsed? Yes, then replace. g. Is float mechanism free free to move open and shut? No, then clean or ease binding parts of mechanism or replace mechanism. h. Is trap inlet or outlet plugged? Yes, then clean it. 2. If trap is hot, then listen to it. A float and thermostatic trap trap modulates to the load, so it discharges constantly. There is always flow if there is a condensate load. If the trap is passing p assing live steam, this not only adds to flow noise, but it also raises the pitch of the sound because of the higher velocity. If a valve upstream or downstream of the trap is closed for a few minutes there will be a back-up of condensate. When the valve is reopened, the float valve should move to wide open until the back-up condensate is clear. If the mechanism is OK, there should now be a reduction in noise. If the mechanism is faulty, live steam will be passed at this time, which can be detected by a higher pitch in the flow noise. 3. Is live steam discharge suspected? Yes, then shut off steam, allow trap to cool cool and open trap. a. Has thermostatic thermostatic element failed open? To check, remove element from trap and place in boiling water. It should close. Mounting the discharge connection of the element on the end of a tube permits blowing into the tube to see if the valve is shut. Page 42 of 45



b. Is foreign material in trap preventing preventing free operation of mechanism? Yes, then clean it. c. Is mechanism binding open or is valve not seating squarely on orifice? orifice? Yes, then ease binding parts, align mechanism, or replace mechanism. III. Disc Trap

1. If trap is cold, then: a. Is steam shut shut off? Yes, then turn on steam steam to check trap. If still cold after allowing sufficient time for purging of initial air, shut off steam. b. Is there a plugged strainer up stream stream of trap? Yes, then clean strainer. c. If no plugged plugged strainer, open trap. d. Is disc free to be lifted lifted from seats? No, then clean it so it is free. e. Is it plugged with dirt at inlet or outlet? Yes, then clean it. it. 2. If trap is hot, then listen to it: a. Is it discharging intermittently, intermittently, about six (6) time/min.? Yes, then it is OK. b. Is it discharging intermittently, intermittently, about twelve (12) times/minute times/minute or discharging steadily? Yes, then it is worn and wasting wasting excessive steam and should should be replaced OR it is too small and should be replaced by larger trap. (New trap of proper size will discharge intermittently intermittently about six (6) times/ minute.) minute.) Or there is excessive back pressure. 3. If a disc trap is connected into a return line, don’t check visually by discharging it to atmosphere through a test valve. This removes the back pressure, pressure, which can cause problems if it exceeds 50% of the inlet pressure. The temperature of the return line indicates its back pressure. IV. Thermostatic Trap

1. If trap is cold, then: a. Is steam shut shut off? Yes, then turn on steam steam to check trap. (Allow sufficient time time for purging of initial air.) If still cold, cold, shut off steam. b. Is there a plugged strainer strainer up stream stream of trap? Yes, then clean the strainer. strainer. c. If no plugged plugged strainer, open trap. d. Has thermostatic element failed shut (Valve should be open at room temperature)? Yes, then then replace it. e. Is it plugged at inlet or outlet? Yes, then clean it. it. 2. If trap is hot, then listen to it. a. Is it discharging intermittently? intermittently? Yes, then it is OK. b. Is it discharging constantly? constantly? Yes, then spray with water. (i) If it discharges more heavily briefly and shuts off, it is OK. (ii) If there is no change in sound — close a valve upstream or downstream downstream or a few minutes. A short time after reopening, is there there a sudden rise in pitch of the flow noise? If Yes, then trap has failed failed open. Shut off steam and allow to cool. Open it and clean it if dirt is preventing preventing proper functioning. If no dirt, remove element from trap and place in boiling water. It should close. Mounting the discharge discharge Page 43 of 45



connection of the element on the end of a tube permits blowing into the tube to see if the valve is shut. If No, then trap is too small. Replace with larger trap or add another of same size in parallel. 3. If trap is capsule construction, construction, non-repairable, remove it from the line in case of malfunction, and apply compressed air or a water stream to its outlet and then its inlet. If this does not correct the problem replace the trap. (Element must not experience more than 40 psi pressure when cold.) V. Sub-Cooling Trap

1. If trap is cold, then: a. Is steam shut shut off? Yes, then turn on steam steam to check trap. If still cold after allowing sufficient time for purging of initial air, shut off steam. b. Is there a plugged strainer strainer up stream stream of trap? Yes, then clean clean strainer. c. If no plugged plugged strainer, open trap. d. Is valve valve on seat at room temperature? Yes, then replace element. e. Is it plugged with dirt at inlet or outlet? outlet? Yes, then clean it. 2. If trap is hot, then observe observe trap discharge to atmosphere (This is the best way to check this trap). Is there live steam? IfIf Yes, then replace trap; if No, No, trap is OK. Traps on Superheated Steam

Do not use thermostatic or float and thermostatic traps, which employ balanced pressure bellows, where superheated steam will will contact the element. Inverted bucket traps can can be used successfully on superheated steam. steam. When functioning properly they will be at the saturation temperature of the pressure involved. If one fails open it will be at the superheat temperature. An inverted bucket trap on superheated steam is one of the few combinations that can be checked successfully by temperature alone. Testing Schedule

For maximum trap life and steam economy, a regular schedule should be set up for trap testing and preventative maintenance. Trap size, operating pressure and importance determine how frequently traps should be checked.

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APPENDIX D Internet Resource Directory Listed below are several useful web-sites from which much of the material in this BP manual was drawn: Steam Trap manufacturers www.spiraxsarco.com www.armstrong-intl.com or www.armintl.com or www.armintl.com www.yarway.com www.tlv.com www.gestra.com www.sterlco.com www.nicholsonsteamtrap.com www.trapbase.com www.trapo.com Others www.oit.doe.gov/bestpractices/steam www.eere.energy.gov www.etsu.com www.steamonline.com www.plantsupport.com

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SABP-A-007

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