4th Stage slow

[Mrescue31]

Our Mako BAM 18.7 cfm compressor 4th stage slowly builds pressure to 4400 psi. Takes about 15 min. without any bank hooked to it. First stage is 45psi and second stage is 170psi and third stage is 550psi and 4th struggles from 4000 on. The first three stages build quickly but the fourth is slow. Any suggestions would be very helpful please. According to the manual first is right on, but second and third are low.

[rcontrera]

Check your valves. If the valves are leaking air then the pistons aren't working efficiently and can be just "massaging" the air instead of pumping it. And, if the second and third stages aren't pumping, the 4th stage is being fed low pressure and it will take a LONG time to get up in pressure.

[sealark]

Sounds like a first stage discharge valve is not sealing. Or a second stage suction

[CraigAClark]

Can you verify that the block on your BAM is a 5407 (5000 psi) or 5407H (6000 psi)? Second and third pressures are low. Second should be around 220-280 at 4400 final and third around 1000-1200 at 4400 final. I would try setting the over ride on the auto drain and shutting the machine off at that pressure (4400) to check for leaks. The over ride will not allow the stages to dump for 10 or so seconds, giving you time to check for leaks. It is located on the drain soleniod, at the base. if it is a new style, it will be a red lever and an old style will have a slot for a screw driver. Each can be turned 1/4 clockwise to activate the over ride.

I have run into a few units that have had the short cooling tube between the third stage separator and final (4th) stage head crack. I've also seen vibration cause the cooling tubes on each side to develope cracks from vibration behind the brackets.

BTW, I'm a Mako tech and work on these units every working day.

Craig

[divemetric]

I'm having a very similar problem. The one we have is a 5409 something something WD - with a Lister diesel. It's supposed to be 30.7 cfm, but I can only fill 12-15 tanks an hour. I can get the exact model number later if it helps.

The second stage is at 100, third is at about 550. I can't tell what the first is because the gauge is broken (naturally). The owner bought a refurbished Bauer K15 that is doing 18-20 tanks an hour. We're doing about 200 tank fills every day at the moment and will be for the next month. He bought the Bauer because the Mako is running so slow. Yes, I know it probably would have been cheaper to simply fix the Mako instead, but that's not how they think. I don't know if it ever ran properly to be perfectly honest. They may have bought it broken and had low expectations ever since. But it would be very helpful to get this thing running at 30 cfm instead of 15. I can definitely tell you it has been neglected and has probably lacked maintenance since they bought it.

The auto drain is disabled and bypassed (naturally)(as are ALL the electronics), so when I shut it off at 3300 (the banks don't work anymore, naturally, so we fill direct), I don't hear any leaks. There is no rpm meter for the diesel engine, but it seems like it revs pretty high and already runs pretty hot, so I don't want to mess with that. But I'm thinking there is definitely a problem between the stages anyway.

Can you tell me if this is something I can check out/fix on my own? I don't have much time to mess with it as we are too busy to have it out of service for any amount of time. I'm not a compressor tech - I'm just the manager, but I know more than anyone else at the resort about compressors, so if it's going to get fixed, it's going to be me doing it. (We're in Utila, Honduras, unfortunately we can only work with what we have, which isn't much).

Any guidance on checking the valves would be very much appreciated. Any technical manuals would be awesome too so I can actually see what I'm doing. I'll end up taking something apart on it one way or another. Tuesday is an off day, so maybe I'll do it on my day off. It could be worn piston rings or broken parts, which I can't do anything about, but if there is something I can tweak, I'll do it. So any help as to what and where to look for would be awesome.

Thanks for reading and helping!!!

Mike

[CraigAClark]

Will the stages hold pressure after the unit is shut off? What is the oil pressure? Trouble shooting is a process of elimination and this is the starting point since the ACD is not in the loop.

Craig

[divemetric]

The oil pressure gauge doesn't work either. The needle has fallen off. When the unit is shut down, the stage pressure gauges seem to hold pressure pretty well. I've doused everything with soapy water and don't see any bubbles. I checked the bleeds just now to see if they were leaking air, but I don't see any leaks - both running and shut off. At 3300psi the third stage makes it all the way to 650psi. The second stage never gets above 110. The first stage shows 15, but I don't think that gauge works. This thing is pretty old and mashed up, as is the norm here!

The exact model is 5409BA-WD
Serial: 5409.2.1a344
30.6 cfm
5000 psi

This model only has 2 "cylinder heads" coming off the block with 2 stages on each head. I'm more used to the Bauer models with 4 cylinder heads for 4 stages. I'll soon find out if beating it with a hammer helps out.

Thanks for helping!
Mike

[divemetric]

I just rechecked the stage pressures after shutting down. The 3rd stage keeps pressure, but the second stage loses it quick. The first stage loses pressure too, but that gauge is messed and drops from 15 to 0. I can't say if that's at all accurate.;

It also loses oil. About 1" in maybe 25 hours of running.

[CraigAClark]

This may seem obvious, but is the air intake plumbing and filter clean and clear? If it is and you can totally rule out any audible leak, check the first stage valves for leak by and carbon build up. If the machine has not had any maintainence done, you may find the valve cover orings in bad shape, making removal difficult and possibly destroying them. If you use any penetrating product like WD-40 you must make sure it is thoroughly cleaned off as it can get in the air stream. The filtration system will not remove it. Once you have the valves out we can proceed with testing them. Can you post pictures of the block from different angles?

BTW, both 1st and second stage valves can be removed as individual pieces. Just keep track of which is inlet and which is discharge.

Craig

[divemetric]

I changed all the filters when I started. The outlet filters were saturated with oil and water and they had the wrong filter setup too. I ran it without an intake filter for a while to test it and there was no improvement in performance. But it's clean now anyway.

The dive manager said he has been there for over 4 years and there has been no maintenance whatsoever on the compressor. So I have no idea when the problems started or how long they have been there. As is the case here, as long as it works, they keep running it and accept it as the new norm. And all information gets lost.

I'm glad you mentioned the disintegrating valve cover gaskets. I was going to try getting the covers off, but I'm guessing the bolts will crack off or the gaskets will disintegrate. I would be left with red silicon as my only sealing option then. I'm not sure that would stand up to the pressure.

I can get some photos today when I go in.