Gas line - section valves with safty function

[Dario2002]

We have some section valves on 20" gas line. Distance is cca 10km. Valves are equiped with actuators which are trigered by preassure drop in gas line. Not all of them have same setting (sensitivity adjusted).

Is there any rule, or calculation for:
WHICH PRESSURE GRADIENT MUST HAPPEN TO ACTIVATE SUCH DEVICE.

Is 0.5 bar/min to small gradient, is 3.5 bar/min to much?
Any expirience or designe resource is helpful.


Main task for this device (shut-down pipeline) is safety of enviorment.

 

[BigInch]

There are no code guidelines on pressure drop to activate shutdown, as long as your MAOPs are not exceeded.

It would be impossible for a code to set pressure drop to activate limits. The pressure drop would vary for each pipe diameter, each operating pressure, each pipeline segment length, each gas or liquid contained within, temperature of pipeline segment, flow into a segment - flow out of a segment (pack/unpack rate), the pressure drop read at the sensor versus the pressure drop at the leak site (which may even be totally different), how your pump or compressors respond to the pressure drop, and probably 1 million other variables. The operating response for a 100 psig pressure drop on a 2" diameter, 250 psig natural gas line at 15ºC would be totally different from a 100 psig pressure drop of a 36" pipeline operating at 2160 psig, or a natural gas line at 1000 psig and 15ºC, versus a carbon dioxide pipeline at 1000 psig and 15ºC.

Shutoff should be accomplished before the start of creating a dangerous condition, whatever that may be, whether it is a given leak volume at a given location, or a high pressure condition, or a pressure drop. Its up to the pipeline engineers to determine whatever they may be. A dangerous leaked volume at one location on the pipeline may be a totally different volume at another section of the pipeline, and normally a great deal of study is done when determining the allowable leak volume limit permitted at any given location along the pipeline. The allowed leak volume may vary with degree of environmental sensitivity, population density, equipment operation sensitivity, value of product lost, plume dispersion, H2S content, could be many factors involved, company risk or insurance policy.

Going the Big Inch!

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