Valves

Question 1

What is 3 types of wastage that may occur on the internal surfaces of a ships side valve made of
modular cast iron?

Answer 1

Erosion
Corrosion
Graphitic Corrosion
Shock

Question 2

With reference to ships side valves?
Why is grey cast iron not suitable?

Answer 2

Graphitic Corrosion when the metallic constituents are selectively removed and converted to
corrosion.

Question 3

With reference to ships side valves?
b) State with reasons two suitable reasonsWhy is grey cast iron not suitable

Answer 3

These will corrode and become brittle which can fracture under load (even temperature
variations. This leaves behind a lattice/matrix of in the shape of the original casting. So it might
not be clear that this has happened.

Question 4

With reference to ships side valves?
State the regular maintenance that the valves should receive, and why?

Answer 4

Should be cycled to prevent scale forming on the sealing faces and when open, silt forming at
the bottom under the gate. This would seriously inhibit the sealing abilities of the valve.
It is part of your surveys to have your shipside valves inspected, Look at the sealing faces of
the valve and gate (wedge) plus look at the gland to make sure there is no leakage.
Note in the engine room log needs to be made that the valves have been exercised

Question 5

State purpose of fitting isolating valves on a ring fire main?

Answer 5

If there was damage to the pipework then it is possible to isolate this section as to not flood the area
with water and provide adequate flow to other areas.

Question 6

State the type of valve that should be fitted for fire isolating sections of the fire main? And why?

Answer 6

Gate Valve, Globe Valve or Screw Down Lift Valve
- Minimal pressure drop
- Flow needs to be in both directions
- Ability to seal on closing

Question 7

How is this operation ensured when requiredon the fire isolations

Answer 7

Testing and cycling of the valve regularly and when required removing and inspecting the valve seats
etc.

Question 8

State the position of the machinery space isolating valve?

Answer 8

Outside the machinery space

Question 9

Sketch a globe type screw lift valve suitable for seawater service?
State with reasons the materials used?

Answer 9

Body - Gun Metal Bronze
Seat Valve - Aluminium Bronze or Copper Nickel
Valve disc (Usually a softer material)
Steam - Stainless

Question 10

With reference to thermostatic 3way valves
a) How do they operate?

Answer 10

Expanding Wax which will rotate the central cock and regulate the flow accordingly

Question 11

b) How are thermostatic valves tested?

Answer 11

In a warm bath or water, where the water is brought up the temperature and the operation of
the valve is visually seen. Must have a secondly means of measuring the temperature

Question 12

c) Where are they used in a diesel engine (thermostatic valve)

Answer 12

Jacket Water Temperature Control
Lubricating Oil Temperature Control
Central Cooling Water Temperature

Question 13

Explain how the diaphragm is replaced, stating the precautions that should be taken?

Answer 13

Complete a risk assesment of the work (if required)
Mitigate any possible risks (use of PPE etc)
Refer to engineering manual to make sure you have the correct diaphragm for the job
Isolate the valve upstream and downstream and drain off any pressure/substance within the line
With reference to the valves engineering manual, loosen the bolts holding down the bonnet cover,
lift seal on one corner to maek sure there is no pressure.
Loosen the fit and remove bolts, Remove the diaphragm and inspect any wear marks on it or
damage.
Look for any damage on the weir/anvil.
Look for any damage on any other part.
Re-install, test etc etc etc

Question 14

With reference to butterfly valves
describe there construction?

Answer 14

Consists of a valve disk that rotates about 90degrees when open to and seats on a seating ring
of a flexible rubber compound. The butterfly is a metal disk mounted on a rod. This rod is
actuated on the outside and liquid is prevented from going outside with packing.

Question 15

a) Advantages and Disadvantages compared to a gate valve?

Answer 15

Light Weight
Easy to operate
Cheap
Fewer Parts
Wafer design doesn’t transfer the weight of the valve into the pipe work
Flow control without wire drawing
Quick Acting
Easy with remote actuators
- Operate too quickly
- Very hard to remove when valve has failed
- Taper pins can corrode
- Booted seats are known to trap the valve in the closed position

Question 16

Sketch a section through a bilge injection (emergency bilge) valve?

Answer 16

Th inlet has a straight pipe that drops down to 300mm above the bilge plate and the a course filter
box around it to prevent ingress of large objects.
The outlet is connected to the seawater inlet manifold of one the vessels fire pumps or sea water
circulating pumps. Bilge suction valves are screw down none return as when there is no flow there is
no flow back into the suction space.

Question 17

Describe how the valve sketched is tested for through a bilge injection (emergency bilge) valve?

Answer 17

Charging up the system, sucking overboard and discharging overboard. Opening the valve for the
suction, feeling the suction with your hand also by placing a wooden block over the suction valve it
can be seen that there is good suction presure.

Question 18

State 3 reasons that may cause a relief valve to lift in service?

Answer 18

Over Pressure
Closed discharge valve
Incorrect setting
Broken Spring

Question 19

State 3 reasons to why a pressure relief valve may not relief?

Answer 19

Spring Seized or Seat jammed
Under pressure
incorrectlyset

Question 20

State how the correct operation of a relief valve is ensured?

Answer 20

Tested, it’s a survey able item, generally sent away and done by a third party for liability reasons.
Valve is pressurized up to a known pressure and the relief is adjusted until it occurs about 10%
above the working pressure. (before design pressure) this adjustment is done with the pressure
adjusting screw at the top. This is then capped, sealed and tagged with the date and rating that it is
set to plus the company that did it.

Question 21

List the valves that are suitable for
- - Fire main isolating Valve
- Main engine Standby cooling water circulating pump discharge
- Main engine lube oil pump delivery
- Fuel service tank outlet
- Ballast tank

Answer 21

• Fire main isolating Valve
  Gate valve for its sealing ability and slow closing so the shock loading is minimal
• Main engine Standby cooling water circulating pump discharge
  3 Way thermostatic valve
• Main engine lube oil pump delivery
  With both a relief valve as it is a positive displacement pump and a screw down none return to
  prevent the standby pump to be operated and not be pressured from the other pump
• Fuel service tank outlet
  Screw down lift with a quick closing mechanism, allonging the valve to operated quickly and
  slam shut.
• Ballast tank
  High flow
  Easily operated remotely
  Unrestricted flow