Technical Dive Equipment 101
So you have signed up for your technical dive training, booked your flights and reserved your hotel, but there is still one thing missing – your gear. What do you pack? Can your recreational dive kit double as technical dive equipment? Is your snorkel going to make the trip with you? Whether you are a seasoned techie or starting out on your first technical diver training, the following is a head-to-toe list of useful things to get ready.
If you are already a cold water diver this small item might not seem so out of the ordinary, but why is this necessary for technical dive equipment? You’ll either be doing longer dives with your accumulated decompression times, going to greater depths with cold upwellings, or entering into overhead environments.
Keeping your head warm is crucial for comfort and a hood provides a bit of protection from hanging formations in caves or wrecks.
For recreational dives one mask will do, but now for your technical dive equipment you will have to have two – one for use and one to store in a pocket for back-up. Most technical divers opt for frameless masks with a low to medium profile.
These masks are easy to fit into a pocket for storage and quick to clear of water. Plastic frames can break when knocked causing them to leak continuously – an inconvenience for a multitasking tech diver.
In terms of colour there are no set rules (personally the tech world cold use a bit more pink), but most techies will choose a black silicon skirt for their mask to reduce reflection and disturbances in peripheral vision.
Probably the most important decision for your new technical dive equipment comes here. Firstly, you are going to need to invest in a minimum of two regulators for your back gas. If you start to go deeper or get into longer decompressions with multiple gas switchs to accelerate deco stops this number will increase. Rebreather divers also need stage regulators for their bailout and many also choose to incorporate a bailout valve (BOV) into their loop for safety. Regardless the type of technical dive equipment configuration you choose you’ll need regulators.
During your research you will most definitely come across the terms ‘unbalanced,’ ‘balanced’ and ‘environmentally sealed’ first stages. Unbalanced first stages means that the tank pressure presses directly on the first stage valve to open it. As the pressure in the tank gets lower there is less force to open this valve making a slight change in breathing resistance. With balanced first stages, the high pressure air from the tank acts on all sides of the first stage valve (never directly on the valve opening) therefore cancelling out the high pressure needed to open the valve and balancing it. This means even as tank pressure drops, the needed pressure to open the first stage valve does not change, making breathing resistance consistent throughout a dive.
An environmental seal on a first stage means a protective barrier (air or fluid base) exists between the working parts of the piston or diaphragm and water. Such seals prevent sediments or salt water from entering into the mechanical parts reducing overall corrosion. They also protect against extreme cold water temperatures in preventing the moving parts of the first stage to freeze. Most technical divers will opt for a balanced first stage with an environment seal.
If you are thinking of doing sidemount diving it’s also important to find a first stage with a bottom fifth low pressure port. Such a port makes it possible to run a 6 inch low pressure inflator hose horizontally in front of the divers chest to connect to the sidemount inflator. You might also want a turret first stage that allows all the low pressure hose connections to turn even under pressure.
In any case, whether environmentally sealed, balanced or unbalanced, or with or without a turret, it’s best to make sure the first stage you choose is DIN. A DIN first stage sits deeper into the tank valve making a better seal for the O-ring to the tank and less of a chance for the first stage to be knocked out of position. If you already have a suitable first stage with a Yoke attachment look into seeing if a DIN conversion kit is available for your brand and make of regulator.
Most second stages are fashioned with a downstream design. This simply means the second stage valve opens in the direction of air flow when the diaphragm depresses against a lever. Little effort is needed to ‘crack’ this valve making breathing virtually resistant free. Very few manufacturers use a pilot design where the lever first opens a small valve that releases pressure and thereby opens a larger main valve that supplies a greater airflow.
You will also find the terms ‘unbalanced’ and ‘balanced’ when searching for second stages, although most manufacturers are producing only balanced second stages. The principles are the same as with the first stage designs, but probably less important because intermediate pressure running to the second stage almost completely eliminates any great effort needed to open the second stage valve.
Lastly, you can find many models with external adjustment valves to increase or decrease the tension needed to open the second stage valve. You can think of these valves as fine-tuning tools to fit your breathing needs. For example, you probably will increase the tension on your second stage deco regulators which remain unused for the bottom phase of your dive to prevent free flow.
Remember for technical dive equipment you will need two first stages and two second stages at a minimum. These will serve as your left and right post regulators on a twinset or on your individual sidemount tanks. Once you choose your configuration, make sure you also add the correct number of submersible pressure gauges (SPG), low pressure inflator hoses and that you also acquire hoses of the right length. A chat with your instructor can help you set up your regulators the proper way.
Don’t worry, you don’t have to bring along your mother’s jewellery. When tech divers speak of necklaces they mean the small bungee hanging around their necks that keep the back-up regulator within reach. It’s a small detail for technical dive equipment but very essential to keep things in their proper place. You can easily make one yourself with bungee cord or buy pre-manufactured ones made from surgical tubing.
Buoyancy Compensating Device (BCD)
Unfortunately the jacket-style BCD you have in your closet will not make the journey with you for your technical dive training. A device with more lift (technical dive equipment means more tanks) and different design is a must to aid with better trim and reliability. The good news is that most BCDs for technical diving are multipurpose. This means you can still use it with one tank or throw it onto a twinset. With some simple adjustments you can turn it into a sidemount harness or place it onto your rebreather. Here’s a look at the most commonly available designs.
Backplate, Harness & Wing
This is the most classic design in diving and for a good reason – it’s simple, durable and it works.
The backplate serves as the connecting point for the harness webbing and tanks. It can be made from several materials, including stainless steel, aluminium, carbon fibre and even harder fabrics, depending on the diver’s needs. Technical divers needing more weight because of super-buoyant exposure suits choose heavier back plates to reduce the need for carrying extra weights on a belt. Others who travel and dive primarily in warmer regions often opt for lighter materials to save on costs when flying.
Regardless of the type of backplate you choose, you will need a harness to attach you to the backplate and tanks. The harness is typically one continuous piece of webbing that feeds through holes in the backplate and around both the shoulders and waist. It also has a separate piece of webbing attaching to the bottom of the backplate and running between the legs up to the buckle of the waist harness – it’s appropriately called the crotch strap. The function of the crotch strap is to firmly secure the dive unit (twinsets, CCR, sidemount BCD) to the diver’s body without any huge gaps.
The wing is the last part of the set and again here you have many options in shape, material, size and number of bladders. For shapes you have either a horseshoe or donut design. With a horseshoe wing the bottom part does not allow passage of air to either side like it does in a donut-shaped wing. Gas inside the wing must be tipped through the top part by the diver rolling slightly. A donut wing allows some gas to remain at the bottom portion just over the diver’s butt and is good for bottom heavy divers. Be careful to check the size of the bladder to determine the lifting capacity of the BCD. When you become a technical diver your equipment and tank needs are greater which make you far more negative in the water. You must ensure your ability to remain neutral at depth and positive at the surface with the correct size of the bladder. Too big for your dive configuration can be cumbersome and difficult to vent properly, and too small can have you plummeting to great depth in no time. Another consideration for wings is whether they are single or dual bladder. Dual bladder wings provide redundant buoyancy and are required with some training agencies. Lastly, the durability and life-span of your wing will depend on the type of material. Most manufacturers produce wings with tough shells, but some materials like cordura is known for its resistance to tearing and abrasions.
They say once you go sidemount you’ll never go back and if that’s the case you might consider investing in a sidemount harness. Depending on your budget and needs you might want something exclusive for sidemount or a system that can double as a wing for other types of dive configurations.
Both are readily available so you just need to do a little research. Some special features of a sidemount harness include side bungees for bringing tank valves more inline with the body and a low profile back BCD.
DIVING Reels and Spools
Diving reels and spools are crucial for technical diving. For your SMB deployment, for emergency procedures, for cave diving, for wreck diving, thus Mandatory! The Reel you will use as your main and the spool is tucked away as your back-up or in overhead environment diving for Jump lines.
DIVING Cutting devices
Two of these should always be with you when you do technical diving. You can help releasing caught fish entangled in lines and nets, you could help a reef by removing and cutting away the lines wrapped around the coral or you could help yourself or your dive buddy when entangled in a line inside caves and wrecks. An other piece of diving equipment that you need to have on you. And as other pieces of equipment 1 main, in direct reach, and one tucked away as back up.
DIVING Surface Marker Buoys SMB
Surface Marker Buoys are devices for saving your life. Not really need any more explanation than that. You have different colors with or without marking on them. The orange and yellow markers with “DIVER BELOW” SMB’s are used the most by recreational divers to let the boats know there are divers below and for the boats to find the divers at the surface. In technical diving they also use yellow marker buoys for emergencies. They would have briefed the dive boat crew about procedures beforehand. When the yellow surface marker buoy comes up, the boat crew, and tour leader will know exactly what to do. Most of the times this means someone got decompression illness and the diver need Oxygen.
DIVING Lights -Torches and back-ups
Every diver has a dive torch. Some use the big ones some like the small ones and they will be mainly used for night diving and photography or to find the littlest creatures hide away in a Fan. In Technical Diving these are unmistakably important. Depending on where you dive, but below 50 meters it can get really dark, or you can have bad viz some where. I am sure you will understand that Torches are mandatory in caves and wrecks, so as a tech diver you will need to carry 1 Main Torch (canister torch) and 2 back-up lights which can be simple and small lights.
DIVING Slates and Wet notes
Diving Slates are Hard plastic Slates you either carry on you with a lanyard or are attached to your arm as a bracelet. The Wetnotes is a little booklet with multiple soft pages and is covered with nylon. Both have a pencil so you can keep track of gas consumption , change dive plans or just communicate when you dont know the handsignal for something, while you are diving. Technical Divers use these on every dive as they need to write their dive plan down and need to carry with so they can follow the plan from start to finish. Tech DIvers go far beyond the No Decompression limits and do mostly decompression diving.
What is no decompression diving? In short – “Normal diving decompression procedures range from continuous ascent for no-stop dives, where the necessary decopmression occurs during the ascent, which is kept to a controlled rate for this purpose, through staged decompression in open water. Decompression may be accelerated by the use of breathing gases which provide an increased concentration differential of the inert gas components of the breathing mixture by maximising the acceptable oxygen content”
What is decompression diving? In short – “Decompression Diving may be continuous or staged, where the ascent is interrupted by stops at regular depth intervals, but the entire ascent is part of the decompression, and ascent rate can be critical to harmless elimination of inert gas. When diving with nitrogen-based breathing gases, decompression stops are typically carried out in the 3 to 21 metres (10 to 70 ft) depth range. With helium-based breathing gases the stop depths may start deeper.
These planed deco stops are written down in a plan on one of these underwater slates, so the diver know exactly where and when to stop and what gas to use.
Depth Gauges / Timing Devices
A depth gauge is a pressure gauge that displays the equivalent depth in water. It is a piece of diving equipment often used by SCUBA divers. Most modern diving depth gauges have an electronic mechanism and digital display. Older types used a mechanical mechanism andanalogue display. All wrist diving depth gauges have timers so the divers know how long they have been in the water.
A diver uses a depth gauge with decompression tables and a watch to avoid decompression sickness. A common alternative to the depth gauge, watch and decompression tables is a dive computer. A depth gauge and an oxygen analyser/oxygen sensor can be used to measure the partial pressure of oxygen of the breathing gas, which is necessary to avoid oxygen toxicity.
Digital depth gauges commonly also include a timer showing the interval of time that the diver has been submerged. Some show the diver’s rate of ascent and descent, which can be is useful for avoiding barotrauma.
As the gauge only measures water pressure, there is an inherent inaccuracy in the depth displayed by gauges that are used in both fresh water and seawater due to the difference in the densities of fresh water and seawater.
Technical Divers use the Depth Gauge as back-up for their Mixed gas Dive Computers and their written down decompression plans.
Mixed gas diving computer
A dive computer, personal decompression computer or decompression meter is a device used by an underwater diver to measure the time and depth of a dive so that a safe ascent profile can be calculated and displayed so that the diver can avoid decompression sickness.
Technical divers use dive computers that are able to calculate decompression schedules for breathing gases other than air, such as nitrox, pure oxygen,trimix or heliox. The more basic nitrox dive computers only support one or two gas mixes for each dive. Others support many different mixes.
Most dive computers calculate decompression for ‘open circuit’ SCUBA where the proportions of the breathing gases are constant: these are “constant fraction” dive computers. Other dive computers are designed to model the gases in some ‘closed circuit’ SCUBA (rebreathers), which maintain constant partial pressures of gases by varying the proportions of gases in the mixture: these are “constant partial pressure” dive computers. There are also dive computers which monitor oxygen partial pressure in real time in combination with a user nominated diluent mixture to provide a constantly updated mix analysis which is then used in the decompression algorithm to provide decompression information.
DIVING Pockets – Shorts
So all of this equipment you need to carry some where. You cant just clip it all to your Wing or Sidemount Harness because you would get stuck and get entangled really easy. You need pockets to carry this around with you. You can either use pockets you add to your waist belt or you can wear them as shorts.
Some shops make these shorts custom made, so you can decide how large the pockets need to be, velcro or zippers and where you want them. Brands such as Scubapro have made it easy for you as they have made ready to go shorts in different sizes. If you wear a drysuit these pockets need to only go on your drysuit or on your belt. Wetsuit divers can decide all of the above, what ever you prefer.