Tank Water to Drafting Improvement Question

[Pelican631]

Not trying to beat a dead horse, but I think this is a unique situation.

Our first due engine has an air-operated tank to pump valve, which makes transitioning from tank water to drafting without losing pressure very, very difficult since it's an "on-off" valve that's difficult to slowly close. I'm looking to improve the situation and so far I've come up with three options:

1) Replace the air-actuation with an electric actuation so that it can be slowly closed. This is probably the most expensive option, and least likely to happen
2) Use a low-level strainer with a jet siphon attachment and use the jet siphon for initial priming
3) Add a second primer valve connected to the intake side of the Hale Master Intake Valve (it's already got the connection there, I'd just need to add a second primer valve teed into the existing suction line)

I'm liking option 3, but I'm wondering if this really helps me. When I'm operating off of tank water I can run the 2nd primer valve and "pre-prime" the hard suction, so now I have atmospheric pressure holding that water in the hard suction. My question is then what happens when I open the master intake valve? I have a vacuum created in the hard suction, but as soon as I open the intake valve isn't the tank water going to force it's way in there and "push" out the hard suction (if for instance I'm only operating one handline) since it's at a higher elevation (pressure)? If so, how is this any different than just opening the intake valve without pre-priming it?

I've got to be overthinking this, but looking for some insight.

Thanks in advance,

Andy

[FyredUp]

Okay how about this, and I apologize if I am misunderstanding the issue.

For the time being the low level strainer with the jet siphon is the immediate answer.

In the long run adding the second primer seems a better solution. Pre-prime the hard sleeve and as you are opening the intake valve run the pump primer to keep the water moving into the pump as you open the valve.

[kuh shise]

Option 3 is probably the best of the three. Take a look at a Trident air primer here: http://www.tridentdirect.com/newsite...e/airprime.pdf

What is causing your difficulty is the volume of air in the suction tube, and the fact that this air enters the pump impeller effectively breaking the prime when you open the master intake valve. By priming the suction tube you will reduce the amount of air introduced to the pump when opening the master intake. It is likely that you will still have some air trapped in the intake, but operating the main primer while opening the master intake the transition should go much smoother and quicker.
Yes, the tank water will try to flow back down the suction tube, but you will be closing the tank to pump anyway. Remember to refill the tank as soon as you have enough water to act as a reserve if you run out with FF's in the building.
If you opt to use the jet syphon, bleed the air from the intake before trying to transition to the drop tank. Then hold the main primer on while opening the main intake valve to clear any trapped air as it comes through the pump.

[FyredUp]

KuhShise...

Did we actually agree on the best option and how to make it work?

That may be a first!!

[Pelican631]

Thanks for the info, the Trident air priming system seems pretty neat. I've got a quote request in to them, but I'm thinking it'll probably be less expensive to just add a second Hale priming valve teed into our existing priming pump. That'll actually cost less than buying a new jet siphon strainer (our existing low level doesn't have the jet siphon).

So the procedure would be:
1) pre-prime suction hose
2) run pump primer while opening master intake valve (electric actuation)
3) Once intake valve is open, close tank to pump (air actuation) and then release pump primer

Sound right?

Andy

[FyredUp]

Add to that sequence to be sure to let the interior crews, AND command, know that you are switching from tank water to drafting and there may be a momentary loss of pressure. Better to warn them so they can prepare than have to run from them when they come out all bent out of shape or worse.

I would also add this thought, depending on the pressure you are supplying to lines in operation you may have to increase engine rpms to make sure you achieve prime. I know with our Mack engine it is far easier to prime at around 1200 rpms than anything lower than that.

[kuh shise]

Geezzzz, Fyredup

I never thought we had many disagreements. Most pumping problems simply need enough practice to work out the rough spots. I like the 1200 rpm point too, but it works better when the tank fill is open and the pump is in series. Blowing the trapped air back into the tank is a good technique. A word of caution, some of the older Macks had the tank fill line plumbed into the volute of the first stage of a Watrous pump. Using the tank fill to cool when in series doesn't really circulate water through the second stage of the pump. Pelican, just go out there and play with the different suggestions discussed in this thread. One way to avoid having to stretch the pre-connect (1 3/4 @ 150 gpm) is to put an old turbo jet on a discharge and set the flow ring at 125 gpm. Then pump the nozzle at 150 psi to flow 153 gpm.

[FyredUp]

Kuhshise,

We haven't had too many disagreements, hence the smiley face.

I did not know that about the tank fill line. I will have to check that out.

Thanks for the heads up.

[Pelican631]

So we decided to go ahead and add the second priming valve to the intake. The results are about what I expected. Although it doesn't completely eliminate the problem, it's a dramatic improvement. We can now make the transition while only losing discharge pressure for a few seconds (and still flow "some" water during that time), rather than ten seconds or more. Here's a short video of one of our guys making the transition:

http://www.youtube.com/watch?v=TP-miorZxxo

You'll see the pressure on the deck gun decrease shortly after the tank to pump is closed, but it's only for a couple seconds.

Andy

[MG3610]

So we decided to go ahead and add the second priming valve to the intake. The results are about what I expected. Although it doesn't completely eliminate the problem, it's a dramatic improvement. We can now make the transition while only losing discharge pressure for a few seconds (and still flow "some" water during that time), rather than ten seconds or more. Here's a short video of one of our guys making the transition:

http://www.youtube.com/watch?v=TP-miorZxxo

You'll see the pressure on the deck gun decrease shortly after the tank to pump is closed, but it's only for a couple seconds.

Andy

I like the video, thanks for posting it. My only thought is by tapping the MIV switch and opening the intake VERY slowly, would you find the transition to be smoother...I think it might make a difference.