Thread: Hydrant Changeover
05-10-2001, 10:25 PM #1PBF8TFirehouse.com Guest
When performing a change over from your booster tank to supply line on top mounted pump.
On side mounted pump panel, the tank to pump valve can be slowly closed while slowly opening the suction.
With the top mount pump, what method are you using to open piston intake valve then get up to close tank to pump valve? Is it ok to open suction all the way, then go up and close the tank to pump?
05-10-2001, 11:55 PM #2ENGINE 52Firehouse.com Guest
Yes it is ok . We have a top mount pump Pierce Arrow with a piston value.What we do is open the piston value then close the tank to pump value. All that happens is that few seconds you back fill in to the tank.
05-11-2001, 10:34 AM #3CAPTAIN WHOFirehouse.com Guest
Most units should have a check valve located in conjunction with tank supply valve .
I instruct my members to leave the tank to pump valve open when switching to hydrant.
The pressure from the hydrant will close the check valve. Yes there is bleed through to the tank from the check valve but it is quite minimal.
The advantage of this is, if for some reason the hydrant was to loose pressure or waterflow was interrupted while doing an interior attack, the pump will start drawing from the tank without interruption giving the operator time to evaluate and safely back out crews with out loss of water.
This works even better if you are using a pressure governor.
05-11-2001, 05:44 PM #4Ten8_Ten19Firehouse.com Guest
CAPTAIN...Did you spec a tank suction check valve? Never seen one but it sounds good.
05-11-2001, 06:59 PM #5CAPTAIN WHOFirehouse.com Guest
Tank suction check valves are standard spec in Canada. The check valve is integral with midship pumps behind the 8 bolt flange the the supply valve is mounted to. Most pumps in the US would have this also unless some one is removing it?
05-11-2001, 08:08 PM #6jpchevFirehouse.com Guest
I agree, open the piston intake SLOWLY! first, then close the tank to pump valve, watch your pressure!! If your pump is running at a certain RPM to supply a certain pressure from tank, it will deliver a lot more if the supply is 50 or 60 PSI from a hydrant. Captain John HJFD
05-11-2001, 08:15 PM #7mongofire_99Firehouse.com Guest
Open the PIV, then close the tank to pump.
The worse thing that happens is the tank will top off (which you should do anyway) before you get the valve closed and then a little bit of water will run out on the ground.
As for check valves, either way you look at it they are an obstruction in the system. If you didn't spec it any different, your tank to pump line should flow about 500gpm as it's probably just a single 3" line. Add a check valve in and your looking at dropping the diameter of the line, maybe by an inch and thus reduce the flow further.
Not much help when you need a blitz attack or a quick blast with the deckgun before the hydrant tap is be made.
05-11-2001, 09:34 PM #8ADSN/WFLDFirehouse.com Guest
Set your relief valve prior to switching to the hydrant and you will not have any problems. Once you have the hydrant open and the tank to pump closed adjust your throttle till the relief valve closes.
It's not a bad idea to fill your tank once your set, just in case something goes wrong with the water supply.
05-11-2001, 11:12 PM #9LHS*Firehouse.com Guest
I guess it all depends how you set up your rig.
If you use an automatic hydrant valve and precon valve on the pump the hydrant will do your change over for you without the pump operator doing anything but hooking the hose to the pumper. The intake valve will open itself when the auto hydrant valve fully opens and if you did not spec a check valve automatically fill your water tank without effecting the crews lines fighting fire.
05-16-2001, 04:31 AM #10eyecueFirehouse.com Guest
The check valve is real! It is a brass flapper type valve not a ball! It clears itself from the water way during tank suction. The loss is minimal.
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