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Introduction
The PressoVac vacuum pump is an old style vacuum pump we often
refer to as a trap plate pump. Some people call these piston pumps, but to us they still
are in the rotary vane family. The rotor is offset in and rotates off-center in the stator
(or ring). The stator (or ring) has slots cut in it where the vanes sit and ride up and
down maintaining constant contact with the rotor using a spring and lever arm to maintain
tension as it rotates eccentrically in the ring. These are one of our most difficult pumps
to assemble for all the parts have to be just right. Because of the assembly process each
pump is almost unique in nature although we are working to make them more consistent
allowing the parts to be more interchangeable. The uniqueness of each pump also makes them
very, very difficult to field repair and bring back to original specification.
We The PressoVac vacuum pump is an old style vacuum pump we often
refer to as a trap plate pump. Some people call these piston pumps, but to us they still
are in the rotary vane family. The rotor is offset in and rotates off-center in the stator
(or ring). The stator (or ring) has slots cut in it where the vanes sit and ride up and
down maintaining constant contact with the rotor using a spring and lever arm to maintain
tension as it rotates eccentrically in the ring. These are one of our most difficult pumps
to assemble for all the parts have to be just right. Because of the assembly process each
pump is almost unique in nature although we are working to make them more consistent
allowing the parts to be more interchangeable. The uniqueness of each pump also makes them
very, very difficult to field repair and bring back to original specification. We
do not recommend field level repair on this pump unless, it is very minor in nature.
On the positive side, the PressoVac, when right, is a tough dependable pump. If
the shaft rotates and the vanes go up and down, one can usually expect a pretty good
number for the vacuum specification. It is a good pump for applications expecting abuse.
It is a reasonable choice for untrapped contaminates.
It is relatively small pump (volume wise) and can not tolerate too leaky a
system. It is important to have little or no air leaks on the system being evacuated.
It has been in use extensively for educational markets and is a good small
system pump. It tends to be a little noisy due to it’s design, which can be a
drawback or benefit depending on system setup and monitoring. The pump sound will change
when high vacuum is reached and users don’t have to watch a gauge, just keep an ear
cocked as to when the system is at high vacuum (full vacuum) pressure.
No Vacuum No Vacuum -
The PressoVac pump is tough to have "no" vacuum present on. It is
possible, but unusual.
First off inspect the pump for correct
oil level.
Second inspect the base of the hose nipple (inlet port) for a good sealant bead.
I can't tell you how many pumps we get with the hose nipple replaced with some other
fitting that is not properly sealed with a good vacuum sealant. For threaded sealing of
HyVac pumps we recommend HyVac PST sealant.
Assuming adequate oil and lubrication has been inspected and is present. Then
remove belt guard and turn pump motor on. If the pump pulley is rotating and still no
vacuum is present then turn the pump off and get some screw drivers and some old rags, we
are going to operate. Remove the top off the pump and the oil baffle plate which is
present inside the pump and visible after removal of the top plate. Remove the oil baffle
plate also. You should now be able to see into the top of the pump. You should see
"one springs" attached to one "lever arm". (sometimes there are more
than one spring). The lever arm presses and forces the vane down onto the ocillating,
rotating surface of the rotor. When no vacuum is present you might see the vane stuck in
the up position. At this time manually actuate the pulley and review vane and lever arm
actuation. The vane should move up and down with the lever arm actuating in tandem.
If the vane is stuck in up position find a set of blunt nose pliers. Remove the
spring from the back of lever arm and put aside the pump. Move the lever arm out of the
way and firmly try and accuate the vane up and down in the pumps vane slot. No gorillas
please, this is a firm but gentle operation. Tolerances of the vane slot is +.001"
and it can get rusted up or have contminants "plate out" on surface causing the
vane to stick in the up position. We are trying in this operation to get plating or scale
scrapped off so the vane can ride freely in the slot.
If the vane is not stuck in the up position, I am stumped for the simple things,
so it is best to send the pump in. It maybe that the shaft is broken or the shaft key is
gone. In any case it is a job for HyVac unless you are very mechanically inclined. Call us
for an RGA / repair order at 1-800-628-0850.
Low Vacuum Low Vacuum -
First off inspect the pump for correct
oil level.
Second inspect the base of the hose nipple (inlet port) for a good sealant bead.
I can't tell you how many pumps we get with the hose nipple replaced with some other
fitting that is not properly sealed with a good vacuum sealant. For threaded sealing of
HyVac pumps we recommend HyVac PST sealant.
Assuming adequate oil and lubrication has been inspected and is present. Then
remove belt guard and turn pump motor on. If the pump pulley is rotating and still low
vacuum pressures are present then turn the pump off and get some screw drivers and some
old rags, we are going to operate. Remove the top off the pump and the oil baffle plate
which is present inside the pump and visible after removal of the top plate. Remove the
oil baffle plate also. You should now be able to see into the top of the pump. You should
see "one spring" attached to one "lever arm". (sometimes there are
more than one spring). The lever arm presses and forces the vane down onto the ocillating
rotating surface of the rotor. When low vacuum is present you might see the vane stuck in
the up position. At this time manually actuate the pulley and review vane and lever arm
actuation. The vane should move up and down with the lever arm actuating in tandem.
If a vane is stuck in up position, find a set of blunt nose pliers. Remove the
spring from back of lever arm and put aside pump. Move the lever arm out of the way and
firmly try and accuate the stuck vane up and down in the pumps vane slot. No gorillas
please, this is a firm but gentle operation. Tolerances of slot are +.001" and can
get rusted up or have contaminants "plate out" on surface causing the vane to
stick in the up position. We are trying in this operation to get plating or scale scrapped
off so the vane can ride freely in the slot.
If the vane is not stuck in the up position. ???? I am stumped for the simple
things, so it is best to send the pump in. It maybe that the shaft is broken or the shaft
key are gone. In any case it is a job for HyVac unless you are very mechanically inclined.
Call us for an RGA / repair order at 1-800-628-0850.
The pump is
locked up
Well you gone and done it now. Check the pump
for oil. Fill to correct level and manually actuate pump, assuming you can. Sometimes it
is possible to manually actuate a pump back into service that has seized due to lack of
lubrication. Other potential problem areas include vanes stuck in down position. See
"No vacuum" section above. Call us if you are unsuccessful.
Oil Problems Oil problems come in various shapes and styles and
are highly dependant on the vacuum pressure the user is trying to achieve. Because there
are many questions related to oil in our type of pumps we have a separate section just for
oil questions and tech support. Hot link to Oil Problems.
Why is the pump
leaking oil?
Vacuum pumps can leak from 3 basic locations
and their causes can be various. The first area and main culprit to examine is the shaft
seal of the pump. This is a mechanically rotating shaft in an area that can wear and then
leak over time. We felt that specifically the PressoVac style vacuum pump had a weak area
here and we moved to improve it in 1996. The new shaft seal is a lip seal. If your pump
employed the old style packing material then you can not use the new style lip seal with
out purchaing a new style trap plate to accommodate this update. If you look inside the
belt guard and down the side of the pump south of where the shaft comes through the pump,
you may find evidence of a shaft seal leak. Usually the side of the pump is shiny from the
oil. Also running the pump for a period of time on top of a sheet of newspaper can
pinpoint a leak.
The second most common location is from the pumps exhaust port. If the pump is
operated at high pressures then high gas flows create high levels of lubricant agitation
inside the pump which can exit the pump, come down the sides of the pump and create what
can be construed as a leak. If this is observed to be your problem we can enclose the top
of the pump and trap the exhaust of the pump using an exhaust filter or by enabling the
user to port the exhaust to a nearby "hood". This will keep the oil and
associated oil mist inside your vacuum pump.
The second solution is to make sure your system is really vacuum tight because
the cause of this problem ia basically a leaky system.
The pump will operate over extended periods with this symptom but it is
important to monitor the oil level of the pump on a regular basis.
Water in
the Pump Water in
the Pump -
Hot link for the answers…. This is a big very common problem. One of our
most common problems is water in the pump.
Why is it bad? Corrosion. Pump distruction.
How does it happen? Waters vapor pressure less than pumps vacuum pressure.
How do I tell? Oil is milky colored.
What are solutions? Freeze those water molecules.
Pump is
corroded. Why?
Water or acids have been present in pump for an
extended period of time. See also water in the pump.
I think all high vacuum pumps are made from cast iron predominately, aluminum
and steel secondarily. We tried making one from stainless steel and will revisit sometime
in future but in a nut shell, it failed. Cast iron and water don't get along. This is the
same for acids like hydrochloric or sulfuric. The tend to attack the cast iron of the
pump and cause oxidation or rust to form. On the outside this is ok but left standing,
formation starts internal to the pump and will cause the pump to seize up after some
period of time days to years depending on contaminant source and level.
I have seen ads for corrosion resistant pumps. Right…., great marketing
ploy. They fail in 4 months instead of 3. Spend your money elsewhere on solutions that
work. There is no cheap solution only correct ones. Teflon coating… phooey. The
vacuum pumps lock up because the rust forms on the cast iron rotating parts
"period". No Teflon coating is going to last long with the metal to metal
contact that we have in rotary vane pumps. Coating the oil sump with Teflon protects the
aluminum housing. I have never seen a pump yet with an uncoated aluminum housing eaten
through, although I have seen thousands of pumps with corroded cast iron parts.
The basic fact of the matter is contaminants must be eliminated from the pump.
You can either deal with it before the pump or after it gets in the pump. For systems with
high contamination potential then probably both types of systems are required. For the
front end or suction side of the pump, employ a vacuum inlet trap. For dealing with
contamination once it is in the pump consider an oil filtration system that can be hooked
up to the pump to re-circulate and de-acidify the oil.
The poor users solution to oil contamination problems "Change the oil
frequently". Create a larger oil sump that lasts longer in getting contaminated.
Why is the
pump is slow to pull down?
Assuming the pump is OK (see below). You have air
leaks in you system or collapsing vacuum hoses. Check system for leaks (Link to
procedures). Fix leaks and time again.
How can I
check my pump to see if it is OK?
Hook you pump up to a good vacuum gauge at the
pump intake port with out the system attached in any manner. This is the best and only
real way to baseline the pump. In problem areas or troubleshooting vacuum systems this is
the first step in the process. Determine the "blank off" pressure of the vacuum
pump. For a PressoVac the blank off pressure is 15 micron or .015mm and for those with
inexpensive vacuum gauges roughly 20 micron, .02mm with thermocouple or TC gauge. And for
you real mizers out there, 29.99 with Bourdon Tube 0-30" gauges and between 0 and 1mm
with manometers (0-760) in both cases depending on atmospheric pressure variables.
How do I
capture the exhaust?
The PressoVac vacuum only model pump requires a
special top that allows for capture of the exhaust fumes. This can be ordered from HyVac
for this use. You then hook up an exhaust line and port the exhaust to a hood or adapt it
to an exhaust filter. The PressoVac vacuum and pressure pump has an exhaust port as part
of its design.
My hose
nipple is too big / too small?
HyVac Products stocks and manufactures a
myriad of solutions for conforming to a users system. If we don't have it, we can get it.
HyVac manufactures both conventional hose fittings and also the newer generation quick
disconnect vacuum fittings often referred to as NW or ISO or KF fittings, flanges, piping,
adapters and clamps which allow a wide variety of connection sizes and terminations.
How do I
change the oil?
Generally we recommend changing the oil through
the exhaust port of any high vacuum pump. This port generally is a straight dump into the
oil sump of most vacuum pumps. The intake port should only be used as a last resort, is
slow but ultimately acceptable. Manual pump rotation probably will be necessary to
accomplish.
Other
problem areas not covered.
You get em to me, I'll post em.
11/27/2005 ©Copyright HyVac Products, Inc. All Right
Reserved
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