Reliance 1.0 Introduction Reliance has executed large number of tankages at various sites and more numbers of tanks are also under construction as per API 650/620. These tanks are constructed by various reputed tank manufacturers at sites. All the tanks are tested as per API standards and based on the procedures submitted by the contractors. As per that partial vacuum testing of fixed roof tank is the most critical one. Partial vacuum testing is carried out to check the ability of the upper part of the tank to withstand the partial vacuum for which it is designed and also to check the operation of the vacuum relief valve on the tank. It is felt for critical test like vacuum testing of fixed roof tanks a procedure shall be developed.
2.0 Purpose Purpose of this procedure is to have a uniform approach at all reliance sites and at the same time as guidance to our engineers.
3.0 Scope Scope of this procedure is limited to partial vacuum testing of fixed roof tanks as per API 650/620. These tests shall be carried out if the design drawings mention the same. The test pressure shall be mentioned by the designer.
Reliance API – American Petroleum Institute QMD – Quality Management Department PSI
– Pounds per Square Inch
5.0 Responsibility and Authority Respective area construction manager is responsible to implement this procedure at his area of working.
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HOD of QMD is responsible for maintaining this procedure.
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6.0 Reference documents API 650 – Welded Steel tanks for Oil storage (clause no.5.2.5) API 620 – Welded large low-pressure storage tanks (clause no.5.10.5.2 & 7.18.5) 2QM00 JEP ME 001
– Procedure for Pressure testing of API tanks
2QM00 ITP ME 050
– Inspection and Test plan for Storage tanks
7.0
Procedure - Vacuum testing
7.1
After completion of the pneumatic testing of the roof, water filled up to the tank shall be maintained at the design liquid level of the tank.
7.2
All roof appurtenances shall be blinded.
7.3
A vacuum relief valve shall be provided on one of the nozzle with the required rating.
7.4
In addition to a vacuum relief valve a quick opening valve shall also be provided at the ground level with proper piping from the roof top.
7.5
Provide a valve on the shell nozzle for draining of the water which will create the sufficient vacuum.
7.6
Provide Manometer 2 nos. at the ground level with sufficient tubing from the roof top on different roof nozzles.
Check all the arrangements have been made as given above.
7.8
Slowly open a valve provided on one of the shell nozzle to drain the water.
7.9
Observe the manometer so that required level difference is achieved which indicates the vacuum test pressure inside the tank.
7.10 During draining if any distortion of the shape is observed then the quick opening valve shall be opened to break the vacuum. 7.11 Stop the draining valve at the required vacuum (manometer reading) and observe the roof surface for any distortion. 7.12 After inspection of the surface all roof nozzles shall be opened immediately to break the vacuum created inside the tank. 7.13 After the above testing one more vacuum testing shall be carried out if it is required as per tank data sheet with the water level at the bottom when the tank is substantially empty as given below. i)
After the initial vacuum testing with the water level at the design liquid height, water shall be drained out with the roof nozzles in the open condition.
ii)
When the water level goes below more than half of the tank height stop further draining.
iii)
Close all the roof nozzles and provide relief valves, quick opening valves and manometer as explained in 7.2 to 7.7.
iv)
Check all arrangements.
v)
Start draining from the shell nozzle slowly until the required vacuum is created inside the tank.
vi)
Stop further draining and inspect for any distortions on the shell or roof surface.
vii)
After inspection of the surface all roof nozzles shall be opened immediately to break the vacuum created inside the tank.
7.14 Final visual inspection shall be carried out for any distortions on the shell or roof after opening all nozzles and the pressure is released.
Reliance 7.15 In the case of low pressure storage tanks as per API 620 appendix Q and R the opening pressure or vacuum of the pressure relief and vacuum relief valves shall be checked by pumping air above the water level and releasing the pressure, then partially withdrawing water from the tank. 7.16 Precaution shall be taken to ensure the partial vacuum in the tank should never exceed the design value.
8.0 Record Record all test details in the vacuum test format EPCMD-2-QM-00-FMT-ME228.
9.0 Attachments Typical testing arrangements shown as per the annexure-1.
