Pressure Test Reqt For Vent Lines ?? 2

[tc7]

I cannot find a specific mention in B31.1 or B31.3 which includes or excludes open ended pipe lines (blowdown or saftey relief exhausts) from pressure test inspection requirements. As such, my inspector is insisting on a 1.5x hydro. (lines are 1" nom. A53 seamless, w/A105 socketweld fittings; these exhaust lines serve compressed air systems).

Can anyone help with a reference or standard practice on this?
Thanks,
Tom

 

[NozzleTwister]

tc7,

B31.1 & B31.3 both exclude systems with design pressures below 15 PSIG. Open-ended lines normally fall in this catagory.

NozzleTwister
Houston, Texas

 

[ApC2Kp]

tc7,
ASME B31.1 Para. 137.3.2 includes statement,
" ...Lines open to the atmosphere, such as vents or drains downstream of the last shutoff valve, need not be tested."

 

[ggarciae]

May be you are manufacturing for Europe according with Pressure Equipment Directive?
PED includes all equipment (including pipes)which withstands overpressure bigger than 0,5 bar, even in short periods.
May you assure that pressure in vents or drains is not bigger than 0,5 bar in any moment?

For more info

http://ped.eurodyn.com/

See guideline 1/42
Question: Is the discharge piping from a pressure safety accessory, which will be exposed to a pressure PS above 0,5 bar, in the scope of the Pressure Equipment Directive (PED) when exhausting to ambient atmosphere ?
Answer: Yes
Reason: Even though discharge piping will be only momentarily pressurised, and such piping is open at the discharge end, it fulfils the definition of piping in paragraph 2.1.2 of Article 1.

Note 1: A silencer installed in the discharge piping is excluded according to Article 1 paragraph 3.16.

Note 2 : The location where the pressure PS is specified shall be such to be


Regards from Barcelona
G. García

 

[tc7]

G. García
That is interesting, I suppose it is very possible that someone in the future may install a silencer on a tank blowdown line. In that case I'm not sure how you would determine the back pressure it would cause? I suppose for design purpose, I would have to assume full system pressure and in that situation I can agree with a pressure test inspection.

ApC2Kp -
Thanks for the excerpt, that is what I needed for the moment.

Regards to all,
tc

 

[ggarciae]

That's the question! People usually don't determine pressure drop.
Does a PSV manufacturer give pressure at flange in the outlet?
As a result, outlet pipe is the same pressure design but bigger diameter so more exigent clasification according PED.

If different pipes end in a vessel manifold, people establish as pressure design the biggest pipe inlet pressure which is usually much more than vessel's design pressure. It's very difficult stablish a test pressure on site in those cases.
Location of safety accesories is very important too.

Regards from Barcelona
G. García