Last January I bought a compressor from TCP global, it’s not longer listed on their site, but it’s a twin piston compressor with a tank. I used it routinly from january until about august, when I took a break from modelling. I fired it back up today, and everything seemed to go ok, it filled the tank quickly, but when it turned off, the air started escaping not from the tank, but from the compressor itself, from what looks like an escape valve on the top.
I’m not familiar with compressors at all, so I thought I would just ask the question here and save some time.
On the assumption that it’s an airbrushing compressor, it’s most likely either the non-return system between the cylinder heads & the tank or a faulty pressure relief valve;
The non-return system generally relies on valves or seals which are located in the cylinder head valve plates - which are located between the main body of the compressor & the finned cooling head, these are usually gloss black . Considerable amounts of moisture can accumulate on these plates & after a period of inactivity this can cause issues with corrosion in the non-return system, which in turn prevents the valves from closing properly & allows air to escape back the way through the head, under the piston flapper plates & out the air intake. The non return system can be either a metal valve of flexible rubberised gasket.
If on the other hand the air is leaking from what appears to be a valve, it’s most likely a faulty pressure relief valve.
The finned cylinder heads are easily removed with basic tools, depending on the model & layout you may have to disconnect the air outlet pipe (it will have a rubber seal so it’s easily refitted) & then removed the finned head covers. Have a look for any excessive corrosion (usually white gunk) & give it a clean, you may also have to strip the valves if they are the metal type & clean them.
Here is an image of a recently cracked open twin piston compressor showing the moisture build up, It’s fitted with metal valves which are the things that look like chrome nuts. This was a reputable, lightly used compressor & the moisture build up you see is quite normal, yours may be somewhat worse than this;
Very interesting picture. What is the difference of the 2 pistons. The right side seems to have a metallic sheen to it and the left seems to be cover with a matt layer. The water seemed to be confined to the cylinder part on the left and overflowed on the right. More details?
It is a piston compressor, the black plates are the valve plates which sit directly above the piston, The sheen from the plate on the RHS is just contamination, some of it is most likely white paint that’s managed to pass through the intake filter & the larger bits will be piston seal material, the piston seals are made from some sort of self lubricating material like PTFE & look to be designed to shed material through the course of their life. There was no real difference in the amount of moisture in either head, everything in there is really glossy & slick like a Tefal frying pan, so the moisture just beads up & rolls around with the minimum of persuasion.
Because the piston seal is flexible, the piston itself doesn’t have an sort of gudgeon pin arrangement to keep it located vertically in the bore, it just tilts from side to side slightly as it goes up & down.
There wasn’t anything wrong with the compressor, I just stripped it out of interest, gave it a clean up & re-built it, it was back together & working & hour after the pics were taken.
Plates removed showing pistons & sleeves;
Piston in sleeve;
The piston, with it’s sleeve removed, showing the con-rod & the surprising amount of play the piston seal has to accommodate;
I really appreciate the pictures that you posted. I have been looking at the exposed view of the Iwata compressor parts diagrams for a long while. They match the parts in your pictures exactly. You finally helped me understand what the cylinder block is and why it has a check valve in the middle of it. Wow, fun time for an engineer’s curiosity.
I’ve spent a fair bit of my working life in the motor trade in service & parts, so I’m familiar with the internals of the internal combustion engine - I figured this compressor was more or less like a small engine with a motor providing the power, I had imagined that it would have had flexible o-rings on the pistons in a similar manner to regular piston rings, but as the piston doesn’t turn on the con-rod I guess these wouldn’t provide adequate sealing, hence the big seal.
I was quite shocked at the amount of water just sitting about in the heads, I had imagined most of it would be expelled with the airflow, but I guess not - I suppose that’s the reason for everything in there being coated / painted.
Wonder what I can tear to bits next - a silent compressor/fridge pump?
I ended up taking the compressor into a local compressor shop, and to fix it would cost $70 an hour, and they didn’t even know if they would be able to find the parts. I don’t think i’ll be buying another made in China, un-branded compressor. While it worked, it worked perfectly…So unfortunatley I guess I am in the market for a new compressor. I’ll gladly pay extra for something that will last longer than a year. Any suggestions?
I’ve looked at the Iwata Smart Jet range, the pro and basic. Iwata’s US headquarters are here in Portland, I don’t know if that helps with finding parts, but it’s a plus I guess. Also, are Badger’s compressors made in the US? They look awfully similar to those Chinese knock offs. At the compressor store I was at, they had a small Maxus compressor, but That would probably be to loud for in the house.
If you have a Hobby Lobby Store nearby, check out the Storm Force Compressor. It is the Sparmax TC-2000 and at $200 with their 40% off coupon this week. It is similar to the Iwata Powerjet without the case. Normally, this compressor should last much longer than one year. Ask them how long a warranty it comes with.
Actually, I think Oregon is the only state without a Hobby Lobby, so I think that is out. I might just bite the bullet and get an Iwata, Ive heard so much good stuff about them. On the Smart jet, I noticed that the regulator isn’t a true regulator, you have to release air through a bleed valve to change the pressure? Is the regulator on the smart jet pro a true regulator, where you can set the pressure without releasing air to change it?
Do you know anyone personally with a reasonable mechanical / engineering background like a mechanic or fitter? Anyone with even reasonable experience would be able to whip the heads of your compressor & rebuild in 10 minutes maximum, stripping & cleaning the valves (if they are repairable) would only take another 5 or 10 minutes on top. I would say that you have a 50/50 chance that a clean up will solve your problems. Call in a favor possibly?
