Transformer room ventilation

[cctdiag]

Hi

Does anybody know if there is a requirement or guide (in UK)for ventilating transformer rooms? We have 2 x 1MW 11kv/415v ONAN tansformers in their own dedicated rooms, both have ventilation grilles in the entrance doors.

I have been asked if they could be boarded up so to create a 'sealed' environment for a gas fire extinguishing system.

Obviously the rise of room ambient temperature may be an issue but generally the transformers run cool, and blocking off the doors may not cause a problem. However am I bound by any requirement to provide a ventilated room.

Jeff

 

[RajT]

There are no legislative requirements in uk for ventillation of transformer rooms except that the ventilation arrangements ( any equipment to ha matter) should be such as to allow for safe operation of the equipment in the rooms.
So by inference the onus is on the operator (say you)to ensure that adequate ventillation is provided.
On the basis that the transformers are running cool(lightly loaded) generally, then one course ofaction should be to block of the vents for a trial period ( say in the summer months for worse case)for a few week and monitor the temp on the transf windg & oil every 2-3 hrs around the clock.
At the end of the trial period you should be able to assess if blocking off the vent grills will present a problem.

 

[seanmcc]

There are two other options to consider

1, Fit fire dampers over the vents, The dampers can then be released electrically by the the fire panel or mechaniclly by the gas being released.

2, Remove the transformer oil and replace with Midel insulating fluid, which is non flammable therefore negating the need for a fire system altogther.

I'm sure you know that allowing the transformer to run hot will cause the oil degrade much faster then normal.

 

[RajT]

I would beg to differ with seanmcc on his option 2, in that both mineral oil and midel are flamable the only difference being that midel has a higher flash point.
For a total non flamable solution, one may consider cast resin type transf but I guess that is not an option in this case.

 

[stevenal]

So gasious combustion products form and fire suppresion gas goes in, but nothing comes out? What is the presure rating of this room, and how big a bomb are you building? I realize that by covering the vents you are not making a perfect seal. Still, if gas forms or is introduced faster than it can be vented, you may have a problem.

Fire suppression usuually works by displacing air. Where does the air get displaced to if vents are covered?

 

[cctdiag]

Thanks for your responses,

Stevenal thanks for your concern, Installation of gas extinguishing systems which discharge into a sealed area should also incorporate pressure relief dampers.

The damper will open on initial discharge and close according to its closing design weight, this should then trap enough gas within the protected area for 10mins.

My installer was to pressure test the TX rooms when he realised his oversight - open vented doors!!

I have two options, either get him to seal the door or to install a drop down fire blanket, operated via the fire panel. The last option he is not to keen about, as he will have to absorb the additional cost involved - blanking doors will be cheaper, but possibly a problem for me later on.

Jeff

 

[cuky2000]

Appears to me that there are few issues with the ventilation for the power transformer that have universal application :

a- The nameplate of the power transformer capacity at ONAN or ONAF (OA/FA in ANSI) are predicated on a maximum ambient temperature. Lock of proper ventilation may require deraiting to the transformer capacity.
b- Safety during fire conditions. Many designers consider a good practice to block the fans under high temperature to avoid supply oxygen to a faire.
c- Fire barrier in combination with fire suppression system such as water sprinkler system, gas suppression system or foam fire extinguisher could add additional safety in the even of fire.
Many insurance companies mandate one of those system in the installation otherwise the facility is expose to paid a premium insurance.