trapped pressure unloader

« **on:** April 24, 2013, 06:51:18 pm »

Right, im looking for an answer to a puzzling question. ive thought about it but i cant work out why it is happening.

when i pull the trigger there isnt instant pressure at the lance. there is a shot of full pressure (exactly like if you pulled the trigger to release the pressure with the machine off) then the pressure builds up until it reaches full.

most machines ive ever used its been a case of pull the trigger and get instant pressure. ive used the larger electric karchers and they seem to work similar to above, where the pressure has to build.

i have a trapped pressure unloader on it too so i thought i should be getting instant pressure. can someone explain why some machines are jnsta t and some need to build pressure?

« **Reply #1 on:** April 24, 2013, 07:25:53 pm »

K5 Unloader mate

« **Reply #2 on:** April 24, 2013, 07:33:15 pm »

This might help http://www.epowerwash.com/wp/archives/631

« **Reply #3 on:** April 24, 2013, 07:33:57 pm »

What you mean mate?

« **Reply #4 on:** April 24, 2013, 07:41:50 pm »

I know how they work mate, although i did learn a few things reading that.

what i want to know is why some machines have instant pressure and some dont. both my machines have trapped pressure unloaders but one give instant pressure and one needs to build up pressure when trigger is pulled. i was just curious as to why some machines need to build up pressure.

is yours instant as soon as you pull the trigger mate?

« **Reply #5 on:** April 24, 2013, 07:46:29 pm »

Matt

The H & M, Thor and my four Hilta/Yanmar are all instant pressure. I have never come across this. Even my old machines have all been instant.

Rob

« **Reply #6 on:** April 24, 2013, 07:57:53 pm »

We've got these

and we have a K5.3

« **Reply #7 on:** April 24, 2013, 08:13:17 pm »

Ive come across it before, mainly on electric machines.

lee, i use the top pic on my van mount. solid unloaders them.

« **Reply #8 on:** April 24, 2013, 08:51:07 pm »

matt the reason you get a shot then pressure builds up on electric machines is because the trapped pressure builds up to ebngage a pressure switch, this turns the machine off, when the trigger is pressed the pressure is release thus disengaging the pressure switch and then the mototr kicks back in, obviously the motor will start from stop or tickover so the pressure will build up in line with this (usually withina second or 2)

Hope this helps? wasn't sure of the question your asking?

« **Reply #9 on:** April 24, 2013, 08:54:12 pm »

Quote from: Kenny83 on April 24, 2013, 08:51:07 pm

matt the reason you get a shot then pressure builds up on electric machines is because the trapped pressure builds up to ebngage a pressure switch, this turns the machine off, when the trigger is pressed the pressure is release thus disengaging the pressure switch and then the mototr kicks back in, obviously the motor will start from stop or tickover so the pressure will build up in line with this (usually withina second or 2)

Hope this helps? wasn't sure of the question your asking?

Also normal engined machines have trapped pressure unloaders but instead of a pressure switch, they go to bypass, the engine stays at the same speed and it just switches from by pass to the lance, because the engine doesn't need to pick up speed the pressure is constant/instant

« **Reply #10 on:** April 24, 2013, 09:01:00 pm »

Ahh ok mate. my main question was why would my machine get that kick of pressure then build up if its an engine driven machine with a trapped unloader?

« **Reply #11 on:** April 24, 2013, 09:11:28 pm »

does it have a low rev facility where as when you press the trigger it revs up to speed?

« **Reply #12 on:** April 24, 2013, 09:26:43 pm »

No mate. it sits on 1750rpm and when you pull the trigger it loads up but the revs dont change hardly at all.

« **Reply #13 on:** April 24, 2013, 09:33:51 pm »

ok, exactly what machine is it mate? is it a dirt driver? aquilla? demon?
Also what model is it? what engine is on it?
Thanks

« **Reply #14 on:** April 24, 2013, 10:12:44 pm »

Its a flowplant trailer. lombardini engine. its the 3 cyl.

Not sure of the exact model, they only have a couple of different trailers. its got a hawk pump on it.

« **Reply #15 on:** April 24, 2013, 11:22:32 pm »

is this yours?
http://www.flowplant.com/H3004D.pdf

« **Reply #16 on:** April 25, 2013, 08:11:12 am »

Yes mate. pretty much. except i have the hawk H5061 pump. its says on hawks website thats its 15lpm but the sticker on the pump says 18lpm.

The engine is a Lombardini LDW1003

« **Reply #17 on:** April 25, 2013, 04:54:09 pm »

The first " kick" of pressure when the trigger is pulled will be the "trapped " pressure in the line between the trigger/hose/unloader releasing . . Hence trapped pressure unloader. Soft unloaders like the K5 are a better option as triggers,unloaders engine woodruff keys etc generally last a lot longer with "soft start" unloaders Depending on the length of the hose it could take a second or too to replenish the pressure. Old hoses also "swell" a bit first coupled with a long length could give you a slight delay...but it would not be much.

« **Reply #18 on:** April 25, 2013, 05:27:42 pm »

Chris,

The delay im getting is quite a bit. when i first pull the trigger it drops to about 40 bar and has to work its way back up to operating pressure.

my other machine, and most other engine drive machines ive used give me instant pressure with the pull of the trigger. no drop in pressure at all.

« **Reply #19 on:** April 25, 2013, 09:08:36 pm »

Send me a picture. Is it gearbox driven? It's not something daft like a cush drive/clutch slipping initially? Disconnect everything and run it as a basic pressure washer ie engine, pump,unloader,lance. ( I take it this is the machine with the boiler etc)

« **Reply #20 on:** April 25, 2013, 10:12:42 pm »

Its direct drive (coupling)

Yeah its got the boiler

Im kind of leaning toward it being the pump but ive changed most of the internals.

Ill get a couple of pics when im down there tomorrow

« **Reply #21 on:** April 25, 2013, 10:20:00 pm »

Slipping coupling/shaft?

« **Reply #22 on:** April 25, 2013, 10:23:38 pm »

That was mentioned to me, but it seems like when you pull the trigger, the pump just takes longer to build the pressure, there is no nois3s, juddering, or rev ups. Everything seems perfectly normal.

Its a puzzler, and I was starting to think maybe this is just the way flowplant machines are set up.

« **Reply #23 on:** April 25, 2013, 10:31:06 pm »

Flowplant ? Have you spoken to them ? If it is a flowplant they are really helpfull

« **Reply #24 on:** April 25, 2013, 10:38:22 pm »

Not the flowplant branch in scotland. not helpfull at all unless your buying a brand new machine or thousands of pounds worth of chemicals they arent interested.

« **Reply #25 on:** April 25, 2013, 10:44:14 pm »

Have you got the pressure up on it yet matt? does it unload properly now?

« **Reply #26 on:** April 26, 2013, 07:41:37 am »

Quote from: Kenny83 on April 25, 2013, 10:44:14 pm

Have you got the pressure up on it yet matt? does it unload properly now?

Hi mate,

its always unloaded properly. when i pull the trigger, no water RTT. but im still only getting 2300psi max. when i let go of the trigger it pressurises up to full then unloads. im gonna have a play with it today. if ive got time im gonna change the pump and check the coupling out and probably do what chris said and run it just as a normal washer (pump-unloader-hose-gun) and see how it runs. atleast then i can rule things out.

« **Reply #27 on:** April 26, 2013, 04:13:06 pm »

Sounds like a trip to the engineers, at least then they will sort it and if they don't then you won't be out of pocket?

« **Reply #28 on:** April 26, 2013, 05:37:11 pm »

Well, i changed the pump over today to a WS201 i had in the lockup. Got a little bit more pressure. Its pushing up towards 2700psi now, (only about 2200/2300 before with the hawk pump) but you can certainly feel the flow with the 201 running at 1750rpm

The extra flow makes up for the little bit of lack of pressure.

Didn't get a change to run it simple like Chris said.

Im starting to think the drop in pressure (when you initially pull the trigger) is just how these Flowplant machines are set up. The guy at Flowplant didn't have a clue when i rang today.

Needed it running again for this weekend, then a few days for it next weekend, then i might bypass the boiler/safety valve etc.. and run it like a straight froward cold washer. See if that makes any difference. If it does, i can narrow the problem down to the boiler, or the safety valve.

Bit over it, but glad its running better, higher flow and more pressure. hopefully find the problem if not, ill sell it..

« **Reply #29 on:** April 26, 2013, 07:59:45 pm »

Ditch the safety valve and fit a burst disc.

« **Reply #30 on:** April 26, 2013, 08:56:44 pm »

Quote from: chris scott on April 26, 2013, 07:59:45 pm

Ditch the safety valve and fit a burst disc.

I wouldnt even know where to start with a burst dics. Just looked at the burst disc holder. It just looks like a nut.

« **Reply #31 on:** April 27, 2013, 12:32:25 am »

It fits a 1/2" nipple and is just a nut with a plastic disc fitted that bursts when the pressure exceeds 110 % of the running pressure - you get very wet when they go, usually when you get a blocked jet in the nozzle

« **Reply #32 on:** April 27, 2013, 06:52:32 am »

Cheers mate. ive seen them before online but never quite knew where they went