Question 92Refrigeration & AC - 1st Asst/Chief

70% to pass

Refrigeration system isolation valves are specially designed with a back-seat, as well as a front-seat. For what purpose are these valves designed in this way?

Aallow for operation as a suction or discharge valve
Ballow for removal and replacement of the valve without shutting down
Cpermit repacking the valve stem under pressure without shutting down
Dallow for operation as a liquid or vapor valve
AI Explanation

The correct answer is C) permit repacking the valve stem under pressure without shutting down. Refrigeration system isolation valves are designed with a back-seat and front-seat to allow the valve stem to be repacked without shutting down the system. The back-seat seals the valve when it is fully open, allowing the valve stem packing to be replaced or repaired under pressure without leakage. This is an important safety feature that enables maintenance to be performed on the valve without interrupting the refrigeration system's operation. The other answer choices are incorrect because they do not accurately describe the primary purpose of the back-seat and front-seat design of these valves.

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Official Resources
46 CFR Machinery & Electrical 46 CFR Engineering USCG National Maritime Center
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