Taylor-Wharton High Capacity GST Storage Tanks User Manual

Page 27

VACUUM PROBE REPLACEMENT

If the VACUUM PROBE TUBE is damaged or is suspected of giving inaccurate readings,
replace it as follows:

Make certain that the VACUUM PROBE ISOLATION VALVE is closed.

Unscrew the VACUUM PROBE from the VACUUM PROBE ISOLATION
VALVE. Using two wrenches.

Clean the threads and opening of the VACUUM PROBE ISOLATION VALVE.

NOTE: Do not use Teflon tape as a sealant on vacuum system fittings.

Thread the new VACUUM PROBE into the VACUUM PROBE ISOLATION
VALVE by engaging one thread. Apply a suitable high vacuum sealant to
remaining exposed threads. Tighten the VACUUM PROBE into VACUUM
PROBE ISOLATION VALVE, using two wrenches. Do not over tighten.

Install a new vinyl cover over the VACUUM PROBE connector.

NOTE:

If corrosion of the VACUUM PROBE is a problem at a particular location,
spray the tube housing with "Krylon Crystal Clear Coating 1301" or
equivalent acrylic spray. Do not spray the contact pins of the electrical
connector; this could cause erroneous vacuum readings.

Open the VACUUM PROBE ISOLATON VALVE and check vacuum following
the above described procedure. The waiting period to obtain a stable reading with a
new gauge tube may exceed the specified 30 minutes. This is due to out gassing of
the new gauge tube and the thread sealant.

ANALYZING VACUUM DETERIORATION

If you decide to re-evacuate because of normal aging and deterioration, contact the factory for re-
evacuation procedures. If vacuum deterioration occurs over a relatively short period and pressure is
greater than 1,000 microns (1 mm Hg) absolute, suspect that a leak has developed in the external
casing of the tank. If deterioration is rapid and causes the VACUUM JACKET LIFT PLATE to
function, suspect leakage from the liquid container or internal piping.

NOTE:

An abnormally high vacuum reading without other evidence of vacuum loss
(excessive pressure, rapid venting, etc.) maybe caused by a fault in the
gauging equipment or by improper operation of the equipment. Be sure that
the Vacuum Gauge and the VACUUM PROBE are in good condition and
follow operating instructions carefully. Always be sure that the VACUUM
PROBE ISOLATION VALVE has been open for at least 30 minutes before
taking a reading.