Taylor-Wharton VJ Bulk Tank - Manual (Page 15)

Refer to the Trouble-Remedy Guide in this manual for maintenance procedures. If the problem is not
readily corrected, replace the gauge with a spare. Field repair and recalibration of the LIQUID
LEVEL GAUGE (LI) is not recommended. Return the defective gauge to the manufacturer for
repair. Include a description of difficulty encountered.
CASING AND VACUUM MAINTENANCE
CHECKING VACUUM
Taylor-Wharton Cryogenic tanks are carefully designed, manufactured, and tested with every effort
made to eliminate vacuum space leakage. An absorbent system is sealed inside the casing to help
maintain the vacuum over a long period of time. However, some vacuum deterioration over time can
be expected due to out-gassing of materials inside the vacuum space. To detect vacuum deterioration,
periodic measurement of casing vacuum is recommended. A thermocouple-type vacuum gauge tube,
located on the bottom head of the tank, is provided for this purpose.
To check casing vacuum:
1. Remove the protective plastic cap from the gauge tube connector.
2. Connect a Hastings-Raydist Vacuum Gauge to the gauge tube.
3. Open the gauge tube isolation valve and wait at least 30 minutes before reading the
vacuum gauge.
4. After the vacuum reading is recorded, close the isolation valve, disconnect the
Vacuum Gauge, and replace the protective cover on the gauge tube connector.
The vacuum reading obtained on a cold tank is initially less than 100 microns (0.1 mm Hg) absolute;
however, gradual deterioration over a period of many months or years is normal. A complete log of
vacuum readings, along with dates when they were taken, can be very helpful in evaluating vacuum
performance and scheduling work.
NOTE:
If the tank is empty and warm, vacuum space pressure will tend to be high because of
the release of gases from adsorbent package inside the vacuum space.
Because re-evacuation is time consuming and usually requires taking the tank out of service, it is not
normally attempted until tank performance becomes unacceptable. Even a relatively high degree of
deterioration can be tolerated in a tank from which high rates of withdrawal are being made.
However, if vacuum deterioration seriously affects tank operation by producing excessive pressure
buildup and high loss rates, use the information in this section to determine and correct the cause of
the trouble.
Necessary repairs must be made before the casing is re-evacuated and the tank returned to service.
Leak detection and repair procedures are often complicated and difficult. Only persons who are
trained and experienced in cryogenic equipment, troubleshooting and repair procedures should
attempt such work. If difficulties in troubleshooting and repair are either anticipated or encountered,
consultation services can be obtained from Taylor-Wharton Cryogenics. Contact the Customer
Service Department at the Theodore, Alabama factory.
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