Hydro Testing Strainers/Vessel

At 30 bar, the force on the blanking plate is a little over 240 tonnes.

If the rating is a little over 10 bar, the reason for testing to 30 bar remains a mystery. It is possible that such forces are causing distortions to materials, leading to leaks.

For 150 PSI and 30 Deg C the Max. allowable non shock pressure is 285 PSI. And hydro testing pressure is about 430 PSI. which is almost equal to 30 bar.. we need to test in this pressure.

Warning: I'm not familiar with AWWA specs. You've quoted the ANSI design. According to your original post, this is an AWWA Class B flange, not ANSI (ANSI Class 150 only goes to 24", I think). A quick web search tells me that AWWA Class B has an ambient rating of 86 psi. I'd recommend you confirm what you have and regroup.

Shock 285 PSI test at 430. Are you using the ASME design for test pressure? which by the way is no longer 1.5 but 1.3.

1.3 times the design pressure is the min hydrotest pressure shall be conducted acc to ASME. But this 1.5 times is specified by the client. There is no word stating that we should not use 1.5 times. Anyways thank u for your comment

OK. So it leaks. So it's no good. Redesign it.

The pressure rating maybe 150# but what is the design pressure for the item?

Whilst this is a piping item and I would expect ti to be good for the limit of 150# piping (ie 285psi) if you have specified a design pressure of say 5 barg (75 psig) then you only need to test to 6.5 barg

I'd also agree that ASME 150# only goes to 24" so you need to identify the flanges / connections that you are using and the hydrotest requirements that they impose.

AWWA Class B are described as 86psi pressure rating. If this follows the ASME limits then trying to guess what this means as an actual design pressure at ambient temp is a lottery. However if the Max Working Pressure = 86 psi then the test pressure would be 112 psig (7.7barg) and so its no surprise the thing leaked at 23barg.

Strainers are (to my mind) a grey area for pressure testing. Some like these are very large but can be designed to piping code which has a different test requirement to vessels designed to ASME VIII or its equivalents.

According to your statement there are no serration on flanges that is Non-confirmation. The serration plays big part in sealing a joint. There is group called joint integrity and they discuss lot of detail like yours. In my mind

you need to establish first the applicability of Code which it is AWWA, ASME Vessel code or ASME piping code.

The Codes varies in requirements for hydro testing. There are many factors I can think of which can result in

you situation. The serrations, the bolt tightening and tightening procedure, wrong thickness of flange, wrong grade of bolts , small scratch on sealing surface, wrong gasket and wrong test pressure all can contribute to the condition you have. Pardon me but I am not familiar with NCAF gasket, is this full face gasket or ring gasket?

I have seen Joint leak due to

1. Scratch in sealing surface

2. Bad tightening procedure

3. Wrong gasket

4. Wrong Hydro test pressure.

Good Luck....

Dear all,

Thank u for your valuable suggestions. I reconfirmed with my team and the flange is AWWA Class D (Which is not Awwa Cls B. Sorry for providing wrong data).

http://www.ade-v.com/PDF/%E6%A0%87%E5%87%86%E6%B3%95%E8%A7%84/AWWA%20C207-2001.pdf

Gives details on the AWWA flanges. In particular

1.3.2.2 .. Class D 150psi rated

1.3.2.5 Test pressure 125% of rating pressure

So for your Class D the test pressure is 187.5 psig (12.93 barg)

This would probably show where the leakage problem occurred.

I will though once again go back to my earlier comment and ask

What is the Design Pressure for this item as specified on the order data sheet?

What test pressure did the vendor state that they had used?

You have seen 150# assumed that this is ASME and then assumed it will be good for the maximum cold temperature of that pressure class. These are not unreasonable assumptions but in this case it looks as though there may be a serious flaw in the assumption.

Now I am NOT an expert in these flanges there are terms used which I feel are confusing / disingenuous. They use ASME bolt circles and terms from ASME like pressure ratings but it looks to me as though the pressure rating is an actual MAWP and not a classification.

THE OPERATING PRESSURE IS 4 BAR ONLY... BUT THE GOVT SECTORS HERE ALWAYS WANTED TO TEST IT IN ITS MAXIMUM... THOSE THINGS WILL BE CLEARLY STATED IN THE TENDER DOCUMENT AND U NEED TO ABIDE BY IT... AND ONE MORE THING, THE FLANGE RATING IS 150 PSI MEANS IT DOESNT STATE THAT THE MAX ALLOWABLE WORKING PRESSURE IS 150 PSI... AS I STATED ALREADY IT WILL BE HIGH.. AND IT DEPENDS ON THE TEMPERATURE..

THE PROBLEM IS SOLVED NOW WE EXPLAINED OUR SITUATION NOW AND THE HYDRO TEST PRESSURE IS NOW REDUCED TO 20 BAR... WE PASSED IT...

THANK U FOR YOUR VALUABLE SUGGESTIONS...

Since you're feeling so EMPHATICALLY high and mighty this morning, why not ENLIGHTEN us all on what the MAWP for a 40" AWWA Class D flange is. After all, you are the manufacturer of this strainer, surely you have the standards and codes that apply to your product at hand. I'm thinking if you were willing to LISTEN and LEARN, you would discover that ASME and AWWA are 2 different animals.

What is the MAWP (or allowable pressure at ambient temperature) of a 40" AWWA Class D flange, from the book?

No no and NO

The operating pressure is not relevant - it is the DESIGN pressure that is important in determining hydro test pressures.

Government sectors want to test it to the maximum - what does this mean? Are you suggesting that because a vessel has 150# flanges you can test it to 19.6barg. If you do that but the vessel is 3.5barg design pressure you are very likely to cause the vessel to fail. Either you do not understand the rules or they are poorly written

The commenters here are all well aware of the MAWP (Max Allowable Working Pressure) v temperature charts for ANSI 150# flanges / piping but as we have all stated AWWA Class D only states (in the on line documents that i have been able to find) a pressure rating of 150psig with no indication if this is a MAWP or what the MAWP is at various temperatures.

The vessel may have passed a test at 20barg but I feel that you still do not understand how these pressures are set and there may have been some damage to the strainer that you have not noticed.

Very thanks for your comment... Shall u pls explain hoe design pressure is fixed in a vessel??? Without relating to operating pressure can u able to calculate it??

It depends on the service for the vessel

The most common calculation for design pressure would be

Design Pressure = Maximum of:

1.1 * Max Operating Pressure

or Max Operating Pressure + 1 bar

or 3.5 barg

However common exceptions to this occur in pump and compressor circuits.

For a strainer in compressor suction the design pressure could be the 'settle out' pressure for the compressor circuit.

For a pump suction strainer the design pressure could be the same as the pump DISCHARGE design pressure (commonly the discharge design pressure is brought back to the suction isolation valve and so would include the suction strainer)

There can be many other cases in which the design pressure is related to an upset case and is designed to remove the need for a relief scenario for that upset case in which case the Dsign pressure will NOT be related to the operating pressure.

Even when it is relayed to the operating if there are several operating cases you need to be looking at the right case.

Thank u bigg!!! u gave me the answer to this... There is nothing to hide... the data available with me is very limited... from the drawing till the hydrotest pressure all were designed by the vendor..

I thought you were the vendor. What is your role in this fiascoproject?

And that is right and proper it is their equipment they should specify design pressure and hydrotest pressure.

But if the data they have given you is poor then that is the fault of whoever compiled the Purchase Order.

In my industry (Oil & Gas) that would be you as part of Engineering (E), Procurement (P) and Construction (C) the classic EPC contract. Clearly you have some involvement in C but the problems seem to be E & P.

I agree with the comments made by bigg but with the one caveat (worry, concern). The available AWWA data at which I have looked specifies a pressure rating at 150psig. The phrase for which I am searching is design pressure (or Max Allowable Working Pressure - MAWP. AWWA may use the phrases inter-changeably and bigg may have seen proper AWWA data instead of the excerpts which I have seen on line.

If the data that you have from the vendor does not include design pressure and hydrotest pressure then either

a) they have not supplied the paperwork required in the purchase order and you should withhold payment until it is received

b) the purchase order was written by a dangerous fool who should be removed immediately

Drawings, design pressure hydrotest pressures are critical and no purchase order that I have ever seen for process equipment would omit them.