COMPETENCE 4

50問 • 2年前

Peter j Zuniega

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問題一覧

In a refrigeration system, the amount of superheat absorbed by the refrigerant is adjusted at the _________.

expansion valve

Refrigerant is circulated through a refrigeration system by the ___________

compressor

Salinity cell is installed in the distilling unit to indicate the ____________.

quality of water produced

Which of the following statements regarding low pressure, reciprocating, air compressor valves is correct?

Due to the physical construction of the valves, a rel

In a low pressure air compressor, the loss of volumetric efficiency normally results from _____.

heating of the air leaving the cylinders

An eccentric reducer, used as a transition piece between a centrifugal pump suction flange and the suction piping flange, must be installed with the eccentric portion below the suction pipe centerline to _____.

prevent the formation of air pockets

When renewing the shaft packing on a centrifugal pump equipped with an external liquid sealing supply, you should _____?

ensure that the lantern ring is aligned with the seal

When installing a new rotary pump, the suction piping should _____.

be at least one size larger than the pump suction

To prevent air pockets from forming in a centrifugal pump suction line installed angled from normal, any gate valve should be installed with the _____.

stem horizontal or pointing downward below the pipe

On a medium pressure, differential piston, reciprocating air compressor, lubrication of the pistons cylinders is usually accomplished _____________.

with metering type cylinder lubricators

When air compressors are arranged for automatic operation, the cylinders can be unloaded during starting by _____.

fitting depressors which hold the suction valve plate

Cylinder inlet valve failure in a low pressure air compressor can be caused by ______.

sticking valves due to carbon buildup on the seats

The static suction lift of a pump is the difference in elevation between the _____.

centreline of the pump and the level of the liquid in

Why is the discharge pressure of a herringbone gear pump steadier than the discharge pressure of a simple spur gear?

One discharge phase begins before the previous dis

If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the _____.

ships service air system

The capacity of a rotary pump, delivering a constant viscosity fluid, will decrease when the discharge pressure is increased, due to________.

increased slippage

A recirculating, or bleed off line is installed on a centrifugal pump in order to _____.

prevent the pump from overheating when operating

If a centrifugal pump operating with a positive suction head vibrates, or becomes noisy, the cause could be ____________.

insufficient venting

If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the _____.

control air system

It is possible to mount a double suction centrifugal pump impeller with the vanes facing the wrong direction. This would cause the pump _____.

efficiency to decrease

Which of the following statements is true concerning the overall efficiency of air compressors?

Two stage compressors are generally more efficient

A compressor operating with an accumulation of dust and grease on the surfaces of an intercooler would result in _________. I. a decrease in volumetric efficiency of the compressor II. higher volume of air to be discharged to the receiver

Neither I nor II

A compressor operating with an accumulation of dust and grease on the surface of an intercooler would result in _____. I. a high consumption of lube oil II. higher than normal air pressure in the reciever

II only

What would be the result of throttling the suction valve to the point where the flow was less than that recommended by a centrifugal pump manufacture? I. The discharge head would be reduced II. The pump would begin to cavitate

II only

What would be the result of throttling the suction valve to the point where the flow was less than that recommended by the centrifugal pump? I. The designed total net head would be reduced II. The pump would begin to cavitate

II only

If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is probably ____________.

misalignment or worn main bearings

When renewing spiral packaging in a centrifugal pump stuffing box, after the packing is firmly seated, the packing gland nuts should be _____.

loosened, and then retightened until they are only fix

To prevent overheating and scoring of the shaft after repacking the stuffing box, which of the following procedures should be carried out?

Tighten the packing in small increments while the p

An advantage of a helical gear pump over a simple gear pump is that the helical gear pump is capable of _____.

producing a smoother discharge flow

Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?

The discharge capacity varies directly with the speed

The function of the spring used with channel or plate type valves for reciprocating air compressors is to _____.

provide positive closing of the valves

A first stage unloader installed in a low pressure air compressor is unable to completely retract. This will result in _____.

an abnormally low intercooler pressure

Liquid is kept from leaking out of the shaft ends of a helical gear pump by _____.

a stuffing box

In a centrifugal pump, the seal piping directs liquid from the discharge side of the pump to the _____________________.

lantern ring

Which of the listed conditions can lead to cavitations in a centrifugal pump?

Vapor pockets formed in the suction flow stream

The leakage of air into the pump casing by way of the packing gland of a condensate pump, is prevented by_____.

a water seal line to the packing gland

The net positive suction head of a boiler centrifugal feed pump should be calculated over and above the _____.

feedwater vapor pressure

Which of the listed parts is used in a lobe‐type rotay pump to allow for wear on the lobe edges?

replaceable gib inserts

An unloader is installed on an air compressor to _____.

remove the compression load as the compressor co

Which of the following statements describes the function of an air compressor intake filter?

Protects against the damaging effects of airborne s

What would probably occur if excessive misalignment existed between a centrifugal pump and its power source?

shaft bearing will overheat

The initial unloading (at startup) of the device shown in the illustration is accomplished by ____________.

discharging the compressed air to the receiver with

Two individual centrifugal pump impellers of the same diameter, width, and rotating speed are to be compared, one is cast with straight vanes, the other with curved vanes. Which of the following statements is correct?

The curved vane impeller is less likely to develop ca

How can we quickly reduce high water level in a steaming boiler?

By the used of surface blow valve

If the discharge valve is closed before the drive motor is stopped, which type of pump will most likely be damage?

Gear pump

One of the main functions of wearing rings, as used in a centrifugal pumps, is to _____.

allow for economical replacement of worn internal

A centrifugal pump operating against a closed discharge valve has a/an _____.

efficiency of 0%

The function of a centrifugal pump double volute casing is to _____.

reduce radial thrust on the impeller

Which of the following changes in pump operating parameters will lead to pump cavitation in a centrifugal pump that is operating in an open system?

steadily increasing pump inlet temperature

What should be done if localized scoring is discovered on a pump shaft sleeve during routine maintenance inspection?

Correct the cause of scoring and install a new shaft

COMPETENCE 1