Chapter 4

Question 1

According to SOLAS what are requirements for cargo tank venting
- what are they to be able to deal with

Answer 1

Day to day variations in pressure caused by localised heating and cooling

Full flow venting conditions during loading or discharge of cargo

Allow the tanks to be purged and or gas freed

Question 2

What are PV valves designed to deal with

Answer 2

variations in pressure caused by local heating and cooling

Question 3

What are pv valves not designed to deal with

Answer 3

to cope with full flow venting during loading

Question 4

What are the venting arrangements for loading

Answer 4

Can be separate for each tank

Can be combined with other tanks

Can be incorporated into the IG piping

Capacity = 125% of max loading rate

Isolation valves, (if fitted), locked open or closed

Question 5

Where are vent masts usually located

Answer 5

forward end of IG line

Question 6

What does HVVV stand for

Answer 6

High Vent Velocity Valve

Question 7

PV for thermal variation should be a min of what above deck

Answer 7

2 m

Question 8

HVVV minimum of 30m/s exit velocity should be a min of what above deck

Answer 8

2 m

Question 9

Common vent line, free flowing venting should be a min of what above deck

Answer 9

6 m

Question 10

SOLAS requires an approved venting system for loading PLUS either:

Answer 10

secondary means of venting
or
pressure gauges with alarms for each cargo tank

Question 11

some parts of the gas plume will be flammable.
How is this controlled

Answer 11

All Tank outlets/vents are minimum 10m from any air intake

High outlet velocities

Height of outlet above deck

Wind speed across deck

Question 12

When discharging a vacuum is created in the cargo tank. As the vacuum reaches the set negative pressure of PV valve (usually -____mmWG)

Answer 12

350

Question 13

What is the most common secondary means of venting fitted on modern tankers

Answer 13

pressure sensors

Question 14

When a vessel carries flammable cargoes, the oxygen level in the tanks ismaintained at below _% by volume. This is done by ______ the tanks.

Answer 14

8
inerting

Question 15

the exit velocity from the main vent mast is

Answer 15

3 m/s

Question 16

What additional monitoring is required when discharging oil cargo and using vapour return?

Answer 16

Return vapour O2 content

Question 17

Who or what dictates maximum and minimum allowable tank pressures?

Answer 17

Class society

Question 18

A liquid filled PV breaker can be considered a secondary means of venting if -

Answer 18

Tank IG isolating vavles are not fitted

Question 19

If the IG valve on a tank is closed during loading what will happen

Answer 19

The HVVV will operate

Question 20

The exit velocity of a high velocity vent valve ensures that

Answer 20

If the vented gas is ignited a flame cannot travel back through the valve

Question 21

When loading oil at a port which offers a ‘closed loop’ cargo operation, what additional manifold will be used?

Answer 21

Vapour manifold