Chapter 9 Piping Equipment and Systems
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Which statements are true for an open hydronic system? Select all that apply. 1) _______
A) Water is exposed to the atmosphere.
B) Most HVAC systems are open.
C) The pump must overcome frictional pressure plus (or minus) gravity head.
D) Flow can be achieved only by pumping.
2) What are the characteristics of oil pumps for boilers and engine generators? Select all that apply. 2) _______
A) They are self-priming. B) They are positive displacement.
C) They are centrifugal or axial. D) They use pistons or gears.
3) What kind of pumps are most used in HVAC applications, e.g., chilled water? 3) _______
A) Centrifugal. B) Gear. C) Axial. D) Turbine.
4) If the flow rate drops by 50% in a hydronic system due to the pump slowing down, how will the
pressure drop and power required change?
4) _______
A) Pressure drop will be 50%; power will be 25%,
B) Pressure drop will be 25%; power will be 12.5%.
C) Pressure drop will be 50%; power will be 50%.
5) If the flow rate in a hydronic system is reduced by closing a valve, what happens to the flow and
pressure?
5) _______
A) Flow will increase and pressure drop will decrease.
B) Flow will decrease and pressure drop will increase.
C) Flow and pressure drop will decrease.
6) Net positive suction head (NPSH) is which of the following? 6) _______
A) The inlet pressure required to prevent cavitation.
B) The pressure at the inlet of a pump at maximum speed.
C) The height to which a self-priming pump can draw upward.
7) Which of the following methods are used to change pump flow to match load in an operating
system? Select all that apply.
7) _______
A) Staging of multiple pumps. B) Variable-speed drive.
C) Adjusting impeller size on the fly. D) Valves.
8) What is the major difference between shell and tube vs. plate and frame heat exchangers? 8) _______
A) Plate and frame can achieve small temperature difference between fluids.
B) Shell and tube exchangers do not need cleaning.
C) Plate and frame heat exchangers are less expensive.
D) Shell and tube must have equal flows for both fluids.
9) Which are correct comparisons between welded joints and mechanical couplings? Select all that
apply.
9) _______
A) Mechanical couplings can offer flexibility for thermal expansions.
B) Mechanical couplings are more expensive to install.
C) Mechanical couplings are stronger and less prone to leakage.
10) Which of the following valves has the highest pressure drop? 10)
______
A) Gate valve. B) Wafer valve. C) Ball valve. D) Globe valve.
11) Which of the following valves would not be a good choice for isolation service? 11)
______
A) Globe valve. B) Wafer valve. C) Gate valve. D) Ball valve.
12) What are the functions of a suction diffuser? Select all that apply. 12)
______
A) Check valve.
B) Balancing device.
C) Isolation valve.
D) Substitute for recommended straight length of pipe.
E) Strainer.
13) What are the functions of a triple duty valve? Select all that apply. 13)
______
A) Check valve.
B) Strainer.
C) Balancing device.
D) Isolation valve.
E) Substitute for recommended straight length of pipe.
14) A closed, compression expansion tank with an air/water interface needs to be located according
to what guidelines? Select all that apply.
14)
______
A) Connected above the air separator.
B) At the lowest pressure point of the system.
C) Above the highest point in the system.
15) What is the major advantage of a diaphragm expansion tank? 15)
______
A) Prevents exposure of water to air.
B) Self-adjusts to changes in atmospheric pressure.
C) Custom fitting allows easy attachment to pump outlet.
D) Light weight allows hanging to save floor space.
16) Which of these is not an important consideration in refrigerant piping design? 16)
______
A) Friction losses, which reduce compressor capacity.
B) Height of compressor with respect to cooling coils.
C) Velocity to move oil in the suction line.
D) Thermal expansion of the hot gas line.
17) Which of the following is not a type of steam trap? 17)
______
A) Thermodynamic. B) Float and thermostatic types.
C) Adiabatic counter-lever. D) Bimetallic.
