Hand Expansion Valves – 1

We have been somewhat busy the last few weeks completing a new project.  The next few blog entries should be more timely.

These valves are used for multiple purposes in ammonia refrigeration systems.  However, they are commonly designated by a single description.  This common term of hand expansion valve (HEV) is sometimes misleading. It may help to consider the actual function the valve provides; throttling of liquid or vapor and the mass flow requirements for the application.

The common applications of this valve are:

• Liquid make-up to maintain a relatively constant liquid level in a vessel.
• Throttling liquid from a higher pressure to a lower pressure (control pressure systems).
• Balancing upstream liquid pressures to evaporators in a liquid overfeed system.
• Throttling vapor flow in float columns to minimize rapid liquid level fluctuations.

The next few blog entries will discuss the multiple applications of these valves.

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