Pressure Washer Relief/Return line???

[r136dg]

I removed this pressure washer from its rickety stationary frame & put in a mobile frame. To truly be mobile I was wondering what (if anything) to do with the return line. It releases pumped water when the sprayers not used into a tank making it immobile (relying on holding tank nearby). It would be nice not to cut the engine when not spraying or randomly wasting water making a mess. I fear plugging it will blow seals, or worse.

Any ideas appreciated!

[Artisi]

You could return the flow from the relief valve back to the pump inlet. 

 

Google something like - " high pressure pump relief flow back to inlet" there should be plenty of info' for you. 

[VocalNeal]

Where does the water come from in the first place? 

 

Which hose in the picture is the pressure relief hose?

[r136dg]

@Artist  I'll research that tonight but thinking might be pressure on pressure, but if the relief is more than the garden hose maybe it will loop. Good idea! 

@VocalNeal  the lower brass fitting will be fed by garden hose' yellow hose is relief, next to the sprayer fittings.

[Artisi]

5 minutes ago, r136dg said:

@Artist  I'll research that tonight but thinking might be pressure on pressure, but if the relief is more than the garden hose maybe it will loop. Good idea! 

@VocalNeal  the lower brass fitting will be fed by garden hose' yellow hose is relief, next to the sprayer fittings.

After the relief valve the pressure will be minimal, actually the same as inlet hose pressure. 

[grollies]

Plug it off at the hose end, you'll blow the hose.

 

Plug it off at the pump head and you'll blow your pump head.

 

The pressure relief should return back to the water supply tank.

 

I personally wouldn't pipe it back to the pump suction, it's a pressure relief valve so excess pressure should vent to an open tank.

 

If you mounted the tank on the frame you could leave the engine running and have the pump relief venting back to the tank in a closed circuit when not spraying.

[Artisi]

1. micropump.com/support_relief_valves.aspx

2. When this pressure setting is exceeded, the relief valve becomes the “path of least resistance” as the valve is forced open and a portion of the fluid is diverted through the auxiliary route. The diverted fluid is usually returned back to either the reservoir or the pump inlet. 

3. The only downside of running on return to inlet for a long period of time is there may be an increase in water temperature - unlikely in your case I would assume bypass is only a temporary condition. 

[Fruit Trader]

What you have there is a 40 bar (approx) spray pump mostly used to feed manifolds or hand held nozzles down on the farm. They are designed to suck spray chemical from a tank and dump back to the same tank via hand adjustable relief valve. Some models are not happy having pressure on the inlet. Dumping back to the inlet will most likely interfere with suction and also cause rapid rise in pump temperature when the dump valve is open for long periods. Engine driven high pressure pumps designed to dump back to the inlet are often fitted with over temperature relief valves.

Do not block the pressure relief valve outlet unless you want to destroy the pump. 

Edited July 16, 2018 by Fruit Trader

[VocalNeal]

7 hours ago, r136dg said:

@Artist  I'll research that tonight but thinking might be pressure on pressure, but if the relief is more than the garden hose maybe it will loop. Good idea! 

@VocalNeal  the lower brass fitting will be fed by garden hose' yellow hose is relief, next to the sprayer fittings.

OK because normally the relief valve vents internally into the pump suction. 

 

Have a portable small tank/large bucket/ for the supply it can be fed from a hosepipe with a toilet type ball cock. Fit hose connection to the container for the inlet and pressure relief.

 

Set up the sprayer/pressure washer. 

Put the tank nearby

connect up the inlet and relief hoses

Connect the garden hose and turn on the water.

[Artisi]

1 hour ago, VocalNeal said:

OK because normally the relief valve vents internally into the pump suction. 

 

Have a portable small tank/large bucket/ for the supply it can be fed from a hosepipe with a toilet type ball cock. Fit hose connection to the container for the inlet and pressure relief.

 

Set up the sprayer/pressure washer. 

Put the tank nearby

connect up the inlet and relief hoses

Connect the garden hose and turn on the water.

Seems to defeat his purpose of a simple mobile unit. 

Relief internal or external is no different 

[grollies]

6 minutes ago, Artisi said:

Seems to defeat his purpose of a simple mobile unit. 

Relief internal or external is no different 

You shouldn't plumb the pressure relief line back to the pump suction for obvious reasons.

[Artisi]

46 minutes ago, grollies said:

You shouldn't plumb the pressure relief line back to the pump suction for obvious reasons.

Why?

[Artisi]

High-Pressure System Design Guide - Cat Pumps

www.catpumps.com/products/pdfs/993330B_GUD_Sys_Design_Guide_LoR.pdf · PDF file

Plumbed on the high pressure side of the pump and as close to the pump as possible for optimum dampening. If system uses an unloader where bypass flow is diverted back to pump inlet

 

https://www.engineeringtoolbox.com/positive-displacement-pumps-d_414.html

A relief or safety valve on the discharge side of the Positive Displacement Pump is absolute necessary. The relief valve can be internal or external the pump. An internal valve should in general only be used as a safety precaution. An external relief valve installed in the discharge line with a return line back to the suction line or supply tank is highly recommended.

[Fruit Trader]

2 hours ago, Artisi said:

High-Pressure System Design Guide - Cat Pumps

www.catpumps.com/products/pdfs/993330B_GUD_Sys_Design_Guide_LoR.pdf · PDF file

Plumbed on the high pressure side of the pump and as close to the pump as possible for optimum dampening. If system uses an unloader where bypass flow is diverted back to pump inlet

 

https://www.engineeringtoolbox.com/positive-displacement-pumps-d_414.html

A relief or safety valve on the discharge side of the Positive Displacement Pump is absolute necessary. The relief valve can be internal or external the pump. An internal valve should in general only be used as a safety precaution. An external relief valve installed in the discharge line with a return line back to the suction line or supply tank is highly recommended.

In theory the return line can go to the inlet and if positioned correctly the pump should continue to suck from a tank. I am guessing the OP is trying to convert this pump into a tank free setup and should be aware that most of these cheap sprayer pumps are not designed for direct connection to a pressurised supply. 

I cant really see much use for these pumps beyond spraying crops from a tank or using the 40 Bar to blow away spider webs.

 

If the OP wants a simple plain water mobile unit then he should look at buying the correct pump with built in bypass and decent washing pressure. The OP's photo shows what looks like a Honda GX series motor for which there are many pumps to bolt directly onto the output shaft and multi application fixing flange. No need for the silly unguarded drive belts.

 

 

[grollies]

11 hours ago, Artisi said:

Why?

The PRV is a safety device to prevent over-pressure in the pump head. Diverting direct to the pump suction end can result in turbulent flow in the suction end, interfering with the operation of the pump.

 

Attaching the PRV line direct to the pump suction can also interfere with the operation of the PRV by creating a low pressure on the PRV outlet, in effect increasing the PRV set pressure.

 

Additionally, it just goes against the grain to do this.

 

Centrifugal pumps can be set up in series, with the discharge from one pump run into the suction end of a second, third and so on. I've done this on 6" HV LP pumps with 6 in series pumping water 3km to maintain flow at the final delivery point.

[Artisi]

13 minutes ago, grollies said:

The PRV is a safety device to prevent over-pressure in the pump head. Diverting direct to the pump suction end can result in turbulent flow in the suction end, interfering with the operation of the pump.

 

Attaching the PRV line direct to the pump suction can also interfere with the operation of the PRV by creating a low pressure on the PRV outlet, in effect increasing the PRV set pressure.

 

Additionally, it just goes against the grain to do this.

 

Centrifugal pumps can be set up in series, with the discharge from one pump run into the suction end of a second, third and so on. I've done this on 6" HV LP pumps with 6 in series pumping water 3km to maintain flow at the final delivery point.

Suggest you contact all major piston pump manufacturers and valve manufacturers and point out the error they are making in directing over pressure discharge into the inlet side of the pump, I'm sure they will be appreciative of this advice. 

[VocalNeal]

13 hours ago, Artisi said:

Seems to defeat his purpose of a simple mobile unit. 

 

You have to pipe water to the pump wherever it is. It doesn't seem much extra effort to run a roll up hose out to a suitable place for the relief? 

 

Does your manifold look anything like page 23 in this? http://www.siebringmfg.com/media/10.pdf

[grollies]

1 hour ago, Artisi said:

Suggest you contact all major piston pump manufacturers and valve manufacturers and point out the error they are making in directing over pressure discharge into the inlet side of the pump, I'm sure they will be appreciative of this advice. 

Nope. Our high pressure triple-ram piston pumps never had the PRV outlet connected back to the pump inlet.

 

But I think we're talking about two different things here. I must admit the big diesel-driven ram pumps we used pressure testing pipelines are a different make-up to the pressure sprayer above. The PRV on those just vented to atmosphere.

 

The pressure washers may simply use a lift valve so when you stop spraying the pressure returns to the inlet side. But that is a different use for the PRV and is not really a safety over-pressure device, rather just part of the pumps normal operation. So you are correct.

 

The OP looks like he is putting his own bit of kit together. If his pump is of the type you describe, there should already be a connection on the pump inlet to connect the over-pressure line.

 

If not, IMHO, with the size of the over-pressure line, I'd still run it back to the tank. Like I said though, just my opinion.

[Artisi]

5 hours ago, VocalNeal said:

 

You have to pipe water to the pump wherever it is. It doesn't seem much extra effort to run a roll up hose out to a suitable place for the relief? 

 

Does your manifold look anything like page 23 in this? http://www.siebringmfg.com/media/10.pdf

Interesting how page 21 seems to indicate the flow from the un-loader / pressure relief /  by-pass valve appears to be connected to the inlet of the pump unit - so seems this is an acceptable method of handling any by-pass flow.

Edited July 17, 2018 by Artisi

[grollies]

7 hours ago, VocalNeal said:

 

You have to pipe water to the pump wherever it is. It doesn't seem much extra effort to run a roll up hose out to a suitable place for the relief? 

 

Does your manifold look anything like page 23 in this? http://www.siebringmfg.com/media/10.pdf

Correct. The pump will only be as mobile as its water tank.

[grollies]

2 hours ago, Artisi said:

Interesting how page 21 seems to indicate the flow from the un-loader / pressure relief /  by-pass valve appears to be connected to the inlet of the pump unit - so seems this is an acceptable method of handling any by-pass flow.

Interesting to note page 14 warning saying you can only leave the pump running for 2-3 mins in by-pass mode before it will start to overheat. I'm with fruit trader and vocal neal on this for the OPs particular set up, return the relief line back to the tank.

[Fruit Trader]

More pump blurb..

 

Unloader valves can be used to unload a pump only when a spray trigger is released or they can be used to constantly control output pressure. Unlike high pressure washers, suction feed chemical spray pumps are often presented with varying demands which results in the unloader valve constantly lifting to dump unused capacity and keep spray pressure constant. These pumps often unload back to a supply tank to avoid long periods of recirculation and to keep a more stable suction manifold.

 

Trapped pressure unload valves on pressure washers almost always bypass via a short path to the inlet.

Our Inter pump on the truck washer has bypass and second safety similar to below.

 

Edited July 17, 2018 by Fruit Trader

[VocalNeal]

2 hours ago, Artisi said:

Interesting how page 21 seems to indicate the flow from the un-loader / pressure relief /  by-pass valve appears to be connected to the inlet of the pump unit - so seems this is an acceptable method of handling any by-pass flow.

I'm thinking you wouldn't do this if connected to the same water source as a house. Unless the pump has integral posts for it as it probably has a check valve.

Edited July 17, 2018 by VocalNeal

[Fruit Trader]

35 minutes ago, VocalNeal said:

I'm thinking you wouldn't do this if connected to the same water source as a house. Unless the pump has integral posts for it as it probably has a check valve.

As an example, our 200 bar washer pump unloads to the inlet port and does not have a non return on the supply line because the unload flow forms a balanced closed loop within the pump. If this loop got blocked at the piston inlet the pump would attempt to charge the supply line to 200 bar.

[grollies]

1 hour ago, Fruit Trader said:

More pump blurb..

 

Unloader valves can be used to unload a pump only when a spray trigger is released or they can be used to constantly control output pressure. Unlike high pressure washers, suction feed chemical spray pumps are often presented with varying demands which results in the unloader valve constantly lifting to dump unused capacity and keep spray pressure constant. These pumps often unload back to a supply tank to avoid long periods of recirculation and to keep a more stable suction manifold.

 

Trapped pressure unload valves on pressure washers almost always bypass via a short path to the inlet.

Our Inter pump on the truck washer has bypass and second safety similar to below.

 

The HP instantaneous coupling on your pump, do you know where to buy male & female in Thailand?

[Artisi]

21 minutes ago, grollies said:

The HP instantaneous coupling on your pump, do you know where to buy male & female in Thailand?

Not sure what you are requesting, do you want male to female adaptor or male and female to threaded connector or to hose tail and what pressure rating? 

[Fruit Trader]

56 minutes ago, grollies said:

The HP instantaneous coupling on your pump, do you know where to buy male & female in Thailand?

The pump in the picture is the same layout as mine but I use standard 22mm screw connect not quick connects.  My lance and pipe gets abused and quick connects would not last a week .

My old parts supply http://www.4163carcareshop.com should have quick connects in stock.

 

I now source everything from Ebay which includes pump seals jets and connectors mostly from the https://suttner.com/ catalogue. Pressure pipe and fittings can be found at any local hydraulic line repair shop.

Edited July 17, 2018 by Fruit Trader