Closing tank to pump before drafting

[marlmucker1]

Question....

We have a new truck and in order to establish a draft you must close the tank to pump valve. This is unsafe should you have people in a building because they will lose their water until the draft is established.

How does it look pulling firefighters out of a house until you establish the draft.

Why would this new truck be like that? It has an EPG, but I am not certain that has any bearing on this.

[BoxAlarm187]

Do you HAVE to close the tank-to-pump in order to get the draft, or is it just much easier to get the draft when you do so? There's quite a difference.

Keep us posted, this could be an interesting thread.

[ChiefKN]

Yea, is there an interlock or something?

I'd be experimenting with that...

[CaptOldTimer]

I want to hear more on this. I think he may have left something out.

[txgp17]

Have you tried switching from tank to draft with the EPG in both modes?

If it's in PRESSURE mode I can see where it would go haywire. It should perform more smoothly in RPM mode.

What size is the pump-to-tank line? If you're used to a truck that had a 4" line, and your new rig has a 3", I can see where you might have trouble.

Also, how many attack lines are you trying to supply while making this transition, and how GPM's is each one intended to flow?

[marlmucker1]

To help clarify - we draft in RPM mode, but have tried both. We can draft using either 2.5" or 4" hard suction and either way has same result - must close tank to pump.

We have tested this using multiple lines and with just one length of 1 3/4". I thought flowing water would have helped, but it doesn't seem to.

One of the issues with leaving the tank to pump open is that the water backfills out of the tank and it's seems impossible to overcome it. If you are trying to draft with a 4" line you aren't long losing all your on board water.

Our other trucks that don't have a EPG work great when drafting.

I wasn't at the call over the weekend, but was told that the pump operator was unable to establish a draft at all until he opened the tank fill. This was with everything closed (all lines were shutdown and tank to pump was closed). I am not certain why the tank fill had to be opened - can anyone help with that one? I suspect he may have had the truck in PSI mode, but I haven't confirmed that.

[ChiefDog]

We spec'ed MIV valves and a primer selector valve. (Valve allows you to switch which intake outside the MIV you are priming.) This allows us to run off tank water with everything closed and prime up to the MIV. Once primed, the MIV is opened and you don't have the problem described.

If you can't figure out the right combo of settings etc... you may want to look at modification with a auxilary primer or valve similar to what we spec'ed.

[westofd1]

Water will come from the path of least resistance! If your drafting from a pond, u will need to close tank to pump valve, cant imagine it any other way. I have switched from tank water to draft while pumping but only left tank valve open long enough, (with primer runnning), to flood pump. I myself prefer to draft in rpm mode also. stay safe

[HuntPA]

I have a couple questions:
1) How big of a pump are you trying to run? If I remember correctly, the last engine we had with 4" suction was a 500gpm. If you are running too many hand lines, you may not be able to get enough water through a 4" draft.

2) If the tank to pump line is 4" (or 2 - 3") and you are trying to draft from 4", the pump is obviously going to drain the tank before pulling a draft. You will get some venturi action, but if your tank is too low on volume, you will be sucking air from the tank before the suction line is primed.

3) In the original post, you say that the engine is new. Have you had the dealer out to show you how to operate per the manufacturer's recomendations? They might have a specific way that the truck was designed that requires a very specific operation to switch from tank to draft. If the dealer is any good at all, they should be there to help you out.

[Tim1118]

I really don't think it has anything to do with the pressure governor. You certainly should be able to set up a draft while running off of the tank. I've done it on several different engines, at several different fires... so I know it can be done.

If this is a new truck (not just new to your department), I would get the dealer/manufacturer involved. As you brought up, you never want to turn off water with a crew inside. It almost sounds to me as if something was not plumbed properly when the truck was built, or it may simply be a training issue.

Personally, until this is resolved, I would not send a crew in until after draft is established.

[westofd1]

Are the suctions gated? not the pony suction! As soon as u take a cap off to hook on sleeves you'll lose your tank water if they're not gated.

[JREGANGFA]

Your flow seems to be to low to impart a vaccum on the intake side of the pump when pulling through your 3" tank to pump. Seeing as you use a 2-1/2 as well as a 4" I would connect the 2-1/2 for this test to the 2-1/2 auxilary intake and close the valve. Start flowing water as you described and gate back on the tank to pump valve to cause a restriction which will increase suction side vaccum. Then crack your auxilary intake for your 2-1/2 suction. if water starts to come up then your good and can open it fully when all air is gone and close your tank valve. If water flows down the hose i would further restrict your take to pump. The trick is to remove the air in the suction hose in small amount so you dont loose your prime. Feel free to cycle the primer as well but I would limit that to 60-90 seconds. Hope this helps. John

[ffp20]

does your new rig have pre-prime capability for the suction and as another asked, is the suction gated? if not you'll likely have issues when you remove the main suction cap and you'll dump a crap load of water on your feet.

[kuh shise]

marlmucker1: I suspect that this is either a front suction or possibly a rear suction hook-up to a portable pond. First, you should NOT be using the EPG in the pressure mode when priming. You should change over to RPM before attempting to establish the second water source. The most probable cause of your difficulty is the construction of the truck plumbing where a portion of it traps a slug of air in the suction hose or piping. Second, you probably have a large or very short tank to pump line on this new rig. Some manufacturers are installing an air operated valve that is either fully open or fully closed. This can be a problem since it prevents the Pump Operator from partially closing the tank to pump line while pulling the primer valve. A tank to pump line should be able to supply at least 600 gpm, so when the hard sleeve is attached and the valve to the portable pond is opened, the water simply runs right past the pump intake and drains into the portable tank. Opening the pump to tank valve will place a large demand upon the supply and it might help to clear the trapped air in the suction line(s). If you have an adjustable tank to pump valve, try the following: 1. Set the EPG to rpm at the correct discharge pressure. 2. Open the suction valve to the portable tank and pull the primer handle.
3. With the primer operating and some discharge pressure still being developed by the pump, slowly open the tank fill valve. Continue holding the primer open.
4. Finally slowly choke down the tank to pump valve until the pump takes a hard prime. Release the primer handle.
5. Finish closing the tank to pump valve & refill the apparatus tank as you are able. As long as there is any pump pressure, air can not break the prime by following the tank fill line back to the pump. The excess flow to the tank will help eliminate any air in the suction side by drawing it through with the tank fill water.

Kuh Shise

[marlmucker1]

Thank you everyone for your input. We are going to do some further investigation and I will let you know what happens.

I am hopeful we can get a solution that does not require us shutting down tank to pump while flowing water because this is a huge safety issue.

I will let you know.

Thanks again.