Pipes and Piping Details
A steam heating system requires careful planning of the piping to ensure both an efficient and a safe operation. For example, the pipe material used (e.g., wrought iron or Schedule 40 black steel) is important because the capacity of a particular weight pipe will depend on both its size and the material from which it is constructed.
The expansion of pipes when they become heated is another factor that must be considered when designing a steam heating system. Sufficient flexibility in the piping can be provided for by correctly designed offsets, slip joints or bellows, radiators and riser runouts, U-bends, or other expansion loops. The pitch of connections from risers must be sufficient to prevent the formation of water pockets when pipe expansion occurs.
Pipe materials, pipe sizes (and pipe-sizing methods), pipe expansion rates, pipe fittings, and piping details, such as wet and dry returns, drips, and connections to heat-emitting units, are covered in Chapter 8 of Volume 2 (“Pipes, Pipe Fittings, and Piping Details”).
Steam Traps
A steam trap is an automatic device installed in a steam line to con- trol the flow of steam, air, and condensate. In operation, it opens to expel air and condensation and closes to prevent the escape of steam. All steam traps operate on the principle that the pressure within the trap at the time of discharge will be slightly in excess of the pressure against which the trap must discharge.
The principal functions of steam traps in steam heating systems include (1) draining condensate from the piping system, radiators, and steam processing equipment; (2) returning condensate to the boiler; (3) lifting condensate to a higher elevation in the heating system; and (4) handling condensate from one pressure to another.
Steam traps may be classified on the basis of their operating principles as follows:
1. Float traps
2. Bucket traps
3. Thermostatic traps
4. Float and thermostatic traps
5. Flash traps
6. Impulse traps
7. Lifting traps
8. Boiler return traps
Pumps
Pumps are used in steam heating systems to dispose of condensate or return it to the boiler and to discharge excess air and noncondensable gases to the atmosphere. The specific function (or functions) of a pump depends on the type of steam heating system in which it is used. The two basic steam heating pumps are:
1. Condensate return pumps
2. Vacuum heating pumps