Class D Fire Extinguishers

[kurnal]

Hi All

Does anybody know of a formula for the calculation of the amount of media required for metal fires? I am thinking of filings of titanium and aluminium as a result of laser erosion ( not together but there may be some cross contamination) and possibly some magnesium in alloys. The bottom of the machine ( 8 sq m ) and the LEV system   tend to become covered in a layer of filings during machining these are emptied into a couple of buckets in the works before being placed in a sealed metal bin in the external compound.

There is currently 1 amerex 20lb sodium chloride  class D extinguisher and I am trying to assess whether this is enough.

[AnthonyB]

Sadly not - there isn't a standard one as such, I would suggest asking the manufacturers of the Powder or Amerex direct (but their US sites detailed technical section doesn't help) or going to any industry bodies for the metals involved.

I do know that a 9 kilo Class D extinguisher or a 12 kilo Cetrimax ABC Powder extinguisher (with low velocity applicator) may deal with up to 1 kilo of Magnesium Powder, but that's all sorry!

[Nick G]

If anybody would like information on automatic detection and suppression systems for Class D Fires please email me I'd be happy to offer some design info.

[Psuedonym]

I have been told to try to design a Class D formula for extinguishers regarding size of can/type(of powder)/burning medium (i.e. type and state of metal) is not possible. This is why you won't find a Rating system for the size of extinguisher per size of risk formula for Class D in the same way as for example a 13A Water and the calculations to achieve this Rating.

There are a couple of earlier threads regarding Class D - mainly explaining the types of powder and their limitations etc.

The best bet is to contact a manufacturer directly and explian your risk problem rather than your service provider. As you already are aware of one manufacturer there is no need for me to advertise one and get my wrist slapped!

(Automatic systems are covered very adequately by Nick)

Another avenue which I found useful involved checking the technical data sheets of the specific metals involved. These can sometimes give you the specific powder types or the powder type (obviously class D but there are differing types for different metals) relating to the metal involved  with any variants for the metal state. They can't provide you with the size of extinguisher requirements though whether 12Kg portable to 50Kg Wheeled Trolley, this can only really be advised from a powder ext. manufacturer.