34-SAMSS-318

Materials Syste Syst em Specif pecific ica ati tion on 34-SAMSS-318

19 October 2005

Automatic Tank Tank Gauging Equipment Instrumentation Standards Committee Members Al-Awami. L.H., Chairman Tuin, R.R., Vice Chairman Al-Dakhil, T.K. Al-Dhafeeri, F.T. Al-Khalifa, A.H. Al-Madhi, F.A. Alqaffas, S.A. Bogusz, Z.J. Ell, S.T. Fadley, G.L. Falkenberg, A.R. Gawargy, N.E. Grainger, J.F. Jumah, Y.A. Mahmood, B. Qarni, M.A. Trembley, R.J.

Saudi Saudi Aramco Aramc o Desk DeskTop Top Standards Standards Table of Contents

1 2 3 4 5 6 7 8 9 10

Previous Issue: 31 December 2002

Scope............................. Scope.......................................... ........................... ................... ..... 2 Conflicts and Deviations.......................... Deviations................................. ....... 2 References............................. References................ .......................... ........................ ........... 2 Environmental Conditions........................... Conditions.............................. ... 3 Level Gauge Design........................... Design....................................... ............ 3 Temperature System.......................... System...................................... ............ 5 Performance Characteristics................ Characteristics.......................... .......... 5 Remote Receiving Equipment........................ Equipment........................ 6 Electrical Requirements.............. Requirements............................ ................... ..... 6 Inspection and Testing........................... Testing................................... ........ 6

Next Planned Update: 1 June June 2010 Page 1 of 7

Primary contact: James L. Sprague on 874-6414

Copyright©Saudi Aramco 2009. All rights reserved.

Document Responsibility: Instrumentation Issue Date: 19 October 2005 Next Planned Update: 1 June 2010

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34-SAMSS-318 Automatic Tank Gauging Equipment

Scope This specification defines the requirements for Automatic Tank Gauging Equipment using either one of the following principles: 1)

Float type, spring motor driven

2)

Displacer type, servomotor driven.

Excluded from this specification are all other types of level instruments.

2

3

Conflict s and Deviations 2.1

Any conflicts between this specification and other applicable Saudi Aramco Materials System Specifications (SAMSSs), Engineering Standards (SAESs), Standard Drawings (SASDs), or industry standards, codes, and forms shall be resolved in writing by the Company or Buyer Representative through the Manager, Process and Control Systems Department of Saud i Aramco, Dhahran.

2.2

Direct all requests to deviate from this specification in writing to the Company or Buyer Representative, who shall follow internal company procedure SAEP-302 and forward such requests to the Manager, Process and Control Systems Department of Saudi Aramco, Dhahran.

References References noted below are a part of this SAMSS and shall be per a specific edition or the latest edition whichever is specified. 3.1

Saudi Aramco Reference Saudi Aramco Engineering Procedure SAEP-302

3.2

Instructions for Obtaining a Waiver of a Mandatory Saudi Aramco Engineering Requirement

Industry Codes and Standards American Petroleum Institute API BULL 2509B

Shop Testing of Automatic Liquid Level Gauges

API MPMS 7.1

Static Temperature Determination Using Mercury-in-Glass Tank Thermometer

National Fire Protection Association NFPA 70

National Electrical Code Page 2 of 7



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Environmental Condition s 4.1

Temperature Instruments and control systems shall operate continuously under the following ambient air temperatures without any degradation of the manufacturer's guaranteed performance: Indoor Air Conditioned (2) 35°C (95°F) 10°C (50°F)

Maximum Minimum

Outdoor Sheltered (1)(2)(3) 55°C (131°F) 0°C (32°F)

Outdoor Unsheltered (2)(3) 65°C (149°F) 0°C (32°F)

Notes:

4.2

1)

"Sheltered" refers to permanent, ventilated enclosures or buildings, or permanently fixed sunshades with a top and three sides.

2)

For instruments which dissipate internal heat and are installed in custom engineered enclosures (e.g., enclosures not included in the original manufacturer's temperature certification), an additional 15°C shall be added to the above maximum temperatures. An example, for "indoor air conditioned" installation, the equipment must perform at 35 + 15 = 50°C. Similarly, for the "outdoor unsheltered" case, the equipment shall be designed for a maximum operating temperature of 65 + 15 = 80°C.

3)

For the outdoor installations only, the designer can take credit for forced or passive cooling to eliminate or reduce the 15°C heat rise. For example, if vortex coolers are used, the heat removal capacity of the coolers may be subtracted from the generated heat. No more than 15°C reduction in temperature will be given as credit. The designer shall substantiate his claim by providing the support data and calculations.

Humidity Indoor humidity design basis shall be 20% to 80% relative humidity. Outdoor design basis shall be 5% to 95% relative humidity (non-condensing).

4.3

5

Unless otherwise specified, field device LAN data concentrators, modems, operator workstations and associated peripheral equipment shall be installed in air-conditioned buildings.

Level Gauge Desig n 5.1

Float Type, Spring Motor Driven 5.1.1

Float shall be guided to allow only vertical displacement.

5.1.2

The gauge shall be provided with a built-in digital level indicator.

5.1.3

Float type gauges shall be provided with built-in operational checking capability to allow manual rotation of the tape storage drum to raise and release the float a short distance, 25 mm minimum, in order to check the system for repeatability. Page 3 of 7



5.2


5.1.4

A hand crank for manual lifting of the float to the top position shall be provided.

5.1.5

In floating roof tank installations, the tape shall not be exposed outside the gauge pipework.

5.1.6

The gauge system shall be designed to prevent damage to the spring motor, due to rapid coiling as a result of tape or wire breakage.

5.1.7

Digital encoders shall be optical type. Brush type digital encoders shall not be used.

Displacer Type, Servomotor Driven 5.2.1

The motor control system shall be provided with an adjustable turbulence integration circuit.

5.2.2

The remote indicator shall incorporate a warning device or blinding mechanism to indicate measurement error or to prevent wrong level readout in case of power supply failure. On power restoration, the gauge shall return to read the liquid level with no loss of electrical or mechanical calibration.

5.2.3

The automatic level gauge shall incorporate a built-in local digital level indicator, mechanically driven by the servomotor.

5.2.4

Displacer type automatic tank gauges shall be provided with two motor limit switches internally wired to the servomotor control circuit in order to limit the travel of the displacer in both directions.

5.2.5

The servomotor system shall be provided with a circuit to enable remote raising of the displacer for repeatability checks and for lifting of the displacer to the top position for maintenance, calibration, or removal.

5.2.6

For top mounted gauges, the gauge enclosure shall be two separate compartments, the measuring drum compartment, and the electrical equipment compartment. These compartments shall be sealed from each other.

5.2.7

Flame arrestor type shaft sealing is acceptable on floating roof tank installations which require vented gauges.

5.2.8

Displacer sizing shall be the responsibility of the manufacturer.

5.2.9

Digital encoders shall be optical type. Brush type digital encoders shall not be used. Page 4 of 7




5.2.10 On low temperature applications, -7°C and below, the vendor shall provide temperature compensation.

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Temperature System 6.1

Spot and averaging temperature elements shall be resistance temperature detectors (RTD) rated, 100 ohms at 25°C (+77°F). The RTD system measurement accuracy shall be ± 0.5°C (± 1.0°F) or better. RTD element configuration, thermowell material, and dimensions shall be as specified on the ISS.

6.2

Averaging temperature elements shall include a specified number of RTD elements of graduated lengths housed in a common flexible metal thermowell. The system shall conform to API MPMS 7.1.

6.3

The temperature conversion shall be performed by means of a solid state analog to digital converter. Null balance servo operated bridges are not acceptable. The digital coded temperature signal should be transmitted to the remote receiving equipment over the same transmission circuits as the level measurement signals.

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Perform ance Characteristics 7.1

7.2

Float Type, Spring Motor Driven 7.1.1

The automatic tank level gauge and associated transmission system shall be such that the control room indication has an installed accuracy equal to or less than 1.6 mm from the actual level in the tank.

7.1.2

Local level indicator incorporated in the transmitter shall have the same accuracy, i.e., equal to or less than 1.6 mm.

7.1.3

Level alarm switches shall be field adjustable.

Displacer Type, Servomotor Driven 7.2.1

The automatic tank level gauge and associated transmission system shall be such that the remote indication has an absolute system accuracy equal to or less than ± {0.03 + 0.0014L(f)} inches, where L(f) is the level range in feet, or ± {0.7 + 0.11 L(m)} mm, where L(m) is the level range in meters. This accuracy shall be referred to a standard displacer size. The standard displacer shall be the largest standard size that will minimize errors caused by changes in relative density of a standard

Page 5 of 7




liquid. It shall be a referenced to a standard liquid with a relative density of 0.8.

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10

7.2.2

The local level indicator incorporated in the transmitter shall have an accuracy equal to or less than 1 mm.

7.2.3

Level alarm switches shall be field adjustable.

7.2.4

Wave integration time, i.e., time to inhibit the servomotor response to transient level fluctuations, shall be adjustable between a minimum range of 2 to 10 seconds.

7.2.5

Displacer vertical speed shall be 5 mm/s.

Remot e Receivi ng Equipm ent 8.1

The display shall be digital with adequate digits to provide the specified level measurement range and accuracy.

8.2

The system shall have a self-diagnostic capability to indicate a fault or a failure in the system.

Electri cal Requirements 9.1

Field mounted transmitters and associated digital encoders, temperature converters, multiple RTD selectors, and related equipment shall be powered from remote receiving tank gauging equipment without requirement for separate power supply connections in the field. Motive power for servo type gauges may be supplied locally. No data transmission shall be powered from this local power source.

9.2

All components installed in the tank or in contact with the process shall be grounded to the gauge housing.

9.3

All system wiring shall meet the requirements of NFPA 70, National Electrical Code (NEC).

9.4

A local isolation switch shall be provided at the gauge head to interrupt all power for maintenance and servicing.

Inspection and Testi ng 10.1

Floats shall be leak tested at 1.5 times the maximum absolute operating pressure for 5 minutes.

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10.2


Tank gauges shall be tested for the following requirements, as applicable: a)

Level and temperature transmission accuracy.

b)

Local level readout accuracy.

c)

Level alarm switches for proper operation.

d)

Level measurement immunity to liquid specific gravity variations.

e)

Wave integration time adjustment (immunity to liquid turbulence).

f)

Multi-element temperature switching operation.

g)

Temperature A/D conversion accuracy.

h)

Servomotor speed.

i)

Repeatability check: Manual or servomotor lifting of level sensor and subsequent release to obtain the same level measurement.

j)

Requirements per API BULL 2509B: "Shop Testing of Automatic Liquid Level Gauges".

Control room multiple tank systems and individual units shall be subject to a complete functional test in accordance with requirements in this SAMSS and any additional requirements specified in the Purchase Order.

19 October 2005

Revision Summary Revised the "Next Planned Update". Reaffirmed the contents of the document, and reissued with no other changes.

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34-SAMSS-318

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