10 minute read
Scuba cylinder valves
tips & curiosities
Scuba cylinder valves
INTRODUCTION AND THEIR IMPACT ON A DIVER’S ACTIONS
Text WOJCIECH A. FILIP
Photo Tomasz Płociński
Every cylinder has a valve of some kind – we usually associate it with the moment when we are getting prepared for a dive: you need to open the valve to check your gear. The next moment when the valve comes into play is when we finish diving – you need to close the valve to disassemble your gear.
Is there any reason for us to know more about scuba cylinder valves?
This article will be divided into 3 shorter texts, with something interesting for each and everyone.*
To start with, let’s pick the most convenient set of information: for simplicity, they will be marked as A, B, C.
A. I’m not interested in cylinder valves – if I need to know anything about them, let it be the bare minimum.
B. I’m using several valves on each dive – I’m interested in learning more than just how to open and how to close it.
C. I know that details matter. I prefer configuring my gearon my own in a way that would increase the comfortand safety of my dives.
ACADEMY
Photo Bartek Trzciński
A.(reading time for the entire article: around 30 seconds)
Do you have your own cylinder? — No, I don’t. Ask your instructor to explain how to open and close the cylinder valve. — Yes, I have one! Ask your instructor to explain how to open and close the cylinder valve.
Valves require maintenance, just like regulators. Have your cylinder maintained, asking for a full service of the valves once a year and each time you experience any issues with opening or closing a valve. Any gas leakage, bubbles near the valve knob or the connection between the valve and the cylinder also indicate that the valve requires repair.
B.(reading time for the entire article: around 4 minutes)
For advanced divers (B): assume that each cylinder (also your argon system) requires annual valve maintenance. The valve is opened and closed multiple times: before, during and after a dive; we tend to carry the cylinder holding it by the valve; the valve knob often gets hit during transport to the dive site – this should suffice as a reason to take care of your valve’s technical condition before it refuses to cooperate.
If you travel and do even complex dives on rented cylinders, you should check your valves’ operation – see details at the end of part B.
LET’S HAVE A CLOSER LOOK AT THE INFLUENCE OF THE VALVE ON DIVER’S ACTIONS
Single cylinder or a twinset on your back
1. Position
The location of the valves behind the diver’s head has direct influence on the diver’s position underwater. Start each trimming exercise from achieving a completely relaxed position, where you can move your head freely all the way up and back. In order to do so, you need to move your valves as low as possible.
2. Reduced ventilation
If your cylinder valves are placed too high, they may, together with your regulators, limit your ability to breathe freely. Being unable to exhale freely (lowered head, partially closing the respiratory tract) results in consistent increase of CO2 in our body, which leads not only to increased gas consumption but also enhances the narcotic effect.
3. Movement and maneuvering techniques
Fatigue when learning to move and maneuver, as well as ascending instead of moving backwards are two most com- mon signals that should encourage you to have a few photos or videos taken, starring yourself. Ask a friend to take a few close-ups on the position of your valves against your head – this is the best way to verify whether they rest on your head or are positioned close to it.
NOTE! You might think that only extremely low positioned valves are the right and safe solution. This is not true. First of all, valves cannot block free movement of the diver’s head, which should lean a bit to the back during the entire dive. But valves must also remain within the diver’s reach, so that they could open and close them freely during the dive.
Photo Mariusz Czajka
Stage cylinders
1. Diver’s position
For stage cylinders, the lower the valve body profile – the better. These of course require proper positioning of the stage regulators (low profile valves require the short HP hose to be place differently), but in return they limit the diver’s overweighing to the front. On average, each regulator with a valve weighs around 1 kilogram. If you strap 2 stages on the front, the resulting imbalance will effectively ruin your position. High profile valves combined with heavy regulators work just like moving your weight upwards or to the front, looking at the horizontal diver’s position. Add to it a twinset that is excessively high on your back and you know why you have to struggle to maintain a horizontal position throughout the dive or look like some technical divers, resembling a horse.
2. Moving backwards with full stage cylinders.
Valves with an excessively high profile on stage cylinders are a pain especially during fine maneuvers (e.g. when reversing), constantly turning the diver with their legs upwards. Placing your left forearm on the valves and pushing them slightly backwards might be a solution, at the same time minimizing the rocking of the stage cylinders forward and backward.
End of part B or how to check your valve in a rented cylinder:
— am I able to screw the regulator into the valve and screw it out easily YES/NO
— am I able to open the valve easily when my hands are cold YES/NO
— am I able to close the valve easily when my hands are cold YES/NO
— are there gentle bubbles at the joint between the argon cylinder and the valve when put into water YES/NO
any of the above, if answered “NO” (with the exception of the argon cylinder), means you need to replace the cylinder/set against one with properly functioning valves.
There should be no bubbles in any cylinder, but those supplying drysuits are often neglected in the detailed inspection. However, even a slight “steaming” instead of clear bubbles may empty our argon cylinder. What does it mean to open and close a valve easily? The valve should operate smoothly from one limit position to the other, turning without jamming, not requiring tightening it with force to close it completely or struggling to open it.
Photo Tomasz Płociński
C.(reading time for the entire article: around 90 seconds)
It is obvious that fitting valves to different diving cylinders and their operation during diving has a great impact on solving emergencies and maintaining diving comfort.
Configurations: Twinset valves.
2x10, 2x12 and some 2x7 sets have the same valve distance. In such sets, the separator knob should be positioned in the direction opposite to your head. This allows to freely operate the valve versus the “towards the head” position, where the separator is located between the regulators, requiring the diver to lower their head and keep it low (partially blocking the respiratory tract) while operating the valve.
2x15, 2x18 and 2x20 sets have a wider valve distance, yielding more space for a hand in a dry gloves with rings to operate the separator valve. Additionally, greater cylinder diameter moves the valves away from your head, which provides enough space to keep your head up while operating the separator which in the case of those twinset types will work better in the position towards the head.
Formally: The valve should close with more than two full turns – this protects it from being rapidly closed accidentally when in contact with the ceiling (so-called left valve roll-off).
Technically: Valve seals (o-rings) should have the hardness of 90Sh. This is particularly important if the valve spindle is butt sealed. A “gummy”, stretchy movement of the valve may be a sign of a wrong seal used or its wear.
Photo Mariusz Czajka
Separator o-rings prevent leakage of the gas from between the cylinders, at the same time allowing separator operation (the pressure load is only on one of 2, sometimes 3 o-rings used at this site).
Practically: It is very rare to hit the separator knob against the ceiling, and it seldom results in failure, even when hitting the right or left valve knob, due to the diver’s low pace. This is different when the dynamic contact happens when on a DPV. If the diver is assaulted by a malicious cave, the left or right valve knob may bend (spindle deformation), resulting in inability to operate the valve. In particularly aggressive caves, such contact may end with shearing the valve knob off, usually not causing a leak, but with a bit of unluck and a preceding roll-off, you may end up with the left regulator supply cut off.
WHAT A LONG ARTICLE ON VALVES… Its length changes with the your perspective on cylinder valves ;)
There could be yet another part to the article, as I did not mention what valve to choose for a single cylinder, whether an extension valve is better than a “T” valve or whether it is worth buying 300-bar valves instead of 230-bar ones.
…and what about the knobs, because there are plastic, rubber and even fluorescent ones?
In the context of technical divers, we did not say anything about the “burst disc”, how our valves get along with the compressor guy or would the valve “syphon” keep the water from the cylinder away from our gear.
Photo Bartek Trzciński
CONCLUSION
Diving experience also increases gear awareness. It wouldbe good if our understanding of the equipment we are usingreached beyond theory. Your growing appetite for deeper andmore complex dives should translate into understanding howequipment works and how can it be used. It is no less importantto anticipate the behavior of your equipment in extreme,unfavorable situations, e.g. when the equipment is not workingproperly. Properly devised practical training should follow.
Various diver training associations use similar, but possiblydiffering in details, valve operating procedures. Therefore, ifanything in this text is not in line with what your instructorsaid, consult with him what you have read.
It might happen that overloaded training programs, withtheir weekend schedules, won’t allow for covering the topicsconcerning operating the equipment on a stress-free levelin detail.
If you want to know more, you're welcome to join TeclineAcademy seminars and workshops to extend your knowledge and skills concerning diving gear. •
See you!WAF
https://teclinediving.eu/tecline-academy/#/
Discount
15%
with code PERFECTDIVER
www.drbacty.com
www.fofuworld.pl
www.kubekcontigo.pl
www.niedajsieokrasc.pl
