Compressed Air Systems

How often should the air receivers on a compressed air system be drained of moisture and emulsions?

Daily

Which of the following compressors would be used for a cold-ship start-up of a ship's service diesel generator on a motor ship?

Emergency air compressor

Which of the following statements represents the proper procedural sequence for adjusting the metering rate of an in-line lubricator as used in a ship's service air system hose station. Assume that the pressure regulator has been properly set?

Establish normal air flow. Determine drip rate. Further open needle valve to increase drip rate or further close needle valve to decrease drip rate, as appropriate.

Which of the following causes would most likely result in excessively high belt-driven reciprocating air compressor drive motor running current draw?

Excessive drive belt tension.

Which of the following problems would be the probable cause for the faulty operation of a reciprocating air compressor suction valve?

Faulty operation of a cylinder unloader.

As an indication that an air compressor air intake filter needs to be replaced or cleaned, what statement is true?

For a given air demand, the compressor would run for longer periods and the air intake pressure as measured between the filter and the compressor inlet would be more negative than with a clean filter.

If a reciprocating air compressor was operating at a compression ratio that exceeded its design parameters, what would be the effect?

Higher than normal discharge pressure and lower than normal displacement capacity.

If an air compressor is fitted with a hand-off-auto (H-O-A) control station, what statement concerning operation is true?

In the hand mode, the compressor will run continuously with unloading.

If a belt-driven reciprocating air compressor is operating at a lower than design displacement capacity (in cubic feet per minute), which of the following would be a cause?

Insufficiently tensioned drive belts.

Which of the listed valve types is typically used for suction and discharge valves on modern low pressure air compressors?

Reed

Which of the following compressors on a motor ship would most likely operate at approximately 100 psig?

Ship's service air compressor

Which of the following statements represents the proper criteria to decide when to drain a filter/moisture separator as used in a ship's service air system hose station?

The bowl should be drained before the moisture level reaches the lower baffle.

If a reciprocating air compressor has cylinder suction or discharge valves that fail to properly seat, what statement is true concerning the result?

The compressor would have longer running periods at lower displacement capacity between operating cycles.

What statement is true concerning carbon deposit formation on reciprocating compressor cylinder valves?

The rate of carbon deposit formation is directly proportional to the extent of cylinder oil pumping and directly proportional to the cylinder compression temperatures.

In a twin-tower desiccant type air dryer using silica gel as an adsorbing agent, what is the procedure for rejuvenating the tower presently on service when the desiccant becomes saturated with moisture?

The towers are shifted, and heat is applied to the off-going tower.

In order to distribute the side pressures over a wide area of the cylinder walls and liners, which of the listed types of pistons are used in modern low pressure air compressors?

Trunk

When checking the oil level on a reciprocating air compressor fitted with a dipstick, under what conditions should the oil level be checked?

With the compressor in the off mode incapable of starting.

The main bearings of a reciprocating air compressor are tapered roller bearings. When mounted, these bearings are given a 'cold' end clearance to __________?

allow for longitudinal expansion of the crankshaft as the unit warms up

The air charge leaving an intercooler, or after cooler of an air compressor can be expected to be __________?

at or below the dew point

If the drive belts on an air compressor were squealing during startup, you should __________?

check the operation of the unloaders

After disassembly, the safest way to remove carbon deposits from air compressor inlet and discharge valves is to use __________?

diesel oil

Operating a reciprocating air compressor without an air filter will cause __________?

excessive wear on valves and cylinder liners

If all of the air charge has been lost from a ship service air receiver, the compressor mechanical unloading system will__________?

fail to function as designed, but the compressor having no load will start with little or no difficulty

In a low pressure air compressor, the loss of volumetric efficiency normally results from __________?

heating of the air leaving the cylinders

Over pressurization of an air compressor intercooler is prevented by the __________?

intercooler relief valve

Excessively low air pressure occurring in the intercooler of a reciprocating air compressor is caused by __________?

leaky discharge valves on the LP cylinder

After coolers are used with air compressors to __________?

reduce the temperature of compressed air

If one drive belt on an air compressor is found to be worn you should __________?

replace all of the belts

A viscous film of oil collected between the valve face and seat of a low pressure reciprocating air compressor will __________?

retard the opening and closing of the valve

The device shown in the illustration is used to __________?

unload the cylinders of an air compressor