Air Testing of Storage Tanks to Annex F.4.4

[AK8824]

I have a question about Air Testing of storage tanks. API 650 Annex F.4.4 calls for testing of vents during or after the Air Test. See extract below:

F.4.4 When the entire tank is completed, it shall be filled with water to the top angle or the design liquid level, and the design internal air pressure shall be applied to the enclosed space above the water level and held for 15 minutes. The air pressure shall then be reduced to one-half the design pressure, and all welded joints above the liquid level shall be checked for leaks by means of a soap film, linseed oil, or another suitable material. Tank vents shall be tested during
or after this test.

Pressure and Vacuum Relief Valves and Emergency vents have set pressures lower than the test pressure. If you want to test the vents during Air Test then you will have problems. The valves would open before you can reach the test pressure. Probably you can test the PVRV and then remove it (blind the nozzle) and then raise the pressure to go to set point of EV and ten remove EV and blind it and then go up to the tank test pressure. Is that how you do?

 

[Roberto1956]

I would say OK if necessary to reach the pressure on shell, shell with botton and so on. Only to check the welding and ANYPOINT that receive a welding heat I prefer the negative air test. This test develop a higher differential pressure than the positive air test. It is safe for everybody. The corner or other parts very dificult to do the negative air test I do the capilarity test with dye penetrant applied at the inner part of the tank and the developer spray at outside 24 hors after. What I am saying is basic, so it would be necessary to issue a procedure before to perform these tests.

 

[Duwe6]

You need the weight of the water to keep the flat floor from bulging and possibly failing catastrophically. To go with penumatic only, the tank needs to be anchored to its foundation, OR braced internally [typically permanent member(s), OR braced externally [typically removable]. And this bracing needs to be calculated.

Much simpler and safer to fill at least 3/4 full and add air pressure to achieve the required test pressure.

 

[AK8824]

Duwe6,

Anchors are not required in my case. The question is about the practice. How do you comply with API 650 F.4.4 in terms of testing the vents. API states- Tank vents shall be tested during or after this test.

Do you test the vets?
Do you test them during the Air Test
Do you test them after the Air Test?
I understand that the Emergency Vent and PVRV will come tested from shop.

Thanks.

Ashok

 

[Duwe6]

My 'read' of F.4.4 is for vents that are site-fabricated, not Pressure/Vacuum Relieving Devices. The devices come tested & certified from the mfr*, so further testing in not needed. Your only requirement is to fully test the nozzles [and manway] that your 'factory' devices will bolt up to.

*this assumes that these devices are from a reputable company and are intended for, and certified for, tank venting. My favorite mfr's are Protectoseal, Shand & Jurs, and Groth. [and yes, these are all North American companies; my experience isn't all that wide]

 

[monirri]

Hi. Does anyone have a procedure on air testing? do you use water venturi? Thanks

Carlos Molina from

http://www.apiexam.com