Twinset

Question 1

What are the cylinder valves referred to as?

Answer 1

Right post and Left post

Direction is in reference to where the are behind the diver’s head when they are wearing the kit.

Question 2

Which post is the primary?

Answer 2

Right post

All primary equipment will be connected in to this post.

Question 3

Which is the backup post?

Answer 3

Left post

Question 4

Which way do the cylinder valves open on each side?

Answer 4

Both anticlockwise

Question 5

What is meant by the terms ‘roll on’ and ‘roll off’?

Answer 5

Based on forward propulsion, the right cylinder valve would turn anticlockwise if it were to make contact with an overhead environment. Therefore, it would ‘roll on’ and be forced open.

The opposite is true for the left post.

Question 6

Where is the backup regulator located?

Answer 6

On a bungee underneath the diver’s chin.

Question 7

Where is the primary regulator located?

Answer 7

The primary is the long hose. It will run from the diver’s RH side (right post) and be looped behind their neck from the left.

It will then be brought around the front to breath from. The excess of the loop now created in front of the diver can be tucked in to the waist strap of the BCD harness.

Question 8

What must you do whenever you remove your primary regulator?

Answer 8

Clip it on to the D ring on your RH shoulder (T-handle)

Question 9

What checks must be done upon entering the water?

Answer 9

Bubble check (initiated with pinching motion of thumb and first finger. Completed by same sign followed up OK signal).

Push under and check for bubbles from manifold, posts, first stages and BCD. Then look underneath and check hoses and regs.

Second check is a long hose check. Confirm entire length and indicate to the other diver. Then re-stow properly and be ready.

Ensure it is not trapped by straps, drysuit hose or accessories.

Question 10

Where does the drysuit hose route?

Answer 10

Underneath the divers left arm.

Question 11

Where should the SPG be connected?

Answer 11

On the left post.

Allows use whilst using a spool/reel or a DPV (right handed operations)

Question 12

Which post should the LPI hose be connected to?

Answer 12

The Right post

Question 13

Should the drysuit hose route inside or outside the harness/shoulder strap on the LHS?

Answer 13

Inside

More streamlined, less snag risk and less chance of being in the way of the backup light.

Question 14

Which post should the drysuit hose be connected to?

Answer 14

Left post - Front port is good as it angles the hose forward slightly.

Question 15

How do you calculate how many L of gas a cylinder contains?

Answer 15

Cylinder size x pressure of the gas

E.g.:

2 x 12L twinset cylinders, each with 232 bar

(12 x 2) x 232 = 5568L of gas

Question 16

Ideal cylinder for my setup?

Answer 16

Round bottom euro 12s

Question 17

Why would you not fit boots on a tank?

Answer 17

Because it can trap salt and cause corrosion, which is then hidden until it is picked up in a test

Question 18

Where should any test or O2 clean stickers be fitted on your tanks?

Answer 18

On the inside (facing the divers back). Protects them from damage in the overhead environment.

Question 19

Should a neck o-ring fail on a tank, how can it be isolated?

Answer 19

Using the manifold. Then breath off of the air in that tank until it runs out (use it before you lose it).

Question 20

If a first or second stage fails on your regulator (free flow, ruptured hose etc), how can you isolate the problem?

Answer 20

Shut off the valve for that tank, cutting airflow to the first stage of the faulty regulator. The remaining regulator will still have access to air from both of the tanks as the manifold remains open.

Question 21

What must you ensure a manifold has when purchasing one?

Answer 21

An isolating valve. There is no redundancy without one.

Question 22

What are the two main types of manifold?

Answer 22

Barrel o-ring
Face o-ring

The majority of new manifolds have a barrel o-ring.

Question 23

What is the advantage of having a barrel o-ring manifold?

Answer 23

If the manifold becomes loose, it allows movement in the centre section without leaking.

Question 24

Why should you not do a 1/2 or 1/4 turn back when opening your valves?

Answer 24

It could cause confusion in an emergency if valves need to be closed. If fully open, it will only turn one way.

Lefty loosey, righty tighty

Question 25

What does DIN stand for?

Answer 25

Deutsche Industrie Norm

Question 26

What advantage does DIN have over an a-clamp/yoke design?

Answer 26

The o-ring is inside the valve, thus preventing a leak if knocked.

Question 27

How should you carry a twinset?

Answer 27

By the cylinder heads.

DO NOT just lift it by the cylinder knobs.

NEVER lift it by the manifold.

Question 28

Where should the twinning bands be placed on a twinset?

Answer 28

The top band should be places at the break of the neck of the cylinders.

The bottom band should be placed according to the eyelets on your wing and backplate.