Equipment Operation Flashcards

A centrifugal chiller's condenser approach temperature has risen steadily over several weeks. What is the most likely cause?

Answer: Fouled or scaled condenser tubes

Scale or fouling on condenser tubes reduces heat transfer, so the gap between refrigerant condensing temperature and leaving condenser water widens.

Before restarting a large centrifugal pump after maintenance, which step is essential to prevent seal and impeller damage?

Answer: Prime the pump so the casing is filled with liquid

Centrifugal pumps must be primed because running dry overheats mechanical seals and can damage the impeller.

In a cooling tower, what is the primary purpose of blowdown (bleed-off)?

Answer: To control the concentration of dissolved solids in the circulating water

Evaporation concentrates minerals, so blowdown removes concentrated water to limit cycles of concentration and scaling.

A variable frequency drive (VFD) on a supply fan reduces motor speed to 50%. Under the fan affinity laws, approximately what percentage of full-speed power is required?

Answer: 12.5%

Fan power varies with the cube of speed, so 0.5 cubed equals 0.125, or about 12.5%.

Which control is the final safety device on a steam boiler designed to prevent catastrophic overpressure?

Answer: ASME safety relief valve

The ASME-rated safety valve mechanically relieves pressure if all operating and limit controls fail.

How often should a steam boiler's float-type low-water cutoff typically be blown down to verify operation on a high-pressure boiler in continuous service?

Answer: Daily

Manufacturers and the ASME CSD-1 guidance call for frequent (typically daily) blowdown of float-type cutoffs on high-pressure boilers to clear sediment and confirm trip.

An emergency diesel generator must be exercised monthly under NFPA 110. What load condition is preferred to avoid wet stacking?

Answer: At least 30% of nameplate kW rating or the manufacturer's recommended exhaust temperature

NFPA 110 requires monthly exercise for 30 minutes at not less than 30% of nameplate rating or a load achieving recommended exhaust gas temperature to burn off unburned fuel.