Globe Valve for Ammonia Service

Service conditions

A globe valve opens or closes its flow path through linear movement of a disc relative to the seat. Disc travel changes the opening at the seat. Throttling duty calls for suitable disc geometry and an assessment of flow demand, differential pressure and the pressure loss caused by changes in flow direction.

Construction and description

Match the operator to the valve load and site operating method. Manual operation needs accessible clearance. Frequent cycling or remote control also calls for assessment of output capability, duty and position feedback.

Define fluid composition and continuous and start-stop operating conditions, then assess body, internals and seals as a combination. Particles, deposits and cleaning affect sealing surfaces and mechanisms; plan maintenance for the actual service.

Service conditions

For ammonia service, identify gaseous ammonia, liquid ammonia or an aqueous system. Assess wetted metals, packing, gaskets and seat materials against purity, water content and operating temperature. Refrigeration selection also needs to consider temperature changes during cycling and defrost, trapped liquid and stem sealing. Define the material and seal combination using the actual fluid conditions and supply documentation.