Maintenance of deluge system ? 1

[Michelsen]

I'm dealing with a "deluge" system (dry fire water sprinkler system) on a platform in the North Sea. We test the system each 6 month in order to verify if any of the spray nozzles are blocked. This initiates 2 problems.

1) The test is carried out by using sea water which increase the corrosion in the piping system ( made of galvanised carbon stell ) and thereby also increase the possibility for blockage of the nozzles.

2) The water deluged over the equipment damage some of our electrical systems.

My wish is to extend the test period (ex. each 2nd year) but this will not be granted by the authorities unless I can prove that the system is reliable. I'm searching for idea how to test the system without using water, i.e. is there any other opportunities on the marked where it will be possible to test the nozzles for blockage (foam, smoke, air etc.)

I hope that you have dealed with the above-mentioned before and have some sort of recommendation or solutions.


With best regards

 

[jay165]

Michelsen:

1. Why would you choose carbon steel for seawater service?
2. Why would the system be designed to deluge water on electrical equipment?



Use potable or treated water to conduct the test or to flush the seawater out after the test. Protect the electrical equipment with shrouds or change the angle and spray pattern of the nozzles.

Another choice is to add enough redundancy and dry testing to get the ystem up to a high enough SIL level to convince the authorities you don't need a wet test.

 

[sshep]

Michelson,

We built a major size dry pipe deluge system for an HF alkylation unit out of galvenized pipe. The bad news is that our insurance carrier made us change it out later- this is the price of trying to do safety systems on the cheap. After a few years during our regular tests, there was alot of chip scale (could be from upstream) regularly found in the spray nozzles so we didn't try very hard to fight the inevitable replacement of the dry-pipe portion. Our spray nozzles are the spiral cone type, and these are tolerant of small debris (i.e. not chip scale), but there may be something better. If you wish to extend testing periods you should get the most plugging resistant nozzles you can; test the pumps and controls on a frequent basis via a bypass that avoids filling the pipe; and test the dry pipe with air by monitoring the flow and back pressure, hopefully in independent sections or flow paths. I don't know of any colored smoke test to visually check the pattern, although this seems a cool idea- good luck on that.

You probably won't get much sympathy for doing this on the cheap with galvanized pipe. In the end I think you must just get together the best plan you can and try to get approval, but only do this if you are comfortable with your system later in an emergency. I have seen a few fires in my career, and more than once was retrospectively thankful that we followed the recommended practices.

best wishes, sshep

p.s. I don't have off-shore experience, but the reason you chose sea water seems pretty obvious.