HYDRO PNEUMATIC TESTING OF CRYOGENIC STORAGE … Rev 7 (3-5-13).pdf · hydro pneumatic testing of cryogenic storage tanks ... api 620 section 7.18.3, ... hydro pneumatic testing of

HYDRO PNEUMATIC TESTING OF CRYOGENIC STORAGE TANKS FOR GRANDE PRAIRIE, ALBERTA

Page 1 of 13 HTP Rev 7

Date: 3/5/2013

1.0 SCOPE OF STANDARD

1.1 This document describes the method and procedures to be applied in the hydro-pneumatic testing of a double walled tank with an enclosed inner tank. The testing shall be performed in accordance with this specification, API 620 Section 7.18.3, and API 620 Appendix Q Sections Q.6 and Q.7.

1.2 Supporting Documents (Download from BMT Document Website): 1.2.1 Drawing “A”: HTP Overview 1.2.2 Drawing “B”: HTP Equipment Connections 1.2.3 Drawing “C”: HTP Equipment B.O.M. 1.2.4 Drawing “D”: HTP Foundation Survey 1.2.5 HTP Supplement

2.0 CAUTION

2.1 During the pneumatic testing of the outer tank (section 8.3 this document, care needs to

be taken not to collapse the inner tank. Pressure must be equalized between the tanks during this operation in order to prevent such an occurrence.

3.0 SUMMARY OF TEST PROCEDURE

3.1 Combined Hydrostatic and Pneumatic Pressure Test of the Inner Tank

3.1.1 Water Fill Operation of Inner Tank (Section 7.4 this document) 3.1.2 Hydro-Pneumatic Pressure Test of Inner Tank (Section 7.5 this document) 3.1.3 Pneumatic Leak Test of Inner Tank (Section 7.6 this document)

3.2 Pneumatic Pressure / Partial Vacuum Test of Inner Tank 3.2.1 Pneumatic Pressure Test of Inner Tank (Sections 7.8.1-7.8.9 this document) 3.2.2 Partial Vacuum Test of Inner Tank (Sections 7.8.10-7.8.20 this document)

3.3 Final Pneumatic Test of Empty Inner Tank 3.3.1 Final Pneumatic Pressure Test of Empty Inner Tank (Section 7.9 this

document) 3.3.2 Final Pneumatic Leak Test of Empty Inner Tank (Section 7.10 this document)

3.4 Pneumatic Pressure / Partial Vacuum Test of the Outer Tank 3.4.1 Pneumatic Pressure Test of Outer Tank (Section 8.3 this document) 3.4.2 Pneumatic Leak Test of Outer Tank (Section 8.4 this document) 3.4.3 Outer Tank Emergency Pressure Relief Manway Test (Section 8.5 this

document) 3.4.4 Outer Tank Vacuum Test (Section 8.6 this document)



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4.0 PREPARATORY WORK

4.1 Prior to this test, all of the required radiographic and liquid penetrant inspection of welds and penetrations shall be completed and any necessary repairs made and re-inspected.

4.2 Reinforcing pads around penetrations, if provided, shall be tested with air pressure no

greater than 25 psig.

4.3 All welds that are required to be tested by a vacuum box procedure shall be leak checked, repaired and re-inspected as necessary, prior to this test.

4.4 The shell to bottom connection on the inner tank shall be leak checked by vacuum box

testing repair and re-tested as necessary.

4.5 Testing of the welds above the design high liquid level shall be performed in accordance with API 620 Q.6.2.5.

4.6 The inner tank anchors shall be attached to the inner tank during the hydrotest with the

tank full of water to the design liquid level, but before any pressure is added to the tank. (See ¶ 7.4.12) Attachment of the anchors shall occur prior to the introduction of pneumatic test pressure.

4.7 No connections of external piping systems or equipment to tank penetrations shall be

made other than those specifically required to perform this test

5.0 PREPARATIONS FOR TESTING

5.1 The tank shall be cleaned to remove any accumulation of loose debris.

5.2 Assemble the test equipment shown on Drawings B, and C

5.3 Determine that the air compressor to be used is clean and free of both carbon and oil in the discharge. Insert a new air filter in the compressor just prior to testing.

5.4 Water per the quality requirements of API 620 Q.6.3 shall be supplied by the owner /

purchaser at such a pressure and flow rate as to fill the tank in approximately 48 hours.

5.5 Ensure that any expansion bellows on pipe penetrations are free to move.



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6.0 PRECAUTIONS 6.1 Avoid introducing oil into either tank during the test by using oil-free filtered air. 6.2 Avoid hitting or striking the tank during the test.

6.3 Do not drain or add water from the tank unless, at least, the top manhole on the inner

tank is open, except when performing vacuum testing.

6.4 Monitor the U-tube manometer and gauges continually during testing because changes in tank pressure or partial vacuum will occur due to atmospheric changes.

6.5 The U-tube manometer shall be of sufficient size so that repeated renewal of liquid is not

required.

6.6 Under no circumstance shall the tank(s) be left unattended during testing.

6.7 If testing must be stopped or discontinued, the tank(s) shall be returned to atmospheric pressure.

6.8 If appreciable changes in shape occur during testing, the test shall immediately be

discontinued, and the Engineering department shall be contacted immediately. 7.0 COMBINED HYDROSTATIC AND PNEUMATIC PRESSURE TEST OF THE INNER

TANK

7.1 Close all openings in the inner tank except for the roof manhole at the top of the tank. Use blind flanges where permanent closures of test connections are not provided.

7.2 Valve off or blank off permanent gauges, breather valves, or any other permanent

fixtures which could be adversely affected by the test. 7.3 The outer tank shall be vented to the atmosphere during the inner tank hydro-pneumatic

test. 7.4 Water Fill Operation of Inner Tank

7.4.1 Make sure that the inner tank roof manhole at the top of the tank is open to the atmosphere during filling of the tank.



Date: 3/5/2013

7.4.2 Check and record the elevation of the bottom of the tank at eight (8) horizontally equidistant points prior to beginning the test. Mark these points for reference, as they will be used for additional measurements during the tank filling operation.

7.4.3 Introduce water into the tank through a bottom connection.

7.4.4 Elevation readings shall be taken and recorded at the same eight (8) points at

the bottom of the inner tank and on the tank foundation when the tank is 25% full, 50% full, 75% full and 100% full. Fill height information, in feet, is provided on drawing A.

7.4.5 Incremental water levels shall be checked though the roof manhole utilizing a

weighted line that has the fill level elevations and the elevation at the top of the roof manhole indelibly marked on them. The elevation to the top manhole shall be established on the weighted line before any filling operations begin by lowering the line to the bottom of the tank and marking this location on the line.

7.4.6 If differential settlement of the foundation takes place the following limitations shall apply:

7.4.6.1 Differential settlement across the foundation (tilt) not to exceed 0.75

inches.

7.4.6.2 Differential settlement around the periphery of the foundation not to exceed 0.375 inches in any 30 foot length of the circumference

7.4.7 If at any point these limitations are exceeded, the filling operation shall be

immediately terminated and the BMT Engineering Department shall be contacted to determine any further actions.

7.4.8 Once the test liquid level is reached as shown on Drawing A, close the fill

valve at the bottom of the tank. The test level as indicated on Drawing A must not be exceeded.

7.4.9 Examine the welds, closures, and valves to be certain that water cannot drain

from the tank. If water drains in this manner, a vacuum would occur on the tank which might lead to a tank collapse.



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7.4.10 Carefully inspect all of the welded seams in the tank shell, around all penetrations in the tank shell and bottom, and in all piping below the test liquid level.

7.4.11 At this point attach the inner tank anchors to the shell of the inner tank in

accordance with the tank construction drawings.

7.4.12 Once the anchors are attached, close the roof manhole and prepare for the pneumatic test of the inner tank.

7.5 Hydro-Pneumatic Pressure Test of Inner Tank

7.5.1 Keep the hydrostatic test water in the tank. 7.5.2 Close all valves and blind flange all connections in process pipe lines

connected to the inner tank. This shall include all bottom, shell, and roof connections.

7.5.3 Make sure that all tank pressure/vacuum relief devices are properly installed

and properly fixed or blinded.

7.5.4 Make sure that the diameter of the over pressure relief device either matches or exceeds the diameter of the pneumatic air inlet line.

7.5.5 Remove all personnel from the immediate area around the tank. Personnel

need to be at least 50 feet distance from the tank during this operation.

7.5.6 Make sure that all pressure reading devices, (gauges and U-tube manometers) as well as the over pressure relief device is both visible and monitored throughout the duration of this test. Visual monitoring is done with the aid of field glasses.

7.5.7 Start the air compressor and make sure to bleed off any moisture. 7.5.8 Air pressure shall be slowly added to the top of the inner tank until the

pressure in the vapor space is half (1/2) of the tank design pressure. (See drawing A for test pressure) At this point, the air supply lines shall be closed for ten (10) minutes. During this time the inner tank shall be monitored to verify that there is no pressure loss. (See paragraph 7.5.6 for monitoring)



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7.5.9 Any loss in pressure shall be investigated. Any necessary repairs to the tank or the test lines and connections shall be made per the instructions in paragraph 7.7 in this document. When all repairs are complete, the air pressure will again be raised to half (1/2) of the tank design pressure and monitored for the (10) minutes. This procedure shall be repeated until no pressure loss is observed. (See paragraph 7.5.6 .for monitoring)

7.5.10 Once the verification of pressure tightness is complete, air pressure shall be

slowly added to the top of the inner tank until the test pressure in the vapor space is 1.25 times the design pressure. (See drawing A for inner tank test design pressure) Any loss in pressure shall be investigated. Once the source of the pressure loss is identified, any necessary repairs to the tank or the test lines and connections shall be made per the instructions in section 7.7 in this document. This procedure shall be repeated until no pressure loss is observed. (See paragraph 7.5.6 for monitoring)

7.5.11 The tank shall be held at 1.25 times the design pressure for one (1) hour.

7.5.12 During the over pressure test no one is to be within 50 feet of the tank. 7.5.13 After completing the one (1) hour hold time, the pressure in the tank shall be

slowly released until the design pressure of the tank is reached. (See drawing A for the inner tank design pressure setting)

7.5.14 Once the internal pressure has been reduced to the design pressure of the tank,

the 50-foot rule no longer applies and personnel may work on or near the tank.

7.6 Pneumatic Leak Test of Inner Tank

7.6.1 While the inner tank is at the design pressure all welds above the high liquid level shall be inspected by the soap film method. The following welds that shall be tested by soap film method are:

7.6.1.1 All weld seams in the tank roof 7.6.1.2 Rim girder welds 7.6.1.3 Attachment welds of the rim girder to the tank shell and roof 7.6.1.4 All welds around penetrations in the tank roof 7.6.1.5 Piping joints that hold pressure that have not been previously tested 7.6.1.6 All shell weld seams above the water line.



Date: 3/5/2013

7.6.2 A solution such as Seamtest Concentrate or Snoop shall be used to test for leak detection.

7.6.3 Hold the tank at the design pressure and visually inspect all weld seams below

the water line for water tightness. These welds include tank shell welds, shell to bottom connection, pipe penetration welds into the tank, and any pipe weld joints.

7.6.4 If any repairs are necessary, they shall be performed in accordance with the

repair procedure outlined below.

7.6.5 Constantly monitor the pressure in the tank, making corrections, as necessary, for changes in the atmospheric pressure and temperature to make sure that there is not excess pressure built-up in the tank.

7.7 Repair Procedure for Inner Tank Welds

7.7.1 All repairs made to welded joints shall be made using an approved welding

procedure.

7.7.2 If cracks or leaks are discovered above the water line:

7.7.2.1 Relieve the air pressure in the tank. (Return to atmospheric pressure) 7.7.2.2 Make repairs in accordance with an appropriate approved welding

procedure.

7.7.3 If cracks or leaks are discovered below the water line:

7.7.3.1 Relieve the air pressure in the tank. (Return to atmospheric pressure) 7.7.3.2 Remove the roof manhole cover. 7.7.3.3 Drain the water to a level at least six (6) inches below the leak. 7.7.3.4 Make repairs in accordance with an appropriate approved welding

procedure.

7.8 Pneumatic Pressure / Partial Vacuum Test of Inner Tank (Only Required if the In-Service Pressure / Vacuum Relief Valves are Installed)

7.8.1 This test is a test of the set pressure for permanent pressure / vacuum relief

vents.



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7.8.2 The applied partial vacuum shall never exceed the design vacuum pressure of the tank. (See Drawing A for inner Tank design vacuum value)

7.8.3 Vent the outer tank to the atmosphere.

7.8.4 Verify that the permanent pressure / vacuum relief vents for the inner tank are

properly installed and that any isolation valves to these vents are locked open.

7.8.5 The pressure / vacuum relief vents for the inner tank should not allow the partial vacuum to reach the design vacuum pressure.

7.8.6 Verify that the line to be used to withdraw water from the tank for the partial

vacuum check is not larger than the vent opening. If a larger pipe is used for withdrawal of water verify that the planned discharge rate of water is within the flow capacity of the pressure vacuum relief vent.

7.8.7 Verify that all valves that could allow air to pass to the inner tank are closed,

except for the pressure / vacuum relief vent and the manometer used to monitor pressure and vacuum.

7.8.8 Confirm that the isolation valves to the pressure / vacuum relief vent and the

manometer are open by adding air pressure to the inner tank and recording the pressure at which the pressure relief vent opens. If the design pressure is reached and the vents have not opened stop pressurizing the inner tank and contact BMT Engineering immediately for proper action.

7.8.9 Return the tank to atmospheric pressure.

7.8.10 Apply a partial vacuum to the inner tank by slowly removing water from the

tank with all other connections blinded or valved off except for the pressure vacuum vents and the manometer.

7.8.11 The manometer operator shall verify that the partial vacuum never exceeds the

tanks design vacuum pressure setting. (See drawings A for inner tank design vacuum value)

7.8.12 The manometer operator shall have a means available to allow air into the

inner tank through a valve near the manometer. The manometer shall be manned at all times during the test and inspection to insure that the vacuum pressure in the tank does not exceed the design vacuum pressure.



Date: 3/5/2013

7.8.13 The pressure value at which the vacuum vent opens must be noted to check for proper functioning of the vent

7.8.14 Upon reaching the vacuum setting of the pressure vacuum vent maintain the

partial vacuum without exceeding the tanks design vacuum pressure.

7.8.15 Visually inspect the inner tank to determine if any appreciable changes in shape have occurred. Contact engineering immediately if the tank changes shape appreciably.

7.8.16 Upon verifying the vacuum set points of the pressure / vacuum relief valve

and the vacuum capacity (external pressure strength) of the inner tank, STOP withdrawing water from the tank.

7.8.17 Fully remove or lock the inner tank roof manhole cover fully open to fully

vent the inner tank to the atmosphere. Visually verify that the test water can be seen through this manhole to ensure that the correct roof manhole has been opened. Double check that this manhole is open and not restricted in any way.

7.8.18 Once the inner tank has been confirmed to be freely vented to the atmosphere,

resume discharging water from the inner tank to an area or other containment as designated by the owner.

7.8.19 Tank draining shall be stopped when approximately 2 vertical feet of water

remain in the inner tank.

7.8.20 The remaining water will be drained after the testing of the outer tank.

7.9 Final Pneumatic Pressure Test of Empty Inner Tank

7.9.1 After the tank is emptied of water and is at atmospheric pressure the inner tank anchors shall be visually rechecked for tightness to tank pad plates. Make sure that all connections to tank process lines have blind flanges installed or have the valves closed.

7.9.2 Make sure that the pressure / vacuum relief valves are free to operate and not

locked open/closed or otherwise prevented from operating.



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7.9.3 Remove all personnel from the immediate area around the tank. Personnel need to be at least 50 feet from the tank during this operation.

7.9.4 Make sure that all pressure reading devices, (gauge and / or U-tube

manometers) are visible and monitored throughout the duration of this test. Visual monitoring is done with the aid of field glasses.

7.9.5 Start the compressor and make sure to bleed off any moisture.

7.9.6 Air pressure shall be slowly added to the top of the inner tank until the

pressure in the tank is half (1/2) the tank design pressure. (See drawing A for inner tank design pressure) At this point, the air supply lines shall be closed for ten (10) minutes. During this time the inner tank shall be monitored for pressure loss. (See paragraph 7.9.4 for monitoring)

7.9.7 Any loss in pressure shall be checked, and any necessary repairs to the test

lines or connections shall be made. Any necessary repairs to the tank or the test lines and connections shall be made per the instructions in section 7.7 in this document.

7.9.8 Once the tank is confirmed to be pressure tight (no pressure fluctuations), the

air pressure shall be slowly raised to the design pressure. (See drawing A for inner tank design pressure)

7.9.9 Once the design pressure is reached, the air supply connection shall be closed.

7.9.10 After the air pressure has stabilized at the design pressure, the inspection

personnel can safely approach the tank. 7.9.11 The tank anchors and the bottom to shell connection shall be visually

examined at their attachment to the tank shell. If any defects are found the test pressure should be immediately reduced to atmospheric pressure and any necessary repairs per section 7.7 of this document. All repairs shall be re-inspected to the original specification requirements.

7.9.12 The tank shall be held at the design pressure as long as is necessary in order to

complete a close visual inspection on all tank seams and other field welds.



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7.10 Final Pneumatic Leak Test of Inner Tank

7.10.1 While the inner tank is at the design pressure all welds shall be inspected by the soap film method. The following welds that shall be tested by soap film method are:

7.10.1.1 All weld seams in the tank shell and roof 7.10.1.2 Rim girder welds 7.10.1.3 Attachment welds of the rim girder to the tank shell and roof 7.10.1.4 All welds around penetrations in the tank shell and roof 7.10.1.5 All field welded piping joints that hold pressure

7.10.2 A solution such as Seamtest Concentrate or Snoop shall be used to test for

leak detection. 7.10.3 If any repairs are necessary, they shall be made in accordance with the

applicable approved welding procedure. 7.10.4 In no case shall any repair be made on the inner tank while it is under

pressure. The inner tank shall be returned to atmospheric pressure before any repairs are made.

7.10.5 Should repairs be necessary, repairs shall be made in accordance with section

7.7 of this document and the inner tank shall be re-tested until it passes this inspection.

7.10.6 Monitor the inner tank test pressure during the inspection operation and make

any necessary corrections for changes in atmospheric pressure and temperature. Visual monitoring is done with the aid of field glasses.

7.10.7 Once all inspections are complete, the tank pressure in the inner tank shall be

reduced to match the internal design pressure of the outer tank. (See drawing A for the outer tank internal design pressure)

8.0 PNEUMATIC PRESSURE / PARTIAL VACUUM TEST OF THE OUTER TANK

8.1 All openings in the inner tank shell shall remain closed. The U-tube pressure manometer connected to the inner tank shall remain in place.

8.2 Confirm that the outer tank anchor straps are welded to the outer tank shell.



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8.3 Pneumatic Pressure Test of Outer Tank

8.3.1 Maintain pressure in the inner tank as established in paragraph 7.10.7

8.3.2 Connect the air pressure line to a connection in the outer tank.

8.3.3 Attach a U-tube pressure manometer to the outer tank.

8.3.4 Apply pressure slowly until the outer tank test pressure value is reached. (See drawing A for outer tank test pressure)

8.3.5 The U-tube manometer shall be used for measuring pressure during this test

8.3.6 At this time check the operation of the breather vent by slowly increasing the

pressure until the vent opens. (In no case shall the design pressure be exceeded.)

8.3.7 Confirm that the vent is operating properly by lowering the air pressure until

the vent re-seats.

8.3.8 The pressure shall be held steady for at least one (1) minute before checking for leaks.

8.4 Pneumatic Leak Test of Outer Tank

8.4.1 While the outer tank is at the design pressure all welds shall be inspected by

the soap film method. The following welds that shall be tested by soap film method are:

8.4.1.1 All weld seams in the tank shell and roof 8.4.1.2 Compression ring welds 8.4.1.3 Attachment welds of the rim girder to the tank shell and roof 8.4.1.4 All welds around penetrations in the tank shell and roof 8.4.1.5 Piping joints that hold pressure that have not been previously tested

8.4.2 A solution such as Seamtest Concentrate or Snoop shall be used to test for

leak detection. 8.4.3 If any repairs are necessary, they shall be made in accordance with section 7.7

of this document.



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8.4.4 In no case shall any repair be made on the outer tank while it is under pressure. The outer tank shall be returned to atmospheric pressure before any repairs are made.

8.4.5 Should repairs be necessary, the tanks shall be re-tested until it passes this

inspection. 8.4.6 Monitor the outer tank test pressure during the inspection operation and make

any necessary corrections for changes in atmospheric pressure and temperature.

8.5 Outer Tank Emergency Pressure Relief Manway Test

8.5.1 Introduce additional pressure into the tank until the emergency relief manway

opens. The U-tube manometer shall be used to monitor the pressure so that the design pressure of the outer tank is not exceeded. If the design pressure of the outer tank is reached and the emergency manway does not open stop the test, vent the outer tank to atmosphere and contact engineering for further instruction.

8.5.2 Once the emergency manway opens, slowly reduce the pressure in the outer

tank until the manway re-seats.

8.6 Outer Tank Vacuum Test

8.6.1 Remove any weights that may have been installed on the outer tank breather vent during the pneumatic test operation. Ensure free operation of all breather vents connected to the outer tank.

8.6.2 Close all openings in the outer tank except for the outer tank breather vent.

8.6.3 Use a fan or some other air moving device to check the vacuum relief vent.

The U-tube manometer shall be used to monitor the vacuum setting on the outer tank. In no case shall the design vacuum limit for the outer tank be exceeded. (See drawing A for outer tank vacuum limit)

8.6.4 When the vacuum setting for the breather vent is verified, return the outer tank

to atmospheric pressure. At this same time, any pressure remaining in the inner tank shall be released and the inner tank shall also be returned to atmospheric pressure.