High pressure trip on reactor setting

[chemks2012]

Hello all,

One very quick query please.

We have a high pressure trip on reactor set at 12barg which stops the reactor reactor pump.
Once the reaction is completed, reactor is depressurised to atmospheric pressure and then vacuum of say 800mbara is applied.
There was a discussion that our instrument department would loop out the high pressure trip when reactor is at the vacuum stage.

My query is

As the high pressure trip is set at 12barg, this trip will not be activated when the reactor is at vacuum and hence no need to loop out anyways. Is my understanding correct or am I missing anything?

Thanks in advance.

 

[MortenA]

why?

 

[Latexman]

In my experience, safety trips are not looped out, because . . . it's for safety. An operational permissive can be looped out, like a low pressure trip on a pump or compressor has to be looped out or time delay for start-up..

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[georgeverghese]

Agreed, typically it wouldnt be necessary to override the high pressure trip switch. May be the instrument engineer has to override this because the PSHH was not specified for vacuum operation, and it would trigger a false trip when pressure is below atmospheric?

 

[Latexman]

True, but that's not worthy of a permanent override, one should get in the proper instrument, calibrate it, and program it correctly. Maybe, a temporary override.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[Compositepro]

Perhaps the discussion was misunderstood. I see no reason to want to remove the high pressure trip under vacuum. However, it probably is necessary to protect the vacuum sensor from being exposed to 12 barg.

 

[chemks2012]

Thanks all for your input and help.

HiCompositepro,

Thanks. Yes, that could be the reason - i will double check. Just one correction though - that looping out might be due to preventing the high pressure switch exposure to vacuum and not other-way round.