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9.0 Maintenance
NOTICE:
It is essential to establish a periodic retesting and preventive maintenance
program for pressure relief valves. The DOT and AAR have set forth a retesting
interval that should be considered the maximum length of time between tests. If your
company’s experience indicates that a shorter interval is advisable, a program with
more frequent retesting should be implemented.
NOTICE:
It is an AAR requirement (refer to D4.04) that new O-rings be installed
when a valve is retested.
9.1
Prior to Maintenance Tasks Performed
9.1.1
Retesting of Valves in Storage
9.1.1.1 Midland valves are factory set and sealed. If they have been left in their original shipping
containers, are undamaged, and are no more than six (6) months old, they may be installed
without being retested
9.1.2
Required Tools
9.1.2.1 Obtain the required tools and supplies before attempting maintenance procedures. Table 1-
3 outlines some suggested tools that will be needed.
9.2
Leak Repair on a Mounted Valve
9.2.1
Repair the retainer O-rings. Exception: When performing that procedure, there should be no
pressure in the test chamber and the retainer O-rings should be loose, not epoxied into the O-ring
retainer as specified in that procedure.
9.2.2
It is possible to replace only the retainer O-rings on an internal-style valve mounted on a
pressurized tank car. This procedure may be conducted to stop minor leakage when valve
rebuilding or replacement must be delayed.
CAUTION:
The repair procedure for a mounted valve is intended only as a
temporary repair. Once the product is unloaded and pressure is relieved, the valve
should be removed for further repairs and full requalification.
NOTICE:
Conducting this procedure may be hazardous (depending on the material
in the tank car). Maintenance personnel should be carefully trained before being
permitted to perform the procedure below on a pressure relief valve mounted on a
pressurized tank.
NOTICE
CAUTION
NOTICE
