Safety zone for pneumatic testing

[DiegoMartinez]

Hi All,

Does anyone know if there is a safety zone when performing pneumatic testing? I couldn't find anything in Asme B31.3.
Any feedback is appreciated.

Rgds,
Brighton

 

[eliebl]

Search for Stored Energy Calculation. I know that NASA has a two page document that is easy to calculate a restricted distance from. It is one that is commonly used.

EJL

 

[JoeTank]

My personal practice for an air test is to be at least one zip-code away from the site.

Joe Tank

 

[vpl]

JoeTank ? funny.

DiegoMartinez ? You might want to look at these threads:
thread378-145123; thread378-156328; and thread794-26767.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

Want to post an image? Look at the FAQ's in forum559

 

[iainuts]

My personal practice for an air test is to be at least one zip-code away from the site.

LMAO @ joe

I don't know of any specific distance requirements, though I'd be interested in seeing that NASA document eliebel mentions. Regardless, there will always have to be someone within that area to do the test.

Note that the piping code requires a leak test, not a proof test. If you're looking to do a proof test (ie: 1.5 times MAWP), then what is typically done is to disassemble the piping system and do a hydrostatic pressure test, and then reinstall the system and do the leak test. The proof test isn't required by code.

ASME B31.3 requires a "leak test" at 1.1 times design pressure. They also require a relief valve set at 10% above that pressure. We always put this relief device at the source of the test pressure, and ensure by calculation that the relief device is large enough to handle the flow from the test source.

When pressurizing the piping system, you should also verify you are only pressurizing those portions of the piping system that are rated for the pressure. Creating a test plan is imperative. Color code a P&ID or something along those lines. Make sure you know what lines you're pressurizing, and make sure the test plan incorporates valve open/close requirements, blanked off piping sections, etc...

I'd also suggest bringing up pressure slowly - in 10% increments. Hold for 5 minutes at each level, and do a soap bubble leak test at each level.

Leak testing requires someone to do the test, so they will always be near the piping during the test. One primary reason for keeping others back isn't just to keep them safe from potentially dangerous pressure, it is to maintain some control over piping and valve configuration. You need to keep people away from valves or other controls that need to be kept in a specific position during test, especially because you're generally in a construction mode and people may be less aware of lockout/tagout procedures.

 

[LSThill]

TEAM MEMBERS

TECHNICAL REVIEW ASME PCC 2 for details.

 

[EastCoastMechie]

I find this information useful as I'm involved in preparing bids for pneumatic testing of LNG facilities. I have another (related) questions:

From what I've learned from my colleagues, many (if not most) LNG facilities are constructed with very few joints, so testing in smaller, risk-managable sections is not an option.

It is an understood fact that in these cases, if pneumatic chosen method of testing the pipework, the stored energy limitations will always be exceeded. For interest's sake, I'd really like to take a look at the code that outlines this stored energy limit. Does anyone know which code/standard addresses this?? I've been through B31.3....

 

[stanweld]

In addition to the calculated stored energy during the test, I also consider the material's ductility, NDE performed, the applied stress versus specified minimum yield strength (leak before burst potential) at test pressure and prior service history, if applicable, to further evaluate risk and provide for greater personnel safety during the test. When risk is very high, I'll be with JoeTank. On more than one occasion, I have not permitted such testing to be performed. The vast majority of pneumatic tests, for which I have provided testing procedures, have indicated leak before burst and all have been conducted safely. Of the literally hundreds of such tests with which I have been involved, no burst event ever occurred.

 

[Gator]

EastCoastMechie:

LNG implies cryogenic piping (unless you're after vapourization, but still...) which means that you will have a minimum of mechanical joints, as you mention. This is to ensure leak-proof operation (cryo fluid leaks can ruin everybody's day), fewer crevices for particulate collection and, to a lesser extent, reduced cooldown time during startup (less mass that retains heat).

If possible, get in contact with some engineering people from Air Liquide, Air Products or Praxair that have cold box experience. They may not be willing to share their secrets though.

 

[EastCoastMechie]

Gator:

Yes, we deal directly with Air Liquide. They don't tend to call the shots in these cases, but I bet they would know which codes & standards deal with stored energy calculations. Don't know why I didn't think of calling them...

I have a feeling that it's an API standard I'm looking for. I just don't want to keep purchasing standards until I find it.

Thanks for the input ; )

 

[dcasto]

From 49 CFR 195
(c) Carbon dioxide pipelines may use inert gas or carbon dioxide as the test medium if—
(1) The entire pipeline section under test is outside of cities and other populated areas;
(2) Each building within 300 feet (91 meters) of the test section is unoccupied while the test pressure is equal to or greater than a pressure that produces a hoop stress of 50 percent of specified minimum yield strength;

 

[stanweld]

We use two stred energy calculations;
1. Change of State Equation based on reversible adiabatic, isothermal conditions( Reference "Mark's Standard Handbook for Mechanical Engineers". Ninth Edition pg 4-10).
AND
2.Isothermal Compression Equation also referenced in "Mark's".

 

[EastCoastMechie]

Thanks all! Big help )