ANSI FCI 87-1:2017 pdf download.CLASSIFICATION AND OPERATING PRINCIPLES OF STEAM TRAPS.
ANSI FCI 87-1 is for the purpose of establishing and illustrating various classifications of Steam Traps in accordance with their basic principles of operation. This standard does not attempt to define details of conception or construction.
2.0 DEFINITIONS
2.1 Steam trap — An integral, self actuated valve which automatically vents air in the steam system and drains condensate from a steam conlaining enclosure while remaining tight to live steam. Most steam traps will also pass non-condensible gases while remaining tight to live steam.
Note: Some designs will allow a minimal steam flow at a controlled or adjusted rate using a separate secondary orifice.
2.2 Production tests – Tests carried out by the manufacturer to confirm that the steam trap functions correctly. These tests may be witnessed by the purchaser or his representative. In this case, these tests are referred to as witness tests.
2.3 Performance characteristics – Carried out to determine the operational characteristics of a particular design of steam trap.
3.0 OPERATING PRINCIPLES
3.1 Factors Affecting Condensate Flow Through a Steam Trap
One of the most common components to all steam traps is the discharge orifice. In some trap types, the valve seat and the discharge orifice are the same; in others, the discharge orifice may be smaller than the valve seat.
3.2 In considering steam trap capacities. therefore, it is important to explain what happens when fluid flows through an orifice.
While in steam trapping we are concerned with the discharge of cold water, air and other gases,condensate and air mixtures, and hot (flashing) condensate, the main function of the trap is to discharge condensate, usually in the flashing state.
The water discharge capacity of an orifice depends on the following factors:
1. The area and shape of the orifice and the coefficient
of discharge CD
2. Lift of valve from orifice
3. The pressure drop across the orifice
4. Density of the water
5. The temperature of the waler.
6. The physical changes that take place when water
flows through the orifice.
3.2.1 Orifice Area and Shape
Theoretically, the flow of cold water through a round, sharp-edged orifice in pounds per hour discharge is very nearly
3.2.2 Valve Lift
The formula in paragraph 3.2. I assumes a lull open orifice. In a steam trap this is not necessarily true. The fact that, in some stream traps, the valve does not lift fully to the equivalent free area of the orifice does not imply poor design. It, however, makes comparison of steam trap capacities on orifice diameter alone unreliable.ANSI FCI 87-1 pdf download.