DieselShip's Online Content Library

Q5. With reference to centrifugal pumps:

(a) state the operating principle of a centrifugal pump and why it is unnecessary to fit a relief valve to it; (2)

(b) State TWO impeller types, explaining which type of application EACH would be best suited for; (4)

(c) Explain why cavitation occurs, and how it is reduced by design; (4)

Q4. With reference to pump selection, state any TWO types of pump for EACH of the following applications, stating why they are suitable.

(a) bilge pumping (2) (b) Cargo oil stripping (2)              (c) Sewage sludge (2)

(d) Lubricating oil circulating (2)               (e) Sea water circulating (2)

Q5. (a) Describe TWO systems of priming centrifugal pumps. (6)

(b) List the advantages of EACH of the priming methods described in part (a). (4)

Q5. With reference to centrifugal pumps:

(a) explain the operating principle of a centrifugal pump and state why it is unnecessary to fit a relief valve to it; (3)

(b) explain why some pumps have a double entry impeller; (2)

(c) describe a routine overhaul of a centrifugal pump, stating the inspections, measurements and possible replacement parts that may be required. (5)

Q4. With reference to centrifugal pumps:

(a) Explain how the performance may be assessed without the need to dismantle the pump; (3)

(b) state the effects of misalignment between the driving motor and the pump; (3)

(c) describe, with the aid of a sketch, how on a new replacement motor, alignment is checked and adjusted. (4)

Q6. (a) Describe, with the aid of a sketch, a constant speed, uni-directional, axial flow pump suitable for hydraulic applications. (6)

(b) Explain, with the aid of a sketch, how the axial flow pump can achieve higher pressures than its radial flow counterpart. (4)

Q4. (a) State the affinity laws for a centrifugal pump. (3)

(b) State the effects on the pump affinity laws of fitting a slightly smaller diameter impeller. (2)

(c)  Explain, with the aid of a Head versus Flow diagram, why a two speed pump is preferable to throttling where high and low capacities are demanded for a large sea water circulating pump.(5)

Q4. With reference to centrifugal pumps and pumping systems:

(a) explain, with the aid of a diagram, the distinction between Net Positive Suction Head available (NPSHa) and Net Positive Suction Head required (NPSHr); (8)

(b) explain how the NPSHa may be increased by design. (2)

Q1. State, with reasons, the materials used in EACH of the following components of a centrifugal pump for sea water circulating duties:

(a) Casing; (2)

(b) Impeller; (2)

(c) Shaft; (2)

(d) Wear rings; (2)

(e) Mechanical seal. (2)