Pressure test safe distance 1

[mati01]

Hi every one,
Please help me by providing a formula for finding the safe distance to keep during hydro test of piping.

 

[XL83NL]

Refer to ASME PCC-3, Part 5, Article 201. Mandatory Appendix 501-III is for safe distances on pneumatic testing, not sure if Article 201 also provides guidance for hydro and safe distance.

Huub

 

[gerhardl]

Normally hydro tests are done by a slight overpressure above the max. operation pressure if the test is for a readily laid pipeline. In this case the pipelines are normally already production tested. Leakage, if any, will have limited qonsequence, and 'common sense' would ne the best formula. Anyway: only inspection crew present.

Other hydrostatic high pressure tests of components, likely or planned to lead to bursting, should be treated and calculated equal explosions. Such tests are normally done in protected chambers or sunken basins, often submerged to dampen results.

 

[LittleInch]

Don't think I've ever seen one other than general guidance.

Hydro implies water.

The issue is in part ejection of small components ( plugs, valves, hoses) which require either secondary attachment to prevent them flying off or whipping around or flooding caused by a leak / rupture or a crater developing.

A crater is probably no more than 5m radius.

Exposed pipework and fitting is your biggest risk so barriers are a key mitigation.

Any road crossing should be reviewed wrt public or private access during the test (hopefully pre tested pipe was used)

There is no such thing as "safe". Only a reduction in risk to an acceptable level.

Some idea of pipeline size, wall thickness, design factor and pressure test level would be good.

Remember a test is a test. They can fail so suspect everything until proven otherwise.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

The other factor in hydro safety is how much trapped air you have.
We used to test units to failure regularly. We had light restraint on the components expected to fail.
We vacuum filled so there was no air inside.
We would stand within a foot and film the failures. I don't recall even getting wet.
When we were pressure testing something that didn't have experience with we were careful that no one was in line with parts likely to fail and we would not have anyone within 10' of any part of the unit.
Air testing is a whole different animal.

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P.E. Metallurgy

 

[Latexman]

The hazard is proportional to [∫]PdV. With hydro (liquid) [∫]dV [≅] 0 and with pneumatic (gas/vapor) [∫]dV is significant.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[robyengIT]

to explain what said by Latexman : Google - Comparative risks of hydrostatic and pneumatic pipeline testing (it's a video)

 

[weldstan]

We regularly hydro tested 12 to 16" diameter ERW pipe to burst in an enclosed containment and the splash zone would lift the steel hinged roof cover and spread nearly 20 feet. When hydrotesting 36" diameter underground pipelines at up to 105% of SMYS, burst failures would lift the soil covering from the burst location with a small geyser of water. We stayed about 20 to 30 ft from the line. When I hydrotested small bore (< 5") gas distribution piping to burst, I stayed about 5 ft from the pipe and never got wet.

 

[XL83NL]

This Dutch company does some nice/crazy testing. See the impact a hydro can have;

https://www.youtube.com/watch?v=kxYZjtiVn74

Huub

 

[itsmoked]

You might find this discussion thought provoking.
thread378-418471

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

Yes, in large volume systems the dV is non-zero enough to matter. The steel does expand, and the water compresses, and the combined effect can be rather attention getting.

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P.E. Metallurgy

 

[3DDave]

The most interesting part of the above video

https://youtu.be/kxYZjtiVn74?t=400

 

[LittleInch]

I didn't see this was piping not pipeline.

So much depends on the level of physical protection.

If these are spools then generally they are taken to a walled off area and no one allowed in during the test rise and only for the minimum period to examine each weld during the hold period.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[robyengIT]

have a look :
1 - thread404-459798

 

[MortenA]

I think these teo videos are illustrative (warning sound is corrupted in first video:

https://www.youtube.com/watch?v=AelS89Az3YA

https://www.youtube.com/watch?v=-w2ROUiXh1Q

 

[chicopee]

I have witnessed many hydro tests on boilers when I was NB pressure vessels (fired and unfired types) inspector during the 70' and 80's and at the time there was no established safe distance. I have never witnessed pneumatic tests because of the possibility of vessels exploding. If you are to do a pneumatic test on a repaired pressure vessel, my suggestion is to be as far from that vessel as possible. I have seen videos of tanks exploding and the damages to nearby structures were incredible and any body in the vicinity would have been killed or maimed.