Plant Operation Practice Test

What is the most common steam trap used after a heating unit?

1. Ball steam trap

2. Float steam trap

3. Thermostatic steam trap

4. Mechanical steam trap

The correct answer is: Thermostatic steam trap

The most common steam trap used after a heating unit is the thermostatic steam trap. This type of trap operates by responding to the temperature of the steam and condensate. It is specifically designed to allow condensate and air to escape while preventing the loss of steam, making it efficient in maintaining the optimal temperature and pressure conditions in a heating system. Thermostatic steam traps typically utilize a sensing element (like a bimetallic strip or a liquid filled bulb) that reacts to temperature changes. When steam enters the trap, the sensing element expands, closing the valve to prevent steam from escaping. As the trap cools down due to the presence of condensate, the element contracts, allowing condensate to be discharged. This cycle effectively ensures that steam is utilized efficiently while preventing water from accumulating, which could lead to water hammer or thermal shock in the system. Other types of steam traps, such as float traps, operate based on liquid levels rather than temperature, which may not be as effective in the quick response required in heating units. Mechanical traps can function similarly but may not be as responsive or energy-efficient compared to thermostatic models. Thus, for maximizing performance in heating units, the thermostatic steam trap is favored.