Pressurized DCS Room in Classified Area
Pressurized DCS Room in Classified Area
(OP)
We are re-locating a room with DCS equipment to an area surrounded by Zone 1 classification.
The DCS room will be pressurized and also has an 'air-lock' (the entry-way will have two doors before entering the DCS room). The design is to have pressure alarms in the room and tied to the DCS for alarming. I believe this to be Type X pressurization per NFPA 496.
Now the problem is, Type X requires that electrical equipment be disconnected on loss of pressurization. Power to the circuits may be continued for a period of time if the immediate loss of power would result in a more hazardous condition. This would shut down all control of the process....not a good idea.
How have others handles this situation?
I know the correct answer is don't build the room in a hazardous area, and I've fought this for 3 months now, but to no avail.
The DCS room will be pressurized and also has an 'air-lock' (the entry-way will have two doors before entering the DCS room). The design is to have pressure alarms in the room and tied to the DCS for alarming. I believe this to be Type X pressurization per NFPA 496.
Now the problem is, Type X requires that electrical equipment be disconnected on loss of pressurization. Power to the circuits may be continued for a period of time if the immediate loss of power would result in a more hazardous condition. This would shut down all control of the process....not a good idea.
How have others handles this situation?
I know the correct answer is don't build the room in a hazardous area, and I've fought this for 3 months now, but to no avail.
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RE: Pressurized DCS Room in Classified Area
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Sometimes I only open my mouth to swap feet...
RE: Pressurized DCS Room in Classified Area
I would emphasize the implications of an orderly shutdown when the pressurization fails. (Not IF but WHEN)
I would be asking the process folk for suggestions as to the best way to implement an AUTOMATIC, IMMEDIATE orderly shutdown WHEN the pressurization fails. Try to have the scheme submitted to the insureres for acceptance.
If I implemented an automatic, immediate orderly shutdown on loss of pressurization, and had the scheme signed off by both the operations department and the insureres, I would feel that I had achieved an acceptable compromise.
respectfully
RE: Pressurized DCS Room in Classified Area
There are lots of ways to keep the building pressurized.
RE: Pressurized DCS Room in Classified Area
The room is unoccupied.
We do have redundant pressurizing systems.
We do have an emergency generator that starts within 15 seconds.
The plant can be taken down orderly, using the DCS, if pressurization fails by reading the pressure in the DCS.
So, my question is: If we loose pressure in the DCS room, do we have to shut down the power feed to the room?
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RE: Pressurized DCS Room in Classified Area
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Pressurized DCS Room in Classified Area
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RE: Pressurized DCS Room in Classified Area
On loss of ventilation;
1. Orderly but immediate shut down of the plant.
2. Remove all power feeds to the room