API 610 (Hydrotest pressure concerns)

[Tilas]

Hi,

I am currently working on OH2 type pump that is in compliance with API 610 11th Edition.
Connection sizes are as follows : Suction : 6" /300lb/RF
Discharge : 4" /300lb/RF
Material of construction selected for this application is A351 CF8M.
I have a concern in terms of hydrotest pressure.
Now,with reference to API 610 11th Edn,6.3.5b)MAWP is equivalent to 40barg at 38 degC.In this regard,Hydrotest pressure should be equal to 1.5 times MAWP,that is 60 barg at 38 degC.
But when i referred to ASME B16.5 for flange fittings,in table 2.2.2,maximum working pressure for flange rating of 300 lb at 38 deg C is 49.6 bar

Having outlined that above,my question is
- Is it feasible to perform hydrotest at a pressure ( 60 barg ) in excess of max working pressure (49.6 barg) of flange fittings at the said temperature ?

Thanks for your reply in advance.

 

[zdas04]

Absolutely. Every hydro test is done at a multiple (more than 1.0) of MAWP. 150% is pretty common, so your 60 barg is right in there, and 62 wouldn't be unreasonable.

Just for your future reference, referring to "ASME B16.5 Class 300" flanges as "300 lb" has led to no end of confusion on this site and in the world. Calling it ANSI 300 class, while obsolete, causes less confusion. When you say "300 lb" most people flip that in their mind to "300 psi" which it certainly isn't. I've been doing this stuff for over 30 years and I kind of stumbled over the "300 lb" in your post even though I've been warning people about it for years.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist

 

[JJPellin]

The published data from one major US manufacturer of API pumps would allow a maximum hydrotest pressure for those flanges in cast carbon steel construction of 2000 psi at 100 °F or more than 137 barg at 38 °C. You are well below the maximum limit for hydrotest of these flanges. However, this same manufacturer sets the required hydrotest pressure as 1.5 times the maximum actual working pressure. Unless you expect the operating pressure to increase in the future, there may be little value in going higher than 1.5 times maximum actual working pressure. Testing to 1.5 times MAWP as Zdas04 suggested gives you the greatest flexibility in case of future changes that require higher pressure.

Johnny Pellin

 

[JJPellin]

I am sorry. I didn't notice your material of construction. For that material, ANSI would allow hydrotest to 75 barg. The above mentioned API pump manufacturer would allow hydrotest to 131 barg. The conclusion is the same. You are well within acceptable limits at the planned test pressure.

Johnny Pellin