Pipeline Test Pressure < Design Pressure

[mch22112]

Hello,

I have encountered a pipeline design code (EN 1594), which specifies the required hydrostatic test pressure as a certain % of the Design Pressure (DP) above the Maximum Incidental Pressure (MIP).

E.g. at the lowest point in a test section the test pressure shall be 0.15 x DP above the MIP.

The MIP can be up to 1.15 x the Maximum Operating Pressure (MOP). The only restriction on the MOP is that it cannot be greater than the DP.

Therefore, if the MOP is << DP, the required test pressure can be less than the DP.

Eg. if my DP is 80 barg, my MOP is 60 barg and the MIP is set at 1.1xMOP = 66 barg, the required test pressure is 0.15 x DP + MIP
= 0.15 x 80 + 66 = 78 barg (which is less than DP).

This seems peculiar, but I suppose it is ok. I guess it is not normal to have a large margin between the DP and MOP and this occurence is not common. Has anyone else encountered this? It seems like a strange method for calculating the required test pressure. In other codes I have used the test pressure calculation is usually a function of the DP, or the DP and MOP, but not the MOP alone.

Thanks

 

[BigInch]

Don't worry. It only proves that a "design pressure" that is markedly different than the max operating pressure is totally redundant; a situation bearing great simularity to many EN codes BTW.

The ASME (pipeline) codes do not define the test pressure s a function of transient pressures (mip), or of design pressure, but rather define MAOP as a percentage of test pressure and MIP as a function of MAOP, making it a rather simple exercise to see that a design pressure deviating markedly higher from your intended MAOP could be a massive waste of capital and that no matter what happened in engineering and design, mistakes made or not, MAOP is the result of a positively proven field test result.

From "BigInch's Extremely simple theory of everything."

 

[mch22112]

Thanks BigInch, I understand what you mean. I'm still getting used to the EN codes.