Mechanical Maintenance Theory

Question 1

List the methods used to prevent chemical corrosion:

Answer 1

Proactive Coating
Modify the environment
Galvanising
Good design
Choice of materials used
Cathodic protection
Reporting serious deterioration.

Question 2

List the factors that accelerate chemical corrosion in unprotected metals.

Answer 2

Moisture
Atmospheric pollution
Heat

Question 3

What is pipework impingement?

Answer 3

The accelerated erosion or corrosion arrising from the continual removal of protective oxide films from inside the pipework by turbulent water.

Question 4

How can impingement be recognised?

Answer 4

By the appearance of pits at the point of accelerated water flow. Pits are horseshoe shaped facing upstream.

Question 5

Why do we use bearing extractors?

Answer 5

To remove the bearing under control without using undue force (I.e. a hammer).

Question 6

How do we use bearing extractors?

Answer 6

Bearing pullers apply the necessary force in the correct areas using a fine threaded bar and arms to create a centralised pull so as not to damage the shaft or housing.

Question 7

Describe the items of equipment used to measure bearing wear and their uses.

Answer 7

Poker Gauge - measures wear on stern tube A-brackets.

Bearing wear down micrometre - used on thrust block bearings.

Plastiguage - used to measure clearances in journal bearings and fitted surfaces.

Bridge Gauge - measures journal bearing wear and alignment on main gearboxes.

Micrometre - Used to measure clearances or thickness over the who surface of the journal bearing.

Question 8

List the parts of a Keelaring coupling

Answer 8

Body
O-Rings
Washers
Collets
Retaining nuts

Question 9

Explain the purpose of using gaskets and gasket material

Answer 9

To fill the space between two mating faces to prevent the egress or ingress of foreign matter. Seals poor tolerance surfaces.

Question 10

Explain the principles of operation for a heat exchanger.

Answer 10

Devices that allow heat from a fluid in one system to pass to another systems fluid, without the two fluids coming into direct contact.

Question 11

List the principles of the 22-step maintenance process to be carried out before undertaking any work.

Answer 11

Obtain permission.

Obtain relevant BR/UMMS/Manufacturers documentation.

Obtain correct tools / equipment.

Order any stores

Report defects in tools / equipment / manpower.

Move all gear to job location.

H&S / COSHH assessment.

Specific risk assessment?

Verify the reported fault - does it exist in reported location?

Check safety of work area

Apply LOTO

Question 12

List 6 areas where impingement is likely to be found inside pipework

Answer 12

Badly mated flanges.
Badly fitted joint material.
Change in waterfowl.
Change in pipe direction.
Badly fitted valves.
Excessively long pipes.

Question 13

List 6 different types of valves

Answer 13

Non return valve
Globe valve
Ball valve
Seacock
Diaphragm valve
Screw down valve

Question 14

List 4 advantages of using Heli-coils

Answer 14

Keeps the original bolts thread size.
Material is stronger than the original thread.
Material relatively corrosion free.
Quick and easy way to repair thread.

Question 15

Describe the purpose of the flexible hose register.

Answer 15

Controls hose life.
Records incidents of hose failure.
Where hoses are fitted.
Hose working pressures.
Assembly date.
Date due for change.
Last inspected date.

Question 16

Explain the use for gland packing and its requirements.

Answer 16

Used to seal valve spindles to the valve bodies.
It must withstand the environmental conditions of all types of fluid, extreme temperatures, pressures, and shaft speeds.

Question 17

List 8 specialized tools.

Answer 17

Torque wrench
Torque multipliers
Go/No-Go gauges
Heli-coil set
Micrometer
Vernier callipers
DTI
Easy outs

Question 18

List 6 principles of the 22-step process for after you have finished a job

Answer 18

Report all findings

Safely dispose of any waste

Re-connect external supplies

Remove LOTO

Run and carry out functional test on machinery.

Return all tools to correct location.

Question 19

Why do we use a torque wrench?

Answer 19

Used to ensure nuts, bolts and studs are tightened down to the correct torque.
Prevents thread distortion and possible stripping.
For example, too much torque can strip threads on cylinder heads.

Question 20

How do you correctly use a torque wrench?

Answer 20

Check the machinery BR to ensure the correct torque and sequence of fastening.
Use the correct range wrench for the torque required.
Ensure it’s within calibration date.
Tighten down until the wrench clicks.
Wind torque wrench off after use.