Fire Valves

[simon]

Anyone know what the flow rate of a fire extinguisher valve is ?

[woody]

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Actual orifice size of fire extinguisher valves.

Kevin Stowe (Kurvy) Sunday, January 26, 2003 - 08:34 pm

Hi all,

We are looking at new valves for our high pressure pneumatic system, in order to increase flow, but there is little point in going beyond the orifice size of the narrowest point, currently the fire extinguisher valve. So does anyone know how big it is, and how convulted the gas path is?
Kev.

Simon (Fargher) Sunday, January 26, 2003 - 09:00 pm
Hi Kevin

I seem to have taken dozens of them apart latly (all different !!!) but from what I can tell the narrowest part seems to be 1/8. Hope that helps.

Mario de Jongh (Maddox) Monday, January 27, 2003 - 01:06 am

The 2 I had were main let trough 8mm, but the valvestem was 4mm. So I calculated 4*4*pi=50.26mm²

2*2*pi=12.5mm²

so the let trough is 37.76mm²

compared to the Burkert this is pathetic.126.67mm²

carl david barrass (Carl) Monday, January 27, 2003 - 11:09 am

whats the orfice area of a fire extingusher then.just wondering.

Mario de Jongh (Maddox) Monday, January 27, 2003 - 01:14 pm

Carl I explained that the fire exinguishersI disassembled had a orifice of 50.36mm², but the stem of the valve is 4mm, so taking a cirkel out of the orifice.Effective let trough 37.76mm².

Disasemble a fire exinguisher and then the valve.. Youll see what I mean with stem and valve.

Kevin Stowe (Kurvy) Monday, January 27, 2003 - 06:32 pm

Thanks guys, seems as though two 1.1 kg extinguishers rather than one 2kg units will be needed!
Kev.

Mario de Jongh (Maddox) Monday, January 27, 2003 - 07:18 pm

2 1.1 botlles are better than 1 2kg bottle.
Better let trough and better heat exchange.

P II used 2 1.5 kg(European allowed, not HSE) for Home testing.Good flow as the tests prove.

Woody (Onslaught) Tuesday, January 28, 2003 - 01:01 am

Kevin... Perhaps you could stick in a high pressure liquid buffer tank ... a large bit of pipe should do the trick ... if you can get it to fill with liquid.

Jeremy Cuss (Jeremycuss) Tuesday, January 28, 2003 - 08:14 pm

Hey, thats dangerous! Unless the buffer tank has the same pressure rating as the bottle, and that is unlikely.



Jeremy Cuss (Jeremycuss) Friday, January 31, 2003 - 10:51 pm

Going back to Marios assessment of the orifice size of the CO2 bottle valve (37.76mm2), I have calculated the max CO2 mass flowrate at sonic velocity through this valve, assumming ambient temperatures and 51barg in the bottle. It is 0.7kg/s (or 22litres/s at 15barg). It will fall as the temperature falls, but it is probably an order of magnitude higher than you need, if you have a reasonable buffer tank.

[woody]

So Simon ..

The cross sectional area is approx 38 sq mm.

The flow thru a standard extinguisher valve is ( according to Jeremy ) 0.7kg/s or 70 litres ish per sec @ full pressure.

Working from the area Mario that gave ..you have an orifice equivalent to 7 mm dia .. and the flow thru a 7 mm bore pipe is 6.85 litres/sec @ 5 bar.
so ... Yes .. 68 litres/sec @ 50 bar.

A 1/2 Burkert valves give a flow approx 3.4 time better....but of course you need a supply orifice of 1/2 or bigger to realise its potential.....Hence the use of H.P.buffer tanks with large supply outlets.

[simon]

Cheers Alan