Valve replacement – Great Plains NP3000A Operator Manual User Manual
Page 117
Great Plains Manufacturing, Inc.
Maintenance and Lubrication
113
2014-04-22
407-613M
6.
Inspect for dirt, sand, grease, paint, damage,
corrosion, signs of tampering or insect activity. If
visible, check the metal surface of the spring.
If debris cannot be easily cleared, replace the valve.
If there are signs of damage, replace the valve.
If there is any question, replace the valve.
7.
If a valve is venting at normal operating pressures,
replace the valve.
8.
Never force a valve closed. If a valve has remained
open after operating, or is leaking, it is seriously
contaminated or failed. Replace the valve.
9.
Never attempt to protect a valve orifice with grease.
Grease can harden over time, and/or collect
contaminants. Either factor could prevent valve
operation in an overpressure situation.
Never plug a relief valve outlet. Relief valves are
economical defense against serious ruptures and
major releases. Help a valve do its job of protecting
you.
Valve Replacement
The safest source for a replacement valve is Great
Plains. Check the latest edition of the Parts manual
(407-613P) or the Great Plains internet parts lookup.
This assures a correct and compatible part that reflects
any engineering enhancements.
Ammonia Exposure Hazard:
Fully discharge the system (page 108) before removing an old
valve. Wear protective equipment. If the applicator was
recently used, or ammonia was trapped, there could still be
NH
3
liquid or vapor behind the valve.
Do not attempt to repair or adjust a relief valve.
Hydrostatic relief valves are factory-set and tested, on
specialized equipment, to discharge at a specific
pressure.
On the component being protected by the valve, inspect
the threaded hole after removing the valve. If there are
signs of corrosion, replace the entire component.
Use pipe sealant when installing a replacement valve.
Use only pipe sealant specified for use with anhydrous
ammonia, such as RectorSeal No. 5. Do not use tape.
Record the replace-by date of the new valve in the
“Replacement Log” section of this manual (beginning
on page 114).
Ammonia Exposure and Rupture Hazards:
Always replace a relief valve with a valve:
▲ that is an external “hydrostatic relief valve”,
▲ that is specified for anhydrous ammonia service,
▲ that has the same NPT pipe thread size, and;
▲ that is rated for the same discharge pressure as the valve
removed (or as otherwise specified by Great Plains or the
manufacturer of the protected component).
Discharge pressure is specific to the valve location in the
system.
Using a valve rated too high could result in bursting of
system components and a major liquid NH
3
release.
Using a valve rated too low could result in unexpected
liquid NH
3
release, and material loss during application.