Orifice Steam Traps are thermostatic steam traps actuated by temperature sensitive devices, responding to changes in condensate temperature.
Thermostatic steam traps respond to changes in temperature and therefore discriminate very well between steam and cooler non-condensable gases. They can rapidly purge air from a system, especially on a cold start-up, and can be installed in various positions. Most frequently, actuation is by means of a bimetallic element or a bellows-like capsule filled with a vaporizing liquid.
Bimetallic actuated devices are characterized by their high resistance to damage from freeze-ups, water hammer and superheat. They are relatively small in size and lend themselves to high pressure designs. The condensate discharge temperature, however, does not follow the saturation curve very well, and the bimetallic elements are subject to corrosion with some reduction in closing force over time.
Bellows actuated steam traps, on the other hand, discharge condensate at a temperature which follows the saturation curve. The weak point is the bellows itself which can be damaged by superheat, water hammer or freeze-ups.
Thermostatic traps respond slowly to changing conditions even though the cause is usually misunderstood. It is not the heat sensitive element that is slow to respond. Rather it is the heat energy in the condensate inside the trap, which is slow to dissipate, that causes the time delay. Insulating thermostatic traps reduces their responsiveness even more. Mounting the trap at the end of a cooling leg in an area where air can circulate improves responsiveness and is the basis for installation instructions recommending a cooling leg at least three feet in length.
Orifice steam traps are seldom used because of their inherent limitations in application range. This device consists of one or more successive orifices. Where two or more orifices are used, condensate passes through a number of successive chambers where flashing occurs. This, in turn, creates a restricting or choking effect and allows the use of larger and less dirt sensitive orifices for a given condensate capacity. In some design executions, these orifices are adjustable valves.
Prior to selecting a steam trap for your application, review steam traps selection with its advantages versus disadvantages and additional steam trap types: Disc Steam Traps, Piston Steam Traps, Lever Steam Traps, Closed Float Steam Traps, Inverted Bucket Steam Traps, Open Bucket Steam Traps, Bimetallic Steam Traps, Bellows Steam Traps and Liquid or Solid Expansion Steam Traps.