Auxiliary Machinery. Test 18 – Online Maritime Tests

During operation: What is one of the most important differences between a centrifugal pump and a piston pump?

A centrifugal pump can not go as low as a piston pump in the vacuum area.
It is easier to damage a centrifugal pump than a piston pump if they run dry.
A centrifugal pump does not need lubrication.
A piston pump is always driven by steam.

If a shaft of a centrifugal pump shows excessive wear by way of the stuffing box, is this caused by :

Excessive heating caused by over tightening of the gland packing.
Wrong direction of rotation.
Incorrect material used in construction of the shaft.
Discharge pressure of the pump too high.

The type of pump used for delivering the oily-water mixture to an oily-water separator governs considerably the degree of contamination in the effluent. What type of pump would be best suited not to churn the supply and produce small oil droplets (less than 200

Axial Flow.
Mixed flow (part axial, part centrifugal).
Screw.
Centrifugal.

What is the primary function of a non-return valve fitted in the suction line of a pump?

To prevent the suction line from draining and keeping the pump primed.
To regulate the flow of liquid through the pump.
To keep the pump from losing its balance.
To keep one foot of liquid in the suction line.

Low temperature corrosion can occur in both oil fired and exhaust/waste heat recovery boilers. Considering a fuel with same sulphur content, the air/fuel number,lamda, in a combustion process also indicates a relation to what temperature sulphuric acid condensates. What is the correct relation between air/fuel ratio and low temperature corrosion?

High air/fuel ratio rises the air speed and thereby lowers the pressure and temperature so sulphur acid condensates.
High air/fuel ratio rises the condensation temperature, and thereby reducing the safe limits between normal operation and condensation temperature.
High air/fuel ratio lowers the boiler temperature causing the sulphur acid to condensate.
High air/fuel ratio does not contribute significant to change of condensation temperature.

What is the meaning of the term purification?

Separation of solid contaminants from a liquid.
Separation of two insoluble liquids with different densities, and at the same time removing of solids.
Cleaning a liquid.
Operation as the 2.nd separator in a serial system.

While their respective characteristics differ in detail, which of the following main operating features do all positive displacement pumps have in common if they are working under non-cavitating conditions?

The pump will develop a discharge pressure equal to the resistance to be overcome, irrespective of speed.
They are self-priming.
All of the mentioned alternatives.
Flow is almost directly proportional to speed.

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