Cavitation shuts unloader

[Chad A 14]

Okay, I promise last question.

Now that I have replaced the check valves and rebuilt unloader(Flow Type) ZK7.2 (4.2-6.6 GPM)

I have cavitation in the intake line.

If I hook the hose to it and not run the tank there is no issues.

But if I run just the tank I get cavitation in the intake line.

When the pumps stops pumping the unloader returns to normal. You see massive amount of air

in the intake line. (Left of the red handle).

Any suggestions.

[Russ Johnson 141]

That suction hose isn't any good. You need either fiber braid or spiral reinforced tubing. When it gets warm this summer sitting in the sun, it'll suck itself flat.

But anyway, what does the rest of the inlet system look like? Any elbows? Maybe a clogged strainer? Hose clamp loose? Is there enough water above the tank outlet? When a pump is drawing, a little whirlpool can form, allowing air in the suction stream.

[Chad A 14]

There is roughly 200 gals in a 525 tank. Double checked hose clamps they are tight. There is 1 elbow and it appears ti be tight. The strainer is clean and I replaced oring in the water filter. Don't see any visible drips in the intake line.

[bks0005 14]

Take Russ's advice and change the suction hose. I have a 1 1/2 ribbed suction hose with a 1 1/2 strainer on mine and it works great. Mine runs like this: tank, cut off valve, strainer, then the pump. I fill the tank directly from the supply line with a float valve.

[mick m 19]

All of the above. Perhaps increase the diameter of your intake hose as well. You can never have too bigger hose on the intake side.

[Christopher 102]

Is that the unloader bypass tying into the suction at the "T" or "cross"?

If you have a tank, I would only supply from the tank, have the pump bypass going into the top of the water tank.

Something to think about, when you connect a garden hose for a supply, there will always be air in the garden hose so you will be forever putting some air into the system causing a little bit of cavitation and over time it might affect your pump like it did now.

Run larger diameter supply hose from the tank, like 1". It looks like you have 5/8" hose or maybe even 1/2" hose supplying the pump.

Listen to Russ, that hose is no good, get a better and larger diameter hose supply line from the tank to the pump.

Do you empty your tank at the end of jobs or when you get on the road to cut back on weight? If so I would put a block valve right at the tank on the line to the pump and block it before you drain the tank otherwise when you drain the tank or get it very low you are getting air into the system all the time. Block in the valve and empty the tank, when you are ready to work and filling the tank, after it is about 1/3 or 1/2 full then open the supply valve and you won't get air into the line. I do this when I travel out of town for work every other week to cut on excess weight on the trailer.

[Russ Johnson 141]

Your inlet plumbing is horrible too. Always use brass, plastic, or stainless fittings for the inlet...no galvanized or black iron. Those 2 tees also give you the equivalent of 2 elbows too. I'd take the suction line off where it is and straight hose barb it into the opposite side of the pump head.

[Jerry 24]

Your inlet plumbing is horrible too. Always use brass, plastic, or stainless fittings for the inlet...no galvanized or black iron. Those 2 tees also give you the equivalent of 2 elbows too. I'd take the suction line off where it is and straight hose barb it into the opposite side of the pump head.

Ditto..

replumb the entite inlet side of your pump.

even if the rusting steel flow restrictors wasn't going to be an issue..

the "suspended weight" against the inlet of the pump will be a broken fitting starving the pump for water after bouncing down the freeway.

Start over..

brass fittings AT the inlet s of the pump.. DUAL inlets, and flexible reinforced hose "lazy-looping" to the filter (with No stressed fittings).

ot 5gpm.. use 1" feed line, not more than 4 feet long, split into a 3/4" line to the 2nd inlet.

Filter should have 1" in n out threads, with a 5 or 10" cleanable screen.

Russ can set you up.. He's a GREAT technical-supplier, and he jumped in here to help you first..

*** support the technical suppliers in this forum ***

:{)

[Chad A 14]

Ok I have done a little diagram. I have looked and the installation diagram from GP.

1. The installation diagram has the chem injector on the hi pressure side but mine is on the intake side. (Good or Bad)

2. I am going to move the tank line to where the chem injector is. The unloader by pass is on the right side of the pump. (Can it stay there if I cap off the Cross section.)

3. I will be replace all the intake with brass fittings.

4. I am changing the intake line from the pump to a fiber reinforced hose.

Thank yall for the help on this.

[Chad A 14]

Okay Great the cavitation is gone while running but now it started another issues.

Pump Pulsates when the gun is released. I left the clear hose in for the time being just in case I have to move or cut it. Then I can use it as a template for the redline hose.

I did a video of it than trying to explain it.

[Jerry 24]

O.K.. unloader "fluctuation" is caused by the flow-actuated unloader..

If the bypassing water isn't enough in volume to keep the valve inthe bypass mode..

it kicks down to the pressure-mode.

What changed ??..

Either you pump's output has dropped, or..

The flow-restriction of your bypass line "helped it stay in bypass"..

Now that you've relieved the flow-restriction.. you need to put back just a little..

Changing the bypass-oriface is what the factory wants you to do, or..

you could use a smaller hose for the bypass back to your tank,

or, drop a stainless steel flat-washer between the bypass-nipple and teh hose-barb..

the little bit of added flow restriction keeps it in bypass !

To double-check this is all you need..

squeeze the bypass line with a pair of pliers, and if the restriction settles id down, you have a plan !

BTW..

if you still have the bypass line running to the inlet side of the pump..

change it..

having it bypass to the tank eliminates the possibility of a bypass overheat.

Also, it makes theh system easier to troubleshoot.

Edited February 16, 2012 by Jerry
sp

[Chad A 14]

The red star marks the bypass line from the unloader to the intake of the pump. From what I am reading that it is safe to run this line straight to the tank. I just purchased a new hi pressure hose for this. So basically this hose does not need to be hi pressure. Am I understanding this right.

So I could run just a 1/4" poly hose from the unloader to the tank and I will be fine. The current hose is a 3/8" 6000 PSI ID and the orfice in the end of the hose appears to be approx. 11/64 but I have not measured it just going off sight.

The 2 yellow stars is really the only thing that has changed other that removing the chem injection system from the pump.

The 2 hose barbs are 1/2" ID compared to the 3/8" ID that was originally on there.

[bks0005 14]

Your bypass line comes from your unloader valve to the tank. From what it appears you have is a bypass from the hi pressure side of the pump back to the inlet side of the pump, that will do nothing for you. I believe if you remove the line altogether that will fix your problem as long as you have a bypass line from the unloader valve to the tank. If you need any help message me and ill talk you through it on the phone.

[Chad A 14]

Here is a pic of the unloader to the right inlet of the pump.

1. Hi Pressure Discharge

2. Hi Pressure Bypass ( I think Hi Pressure)

3. Hi pressure discharge from unloader to burner

4. Thermal Relief Valve

5. Goes to a weeping valve that is connected to the Beckett Fuel pump for burner.

I really do appreciate all the help that yall a giving me on this unit.

[bks0005 14]

Hose #2 ( bypass hose ) needs to go back to your water tank not the pump. That should correct the problem with the unloader. What type of switch do you have ie -flow or pressure that turns your burner on? Not sure why your thermal relief valve is located there, mine is on the outlet side of the burner coil. To double feed the pump you could have a elbow on the right side bottom of the pump and a tee on the other side. I would strongly recommend using a 1" suction line for this. The left, top side of the pump is the high pressure, this line goes to the unloader valve. On the unloader, I would have the bypass line run directly to the tank with a clear braided hose. The hose I use for this is rated for 800 psi.

[Christopher 102]

Before you do anything else and possibly add more wear to your packings, go and re-read what all of us have told you to do and get it done.

If you have any problems then post them. Not changing this or not changing that is only wasting time, causing aggravation and has you continuously asking more questions.

Tear all that junk off the pump and plumb it like we all told you to do and be done with it.

You will be glad you did.

The bottom ports of the pump is the inlet, the top ports of the pump are the outlet.

In at the bottom from filter from tank, out to unloader with the bypass line to the tank, not back into the pump. Use Brass or plastic fittings on the pump head, not galvanized or regular metal as they will start rusting tomorrow.

Let us know how happy you are when you get this all done.

[Russ Johnson 141]

Hose #5. Goes to a Clippard valve? I haven't seen one of those in ages.

[Chad A 14]

Is a clippard valve a good thing or bad thing. Is there a way to bypass or is it needed.

[Russ Johnson 141]

They used to use them to shut off the flow of fuel to the burner instead of an electrically controlled solenoid. The bypass line is orificed to create back pressure against the valve, shutting it off. If you run your bypass line to the tank, you'll have to install a solenoid on the burner, and a switch to control it.

[Chad A 14]

Russ,

I took a picture of the burner it is a Wayne Ehasr .75 - 3.0 gpm 1450 rpm

It has a 110 volt fuel solenoid on the burner that is controled by an on/off switch which activates the burner.

So will it be safe or not recommended to remove the clippard valve in this case.

Thanks for your help and everyone else too.

[Chad A 14]

I want to thank Brian, Russ, Christopher, and Jerry

A big hi five and thank you. Ya'll deserve it.

Tell ya what I done and all I can say is WOW. What a difference those changes made.

The first image is where the clippard valve use to be. I did some reading on the old whitco units. They use the clippard valve on the older burners which didn't have a fuel solenoid. Good thing for me this is a newer burner which has the on board fuel solenoid. So I removed everything associated with that valve.

The second image is where the bypass was that went to the pump. I removed all of that hi pressure hose for the bypass and ran a 300 PSI (Which after reading the unloader instructions it should be atleast 600 PSI) to the tank. Cavitation what cavitation its gone completely, even the unloader stopped pulsating after the release of the gun. The unloader had a #2 orfice in it where the bypass hose hooked up so I just ran that 300PSI 1/4" to the tank. Its about a 8 ft run.

The third image is the pump. I used what is called tigerflex rated 300PSI with a crush rate of 100#'s. I changed the original hose barbs on the pumpfrom 5/8" to 3/4" brass hi flow barb. Pulled all the galvinized crap off the pump and used 2 3/4" T's one for the hose barb and one for the thermal valve and put a plug om the end of the last T for purging air out of the system.

I bought this unit as a backup for hood cleaning since my son n law wanted to join in on the family business. I think I have a beast now. Just actually have to check the PSI coming from the pump.

Again thank yall all of yall.

Chad