Steam and Hot Water Systems, Piping, and Valves
What this domain tests
Steam and Hot Water Systems, Piping, and Valves tests your understanding of how steam and hot water travel, how condensate is removed, how piping accommodates expansion, and which valve suits which duty. Questions are practical rather than code-heavy.
Core rules
- Slope steam mains in the direction of flow; fit drip legs at low points, before risers, and ahead of valves, with a trap at each drip point.
- Water hammer comes from slugs of condensate driven at high velocity. Cure it with trapping, draining, slow warm-up, and correct slope and support; never by opening a valve faster.
- Thermal expansion for carbon steel is about 0.0000065 in/in per deg F; accommodate it with loops, expansion joints, anchors, guides, and rollers.
- Valves: gate for on-off with low pressure drop, globe for throttling, ball and butterfly for quick isolation, check for one-way flow, safety and relief valves for overpressure only, pressure reducing valves and steam traps as control devices.
- Hot water systems need an expansion tank, air elimination, a circulator, a pressure reducing valve, and a relief valve.
Worked example
120 ft of steel main warms from 60 to 260 deg F, so delta T is 200 deg F. Expansion = 0.0000065 x 120 ft x 12 in/ft x 200 = 1.87 in. Because nearly two inches of growth cannot be absorbed by the pipe itself, the line needs an expansion loop, slip joint, or anchored flexible section, and the guides must keep the pipe moving in the intended direction.
Traps that cost marks
- No drip leg before a riser or valve, so condensate is thrown into the valve.
- Selecting a gate valve for throttling service.
- Treating the safety valve as a pressure regulator.
- Ignoring cold-start expansion when setting pipe supports and anchors.