Best practice no 23

2. P1 (Inlet pressure to control valve) = 75 psig

3. P2 (Outlet pressure from control valve to heat exchanger) = 60 psig

4. Pressure drop (heat exchanger) = 10 psig from TEMA sheets

5. P3 (Inlet pressure to steam trap) = 50 psig

6. P4 = Outlet pressure from steam trap = 0 psig (atmospheric tank system – gravity drainage)

7. Flow rate = 3624 lbs. per hour

8. Sizing factor = minimum of 1.5 to 1, prefer 2 to 1 = 7248 lbs, per hour. Conclusion: The steam trap should have a capacity of 7248 lbs. per hour at a differential pressure of 50 psig and an orifice rating of 100 psig or more. Steam trap sizing requires experience in the operating characteristics of many different pieces of equipment. The end result depends on the quality of the data. The steam trap piping size can be selected after orifice sizing. The high condensate capacity steam traps will be available only in larger pipe sizes. If the heat transfer equipment has a two- inch piping outlet, don ’ t select a half-inch steam trap, as condensate flow would be restricted. Always select a steam trap with a connection equal to or larger than the process outlet connection. 1.5 in. process outlet = 1.5 in. steam trap. Many industries use ¾ in. steam trap piping as a minimum size to provide piping rigidity, and most important, standardization. Traps types Thermostatic (operated by changes in fluid temperature). The temperature of saturated steam is determined by its pressure. When condensate and saturated steam reach the steam trap, the condensate cools. A thermostatic trap passes condensate when this lower temperature is sensed. As steam reaches the trap, the temperature rises and the trap closes. Inverted Bucket and Float Traps. Mechanical (operated by changes in fluid density). This range of steam traps operates by sensing the difference in density between steam and condensate. These steam traps include ball float traps and inverted bucket traps. In the ball float trap, the ball rises in the presence of condensate, opening a valve and passing the denser condensate. With the inverted bucket trap, the inverted bucket floats when steam reaches the trap and rises to shut the valve. Both are essentially mechanical in their method of operation.

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