6
JB INDUSTRIES
• PLATINUM OPERATING MANUAL • 800.323.0811 • [email protected] • JBIND.COM
TESTING THE VACUUM PUMP’S
ISOLATION VALVE (CONTINUED)
First, let’s look at the construction of JB’s isolation valve
(Figure 16)
This figure
shows the isolation valve in the closed position The brass ball is sandwiched
between two Teflon seals, making a positive seal, with a solid brass surface
blocking access to the intake chamber The adapter nut on the top, outside of
the pump, is where the intake fitting is connected It is sealed with Loctite and an
o-ring If this nut has not been disturbed, the chances of a leak are very minimal
The stem has a dual o-ring seal and, even if this leaked, with the isolation valve
in the closed position there would be no effect on holding a vacuum A leak at the
stem would effect the depth of vacuum the pump could achieve
With a micron gauge connected directly to the intake of the pump and vacuumed to
50 microns, closing the isolation valve will result in a rapid rise in pressure, almost
to atmosphere Look closely at the area around the isolation valve Even though
small, air is trapped in this area When we begin to close the isolation valve, there is
a position of the ball that allows this trapped air to enter the vacuum being created
On a large system, this small amount of air would not create a conspicuous change
in microns However, with almost no volume, the sudden introduction of air to this
direct hook-up is obvious and would be displayed on a micron gauge Refer to the
previous page for the isolation valve positions When the isolation valve is put in
the pause position, this gives the cartridge (the pumping mechanism) access to
the air trapped in this area and within a few seconds, that trapped air is removed
Moving to the connections on the pump, the factory intake is loctited into place
and each pump is tested for leaks If this is not disturbed, the chances of a leak are
virtually non-existent Any leak would come from the connection at the port being
used and to the connection to the system
One of the most common errors with both the o-ring and the gasket couplers is
the wrenching down of these couplers with a pair of pliers or channel locks
(Figure 17)
Please refer to our
Principles of Deep Vacuum
article This article
can be found at www jbind com under Product Support
DO NOT
Wrench down on coupler (Figure 17).
The article,
Principles of Deep Vacuum,
shows there is a need for sealing with
a vacuum tight o-ring
(Figure 18)
Gaskets, like those used in charging lines,
are made for pressure What wrenching of the coupler does is to smash the brass
cup that holds the gasket or o-ring against the male flare fitting This causes the
brass cup to expand outward against the threads of the coupler and makes it tight
to turn This causes the o-ring to fall out of the cup that is holding the o-ring or
gasket in place
Another error seen is that technicians have a brass adapter fitting on the intake of
the pump with no copper gasket The first time you wrench the adapter into place,
it might seal But, as soon as you break the seal and re-tighten, there is a chance
for a leak The best hook-up that guarantees there are no leaks in the system is by
using JB’s valve core removal tools
(Figure 19)
Charging lines have been used for many years for the vacuum end of air
conditioning and refrigeration servicing Charging line use stretches back as far
as when inches of Mercury (inHg) was the way measuring of a vacuum on a system
was taught A charging line hose can be vacuumed to 50 microns if it is clean New
environmental hoses, fresh off of the shelf, will only reach about 300 microns until
they are cleaned out with alcohol and vacuumed out for a while Why is this? First,
the charging lines are mostly gaskets made for positive pressure Second, they are
permeated See page 7 for how permeation occurs
The only vacuum tight hose is a flexible metal hose Third, the compound of
the hose inside will out-gas when under a vacuum until it is cleaned out, as
discussed earlier
Brass Isolation Ball
Stem w/O-Ring
Retainer Ring
Adapter Nut w/O-Ring
Teflon Seals (2 Each)
Retainer Plug w/O-Ring
Poly Ball 7/16”
(Oil Check System)
Figure 17
Figure 16
Figure 18
Figure 19
Flare
Fitting
Specially
Designed Groove
Locks O-Ring
In Place
45° Positive
Stop
DEEP VACUUM
O-RING COUPLER CUT-AWAY
