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Discussion Starter #1
Greetings all. Inherited a little twin cylinder compressor w/what I'm guessing is a 20 gal tank made by Melben of Ohio. Did some research and understand the history of the Co., but need some model specific info. The tag reads, in part, MPCO MFGRS No 397286. Second line DIV 1 WP133 TEMP 250 and third line W SH 095 ?D 094 RAD 12. So I bolted on a 1/2 Hp motor after a little cleanup and it pumped up to 90PSI with no leaks or hickups.

Can't find any specific info on this little critter and I'd like to know the cfm and the compressor rpm (not the motor rpm) and the max psi. Doesn't seem to be any markings on the compressor block itself.

Any help??
 

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Most compressor pumps run about 1000 RPM and if it is a single stage compressor 100 to 120 PSI is the normal shut off pressure. If it has an adjustable pressure switch I would set it at a max on 100 PSI as it is an old tank. I am surprised a 1/2 HP motor will run it. Roger
 

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Discussion Starter #3
Thanks, how to??

@rhenning, thanks for the info. I was hoping that someone here might have a xref to models built under the C-H name, or a specific Melben contact (not getting any reply from the one contact I found). The little 1/2 Hp 3450 motor had a tiny drive pulley on it, and as I stated, ran it up to about 90 psi before the the compressor stalled it. The cutout/pressure switch never tripped, although I subsequently backed it off to around 80 and it did function.

The P/S is a Square D unit and appears much newer than the compressor, so who knows what motor or 110/220 was originally configured is ????

However, the tank is pristine, not a spec of rust anywhere, and the filter and oil were also clean. It has two plugs on the tank, a 3/4 and a larger 1.25. I took out the 1.25 and ran my fingers inside the tank and just slight rust dust w/no moisture at all. **** nice 60 ft hose that was stored in plastic wrap or kitchen cling wrap.

I have a number of motors and pulleys I could mount on this thing. Could even slap on an 8Hp Tecumseh that was just rebuilt. And I don't have need for anything more than 120 psi in the tank, but a fast recovery portable would be really handy...especially since it's essentially free.

So, 1000 rpms, there abouts? Let's assume I gear it for 750, should be a safe operating speed?

And how could I tell if it is a single stage or compound? All I can see by removing the filter on the head is one small valve on each cylinder (appears to be intaking air individually to each cylinder, so single stage is first guess) It is a vertical monoblock with a common exhaust to the tank. The P/s is fed by a line off one of the cylinder heads, not the tank, which would lead me to believe the opposite, that is a two stage.

Thoughts??
 

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On a two stage machine, one cylinder (larger) pumps air to the other cylinder (smaller), then to the storage tank.
 

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@cedgo, thanks. After my post I did a little more general research and picked up on the idea of the second stage cylinder being smaller for greater compression. So this is definitely a single stage.

A little more general research leaves me with the impression of running slower than max rpm could also lengthen the life by reducing internal heat. Which is rational, but, perhaps not relative. I mean, what might the expected lifespan be, in the first place.

Even though it came to me free, there's no need to press it into an early scrap heap...and likewise, there is no need to baby it at unnecessary low speed other than general safety.

Got an email back from C-H, no help. Seems they either didn't keep or don't want to reference any Melben P/N's even though they continued to produce the exact models for years after the company buyout. Sigh, the good old corporate philosophy of build it once and forget any thought of it having any value to someone down the road.
 

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I just bought a Melben compressor. It's a 20 gallon tank and has the original 2 HP 3450 motor on it. I just put new bearings in the motor and am looking at tuning up the pump.
 

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I pulled the head on the pump, removed the valves and cleaned them. Cleaned the head too--the area around the intake ports was really grimy and dirty from sitting in somebody's garage for the last few decades.

 

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I thought guys might like to see what the business end of the head looks like. This pump was made by Campbell Hausfeld, and is similar to allllllll the CH pumps made over the many decades they've been in business. Meldon was a company CH took over in the late 1960's I believe. As you can see, the valve seats appear nice and flat. The valves themselves were all very straight, with no deflection or bending, and I took that, along with the condition of the exterior of the compressor to mean it had few hours on it. The guy I got it from was given this compressor by a friend's uncle. He sold it to me for $75. Good buy!!

 

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How to add oil to this compressor?

I just bought this same compressor off craigslist and never owned one before. I drained the old oil but am having trouble adding new oil. I tried adding it to the port having the tiny fill funnel above the shaft but it does not accept much oil and spits it out when I turn the shaft by hand.

I am confused.

I just bought a Melben compressor. It's a 20 gallon tank and has the original 2 HP 3450 motor on it. I just put new bearings in the motor and am looking at tuning up the pump.
 

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To me, the plug is a drain. It is low on the oil sump. If there is no fill plug (and I think there should be), you may have to tip the whole compressor on its side to fill it. Then the question arises how much oil do you add? I would use 30 wt NON-detergent oil. Any auto parts store will have it. DO NOT USE 30 wt HD or any multi wt oil like 10w-30.

I would really look for a fill plug and fill it to the bottom of the plug hole.

How about some pictures?

keep us posted.

bernie
 

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I found the fill plug. It is about 1 1/2 inches up and 1 1/2 inches to the right of the drain plug in the photo.

I replaced the foam filter media on top.

I drained the old oil and replaced it with "compressor oil" from the hardware store. The old oil was very dirty. I ran the compressor for a few minutes up to 110 psi and it held the pressure. I replaced the oil again as it was still very dirty and black. I stuck a Q tip into the oil sump and it came up looking like the end was black tar.

I. Short of taking apart the compressor, are there ways of running fluids through the compressor to clean out the old oil? Should I run anything into the air intakes?

2. There is a small 1 inch high sheet metal tube for oiling the bearing or axle above the axle on the compressor. It leads down into a hole in the journal or bearing or whatever on top of the axle. What should I add to that?

Thanks
 

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glad you found the oil fill. being a "jack of a few trades and an expert in none of them" my advice is as follows. If after an oil change and running up the pressure a few times and it remains dirty, change the oil again. I assume the compressor oil you bought is non-detergent (which it should be). Non- detergent oil does not hold dirt in suspension, it settles out on the bottom of the oil pan. My compressor (Pelton) has had 1 oil change in 20 years that I know of. The oil was clean coming out and still clean after some minimal use. No dirt in oil pan as close as I could tell. I did pull the head on mine, some carbon from an oiled felt air cleaner( i assume). see my thread for pictures. I have no idea about the tube you are referring too. any pictures of your compressor?

good luck

bernie
 

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the tubes you are talking about are for supplying oil to the bearings i'm not 100% sure on this but i believe you are supposed to use the same oil in them as you do with the pump from my experience with other machines that have the same setup for lubing the bearings you refill them after so many operating hours they basically are an automatic oil system and just let a small amount of oil in to the bearing as its needed
 

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Thanks for all the help

I have been out of town lately, no time for compressor or to take photos.

I will continue to run it to get the oil warm then drain it and replace until it comes out looking OK.
 

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Hello i think I put this post in the wrong area the first time. But here goes again. I have a melben compressor 2 cylinder cast iron. Compressor seems fine. But the 1hp motor couldn't take it. I'm replacing with a 5hp. My problem is I cracked the small pulley on the motor shaft ggrrrr its a 6 spline. Anyone know where I might get one of these. Thanks guys.
 
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