We have a fire fighting training ground in our plant. Various fire types are simulated for training sessions , viz LPG fire and Diesel fire, and the fire men demonstrate how to put off the fire.
The good ole blokes from the fire department have requested me to study the diesel fire system.The brave folks complain that the spray nozzle aint very effective in terms of creating a fine mist and the fire isnt big enough to suit their professional skill. It was also highlighted that much of the diesel just spills without burning resulting in wastage etc.:
System description as follows:
We use a Fillrite (Tuthill pump) - 3/4 hp rotary vane pump for the diesel application. From the limited data available from the pump catalogue (and website) the specs are as below:
Q = 35 GPM
P_discharge = about 13 psig at 35gpm (using 15 ft of 1" hose); 25 psig at 20 GPM (using 15 ft of 1" hose)
(pls take a look at the following website -> http://transfer.tuthill.com/products/fluidpumps/highflowacutility.html
Just for your info - We dont use a hose. The hose info is used by the mfr, probably to identify the pressure available for typical pumping station users etc.
The maximum pressure (printed on the pump label) is given as 50 PSI. There is an internal check valve and relief valve inbuilt to the system, but I have no idea what is the set pressure of the relief valve? The maunfacturer shows 25 psi as discharge pressure in the website - so am i right in assuming that the set pressure is limited to 25psi?
We have about 15 mts of 1" piping and 10 mts of 0.75inch piping installed. I did a line loss calculation (using instu_calc) and found that the 35 GPM flow is just too high (assuming 25 PSI discharge pressure). With few trials i could find that at a flow of 20 gpm the discharge pressure would be about 5 psi.
(The piping is existing, and please dont recommend me to change it - the good fire dept guys just dont have that budget and the earlier designer probably gave just gave two muted hoots about the pressure drop calcs thru the pipe etc. )
3) Safety relief valve:
3.1) Assuming that the safety relief valve is set at 25 psi; If I want to size a spray nozzle at the outlet then I have for this spray nozzle only 5 psi and 20GPM, and the rest of the flow of 15 gpm(remember the capacity = 35 psi)would be internally relieved from the pump. I dont think a good enough spectacle of a fire (i.e. a good spray pattern) will be created by using the sprayer with a delta P of only 5 psi. What do you guys suggest?
(In the current configuration also, there aint much of a spray pattern from the nozzle - probably there just isnt much pressure left at the end to create the necessary spray pattern)
3.2 Assuming that the relief valve is set at 25 psi; i guess most of the time the relief valve is in open condition in the presence condition too - any idea if this mode of operation is a cause for concern (say pump failure etc)
It is commercial diesel (taken from the pumping stations). I searched various websites and i gather that the commercial diesel may have a viscosity of 2 to 5 cST and sp gravity about 0.8~0.9. ANyone has better idea on this.
5) ALternate pump selection:
The fire dept guys are open to the idea of investing in one pump. Assuming that i need about 20 psi available at the end of the pipe to design a suitable spray nozzle (for say 35 GPM and 20 psi) then is there an alternate pump type available for diesel fuel application that I can use?
For the pump I guess the following may suffice:
20 GPM / 40 PSI . However, the electrical rating shall be limited to < 1 HP (because the elctrical cables are already laid out rated for 3/4 HP - and a higher rating means making changes at associated electricals)
If anyone is having a fire training ground facility knowledge then please let me know what system you are using for simulating diesel fire.
Sorry for this long post. Please feel free to ask for any clarification. Looking forward to hearing your thoughts...