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Joslaz
23-08-2012, 06:17 PM
Hi folks,

According to EN378 when ammonia concentration in machinery room rises up to 30000 ppm,
1. Must leak detector, 230v power supply and not ATEX classified switched off?
2. Warning (beacon and audible) must go on inside and outside machinery room? If yes inside, warning must be ATEX certified?

Thanks a lot.

Jahangir
09-09-2012, 10:25 PM
Dear folks,
Hi, could you please send me a copy of EN378:2008 .PDF for me?
E-mail: jahangir.torkian@gmail.com

Regards

Joslaz
12-09-2012, 06:01 PM
I am sorry. I do not have it. We work with the Spanish legislation, which is almost a copy of the EN378.

Jahangir
13-09-2012, 09:29 PM
hi, i don't have the document , but i advise you to have a clean water supply line near your plant in emergency event to decrease the effect on large leaking ! be careful .
regards.

Teuria
14-09-2012, 06:31 AM
Hi folks,

According to EN378 when ammonia concentration in machinery room rises up to 30000 ppm,
1. Must leak detector, 230v power supply and not ATEX classified switched off?
2. Warning (beacon and audible) must go on inside and outside machinery room? If yes inside, warning must be ATEX certified?

Thanks a lot.

Hi

I don't see why those should be atex classified, because in that case you should have all electric devices also atex class. lights etc etc. but if all other is allready atex classified then it's must have.

I think that the most important thing in nh3 machine room is good ventillation when leak occurs and that keeps concentration low enoungh to prevent ignition / explosion levels of nh3.

Grizzly
14-09-2012, 07:13 AM
Hi Guys.
If you are in a EU country then EN378 applies. Each individual country will have slight variations on these rules.
Due to how they are incorporated into that countries own legislation.
In the UK Ammonia plant rooms with a large enough system charge, that means that they need to comply with EN 378.
Will have automatic leak detection. Which will be set to alarm levels way below the 3000ppm mentioned above.
When activated on first stage at 0,75% of LEL (Low Explosion Level) the alarm system will operate beacons and or sounders.
At stage 2, 1.0% of LEL the system will shut the main incoming supply to the whole plant room!

Included within this is ALL Electrical Equipment within the Plant room.
I have even known the outside emergency shower to have been an electrically operated one, which was also affected.
That should of had its own individual supply but had been wired as is so often the case.
By an Electrician who did not know of the "Specialised Machinery Space" rules and regulations which apply!
Basically guys you need as "Engineers" who if working with Ammonia plant to know what should be in place and how that should work.
Reading EN378 is a good start! Training from some of the excellent trainers about is another.

In answer to the above comments.
Lighting and extraction fans etc, even the alarm beacons which are normally low voltage. Should be explosion proof!
Some of the regs are there to protect individuals and some are there to protect the plant.
Having a water supply available is helpful, but unless you know what you are doing. Spraying large amounts of water around is not good.


Grizzly

Joslaz
15-09-2012, 05:42 PM
Hi Grizzly,

That's what I thought, all electric equipment which works in machinery room at stage 2 shall be ATEX. So, leat detector must be swiched off.
Do you install an ATEX switch to control leak fan inside machinery room or just outside?
Beacon & audible alarms inside & outside of machinery room or just outside?

Thanks.

Tycho
28-09-2012, 05:19 PM
The rules may differ a bit from land to ship, but i'm mostly on ships and have to follow the DNV reefer class.

gas levels according to the DNV class are 2500, 5000 and 10.000 ppm, my company uses the following standards:

250 ppm - sounder and beacon
500 ppm - shut down all equipment that moves ammonia ( start emergency fans and close quick closing valves on liquid line and hotgas line on this stage)
1000 ppm - power off all non ex (ATEX) equipment. dnv class says emergency ventilation at this point but we do it at 500 ppm.

if someone acknowledges the sounder and beacon at any level, the sounder will go off, but the beacon stays on until the level is safe, also if the sounder and beacon is acknowledged at a low level and the concentration increases, the sounder will come back on as it reaches a new level.

it does not say that there should be a sounder and beacon inside the machinery room, however on some of the installations the dnv surveyor has interpreted the rules in a way that we had to install one, and they have to be EX (ATEX) proof.

Also, we use EX (ATEX) gas detectors from monicon (T-100 I believe) so we can monitor the gas level even when everything else has shut down.

My company are petitioning the DNV to expand their regulation to also cover the production area, because during operation 70-80% of the liquid NH3 will be in the production area where all the people are working, but the focus is on the machinery room where all the electrical components are.

But I guess production workers can be replaced :P

Joslaz
29-09-2012, 10:08 AM
Thanks Tycho.