Suppressing the Pipeline Noise Burst

Hi All,
I am reaching out to find out what is available in terms of gas vent silencers for double block and bleed gas safety system.

We have 3 units GE Frame 9B in our power station and each time we shut down a unit, it shuts off two block valves, then opens up a vent valve to release trapped gas from between the shut valves.

The released gas is discharged from the end of a two inch pipe off the side of turbine building.

Initial pressure of release, 1600kpa. Volume,3 m3 at standard pressure.

Noise level, very high locally at site.

Just wondering what is available on market to fit over end of piping to suppress the noise burst.

Thanks,
Hjams
 
The disadvantage of sending unburnt gases through a silencer is the possibility of an explosion, particularly where you would have a gas/air mix.

The argument for having double block and bleed has changed over recent years.
Sending trapped gas to atmosphere is not a good idea in principle, and 3 cubic mtrs even on rare events is a fair amount.

Maintaining the double block configuration but not bleed unless there is a suspect faulty upstream block valve seems the way forward. A faulty downstream block valve would reveal itself by loss of pressure.

You just have to persuade Process Engineers safety levels remain unchanged!
 
Hi all,

Not sure if this would be allowable under the relevant codes, but might it be possible to put a short delay (maybe just 1 sec.) between closing the upstream block valve and closing the downstream valve, to allow the pressure to dissipate into the appliance before opening the vent valve?

Ian
 
>Not sure if this would be allowable under the relevant
>codes, but might it be possible to put a short delay (maybe
>just 1 sec.) between closing the upstream block valve and
>closing the downstream valve, to allow the pressure to
>dissipate into the appliance before opening the vent valve?

Thinking about it a bit more (and again, if allowable under local codes) the functionality described above might be achieved with a couple of simple hardware mods. That is, assuming the DB&B valves pneumatically operated, the block valves are fail-closed and the vent is fail-open, you may be able to slow down the closing of the downstream block valve and the opening of the vent valve by adding simple exhaust restrictors to their actuator outlets.

I can't see any issue if the three valves don't reach their final limits for a few seconds after the shutdown command, especially if the upstream block valves still operates at maximum speed.

As mentioned I'm not fully up to speed on regulations and codes for this type of system anymore, so I'd be interested to hear the opinions of practioners with up to date knowledge in this area.

Ian
 
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