Primimg without a primer

[deepember123]

Hey there - question for my fellow drivers. I remember something about being able to prime my fire pump without a primer lf it malfunctions, is inoperable, etc. by either opening the lowest discharge or the highest - I can't recall which. Could someone please correct me and explain breifly the physics involved by doing so? Thanks.

[ullrichk]

If you have enough water in the tank you can pump at high pressure (to the point of cavitation) through a nozzle directly attached directly to a discharge. The pressure is lowered in the hard suction by the venturi effect - the same principle as a foam eductor - and you can achieve prime without a primer.

[ADSNWFLD]

If you have water in the tank you can back flush to get prime.
Open your tank to pump, then if equiped open the intake. The water will come out the suction hose, when the bubbles stop throttle up and you should have it.
Their may be a few bubbles but if flowing enough they shouldn't make you loose prime.

You can also put a line into the suction hose and it will get you primed through venturi.

Practice these procedures and see what you like, it is always good to have several things in the tool box

[ullrichk]

Don't you need a foot valve to get prime by "back flushing"? The tank-to-pump on my engine doesn't flow enough to fill an open-ended 6" hard intake.

[tribe9a]

Yeah I think with the surface of the body of water and the tank both being open to the atmosphere that the water would seek its own level and not back-up in the suction line. I know thats the idea behind foot valves and why they work.

[GggFF3P]

What ADSNWFLD was saying (I have done the same on many occasions) is have the pump engaged but at idle, then open the tank to the pump which will fill the pump.(some people will open a discharge to let the air out) Then open the suction valve, water will flow out the suction hose. When the small bubbles just about stop flowing out of the end of the suction you turn up the throttle and you will have prime. No foot valve needed. As far as the question about high or low discharge to open it would be high because you are trying to let the air out of the pump so more water can get in.

[SpartanGuy]

I've done it the same way that ullrichk did, it's just we were flowing water through a hoseline instead of a nozzle directly on the discharge.

Then again, the people who pump test our engine say the pump is abnormally well sealed in that it picks up a prime easy and rarely loses it unless you almost try to.


Which is good for n00b MPOs.

[jasonsfd]

YOU HAVE TO BE CAREFUL NOT TO DUMP ALL OF WATER OUT OF YOUR TANK INTO WHATEVER YOU ARE DRAFTING FROM. IT WORKS THOUGH AS A LAST RESORT. HAD TO DO IT ONE TIME.

[SFDchief]

Originally posted by ullrichk
Don't you need a foot valve to get prime by "back flushing"? The tank-to-pump on my engine doesn't flow enough to fill an open-ended 6" hard intake.

No, we have no problem back flushing to prime without a foot valve. You have to do it with all discharges and drains closed and pump running.

When you open your tank suction you wait until you see the water coming out of the strainer. Once you close the tank suction there should be an sufficiant seal at the pump for the water not to flow back through.

It's the same principle as if you stick a straw in a glass of water and hold your finger over the top of the straw. Once you take it out of the glass, the straw is still full.

[mohican]

A centrifical pump needs a primer only if there is no water in the impellor.

If you want to draft with a broken primer you have to start flowing from the tank, and gradually feather the suction line valve open while gradually closing the tank to pump valve.

If you have a truck that is problamatic while drafting, either with or without primer, I would recommend using the shortest possible suction lay possible. On midship pumpers, this would mean using the suction on eather side of the pump panel and not using a front or rear suction.

[Driver76]

On midship pumpers, this would mean using the suction on eather side of the pump panel and not using a front or rear suction. [/B][/QUOTE]

______________________________ _____________


Most front suctions have dips and bends where they are piped over and around the engine and front axel, giving you the most friction loss even in ideal stiuations.

Another option is to lift your suction tube up out of the water source and, after removing the strainer, fill the tube using a bucket. Place a steamer cap on the end, lower the tube below the surface, and hit your primer. When you achieve prime you need, to remove the cap and put the strainer back on. It can be tricky but I've seen it work a number of times.

-bob-

[DaronG]

The way we use as a backup for drafting in case of primer failure is simple and almost foolproof(firefighterproof). The procedure we use is: With the pump disengaged, unscrew the steamer cap off of whichever side you will be drafting from. Hook up hard suction lines as normal except instead of a strainer put the steamer cap on the end of the hard suction line. Put the hard suction line into your water source. Open up your tank to pump valve, BTW this will require anywhere from 100 to 300 gallons of water from your booster tank depending on your pump configuration, and open up your highest discharge. As the hard suction fills you will see water along with a few bubbles coming out of the discharge as it pushes the air out of the system. Once as the water turns to a good steady flow, engage the pump and you should see about 50 lbs of pressure on your gauge at idle speed. At this point you will need to take the steamer cap of the end of the hard suction while still at idle speed and making sure not to break the surface of the water. The intake ind must stay submerged at all times once as the air is out or you will lose your draft. And hook up your strainer and then draft at required speed. I have done this a number of times now and although it sounds time consuming a trained 2-man crew can do it in under minutes. Almost as fast as setting up a draft with a prime pump. It does takes practice though. The only draw back is one person will have to get wet, but unless that person was planning on making entry later in the games it really isn't that big of a deal when compaired to the water supply you just got access to.

[mikecarver]

we use a butterfly valve mounted on the steamer upside down with the drain on top. pump in gear pumping from the tank. hard suction under the water. open the gate and the hard suction will fill raise the pressure and secure tank to pump and fill apparatus

Also we use a low level strainer with a 11/2 hose attached to it. drop the hose in the dump tank or the lake and fill the hard suction until water comes from the drain which all the air is gone. Then open the butterfly valve that is omounted on the steamer and fill your tank.
Works great on water shuttle operations.
Thanks Camden

[LtTim556]

While flowing water through your attack line at the proper pressure. First ensure all caps and hoses are tight and drain valves are closed, this it the most common reason for failure to pull a draft. Using a butterfly valve or piston intake valve open it slowly while slowly closing the tank to pump valve. Don't let discharge pressure drop below 50psi. You must keep water flowing. This is a two handed operation. Closing the tank to pump valve increases the suction in the draft hose. What you are doing is creating a negative pressure in the draft hose. Maintain your draft by discharging a booster line or inch and 3/4 line into the porta-tank. This keeps water flowing. When drafting your intake gauge should be reading in the negative.
Master this technique during training never try it the first time on the fireground. I sometimes joke with the firefighters during training saying that using the primer is cheating. I hope this helps but try the techniques suggested in this forum and see what works best for you. Good luck.