Test of deluge system ? 2

[Michelsen]

I'm contacting you as I have visit your site on the internet and it might be that you could help or guide me to solve the problems mentioned below.

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 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

Bo

 

[Guidoo]

I agree that reducing test frequency to once every two years is not a good idea. NFPA 25 required test frequency is once a year. Flowrate: full flow for 15 minutes (in order to check spray pattern for each nozzle etc.).

As far as I know, testing with sea water is common practice at offshore platforms. It should be possible to test with fresh (sweet) water, but this requires modifications to the system (fresh water tank with pump and piping).

Testing with fresh water reduces the corrosion problems and maybe also the problems with electrical equipment.

When you test with foam, smoke or air you may see whether any nozzles are blocked, but you cannot check the spray pattern.

You write that you have problems with corrosion of the (fire water) piping system when you test with sea water. This raises the question whether the correct material has been selected. For these systems, I am used to see Copper/Nickel or even titanium pipes. (Galvanized) carbon steel is not acceptable because of the corrosion and blockage issues.

 

[BSQUAREDBUCKEYE]

Before I float my "out of the box" idea. How many nozzles are there? Tens, hundreds, thousands???

 

[Michelsen]

Hallo Bsquaredbuckeye!

We are talking about 100 to 200 nozzles.

 

[Guidoo]

Are you aware of the following report from the UK Health & Safety Executive: "A review of degradation of firewater piping & nozzle performance due to blockage". It can be downloaded from

http://www.hse.gov.uk/research/otopdf/2000/oto00035.pdf

Especially pages 21-25 are recommended.

It states that with CuNi 90/10 there are usually no corrosion/blockage issues, so that testing frequency can be reduced. For (older) systems based on mild steel (galvanized or lined), measures are proposed to reduce likelihood of blockage: use nozzles with large orifices and without integral strainers, ensure dry pipe is fully drained after operation, apply anti-corrosion coating to pipe internals and provide dummy nozzles at end of pipe runs.

Before flow/wet testing is done, normally considerable preporatory work is to be done to "bag-up"/protect equipment from water ingress/damage.

 

[RRAABB]

Running with fresh water would be optimal, but due to the large volume required, it is usually impossible. I may suggest to do your normal function testing with sea water, then follow up the test with a smaller freshwater flush. this will reduce the corrosion problems within piping and on equipment. As for your electronics, you must cover them during the test.

 

[BSQUAREDBUCKEYE]

OK here is my "out of the box" idea. At 200 nozzels it may well be out of the question finacially.

Recently I've read about an accustic sensor. Gases and fluids apparently generate an ultra sonic frequency through orifices. This instrument when bolted to the valve or steam trap or potentially your nozzel could provide a frequency profile that would identify the nozzel's spray pattern. This idea is currently being used on eyewash stations.

A brewery used this technique to qualify the spray washing of their kettles and found it to be very accurate saving them thousands of dollars in production of contaminated product.

First testing to see if it will generate a signature of the nozzel cleaned and dirty and then if sucessful mounting one of these on each nozzel. They are about $1K a piece and are Cl.1, Div.1 Intinsicaly Safe.

This would allow you to test with air or nice clean dry nitrogen instead of a liquid and test as many time a week as you would like to.

What will it cost to wire all these up? Nothing, they are wireless...

200 sensor at $1K, 4 base radios at $1.25K and software at $1.3K equals $206,300 for the equipment

I told you it was "out of the box".

http://www.accutechinstruments.com/