Welch DuoSeal 1400 Vacuum Pump Rebuild
Posted: Wed Dec 02, 2015 11:56 pm
Begin Build Log:
I went to SkyCraft the other day, a local electronics surplus here in Orlando to look at a vacuum chamber I remembered seeing there. While there, I also saw an old Welch 1400 vacuum pump sitting in the same aisle labeled "$25, Needs New Motor". It was in pretty bad shape but for $25 bucks, I couldn't resist. Even if I couldn't get it up and running, I have always wanted to rebuild one of these older belt driven pumps. I brought it back to the engineering lab I work at and did a quick external clean up. This consisted of scrubbing off the rust/dirt/oil build up on everything. Here is a picture after the initial clean up.
The next day, I got to work on the internals of the pump. I glanced at an exploded drawing of it on my phone and dove in (Probable should have sat down and carefully gone over that drawing before starting). The entire inside was gunked up beyond belief. I started with paper towels, but ended up using a putty knife to scrape away the gunk. Here are some pictures of the inside.
Disassembled Pump:
After a few hours of scraping, scrubbing, and washing, the insides were fairly clean. Unfortunately in the process, the exhaust valve, a small metal flap, was broken by the putty knife. Also, the oil case gasket, and intake gasket for the filter chamber were damaged/disintegrated. Here is a picture of the broken parts:
Welch actually sells two repair kits for this pump, a minor, and a major. These include basically all the parts that wear out or disintegrate over time. The two gaskets and exhaust valve were included, however, these kits cost $200-$300. So, I decided to try some workarounds. The gaskets were pretty easy to do. I took some basic measurements and looked at photos for reference and drew up a sketch as a vector model. I went to NAPA autoparts and got some 1/64" fiber gasket material for about $4. Since we have a laser cutter in the engineering lab, cutting these out was a quick and easy job. The end product worked perfectly and I still have a roll of extra material for future use.
You can download the gasket template here:
The exhaust valve was a bit trickier. Originally, I went looking for a thin spring steel to grind down to size, but noticed that it looked a lot like a feeler gauge. Sure enough, after taking some measurements and comparing it to a Sterret set I had on hand, it was almost identical. Even the hole was the same size. I picked up a cheap set from autozone, cut it down to size, and installed it. It seemed to have trouble at first, but it was because there was no oil in the reservoir. Also, I decided to test out the motor. It runs fine, but has trouble starting, perhaps it is missing a starting capacitor or the centrifugal switch is not contacting. Either way, this should be an easy fix later.
Before putting it back together, it was time for a coat of paint. I picked up some blue engine paint while at NAPA. This paint was used because of its good bonding to metal surfaces and durable finish. The pump was separated into its parts, cleaned with acetone and painted. Here is a before and after of the parts:
After drying for about 20 hours, the pump was reassembled, filled with vacuum oil from autozone, and run for a few minutes. This ensured the oil was circulated to remove any other debris and also to test the internals. Everything worked great! Although I haven't measured the vacuum yet, I can tell it was pulling a very good one. Unfortunately, the little oil drain valve and the shaft seal leaked quite a bit overnight. I drained out the remaining oil, now brown from circulating, and put an order in for the required parts and a few others. I found a supplier that sells the parts individually for pretty good prices. Here it is: https://www.duniway.com/catalog/mech-pumps/welch-style-pump-parts
Well that's it for now, I will be updating this post when I get those parts in!
I went to SkyCraft the other day, a local electronics surplus here in Orlando to look at a vacuum chamber I remembered seeing there. While there, I also saw an old Welch 1400 vacuum pump sitting in the same aisle labeled "$25, Needs New Motor". It was in pretty bad shape but for $25 bucks, I couldn't resist. Even if I couldn't get it up and running, I have always wanted to rebuild one of these older belt driven pumps. I brought it back to the engineering lab I work at and did a quick external clean up. This consisted of scrubbing off the rust/dirt/oil build up on everything. Here is a picture after the initial clean up.
The next day, I got to work on the internals of the pump. I glanced at an exploded drawing of it on my phone and dove in (Probable should have sat down and carefully gone over that drawing before starting). The entire inside was gunked up beyond belief. I started with paper towels, but ended up using a putty knife to scrape away the gunk. Here are some pictures of the inside.
Disassembled Pump:
After a few hours of scraping, scrubbing, and washing, the insides were fairly clean. Unfortunately in the process, the exhaust valve, a small metal flap, was broken by the putty knife. Also, the oil case gasket, and intake gasket for the filter chamber were damaged/disintegrated. Here is a picture of the broken parts:
Welch actually sells two repair kits for this pump, a minor, and a major. These include basically all the parts that wear out or disintegrate over time. The two gaskets and exhaust valve were included, however, these kits cost $200-$300. So, I decided to try some workarounds. The gaskets were pretty easy to do. I took some basic measurements and looked at photos for reference and drew up a sketch as a vector model. I went to NAPA autoparts and got some 1/64" fiber gasket material for about $4. Since we have a laser cutter in the engineering lab, cutting these out was a quick and easy job. The end product worked perfectly and I still have a roll of extra material for future use.
You can download the gasket template here:
The exhaust valve was a bit trickier. Originally, I went looking for a thin spring steel to grind down to size, but noticed that it looked a lot like a feeler gauge. Sure enough, after taking some measurements and comparing it to a Sterret set I had on hand, it was almost identical. Even the hole was the same size. I picked up a cheap set from autozone, cut it down to size, and installed it. It seemed to have trouble at first, but it was because there was no oil in the reservoir. Also, I decided to test out the motor. It runs fine, but has trouble starting, perhaps it is missing a starting capacitor or the centrifugal switch is not contacting. Either way, this should be an easy fix later.
Before putting it back together, it was time for a coat of paint. I picked up some blue engine paint while at NAPA. This paint was used because of its good bonding to metal surfaces and durable finish. The pump was separated into its parts, cleaned with acetone and painted. Here is a before and after of the parts:
After drying for about 20 hours, the pump was reassembled, filled with vacuum oil from autozone, and run for a few minutes. This ensured the oil was circulated to remove any other debris and also to test the internals. Everything worked great! Although I haven't measured the vacuum yet, I can tell it was pulling a very good one. Unfortunately, the little oil drain valve and the shaft seal leaked quite a bit overnight. I drained out the remaining oil, now brown from circulating, and put an order in for the required parts and a few others. I found a supplier that sells the parts individually for pretty good prices. Here it is: https://www.duniway.com/catalog/mech-pumps/welch-style-pump-parts
Well that's it for now, I will be updating this post when I get those parts in!