No it is not allowed. Ctrl + F your API 598, looking for 'soap' and 'test fluid' you'll find out why.
Para 5.6. Test Fluid ....liquid viscosity is not higher than water....
Para 6.4.4 ...soap or similar solution does not constitute an acceptable low pressure closure test..
My personal view:
- Snoop is a trademark, so far I hardly see any trademark name e.g. snoop, Stellite, Teflon, etc. in any standards. So soap solution cannot be standardized.
- viscosity of soap is higher than water, hence not according to the statement above within 598. Imagine a very small leakage, and bubble solution is very thick even with the size of a palm it won't break. It's leaking for sure, but the size of the bubble cannot be justified.
- Snoop is only for leak indication, never seen one does it for quantitative measurement.
- Leak rate unit in 598 is volume/time or bubble/time. Having said that, applying snoop on a surface already have bubbly result. No clear preference.
Thank you for your response. Let me rephrase my question with more info.
Can we use soap solution for leak test (by spraying the other side of the valve)? Blind flange installed on one end where Nitrogen is introduced and then pressurized it @72.5psi.
The requirement is no leaks and we are not counting bubbles.
Let me rephrase my answer and interpretation over your question. But first allow me to synchronize common terms used, so we could have the same understanding:
a. Seat/side A is upstream side = side where source of pressure (in your case: nitrogen) is being applied
b. Seat/side B is downstream side = in closure test condition, this side should be pressure-less. An observation side for internal leakage. Normative, there should be nothing between obturator (ball/wedge/plug) and test fluid
c. Closure test = seat test = internal leakage test when valve in fully close position.
d. Test flange = a flange with nipple (usually threaded) hole. Function for nipple connection (hose/tubing)to 'safe location' medium.
e. Blind flange = a solid flange without hole (aside from bolting connection).
b. Test medium = any medium (liquid) which are defined by API 598 or have similar or smaller viscosity shall compared to water. Or gas e.g. nitrogen, air, helium
c. No visual leakage = for gas testing meaning no bubble visually seen (not even one bubble). for water meaning no water drop whatsoever.
d. How to apply test pressure? pressurized side A up to designated pressure, and after stabilized > close the regulator/valve from accumulator vessel and/or shut off the (booster) pump.
Now to your case:
You will apply 72.5 psi on side A presumably using direct a test flange connected to nitrogen bottle, valve in fully close position. However for some reason, on the other side you will apply Blind flange connected to side B flange (presumably with a proper gasket) > And will perform snoop method on this gasket circumferential?This is not allowed.
Soap should only be used for shell/body test, in addition with pressure drop noticed on the pressure gauge (located after pressure source). And also for leak detection for small tightened-able location e.g. nipple connection, flanges connection, etc. But not for seat leak.
Standard seat leakage is either bubble or water drop, and always quantitative. Hence it is impossible to do this with bubbly snoop/soap solution. Plus your method has one major flaw: any leakage will be 'stopped' by the gasket first before noticeable visually.
I only assume some situation restrict you from using a test flange (flange with a hole), what I usually did in the past in such circumstances is flip the valve, stem horizontal, side A facing below connected to nitrogen, side B facing up without flange. Apply pressure on side A, pour water on side B. Observe bubble on water pool B.
Still not doable, then drill your blind flange, install a straw, connect the straw to a glass of water. After usage, weld the hole again.
Thank You for this info and terminologies.
This is a closure test with test flange connected to nitrogen bottle on side A and no blind flange on side B.
We spray soap solution directly to side B and check if there's leak on the closure.
Can you use soap solution to check for leakage during a closure test? Answer is yes, but if it is a metal seat, you are not able to compare to the allowable bubbles in an air test of metal seated valves in the API 598 Table.
Does API 598 prohibit you from doing this? Answer is no unless it is a gate valve and you are trapping air between the seats and using soap solution to check for leaks. API 598 prohibits this in paragraph 6.4.4
Last part. Should you use Snoop to check for seat leaks during a closure test of any valve? Answer is no. Snoop is intended to be used to check for leaks in static joints. Threaded or compression fittings on gas lines for example. Snoop and other brands of soap solution are highly discerning and can report very small leaks that would not normally be observed in a closure test using air and looking for bubbles in water. The valve closure element and seat are dynamic seals that are intended to move relative to each other. You should not be using high sensitivity leak detection fluids intended for static joints unless you want to cause yourself unnecessary aggravation.
