Help ID old compressor

[Red'n'Black]

Hi,

Picked this up cheap on ebay, very little description, was hoping someone could help me ID it?

It's a 3 HP 150 litre machine, only marking is 'Clarkes Compressors Ltd, Lower Clapton Rd, London E5'. Is this the same company as the modern-day Clarke?

The motor is made by GEC, I'm guessing early 1980s?

The pump is a 2 stage design with unequal size cylinders, only marking I can see stamped on the crankcase is '7 E D'.

Given the age and the low price I wasn't expecting much, but I was pleasantly surprised to see it runs and builds pressure, given the obvious bodges that need fixing (more of which later)
I turned it off when it reached 80 PSI after a minute or so.
I can't see any rating plate on the tank, so that was as high as I wanted to take it until I find out more. I did have a look inside with a USB borescope camera and there's a bit of surface rust but nothing serious.

Stuff that obviously needs sorting out:
- It's covered in decades' worth of grease and gunk, the pic above is after I'd cleaned it a bit!
- Wiring is horribly bodged. Some previous owner had fitted a NVR motor starter (held on with one bolt), but the contactor is wired all wrong so the stop button doesn't work. There is a connection from the starter box to the pressure switch, but the wires are just dangling in mid-air. Removed the whole thing and added it to the come-in-handy pile for some other project.
- Looks like the belt has snapped at some point and made a gash in the cover. I straightened it up OK, welded, painted and put back on.
- Pressure gauge has lost its glass (it still seems to read OK). It has the same maker's logo as on the tank and goes up to 200 psi, does this give any clues to the working pressure?
- Motor fan cowl is missing. There are a few people selling them on ebay, but I'm having trouble matching up the size. I might just make one.

More later, if I can ID the thing and get hold of a manual that would be a good start!

Thanks

R.

 

[Ruffian]

Make sure the pressure relief valve works, (should blow about 120/140psi but most compressors will cut in at 50-70psi, cut out around 95psi but controlled by the pressure switch.

Most tanks will take +150psi,

 

[RonA]

Looks to be well made, unlikely to be any connection!
RonA

 

[WorkshopChris]

Is this the same company as the modern-day Clarke?

Yes good strong well built compressors.
All tied back and related to the modern day Clark and Machine Mart companies.

 

[Red'n'Black]

Yes good strong well built compressors.
All tied back and related to the modern day Clark and Machine Mart companies.

OK thanks, I will try contacting Clarke with a few pics and see if they can put a model no to it.

 

[WorkshopChris]

I would expect around 9 cfm going by the pump size.

 

[Red'n'Black]

OK I have tidied up the wiring and put the pressure switch back in circuit. There is a toggle switch on the side, that works OK but the pressure cut-off doesn't seem to work, it got to about 145 PSI before I pulled the plug. The safety valve was starting to vent at that point so at least that works.
The pressure switch is a Danfoss

If the PO has adjusted it all the way to max that would explain it. I'm assuming the big spring and nut on the left is the adjuster, and that less preload = lower cutoff pressure? Will try it tomorrow.

If it does need a new switch I think it needs to be a type with built-in unloader? I say this because with the toggle switch in the 'off' postion I can hear pressure venting somewhere. There are two connections to the switch, 1/2" BSP direct to the tank and a narrow-bore pipe which goes under the motor and pump and joins up with the pump outlet:


I take it the brass hex fitting on the right has a check valve of some sort and the unloader vents the narrow pipe until it sees the pressure start to rise - or am I barking up the wrong tree with this?

[Edit - just found this http://www.mmcdanfossdistributors.com/danfoss-cs-pressure-switches which confirms the unloader is built in]

 

[WorkshopChris]

I take it the brass hex fitting on the right has a check valve of some sort and the unloader vents the narrow pipe until it sees the pressure start to rise - or am I barking up the wrong tree with this?

Yes to got it.
If the switch is US then its an easy off the shelf item you might have to mod the small pipe as the new one may be 6mm push fit, but that is a easy fix.

EDIT> ps, welcome to the forum.

 

[Red'n'Black]

Yes to got it.
If the switch is US then its an easy off the shelf item you might have to mod the small pipe as the new one may be 6mm push fit, but that is a easy fix.

EDIT> ps, welcome to the forum.

Thanks, have been visiting this site for years and taught myself to weld from reading the guides and forums, really helpful stuff.
This thread http://www.mig-welding.co.uk/forum/posts/807489/ was what inspired me to have a go at doing up this one.

 

[Fintray]

Check the oil level as it should be level with the red dot in the centre of the sight glass.

 

[Red'n'Black]

Check the oil level as it should be level with the red dot in the centre of the sight glass.

Yes it does seem to have dropped a bit. Do they need a specific type of oil or will the SAE 30 stuff I put in the lawn mower be OK?

 

[Red'n'Black]

Had a reply from Clarke, apparently it's a model SE14A, pump is a type T20. Last manufactured in 1990 so no spares or manual available. Still the few bits that need sorting out can be done with generic aftermarket parts, looking OK so far

I think the non-return valve in the unloader is leaking, that's why it vents continuously when the switch is off. Will see if it will come apart for a clean-up tomorrow, if it's FUBAR new ones don't seem very expensive.

 

[Fintray]

Yes it does seem to have dropped a bit. Do they need a specific type of oil or will the SAE 30 stuff I put in the lawn mower be OK?

You can get compressor oil, so you could search online for a suitable grade for your compressor pump.

 

[WorkshopChris]

Do they need a specific type of oil or will the SAE 30 stuff I put in the lawn mower be OK?

https://www.toolstation.com/shop/p94582?searchstr=compressor oil
But to be honest its almost the same as hydraulic oil.

 

[Red'n'Black]

Making slow progress with this, too many projects on the go at once...

Made a new motor fan cowl:

Drew up a template in AutoCAD, print out 1:1 and glue to a piece of 0.8mm steel sheet, which was once the side panel of a tumble dryer.

Cut out

Cut a piece of scrap chipboard to act as a form, clamped up tight with a ratchet strap. Some fettling needed to get the diameter to match the cut length of the metal. Tacked & welded up the side seam

Push the support board down, fold the 'petals' over and tack together at the inside edge

Weld up all the seams and flattened as best I could with a flap disc. Long out of practice welding anything this thin, it blew through and needed filling in in quite a few places.

Found a piece of expanded metal in the scrap pile, cut to size and tacked in

Trial fit. This was the 2nd attempt, it needed a piece cut out at the bottom to clear the motor platform

Coat of red oxide primer, then a top coat in the nearest colour I had to the rest of the machine.

Fitted:


Well that's one job off the list, one step nearer being safe to use now.

 

[rtbcomp]

...

I think the non-return valve in the unloader is leaking, that's why it vents continuously when the switch is off. Will see if it will come apart for a clean-up tomorrow, if it's FUBAR new ones don't seem very expensive.

There isn't a non-return valve (NRV) in the unloader. The valve in there is operated by the switch to empty the delivery pipe (between the pump & non-return valve on the tank) so that the motor doesn't start under load. If you get a continuous stream of air from the unloader it means the NRV in the tank where the delivery pipe connects is leaking.

 

[Red'n'Black]

Yes that was worded a bit badly. I had a chance to strip the NRV down earlier. Looks pretty simple:



The spring is broken, the brass seat is mushroomed over and the metal disc has a wear groove half a mm deep in it - not really surprised it isn't sealing!

The disc seems to be mild steel, at least it sticks to a magnet.
Turned up a new one from a piece of 1.2mm sheet:


Lapped it on a sheet of plate glass with progressively finer grades of emery paper, 600 was the finest I had.



Also gave the brass seat a very light cleanup in the lathe.

Which just leaves the spring. Dimensions are
12.7mm dia.
Free length is about 22mm as near as I can judge.
Wire dia. is 0.6mm.

Don't know how critical the spring rate is? Too weak and it'll still leak, too strong and it'll upset the efficiency and/or CFM.

Currently trawling through eBay for a replacement. Anybody have any recommended spring suppliers who deal in small qtys?

 

[Red'n'Black]

The pressure switch does work after all, ran it up to 120 PSI, disconnected from the mains and backed the adjuster screw off until I heard it click. Now cuts off at 120, back in at 80.
Seems like quite a large difference, or is that fairly typical?

 

[rtbcomp]

The spring doesn't need to be that strong, it's the pressure in the tank that holds the valve closed.

You can sometimes adjust the pressure difference (hysteresis), the screw may be marked with a 'delta' symbol. The cheaper preset ones usually have a hysteresis of 30 psi. Too large and you get excessive pressure drop in the tank, too small and the pump cuts in and out too often.

 

[Red'n'Black]

Found an exact match spring at work.
All re-assembled and... the thing's still leaking, if anything it's slightly worse.

Delivery pipe thread is 1/2", tank thread is 3/4". Nearest match I can find is this one https://www.machinemart.co.uk/p/3-4in-bsp-non-return-valve/
Should be able to get it to fit with a reducer on the inlet. At least I can take a look at it in the shop first.
The connection to the unloader is narrow bore copper pipe, so I take it I'll also need a flaring tool? Never used one before.