Valve pressure test fluid 5

[KM0818]

Hi. We are purchasing high pressure valves and setting up test equipment to verify valve test performance based on the methods of ASME B16.34.

My question is about the test fluid. The specification and similar specifications call for the tests to be done with water, which may include a corrosion inhibitor, with kerosene, or with another suitable fluid with viscosity not greater than that of water.

Can anyone explain or clarify for me? Why is kerosene allowable, while its viscosity may be substantially greater than that of water, but no other fluid with viscosity greater than that of water is allowed? I have researched a little and I see some test fluids are rated for "penetration capability", which may not be well correlated with viscosity, so this may be the reason, but I am not sure.

Are any other fluids typically used?

Thanks.

 

[gerhardl]

A general answer, as I am most familiar with European tests and descriptions:

1. No: a certification according to a test is a certification according to a test.

Two exceptions:

a) the end users allows or specify exception, which is highly unlikely (the test is then not valid as such for other parties)

or

b) The issuer (owner) of the test description says otherwise.

Answers for both a and b will lead you into a loop:If this exception is (generally) included in the test description go to 1, if not go to same answer / reason as under point a).

It is completely another question if the description is practical, complete, or ripe to be revised because of this or of other reasons.

 

[KM0818]

Thanks, gerhardl.

Although we are not certifying to the ASME spec and not asking the supplier to do so, we intend to follow it almost exactly. So, from my perspective, I agree with your comments. I won't make an exception unless I can find a strong justification to do so, which I don't have right now. I have to assume the ASME requirement is written that way for a reason. If I don't know the reason, I don't want to take the chance of straying from the requirements.

Even as a matter of education for myself, I would like to know why there "seems to be" a contradiction in the viscosity requirements for kerosene vs. other fluids. But there may be a very good reason for it and may not be a contradiction at all.

 

[bcd]

Consider that the first valve testing standards were written many years ago. Before most of use were born. The most commonly available fluid with a viscosity close to water was Kerosene. Yes it's viscosity is higher than water, but not so much to invalidate leak test results.

Why Kerosene, if you use untreated water to test carbon steel valves, inevitably, some water gets trapped within crevices inside the valve and can rust and damage critical sealing surfaces or lock the valve shut. If the water is very unsanitary, you can also initiate microbiological induced corrosion (MIC). So Kerosene was used.

Other petroleum products that happen to have a viscosity less than water are not safe to use for testing (e.g., gasoline). Not that Kerosene is that safe either.

I haven't seen anyone use Kerosene for valve testing during the last 30 years. Nearly everyone uses air or treated water.

The requirement for viscosity less than water is so micro-porosity through the wall will not be plugged by the viscous fluid. That is why gas is the most discerning test fluid, but the explosive behavior of a sudden failure makes it undesireable.

 

[KM0818]

bcd, thank you.

You have described well the situation we face.We don't want to use kerosene for safety reasons. Someone we contracted set up some testing for us with water with a corrosion inhibitor, but they were complaining about the odor of the parts after they sit on the shelf for a while, and so wanted to switch to another fluid. We have been considering treating the water to prevent this and have asked them to do so. We are just being careful about it and trying not to stray from the requirements.

Thanks again.