Unloader - over pressure, no flow

Fox , pressure spike is the momentary increase in pressure when you close the gun before the unloader 'unloads'. If you have a gauge you will see the needle 'jump' up and then drop. You want to 'loosen' the unloader until the jump only goes a little past the pressure you run at.
 
tomtucson said:
Fox , pressure spike is the momentary increase in pressure when you close the gun before the unloader 'unloads'. If you have a gauge you will see the needle 'jump' up and then drop. You want to 'loosen' the unloader until the jump only goes a little past the pressure you run at.
Click to expand...

Hey Tom,
Thanks for the clarification, I got it now :). I'll be putting it tomorrow. So if the spike is too much, I should lower the pressure?
Now when I understood what pressure spike is, I think my hydrotek has a crazy pressure spike. It has the K7 unloader. I have replaced probably 10 plugs for the past month. They all get worn out as they build a little edge and become very hard to disconnect. I should take a look at this one too...
 
This is what I discovered inside the old unloader. The piston had a missing piece, the o-ring was totally worn out and the spring on the piston was half gone.. I would suggest everyone with machines that have worked well for years, inspect your unloaders :)..

IMG_2779.jpg

IMG_2783.jpg
 
Russ, is that a special O-Ring?

Do you have to get a rebuild kit to replace that O-Ring?

Talk to us about it please.

Thank You.
 
Great info guys.

tomtucson said:
Fox , pressure spike is the momentary increase in pressure when you close the gun before the unloader 'unloads'. If you have a gauge you will see the needle 'jump' up and then drop. You want to 'loosen' the unloader until the jump only goes a little past the pressure you run at.
Click to expand...

I run pump at 3600 psi on the head of the TSF2021, the "spike" pressure when I release the trigger on 1/2" hose 200ft is 4300 psi on the head,.

I want to run the pump at the max pressure, how can I do that and still be within the 7 to 10% "spike" range. (I have pulsation dampener on the head to slow the rate of "spike", on my 4 gpm machine without pulsation dampener you would almost need a high speed camera to catch the max. spike)
 
810f250 said:
Great info guys.



I run pump at 3600 psi on the head of the TSF2021, the "spike" pressure when I release the trigger on 1/2" hose 200ft is 4300 psi on the head,.

I want to run the pump at the max pressure, how can I do that and still be within the 7 to 10% "spike" range. (I have pulsation dampener on the head to slow the rate of "spike", on my 4 gpm machine you would almost need a high speed camera to catch the max. spike)
Click to expand...

I have the same pump. Isn't it rated at 3500PSi 8GPM?
 
tomtucson said:
Fox , pressure spike is the momentary increase in pressure when you close the gun before the unloader 'unloads'. If you have a gauge you will see the needle 'jump' up and then drop. You want to 'loosen' the unloader until the jump only goes a little past the pressure you run at.
Click to expand...

Ok, so now I am confused.

I just installed the new unloader, but all my tests dont show any pressure spike. When I messure the pressure through the coil, it's 1000PSI higher than without the coil, with gun off. What does that mean? I haven't flushed the coil yet. Should I adjust the unloader with or wothout the coil?
When I had the old unloader, when the gun was off, the gauge at the head showed 0PSI, now with the new unloader there is pressure all the time.
new-unloader-old-unloader.jpg


Here are a couple of test vids through the coil and without the coil:


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<object height="344" width="425">


<embed src="http://www.youtube.com/v/ik9aM1V9i50&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" height="344" width="425"></object>
 
The guage should show 0 psi when you release the trigger, as you say the old unloader used to do.
I dont know whats the problem. The connections to the unloader look correct. (double check that still)

I see it going in to bypass, but pressure remains on the guage

Humm!

You got me doing some extra reading. What model/part # is the unloader?
 
Now that I think about it, .....the pressure on the head is probably zero when it is in bypass, but because of where you have both the guages placed on the system it is showing trapped pressure and not unloaded pump head pressure. Put a guage up stream the inlet to the unloader or on the pump head directly.

Can someone confirm that.
 
Yeah, that port is reading trapped pressure. There are gauge ports on that general head if you put the gauge there it will tell you what the pressure is at the pump. The way it's set up now there's not a spike but I think you should be able to adjust that 'hold' or trapped pressure to 7 - 10 % instead.
 
tomtucson said:
Yeah, that port is reading trapped pressure. There are gauge ports on that general head if you put the gauge there it will tell you what the pressure is at the pump. The way it's set up now there's not a spike but I think you should be able to adjust that 'hold' or trapped pressure to 7 - 10 % instead.
Click to expand...

Thanks Tom!!





This thread has lead me to read more about unloading a pump. Thanks guys.

"spike" increases with hose length (generalpump.com)

Some questions I now have, I dont want to hijack this thread but this one may be "sticky" thread material

Why most of the industry uses "unloaders" and not "regulating valves" even on bigger industrial systems.

What are the pros and cons of regulating valves besides being more suitable for multiple gun compatibility operation?
 
Thanks for your input guys! I figured the same about the trapped pressure.
The model of the unloader is PA VB 80/280. When we talk about adjusting the unloader, I am left with the impression that it could be adjusted in two directions: 1) working PSI with open gun and proper 0 nozzle ; 2) pressure spike which needs to be 7-10% of the working PSI on the head with open gun and proper 0 nozzle. On the other hand the only way to adjust the unloader is with the bolt on the spring. I am assuming that the first adjustment defines the other? I will not adjust the unloader to more than 3300PSI head pressure. Please correct me if I am wrong.
Should I adjust the unloader through the coil or without it? I will flush the coil the next few days, but tomorrow I have a big job where both machines of mine will be in use. I don't want any surprises.

Thanks!
 
FoxSweeping said:
Thanks for your input guys! I figured the same about the trapped pressure.
The model of the unloader is PA VB 80/280. When we talk about adjusting the unloader, I am left with the impression that it could be adjusted in two directions: 1) working PSI with open gun and proper 0 nozzle ; 2) pressure spike which needs to be 7-10% of the working PSI on the head with open gun and proper 0 nozzle. On the other hand the only way to adjust the unloader is with the bolt on the spring. I am assuming that the first adjustment defines the other? I will not adjust the unloader to more than 3300PSI head pressure. Please correct me if I am wrong.
Should I adjust the unloader through the coil or without it? I will flush the coil the next few days, but tomorrow I have a big job where both machines of mine will be in use. I don't want any surprises.

Thanks!
Click to expand...

I would think that you could adjust the unloader to set the desired or max pump head pressure,.... with either of your described methods if you use the correct size nozzle or smaller ("smaller nozzle" only because you have a trapped pressure unloader), so long as you have an accurate guage on the head of the pump.

The reason I say you could use a smaller nozzle this is because (or if the coil has a restriction, same effect), ......from what I understand how an unloader works, .......when you adjust the unloader (with flow through the gun with smaller or correct size nozzle) and you achieve the maximum or desired head pressure (pressure guage on pump head) for the pump volume displaced the remaining water goes into bypass (once the unloade is functioning properly).

Now if you used a bigger or worn nozzle and you adjust the unloader to the maximum head pressure and you later inserted a smaller or correct sized nozzle for the same pump rpm the pressure would me more that the max pressure.
.
.
.
.

5% is desired to go into bypass with correct size nozzle to minimize "spike" for the a systems pressure restriction (which is caused by water hammer, hose size & length, fittings and coil).

{I think I answered my question below}

810f250 said:
Great info guys.



I run pump at 3600 psi on the head of the TSF2021, the "spike" pressure when I release the trigger on 1/2" hose 200ft is 4300 psi on the head,.

I want to run the pump at the max pressure, how can I do that and still be within the 7 to 10% "spike" range. (I have pulsation dampener on the head to slow the rate of "spike", on my 4 gpm machine without pulsation dampener you would almost need a high speed camera to catch the max. spike)
Click to expand...
 
I believe pressure should be taken at the pump head. Lets say you know what your pump 'should' be putting out at the rpm your engine is running at. Then select the correct nozzle and spray the gun. Now while spraying loosen the bolt on the unloader and watch the pressure drop, then tighten it back up until it just reaches the operating psi and stop there. If you can keep tightening the bolt and the pressure keeps going up a lot then your pump is putting out more water than you're using, if it's still within the specs of your engine you 'could' put on a bigger nozzle and try to get back up to pressure. When you're tightening the bolt (while spraying) and the pressure stops going up, then thats all you got. Fox, because you have like 4000 + in your line, I would guess the unloader is set too high - you should be able to loosen the bolt a few turns while spraying without the pressure going down - try loosening it while your spraying until the pressure starts to drop. I'm gathering you weren't adjusting while spraying?

I think the point is to minimize the spike? The 7-10% is supposed to be the maximum?
 
Nigel - How are you. The 5% is only for flow unloaders, right? I think its to keep the 'piston' open so when it shoots into bypass the water doesn't hit a closed 'door' (that's a guess). A trap unloader should be able to be set at any pressure - big nozzle, small nozzle - and then use any size nozzle. In practice the pressure will go up some with a smaller nozzle. The one catalog I saw regulating valves in, they all had max pressure less than 3000 and they were pricey, maybe thats why they're not standard. I wonder, the spike increasing with hose length, if thats because of the stretch of the hose under pressure?
 
tomtucson said:
Nigel - How are you. The 5% is only for flow unloaders, right? I think its to keep the 'piston' open so when it shoots into bypass the water doesn't hit a closed 'door' (that's a guess). A trap unloader should be able to be set at any pressure - big nozzle, small nozzle - and then use any size nozzle. In practice the pressure will go up some with a smaller nozzle. The one catalog I saw regulating valves in, they all had max pressure less than 3000 and they were pricey, maybe thats why they're not standard. I wonder, the spike increasing with hose length, if thats because of the stretch of the hose under pressure?
Click to expand...

I cool Tom! and you?

I dug the previous info up on generalpump.com,

the 5% was on their website for some trapped pressure unloaders too. (I was surprised also).

The water hammer is a function of the speed the trigger & unloader closes and the pumping fluid properties, and the fact that the shock wave hits another "closed door",.... the check valve in the trapped pressure unloader.

There are regulating valves that I have seen that max at 5800psi and flow as much as 120gpm.

I wonder what will happen if you remove the check valve inside of a trapped pressure unloader? Would it work like a regulating valve?
 
Flow restrictions

Yes, yes, yes, all that, ..and a cup of tea, Eh?
It's great to see you guys thinking this all through, so..

The moral to the story..

A) Get a pressure gauge on the head of the pump,
and at the hose reel..
the first one tells you the performance of the pump system,
the other tells you the flow restriction thru the coil, and the actual spike-pressure against the outlet side of the system,
including "water-weight" (aka inertia) in that more-than 50 ft hose you have.
Don't leave more than 150 ft of hose on your reel for that reason, and the reel will last longer too.

B) you need actual, methodical, proven "Guidelines" for adjusting an unloader valve SAFELY and for long-term-low-cost.
e-mail me for FREE copy of that info.

C) when you check system pressure, use your O-degree nozzle,
as it is more accurate, since it has a more durable oriface.
Your worn nozzles are a problem to the reliability of system components..
If you adjust that unloader "perfectly" with a good nozzle,
when you use the worn nozzle, you won't have as good a working-pressure as possible,
and you won't be bypassing as much as the unloader needs to for long wear, and lower pressure-spikes.
It's better to go down a nozzle-size to bypass a little water, and enjoy a better working pressure,
than to "flow the whole flow" with reduced pressure, and the unloader hammering itself to death.
e-mail me for a copy of the "Nozzle chart" and learn how to use it ACCURATELY

D) More and more of you guys are going over the recommended 7gpm max through 3/8" hose..
the flow restriction is horrendous.. 5gpm through a 100ft hose sees about a 130psi drop..
Put 8gpm through 3/8" hose and loose 300+psi for every 100 ft.. that's right,
in 200ft, you may see 3600psi at the pump, but it drops to barely 3000psi at the wand.
If you use 1/2" hose, you would have 3440psi at the wand..
only 80psi drop per hundred !
So while you're having to scrape gum, the guy that has the first 200ft in 1/2" hose, and the last 50ft in 3/8"..
he can blast the gum away, without bending over a scraper. ..at 250ft.
e-mail me for a copy of the "restriction-to flow" chart.


E) What !? no mention of the Pressure relief valve, that should have spewed at 4300psi on the 3600psi system !?? Aaarg !
:slap:

RESPECT the tech !!
CALL for more info.
we aim to be your favorite supplier. :dirol:
 
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