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Various older belt-driven Welch models appear from time-to-time on eBay and elsewhere but listed information for them
- including what I have above for pumping speed
and even the number of stages - may not be reliable.
Notes 1. The "Pumping Speed" values used here are the manufacturer's
free air displacement ratings. These photos are prettier
than the ones on the Welch Web site and I believe the captions match the pump which wasn't the case the
last time I checked there. Exploded parts diagram and parts list available on Welch's Web site.
The specs for the 1405 on Welch's Web site show 3.1 cfm
(91 l/m) but I list those I've seen everywhere else. The 1373 only
shows up in the "Parts Diagrams" portion of the Web site but without specs.
Here is a chart of the most important specs for a variety of Welch belt-drive rotary vane vacuum pumps.
And, those 50 year old pumps are still serviceable, requiring at most a cleaning and relatively inexpensive rebuild kit to meet original factory
specifications. These appliances and machines often require
the expertise of technicians and engineers who are skilled in working on them.
We have experienced technicians who are trained in the best industry standard.
After disassembling it for the second time and finding the problem, I unstuck the rubber from the shaft,
lined up the broken pieces as best I could, and added an additional spring of my
own to keep them together - hopefully. I suggest
you use a shop vacuum cleaner to get all the drilled metal
pieces into the vacuum cleaner, not the transmission. The kickstart parts were soft & use of the
kickstarter is not recommended. They also have repair parts and kits for all their pumps as well as exploded
diagrams (with repair manuals and more coming soon) should your acquisition turn out to need a bit of
maintenance or a miracle. I also don't think direct-drive pumps have quite the same aesthetic appeal as belt-driven pumps.
There have also been a number of articles on vacuum
systems and technology in the Amateur Scientist column of Scientific American. Lesker Vacuum Systems and Components, a supplier of
vacuum related equipment and supplies, has basic technical notes on vacuum pumps, gauges, and other product related topics in their
"e-Catalog". Pfeiffer Vacuum has several documents on basic vacuum technology under "Downloads".
As far as convenience goes, you only have to
type in basic contact info to get a quote. Whether your type of door is closed by
hand, or by an electronic device, regular maintenance can prevent
major disasters down the road. With available alternatives which ranges from laminate refinishing to hardwood refinishing,
the professionals can certainly help refresh various hard flooring products to give enhanced look as well
as safety for many years of more overall performance.
However, I do believe that both these pumps would benefit from another oil change and
flushing might help the 1402 even more. Again, if you are certain that your appliance is broken, then you must secure the help of experts and professional service providers straight away.
You may be strongly tempted to call an amateur to come and fix your damaged appliance.
Actual performance may be slightly lower. Typical performance with fresh belt-drive pump oil will be a fraction of a Torr for
single-stage pumps and a few microns for two-stage pumps.
The vapor pressure at 25 °C for Welch Duo-Seal oil is about 5 times
the listed base pressure for two-stage Welch pumps!
2. The specifications for "Ultimate Vacuum", especially for
two stage pumps, are generally overly optimistic and not achievable in practice except under the most controlled conditions with the pumps in perfect mechanical condition, new from the
factory or after several flushes, and filled with special low vapor pressure oil.
The Electronic Bell Jar has a detailed article on refrigeration service pumps.
When you're coming up with a pick, take the time to look at
the examples below these are rated the most
effective in the arena of fridges and finding a repair service and
appliance components for them isn't hard. I still doubt they would reach spec'd pressure though I have seen another pump (Ulvac Sinku-Kiko G-50D) come in well
under its more conservative rated base pressure of 0.75 microns
after a flushing and two oil changes. Newer 1405s are externally similar
to 1402s with the large oil case but older versions have a very small oil reservoir above the pump chambers and no other oil case.
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