4. Valves on steam lines are commonly encountered and you should know how they work.

For most valves, the change in velocity of the fluid flow is negligible. Apply this principle

to solve the following problems.

a. A pressure gage on a high-pressure steam line reads 80 bar absolute. A small

quantity of steam is bled out through a valve to atmospheric pressure at 1 bar. A

thermocouple placed in the bleed stream reads 400°C. What is the temperature

inside the high-pressure line?

b. Steam traps are common process devices used on the lowest points of steam

lines to remove condensate. By using a steam trap, a chemical process can be

supplied with so-called "dry" steam, i.e. steam free of condensate. As

condensate forms due to heat losses in the supply piping, the liquid runs

downward to the trap. As liquid accumulates in the steam trap, it causes a float

mechanism to move. The float mechanisms is attached to a valve, and when the

float reaches a control level, the valve opens to release accumulated liquid, then

closes automatically as the float returns to the control levels. Most steam traps

are constructed in such a way that the inlet of the steam trap valve is always

covered with saturated liquid when opened or closed. Consider such a steam

trap on a 7 bar(absolute) line that vents to 1 bar (absolute). What is the quality

of the stream that exits the steam trap at 1 bar?