quizzical1
Mechanical
Hi All,
Is there a best practice for testing 100% of the machined castings.
Is there a best practice for testing 100% of the machined castings.
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Hydrotesting methods for production valve castings...
- Thread starter quizzical1
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The Obturator
Mechanical
What castings?
What specifications?
What pressures and why?
etc.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
What specifications?
What pressures and why?
etc.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
- Thread starter
- #3
quizzical1
Mechanical
Bronze castings Class 125 to 400 psig (2X the 100F rating of 200 psig)
Checking for porosity issues.
Checking for porosity issues.
The Obturator
Mechanical
OK Good. Getting closer.
Are these body castings valves and/or pressure containing? For what industry/use?
Where have you got 2x from?
What grade of Bronze do you have
ASME B16.34 (2019) Section 7.0 Gives some guidance. Typically hydro test is x1.5 of the flange rating for a specific material grade also published in this standard. I attach a section of Part 7 for you to see if we're heading in the right direction..
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
Are these body castings valves and/or pressure containing? For what industry/use?
Where have you got 2x from?
What grade of Bronze do you have
ASME B16.34 (2019) Section 7.0 Gives some guidance. Typically hydro test is x1.5 of the flange rating for a specific material grade also published in this standard. I attach a section of Part 7 for you to see if we're heading in the right direction..
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
TugboatEng
Marine/Ocean
Don't forget to use hollow fasteners for testing, the porosity can often be in the bolt holes.
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- #6
quizzical1
Mechanical
Thanks guys!
Are these body castings valves and/or pressure containing? Yes, containing water
For what industry/use? Plumbing NSF rated
Where have you got 2x from? ASME B16.15
What grade of Bronze do you have - CDA87500
Are these body castings valves and/or pressure containing? Yes, containing water
For what industry/use? Plumbing NSF rated
Where have you got 2x from? ASME B16.15
What grade of Bronze do you have - CDA87500
The Obturator
Mechanical
ASME B16.15 does not require pressure testing of fittings, but states that if required it shall be done at 2x the pressure rating, as indicated by you. The hold pressure of the test fluid is 1 minute. There is no wording of what the test fluid is or for that matter, no mention of hydrostatic testing (at least not in the 2006 revision of the standard I am reading).
I guess that you are concerned about porosity and want to conduct hydrostatic testing on these individual fittings, rather than later when tested as a component in a complete system under test? Is that correct? All specs indicating pressure testing just give the main parameters not the methods, which would normally be unique to the manufacturer.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
I guess that you are concerned about porosity and want to conduct hydrostatic testing on these individual fittings, rather than later when tested as a component in a complete system under test? Is that correct? All specs indicating pressure testing just give the main parameters not the methods, which would normally be unique to the manufacturer.
Per ISO-4126, only the term Safety Valve is used regardless of application or design.
- Thread starter
- #8
quizzical1
Mechanical
Yes, correct!
Though not systemic, we have noticed a few cast valve bodies out of 100 that had slight porosity leaks.
We can incorporate the hydrotest into the assembly / test of the valve and find that low-pressure air (30 psig) and FasTest quick connect fittings suffice.
There was questioning from our QC dept regarding getting a faster result if we increased air pressure to 90 psig (test specimen produced the leak within 10 seconds @ 90 psig vs 90s @ 30 psig) but I warned them of the danger of using compressed air at higher pressures.
Though not systemic, we have noticed a few cast valve bodies out of 100 that had slight porosity leaks.
We can incorporate the hydrotest into the assembly / test of the valve and find that low-pressure air (30 psig) and FasTest quick connect fittings suffice.
There was questioning from our QC dept regarding getting a faster result if we increased air pressure to 90 psig (test specimen produced the leak within 10 seconds @ 90 psig vs 90s @ 30 psig) but I warned them of the danger of using compressed air at higher pressures.
Specification define the minimum requirements. Manufacturers are free to add additional testing above the minimum requirements based on their experience and desired level of quality. Extra tests cost more money, and you need to compare the extra testing cost to the potential warranty cost from customer claims.
It is very common for copper based alloy castings to have very small porosity. Bronze, Monel, etc. Sometimes the porosity is small enough that it does not leak during a short duration water test. The viscosity of the water is high enough that it can take several minutes for the water to pass through and show on the outside of the valve. Best solution is to do a low pressure gas test. Around 5 to 7 bar is usually enough pressure with air to quickly find leak from micro porosity with soap solution. Just be certain to do the air test first. If you test with water first, you can plug the leak so that it does not appear with an air test.
This additional air test is not required by any standards, but is commonly done by manufacturers. Some mix it in as part of a valve closure test since in many cases, the closure test is also done with air at low pressure.
It is very common for copper based alloy castings to have very small porosity. Bronze, Monel, etc. Sometimes the porosity is small enough that it does not leak during a short duration water test. The viscosity of the water is high enough that it can take several minutes for the water to pass through and show on the outside of the valve. Best solution is to do a low pressure gas test. Around 5 to 7 bar is usually enough pressure with air to quickly find leak from micro porosity with soap solution. Just be certain to do the air test first. If you test with water first, you can plug the leak so that it does not appear with an air test.
This additional air test is not required by any standards, but is commonly done by manufacturers. Some mix it in as part of a valve closure test since in many cases, the closure test is also done with air at low pressure.
HitokiriAoshi
Mechanical
90 psig shop air is honestly, not that dangerous at all. wear some proper ppe, maybe overkill use a shield.
We test thousands of valves a day with shop air. used to even test full pressure with pneumatic pressure for class 150-300 (i stopped that) it did however catched 5 extra valves a month that had micro porosity.
if 90 psig air is catching the porosities, that's some pretty crappy castings imho.
Luke | Valve Hax |
We test thousands of valves a day with shop air. used to even test full pressure with pneumatic pressure for class 150-300 (i stopped that) it did however catched 5 extra valves a month that had micro porosity.
if 90 psig air is catching the porosities, that's some pretty crappy castings imho.
Luke | Valve Hax |
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- #11
quizzical1
Mechanical
Thanks guys! I appreciate all the input.
For what it’s worth, the casting used to be made out of CDA 836 which has a higher percentage of lead we saw no porosity issues. Once we switch to the CDA 875 to pass NSF-61 that’s when the issue started showing up.
For what it’s worth, the casting used to be made out of CDA 836 which has a higher percentage of lead we saw no porosity issues. Once we switch to the CDA 875 to pass NSF-61 that’s when the issue started showing up.
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