Rebuilding a compressor

[threedee]

Hello people.

I've been given an old 200L compressor, with 2stage ABAC B70(B60?) air pump.
Its been sat for a while, fins are dirty, no intake air filter box, but other than that it got all the bits attached. Except motor, left it where it was stored as it weighed 3/4 of the compressor+tank itself. Some bright spark attached 15kW 3ph motor to it...yeesh...
Compressor shaft turns freely, compressor breathes when done so.
Its grimy to the point i will need to repaint it. Never done something like this before.
Planning to strip it down completely, strip paint off the tank, repaint, get new or clean existing fittings, wash the tank itself, fit 1ph pressure switch, gauges and motor, etc... full rebuild...

Questions:
1. Compressor shaft pulley. Any advice on how to pull it off without gear puller ? Dont have one. Its fixed by a bolt in the shaft, but i cannot pull it off after removing said bolt. No key in the shaft.
2. Stripping the tank. Is it safe to just wirewheel the whole thing ? What to do after to prevent surface rust until i paint it ? At the moment its sat outside, covered from rain, etc.
3. Painting. I plan on brush painting it. Recommend good (cheap'ish) durable paints that would be suitable for the job. Any other prep ?
4. Cleaning compressor block. Aluminium fins, some oxidation, very tight squeeze between, how to well clean that ? Not looking for harley davidson shine, but clean is good. Maybe will spray it with something to prevent further oxidation (silver paint?).
5. Cleaning brass safety valves ? Dunk em in kerosene and brush grime off ? Or is it absolutely neccessary to replace them ?
6. Motor/pulley. I have a new 1.1kW 1ph motor, 2700rpm. No idea what is rated rpm of the pump, cant find any technical info on it and not knowing that i cant buy a motor side pulley. Anyone got B60-B70 service manual ?

The rest is mostly just changing oil and gaskets, wiring pressure switch. Oil is simple, gaskets are super-expensive, so i'll just cut them myself on my laser cutter.
By the way, service kit for B60 is about 400 quid...what ?

Should be a brilliant compressor when i'm finished (unless i cock something up badly...)

Any advice on any part of this post is much appreciated. I really want a big compressor, after owning 25l whiny/super-loud/useless/cheap pos one...

Cheers

 

[Burnerman]

Interesting! A man after my own heart.

1) If there is no keyway visible, its safe to assume that the pulley is tapered onto the shaft, and you'll need a cheap puller. Tighten it well then whack the end of the puller so the pulley jumps off.
2) Clean / derust the tank anyway you can, give it a coat of Kurust followed by a red oxide primer (Screwfix). After that, preferably spray Hammerite or risk brushing. Whatever it is and despite many claims its a tough paint at the end of the day.
3) As above.
4) Fold emery cloth into a towel, and take the rest of the week off as you rub / wire brush / curse etc. Rust treatment as before.
5) Check the operation of the safety valves as soon as you can, dismantle and lube with WD40 or whatever - they are usually reliable but you need to ensure the main safety valve shuts off at around 130 psi or whatever.
6) I'd guess for a beast like this you'll need a 3hp motor, hard wired. Pulleys can be bought or indeed created by using Powerlok gear from Eriks or whatever.

As for compressor oil, light grade mineral oil is fine, SAE30 is the norm.
Unfortunately, we mere mortals have no way of telling in what condition the receiver tank is like on the inside, where most corrosion takes place. Can't help with that one!
John

 

[threedee]

I'm working on a budget of zero. Just spent figton of money on laser cutter, wife's gonna have a fit if i spend anymore...
So, whole kurust/redox/hammerite treatment might not fly as too expensive. Wirebrush+paint direct to steel works ? Or do i absolutely have to primer it ? Paint direct to bare metal ? I do have a cheap spray gun and ****ty small compressor, but never in my life spray painted anything...

Motor i have is 1.1kW induction, translates to about 1.5hp ? Wouldnt it be enough ? Any way to add soft start to 1ph motor ? Inrush is dimming the lights in the house

As for pulleys, what i meant was not knowing rated compressor shaft/pulley rpm i cannot calculate motor pulley size. Motor turns at ~2700-3000, but what a compressor should turn at ?

Compressor block is aluminium, not cast iron, no rust, just grime/oxidation.

 

[bernardgreen]

what condition the receiver tank is like on the inside,

There is a small risk of the tank being so badly corroded internally that it leaks or worse splits open when under pressure.

 

[threedee]

I will be flushing it anyway, then inspect it with endoscope.
Need to figure out how to undo 65mm bung...

Compressor in question:

 

[Burnerman]

Hopefully you can afford a can of primer paint direct to metal ain't a good idea!
For a compressor that size, a 1.5hp motor isn't enough - that machine needs somewhere in the region of 3hp to keep it spinning when it's charging the receiver tank. Assume the compressor needs to be spinning somewhere in the region of 700 RPM.
That electrical / pressure sensing switch (far right) doesn't look too healthy!
Big compressor manufacturers use ultrasound to determine the health of the tank internals - of which the bottom, naturally enough - is the prime suspect area.
Like any other pressure vessel, they are tested using water which is much safer than air.
John

 

[threedee]

The pressure switch is going one way or the other - its for 3ph.

I would love to test the tank hydrostatically, yeah, but cant find anyone local. Thats the one expense i would justify, tbh.

 

[threedee]

Oh dang it. Any ideas how to pull the wheel off the shaft ?
Pullers i find here are not big enough.
Inner hub diameter is 140mm, thickness about 45mm.
Not keen on banging on the shaft...

 

[threedee]

Got the puller...
And here's the first hurdle - the wheel is so seized on i'm afraid to break it.
Puller damaged some of the fan blades on it, but no biggie, however after considerable effort and heating and loads of wd40 it didnt move a millimeter...

Rechecked it for setscrews, just in case i'm selectively blind... nope, no set screws or any other retaining elements. Just steel shaft and aluminium stuck together.

Any idea how to losen it short of banging on a shaft with a sledge ?.

 

[Burnerman]

It can be a difficult one, to be sure. Consider leaving the thing under as much tension as you dare overnight , keeping the thing well soused in WD40 and then giving it some serious gas heat in the morning, tapping the puller head as you go.
John

 

[Harry Bloomfield]

Make a puller - large bolt, piece of thick steel drilled and tapped, then a couple of bits of angle iron or similar to hook onto the pulley. Heating the pulley/ cooling the shaft might make it less reluctant to come off.

 

[threedee]

Sadly, i have to report that compressor is a write off.

Taken off compressor unit, disassembled it.
1. One of the pistons, connecrting rod and rings are in bits (smaller one, high pressure ?);
2. Broken pistons crank shaft side torn to shreds;
3. Cyllinder liner chipped on the bottom.
4. Evidence of running without oil
5. No gasket between head and valve plate.

Sadly i cannot even find parts for sale to rebuild it. In this case filters and gaskets are not spare parts i'm looking. And no other parts are available for sale even. Hence writeoff.

If anyone know where to get a donor B60/B70 compressor unit let me know.
Or where to get actual spare parts for these heads.

Sad, so sad...

 

[bernardgreen]

Have you tried
E Mcintyre & Sons, Kilrea
Address:
14 Drumagarner Road
Postcode/City:
BT51 5TB Kilrea
County:
Londonderry Northern Ireland
Phone:
028 295 40300
Fax:
028 295 41069

They have the same phone number as on the compressor's label

 

[threedee]

They have a tool shop in Dungannon, close to me, but to my knowledge they only sell tools, no service.
Will have to call them up on monday, but i dont have high hopes.

 

[Burnerman]

All of the damage is caused by running without oil.....I find that compressors are run until they fail and then its time to buy new. My previous machine mart compressor suffered a cracked cylinder head after 15 years use.....goodness knows why it went that way. A new pump was £300 plus and spare heads werent available.
John