LPG piping code 2

[msalajeel]

dear forum,

i have confusion about LPG pipelines design. we usually deals with gas standard 31.8.
my question is which ASME code shall we use to design LPG pipeline? if we consider the liquid standards, LPG can go to gas phase easily if its not stable during the transportation.

best,

 

[LittleInch]

The intent is clearly to transport the fluid as a liquid, hence use 31.4. The gas phase is an upset condition due to low pressure? so shouldn't be your design intent.

You might be better to use something like ISO 13623 which doesn't differentiate.

A code like BS PD 8010 provides guidance with respect to separation distances and population density for LPG to deal with the intense vaporisation of cold gas if there is a leak or rupture.

You need to look at a decent QRA which addressee these issues if you're going near any population.

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

 

[msalajeel]

thank you LittleInch. appreciate your answer.

 

[dcasto]

In the US, the regulations let the owner decide, 31.8 Or 31.4, then follow the rules of whatever you decide. For example, in the late 70's my company built a line for ethylene under gas, every line we interconnected to was classified liquid, how can that be? Under liquid codes, the debating is a constant 72%, but gas was lower as the line went through people's backyards. Ok, so what does that have to do with the question? Under liquid 31.4, the assumption is that the transported fluid is liquid, even if released and the energy of the fluid is all hydraulic, but, in reality, your propane is a gas when released and not hydraulic in energy.

I actually converted our ethylene line in question above from gas codes 31.8 to 31.4 liquid. The liquid codes require more stringent naintenance, but so what, we had a propylene line 1 foot away, so no increased monitoring. But the 31.8 is more stringent on the design.

To me, the iso standards are over specifications and no room for risk reward analysis. They over complicate to appease the EU, not the science.

 

[LittleInch]

You clearly haven't read ISO13623. It allows a wide range of designs providing you show you have "considered" x.y and z. Much less prescriptive than 31.4 or 31.8 which actually require people to design or consider safety and not just install something because clause 403.2.2 a) says so or allows them to.

The key in your response is that the fluid changes when it is released. This needs to be considered properly in terms of public safety and routing/protection but in terms of design or normal operation works much more like a liquid than a gas (e.g. surge pressures)

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