4 replies to this topic

[Bill B]

We like your input on the following, which seems to frequently surface. We are evaluating RV protection of piping that are in tankwagon and railcar loading areas - i.e. there is a potential source of a fire from the trucks and/or rail car moving equipment.

Is piping usually provided fire protection in this case. In cases above, system could indeed be blocked in liquid, and a source of a fire could be present.

Regarding Code, ASME 31.3 states "Provisions should be made to safely contain or relieve any pressure to which the piping may be subjected", and "Pressure relieving devices required ... shall be in accordance with ... Section VIII ...... The terms design pressure and piping system shall be substituted for maximum allowable working pressure and vessel, respectively, in (the Section VIII Code)". This confirms that piping must be RV protected.

The question then becomes "Is process piping normally protected in the event of a fire scenario"?

I would welcome your thoughts. Thanks.

[fallah]

The question then becomes "Is process piping normally protected in the event of a fire scenario"?

Bill B,

The answer is: Normally no, but if piping system containing more than around 2-3 tons flammable gas, or liquid HC, or liquified HC can be isolated and also can be exposed to fire it is needed to consider PSV fire case for protection of that part of piping has been isolated against overpressure due to fire scenario.

Fallah

[Bill B]

Thanks! Can you provide a reference for the "2-3 tons of flammables"?
Bill

[fallah]

Thanks! Can you provide a reference for the "2-3 tons of flammables"?
Bill

Bill B,

Actually the concept behind this criteria is the fact that an isolated part of a piping system containing such amount of flammable gas/liquid above a specified value tends to be similar to a pressure vessel needs protection against fire scenario. I have seen these values in engineering practices of some oil&gas companies.

Fallah

[S.AHMAD]

1. As mentioned by fallah, PSV for protection due to fire is not being considered. Since piping is normally connected to pressure vessel which is normally PSV protected. If the vessel is not overpressure, piping will also be not subjected to overpressure.
2. The protection as per ASME Code is for overpressure due to other reasons such as blocked discharge of a pump where the shut-off pressure exceeded the piping design pressure or possibility of thermal expansion due to blocked-in situation.

Edited by S.AHMAD, 26 January 2012 - 09:18 PM.