JUST BETTER 539-VACUUMPUMP-001 Deep Vacuum Pump Instruction Manual
- June 12, 2024
- JUST BETTER
Table of Contents
PRINCIPLES AND APPLICATION
DEEP VACUUM
INTRODUCTION
With deep vacuum, we are sure of our results before we leave the job. No more
waiting to see if we get a call back to determine the results of our work.
Deep vacuum is the only method we can use to tell us, for sure, that a system
is thoroughly dry and free of noncondensables and leaks.
MEASURING EVACUATION – MICRONS OR INCHES?
A micron is a measurement of pressure starting from a perfect vacuum (no
pressure) expressed in linear increments. One inch equals 25,400 microns. It
should be noted at this point that when we discuss vacuum in terms of microns,
we are referring to total absolute pressure as opposed to gauge pressure.
Besides using a more accurate unit of measure (you can’t read fractions on a
bourdon tube type gauge), we are also starting from the same measuring point
(theoretical perfect vacuum).
The bourdon tube type gauge, you will also remember, uses atmospheric pressure
as its reference point, which is constantly changing during the day. The
weather forecaster always includes this reading, barometric pressure, along
with the temperature. When an area is covered by a HIGH, it translates into
high barometric pressure and vice versa for a LOW.
PUMPS AND HOW TO SELECT THEM
Deep vacuum pumps are the first item to come to mind when we think of vacuum
tools. Unfortunately the first mistake is usually made in the selection of
these pumps with reasoning that goes like this— “The larger the pump I get,
the faster I can do the job.” Pump capacity has very little to do with
evacuation time in refrigeration systems, as is easily seen when we examine
the following.
The refrigeration system itself is constructed of several feet of small
diameter tubing with return bends and metering devices to offer
restrictionduring evacuation. Compound this with the fact that service valves,
when provided, have 1/4” male flare ports which only have a 3/16” orifice. We
also know that the only way to get more flow through a given orifice is by
increasing the pressure across that orifice. But does a pump create pressure
that increases the flow? No. We tend to forget two basic principles. A vacuum
pump creates a void toward which the system pressure flows. The second point
is that as pressure decreases in the system during evacuation, flow decreases.
Therefore, it’s impossible for usto increase pressure or flow through our
gauge ports with a larger pump.
Pumps in the 1-1/2 to 10 CFM class are adequate to handle 99% of our work. As
a rule of thumb, the CFM rating squared equals the maximum system tonnage.
A 7 CFM pump is rated for 49 tons; 3 CFM pump is rated for 9 tons. They are
all that should be purchased for service and installation. In many cases,
depending on the system line sizes of large tonnage systems, it is better to
put two or more of the small, easily handled pumps at different locations.
This will overcome some of the pressure drop problems and actually be faster
than a single large pump.
PUMP CONSTRUCTION
Rotary vane deep vacuum pumps are readily available and are best suited for
our work. Piston type pumps, because of the clearance necessary between piston
and head, are incapable of producing a deep vacuum or at best are very
inefficient. Many single stage compressors, similar to a hermetic compressor
will not evacuate a system into a micron range, the last inch of pressure on
the compound gauge, nor will it condense any moisture vapor in the system.
Two stage pumps (2 pumps in series) have the best record in our business
because they are capable of producing consistently lower pressures and are
much more efficient when removing moisture vapor. The pump should be equipped
with a blank-off valve which allows us to perform the isolation test (pressure
rise) which is required in deep vacuum procedures.
The gas ballast feature should be on all pumps for refrigeration. At the
beginning of evacuation, water vapor is quickly removed and if a system is
laden with moisture, can very quickly contaminate the oil. Through thegas
ballast, a fine metering valve connected to the second stage of the pump, a
small amount of relatively dry ambient air is admitted to help prevent the
moisture vapor from condensing in the oil. So far, we have defined our pump
requirement as follows: 2-stage, rotary vane; blank-off valve; gas ballast
valve; 1-1/2 to 10 CFM. A system is evacuated to between 300 and 400 microns
so obviously these pumps should be able to produce vacuum in the low micron
range with a safety factor of at least 25 microns total absolute. Thus, the
pump should be able to achieve vacuum readings of at least 25 microns total
absolute. We should also look for light weight and rugged construction because
we all know the vacuum pump will be at our side as we climb thoseladders to
the roof top.
Finally, when checking out pumps, look at safety. Belt driven units should
never be used without belt guards—if you don’t give a darn about your own
fingers, etc., give children and others exposed a chance. Hospitals and court
rooms around the world are full because of this negligence. THE ELECTRONIC
VACUUM GAUGE Coupled with good procedures which we will get into later, the
electronic gauge tells us positively that we have a noncondensable and a leak
free system. In general these gauges are heat sensing devices, in that the
sensing element which is mechanically connected to the system being evacuated
generates heat. The rate at which this heat is carried off changes as the
surrounding gases and vapors are removed. Thus, the output of the sensing
element (either thermocouple or thermistor) changes as the heat dissipation
rate changes. This change in output is indicated on a meter which is
calibrated in microns of mercury.
The electronic vacuum gauge is the least purchased deep vacuum tool. Yet,
without this instrument you might just as well forget about deep vacuum
altogether.
Evacuation is complete when a system holds at 500 microns. The compound gauge
only indicates that a vacuum is being produced. The vacuum gauge on the other
hand, is the only tool for accurately reading that low pressure.
VACUUM GAUGE SELECTION AND ACCURACY
The most important feature of all is range. If the vacuum gauge only indicates
from 50 to 1,000 microns, you will not be able to determine whether you are
pumping against a leak or against moisture. Look for aninstrument that reads
from 50 microns to at least 9,000 microns. A digital display with easily read
numbers gives you instant and continuous readout, whereas a gauge with color-
coded lights, displays the reading “within a range” of microns. You have a
“wait” period to seewhether the system is going up or down in microns.
Portable vacuum gauges typically operate from battery power and shouldhave a
low battery sensor. Some models have AC adapter capability so you won’t run
out of power on the job. Another feature to look for is a sturdy case to
protect the instrument. Finally, when you buy instruments of this type,
remember that you are really only buying answers, and the instrument should
give you these answers quickly and accurately. You get paid for adjusting
refrigeration systems, not your tools.
EVACUATE THROUGH THE GAUGE MANIFOLD
Evacuate through the gauge manifold if, and only if, it is O-ring sealed,
piston construction. Other types leak under vacuum. Next look at the design of
the center port. In order to handle the full capacity of both the high and low
side, the center intake should have double size flow path throughout its
length. All J/B 1/4” manifolds have this feature.
We suggest the fitting be replaced with a 3/8mf x 1/8mp. You will now have a
full flow 3/8” to the vacuum pump. You also have the option of using the
M4-Series manifold which is designed to evacuate, charge or test a system
without disconnecting hoses and
features a 3/8” fitting.
DEEP VACUUM O-RING COUPLER CUT-AWAY
LEAK-PROOF HOOK-UP
Deep vacuum has it own unique properties which requires leak-proof design not
only in the manifold but in all components. The only connecting lines that are
absolutely vacuum tight are soft copper tubing or flexible metal hose.
Charging and testing hoses are designed for pressure. Even with the advanced
technology of today’s hoses, permeation through the hose compound still
exists. When checking pressure rise, the atmosphere will permeate to the lower
pressure in the hoses and the micron reading will slowly rise.
Another source of leakage is the gasket seal in valve and hose couplers. This
seal is designed for charging and will not give a perfect seal required in
deep vacuum service. An O-ring seal coupler, such as that made by J/B, forms
around irregularities in the flare fitting. When the coupler is screwed down,
we get a metal to metal seat and the o-ring lays around the lip of the flare
to give a positive seal.
CONNECTING LINES
We have now covered the simplest hookup to this point; gauge manifold with two
1/4” I.D. connecting lines to the system and a 3/8” connection to the pump via
line or fittings. Much has been said and written regarding line size, which
would lead us to believe the bigger line we connect, the faster job we’ll do.
This would be true except for the compressor’s service valves 3/16” orifice.
Therefore, we only need to keep the connecting lines’ I.D. larger than 3/16”
This is one of the limiting time factors in evacuation.
Evacuation should always be done from both the low and high sides of the
system. This could save as much as 3/4 of the time when evacuating from only
one side. Short connecting lines will save some time; however, not nearly what
some maintain. In relation to the lengths of tubing in the system, we add very
little restriction via connecting lines.
- Stem seats retract completely from flow path.
- Double size flow path throughout length of center port.
- Convert to 3/8” port with 3/8mf x 1/8mp
BEFORE YOU START
It is a good idea to attach the vacuum gauge to the vacuum pump to make sure
the pump pulls down to at least 50 microns. If it doesn’t, your pump is
contaminated and the oil should be changed. Do not shut-off the blank-off
valve on the pump and expect the gauge to hold a vacuum as the gauge will fall
back to atmosphere. The reason for this is that the sensor is too close to the
pump and the gauge’s sensor doesn’t have time to equalize.
MOST LEAK-PROOF VACUUM GAUGE HOOP-UP
The most leak-proof setup is by using the DV-29. This unit creates a closed
system eliminating any leakage under deep vacuum.
DV-29 CREATES A CLOSED ENVIRONMENT TO CHECK FOR SYSTEM LEAKS
- Works with all vacuum gauges
- No Additional equipment needed
- Leak-proof components
The DV-29 test unit (see illustration) eliminates other problems when
attaching the vacuum gauge into the system. If the vacuum gauge is attached
directly to the vacuum pump or with 3′ dedicated hose, we will get a lower
reading as the gauge is sensing what the pump is doing and not what the pump
is doing to the system.
DISPELLING THE ARGUMENT OF “NO DEEP VAC ON HEAT PUMPS, ETC.” The word
“sublimation,” the ability of moisture to go directly from solid ice to vapor
without passing through a liquid state, is commonly used in vacuum. This
phenomenon is observed when the wash is hung out in the winter and freezes
solid. Still, in time it dries due to sublimation (drying). If lines are in a
cold ambient, it is possible to have ice in the system. It will be removed
during evacuation. Of course, the addition of heat (heat gun only) at these
cold spots speeds up the job.
GENERAL VACUUM GAUGE HOOK-UP
When designing your hook-up system, choose from the following hoses, valve and coupler designed for leak-proof service in a deep vacuum environment:
- D10436 or D10427 1/4” Metal Hose and D10636 or D10660 3/8” Metal Hose with o-ring couplers. Your hook-up through manifold, pump and if desired, to the vacuum gauge.
- A34000 Quick Coupler Tee w/o-ring seal. Since the most accurate reading is obtained at the compressor’s high or low side, use to tee-off the gauge.
- D10162 ball valve with O-ring quick coupler to valve off gauge before charging. Depending on the gauge, it should be remembered that the electronic gauge’s sensors will not take pressure beyond 1 to 100 pounds. Depending on hook-up, use with metal hose or A34000 coupler.
PRESSURE RISE TEST
We previously mentioned that the only difference between deep vacuum and the
methods of the past is that we can measure what we have done.
This is called the Pressure Rise Test.
When the sensor reads between 300 and 400 microns:
- DV-29 Method – Blank-off the high and low side ball valves attached to the system.
- General Hookup Method – This includes using copper tubing or metal hose to the high and low side. Close blank-off valve on the pump. This will isolate the gauge from the pump.
Wait for at least 5 to a maximum of 20 minutes to allow system pressure to equalize. The reading you see at the end of this test will be very close to what you actually have in the system. A rapid rise during this test to atmospheric pressure indicates a leak, while a slower rise to around 1500 microns indicates moisture is present.
READINGS AFTER 5-20 MINUTES UNDER 500 MICRONS Evacuation Complete SLOW RISE
TO 1500 MICRONS Moisture RAPID RISE TO ATM Leak
There are many evacuation level recommendations including the statement
“evacuate the system to below 200 microns.” This should not be considered.
Note we say “system” because it is possible to evacuate piping or some
component other than the compressor to below this level. Refrigeration oil has
a vapor pressure and by going below 200 microns, you will degas particles of
the refrigeration oil. By changing the makeup of the oil, it will no longer be
a true lubricating oil.
PREVENTING “HARD START-UP”
After closing the is olation valve, open the gas ballast valve and shut the
pump off.
EVACUATION BRINGS OUT THE WORST IN A SYSTEM!
Remember, hydrofluoric and hydrochloric acids, and their pal, moisture, do
collect in the oil. Having nothing but time on their hands, they effectively
destroy pull down and act as an abrasive on internal surfaces. If left sitting
in an idle pump, these culprits keep
busy by rusting and corroding internal surfaces. Deep vacuum pumps need a fill
or two for every job. In order for your pump to pull a near perfect vacuum,
oil must be clean and moisture free throughout evacuation. Just take a few
minutes during and after each job to drain, flush and refill. Keep your pump
running at peak performance and maintenance free for years to come. Always
store your vacuum equipment plugged or capped to prevent contamination due to
condensation and dirt. Because a slight cut or dirt on the o-ring seals can
cause leaks, the mating flare fitting faces should be wiped and checked for
damage before hookup. Vacuum pump oil makes a fine lubricant at these
connections.
JB INDUSTRIES • DEEP VACUUM
800.323.0811
SALES@JBIND.COM
JBIND.COM
Documents / Resources
| JUST
BETTER 539-VACUUMPUMP-001 Deep Vacuum
Pump
[pdf] Instruction Manual
539-VACUUMPUMP-001, Deep Vacuum Pump, 539-VACUUMPUMP-001 Deep Vacuum Pump,
Vacuum Pump, Pump
---|---
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>