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Diesel fuel pump and nozzle for fire training groundHelpful Member! 

alwayslearning (Mechanical) (OP)
27 May 04 12:18
Dear All,

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:

1) PUMP:

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?

2) Piping:

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)

4) Fuel:

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...

Regards
NCMog (Mechanical)
27 May 04 20:39
I've used gear pumps in low flow, high head applications including flammable liquid service.  Viking has a nice selection of gear pumps (www.vikingpump.com).  You'll find that the discharge pressure will be more than you're looking for, but that is easy enough to deal with.  Are you sure 20 psig will give you the spray pattern you want at the nozzle?  Sounds kind of low, but I may be wrong.  Good luck.
Helpful Member!  rmw (Mechanical)
27 May 04 23:01
I think you are fairly well stuck with the pumping and piping arrangement you have, and will have to come up with a solution within those parameters.  Even changing the pump to something with a higher head will still result in a significant amount of head loss in the piping that there is no budget to change out.

Have you considered using air (steam if it is available) as an atomizing medium??  It might just be that you take what you got, and work on doing some atomization at the nozzle and get the fire you need.

Except that your situation is a training fire, it is not terribly different from a boiler or gas turbine trying to atomize the same fuel to burn it.

It also may be that with some type of air atomization at the tip, that you would get a good enough fire that you could reduce the flow to the nozzle, and reduce the pressure loss in the piping so that you had higher pressure available at the (nozzle) tip.

Now, having said that, I never would want to try to operate a boiler or turbine with just 5 psig at the burner tip, unless dynamite was the atomizing medium.  However, I think you can come up with a venturi arrangement, or an air driven jet that would induce flow into it with the air motive, and produce a finely atomized exhaust in the process that would give you one heck of a fine fire.

Then all you pump has to do is get the fuel to the jet.

Try it.

rmw
alwayslearning (Mechanical) (OP)
27 May 04 23:05
Dear NCmog,

For the spray pattern I guess 20 psi may not be the best. Probably 30 psi will do. I just have to live with it and make sure I dont increase the head too high lest it would increase the power rating too. I have a constraint of 0.75hp (cost consideration of course!) on the electrical side.

Just had a look at viking site. It is quite instructive. I understand we have wide variety of choices for my particular application. I just posted them a query for suitable selection for my application. Which will be economical for my application - any ideas...

Can anyone tell me about the Fillrite pump - what pressure it is the safety relief valve set at, etc...


Regards


alwayslearning (Mechanical) (OP)
27 May 04 23:21
Dear rmw,

Thanks for your detailed post - you read my post correctly and know my constraints - kind of deja vu feeling possibly ;)

Actually the fire training ground is far removed from any utility and air and steam is nowhere in the vicinity. Just to clear your doubt, in fact we do have an LPG stream which provides the source for buring of the diesel fuel! Now dont ask me what sense it makes to burn LPG to burn diesel ("that was not my design..." - that's all i can blithely say at this point).

{just a clarification: the fire department guys distinguish diesel fire from LPG fire and demonstrate ways to tackle each of these kinds of fires. Only that for the diesel fire case they have to use the LPG stream to keep the diesel burning.}

Your post has given me a clue that i can pursue. I will check if we can use some small air compressor to get the atomization that is needed. Can you recommend me a suitable venturi type if i were to use air for atomization for my application.

Regards
rmw (Mechanical)
27 May 04 23:36
While I go look for the link I want to send you to, just a thought.  Does any of the fire truck equipment have an air brake system that can be tied into on a temporary basis for the air supply??

I was fire fighter trained in the navy, (we all were, back when kids used to wear clothes that said 'new navy') and yes, there is a vast difference in those two types of fires.

later,

rmw
rmw (Mechanical)
27 May 04 23:47
The link I wanted to check to make sure I had it spelled correctly is;

www.vacuum-guide.com

You should be able to find something suitable there.

If not, post back, and I can post some specific companies that I have experience with in the USA.

rmw
alwayslearning (Mechanical) (OP)
28 May 04 5:51
Dear rmw,

I searched the proposed site quite extensively and found nothing of interest as far as info regarding "a small venturi for creating atomization".
Well, I did end up reading Torricelli's boigraphy though - it says he could be credited as the father of hydrodynamics, that he was an excellent lens grinder, that he was close to inventing calculus, and that he dabbled in experiments to measure the velocity of sound thru vacuum, etc. and also that he charted the trajectories of projectiles, etc. Gives us a feeling that Newton literally meant it when he spoke (that's what I guess they say he spoke) that "he saw things from the shoulders of giants" or some such things :).

Regards

rmw (Mechanical)
28 May 04 23:59
Always,

Here is the type of device I had in mind.

http://www.directindustry.com/comm/versatile_tank_mixers_heaters_from_schutte_koerting_5714.html

This is commonly used with steam as the motive to circulate and heat a fluid.

In your case air would be the motive, and the fluid coming out of the end of the eductor would be a highly agitated (aerated) diesel fuel just looking for a good place to burn.

Eductor is the word you want to search on.

Give this a shot.

rmw
alwayslearning (Mechanical) (OP)
1 Jun 04 5:20
Dear NCmog and rmw

I am trying a viking internal gear pump. The capcity is somewere about 9 gpm, and 50 psi pressure and can be with a 0.75 hp. This satisfies the pressure consideration. Now for the flow, the quesion is:
1) Does a 9 gpm flow rate create enough blaze not to disappoint the firefighters or dampen the trainees' fiery spirits? I know this is so much subjective but I am sure rmw will have some practical thoughts on this.

2) My next step is to buy a spray nozzle. What kind of spray nozzle should i go for: a) Solid cone spray nozzle or b) Hollow cone spray nozzle.

I was thinking that the full cone spray may give the appearance of a burst of solid fire. On second thoughts I am thinking whether a hollow cone would be a better choice because it would allow for a larger surface area for burning and may allow for complete combustion.

I look forward to hearing your thoughts.

rmw, In fact we do have a portable air compressor that can, in priciple, be utilised. I may still pursue the venturi (air motive fluid) option, which I guess would require least modification to the configuration. Lets see which direction the cost drives this little pyrotechnical project :)

Regards
rmw (Mechanical)
4 Jun 04 23:09
Always,

I recommended what I did, on the assumption that you were farly well restricted to the piping system and pump you described, and that you needed that amount of flow for the training exercise.

By reducing the flow rate of the fuel, you can reduce the pressure loss in the piping, and have more pressure available at the end for sprays and or atomization.

However, you still would have a cone or otherwise type of spray which would not burn as well as an atomized spray.

I recommended the eductor type device for two reasons.  One, the eductor motive I recommended, air would serve as an atomizing medium for the fuel, so that the exhaust of the eductor would be a well aerated and atomized mixture, ready to burn.

Eductors, or jets work by converting motive pressure to velocity, and using this velocity to entrain the load, or in your case, the fuel.  The result would be finely atomized fuel.

Secondly, the 'vacuum creating' effect of the eductor would help reduce the pressure loss in the piping.  In other words, the eductor device would give a 'pull' on the fuel in the piping, helping overcome pressure losses.

Good Luck on your project.

rmw

tickle (Chemical)
6 Jun 04 20:48
Does the rotary vane pump have an in built over pressure protection valve?  Can this be wound in or changed to give you a higher pressure at the pump?
alwayslearning (Mechanical) (OP)
7 Jun 04 2:43
Hi tickle,

I have been looking around for the set pressure for this over pressure protection valve. There is no mention of this in the publisher's catalogue. In my original post i have given a link to the website of the mfr wherein the pump perf curve is given (with 15 ft of 1" hose); the pump catalogue states that the pump rated for 25 psi. The pump casing has a label which states "50 PSI max".

I believe that the mfr doesnt recommend operation of the pump beyond 25 psi, and probably the set pressure would be around 27 psi etc (just a guess). I am hoping that some Tuthill bloke reads this post and advises.. (incidentally i sent them a mail but coudlnt elicit a response).

Regards
tickle (Chemical)
7 Jun 04 2:54
I have just installed a Ebsray pump and the manual does not mention about the setting of the bypass.

It was the first time that I had installed a rotary vane pump and initially the bypass valve spring was too low so that the pump was meeting the system pressure, then the valve started chattering and made for a noisey pump shed.  Changing the spring solved the problem.

Next time I will know.

I would have a play with the setting of the bypass valve, with a pressure gauge on the outlet and see what happens.  Assuming of course that the pipe work is suitably rated, and the PSV set pressure is increased.



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