Category — Configuration

Stage cylinders are generally used in addition to “back mount” cylinders or in addition to “side mount” cylinders while cave diving.  The reasons that cave divers, wreck divers and technical divers use stage cylinders include but is not limited to increase the total volume of gas during a dive so that penetration distances or dive times can be greater, to hold different gas mixes (for example a decompression mix, a travel gas, or a bottom mix), to hold a volume of gas needed for team planning or as a safety bottle, and to provide an open circuit bailout source during Rebreather diving applications, to provide safety air volumes needed when planning dives using DPV’s and calculating for failures requiring a swim out.  The diver throughout the entire dive may carry these cylinders, depending on the objective and dive plan, or they may as well be placed along a cave or anchor/ascent line to be retrieved during the exit from the dive depending on the environment and conditions they are diving.

Diving with single and multiple stages in the overhead environment (cave, wreck, or decompression) should only be attempted by divers who have perfected diving skills in their back mount or side mount gear.  These advanced techniques are to be used only once a diver has achieved perfection in the environment they are diving and have a real need and desire to progress greater into the dive.  The reasons divers use stage diving techniques may be enticing but as well with these practices comes a greater responsibility and greater risks for divers to be aware of.  Divers are now entering further into the overhead environment, they may be leaving tanks in water filled caves which may impact the cave, and they are increasing task loading during the dive while making a more complex dive plans.  Divers using the techniques and information in this manual must as well understand and completely accept the risks involved in planning extended penetration dives.

Stage bottles need to be secured to the divers harness via clips to the d-rings. The preferred clip is a bolt clip made out of stainless steel due to a longer life span and ease of use while brass clips become more difficult to operate with time. The size of the clips is depending of the environment, where cold water divers need larger clips due to the gloves or mittens worn. A carry strap can be attached to the stage bottle with the two clips firmly attached to the strap. The strap is used below water to handle the tank and less for the surface. A stainless steel clamp covered in a tubular webbing makes a perfect tank band to hold the strap in place. The connection from tank to clip should be of a cutable kind, a metal to metal connection is not desirable since it can not be cut in case of a clip failure or entanglement scenario when it becomes important to drop or remove the stage tank to solve the problem.

All stage tanks should be labeled clearly in regards to what breathing media is inside the tanks, the marking of maximum operational depth on the side of the tank in large number does have the advantage of the team members being able to see and verify that the correct breathing mixture is being used ant the correct depth.

Each stage regulator does need its own pressure gauge with a preferable short high pressure hose of about 15 cm length. The gauge is bend upward during use and attached to the first stage via a bungee cord or surgical tubing. During periods of non use the gauge can be released to ease the stress on the hose. During the dive when the stage bottle is not in use the valve is to be maintained close, during descent and at maximum depth the valve should be opened shortly to pressurize the first stage, a prevention of water entering the first stage due to pressure differences.

Safety and Deco
Decompression diving and accelerated decompression schedules are in need of a variety of breathing gases ranging from bottom gases to travel gases and a variety of decompression gases. All these breathing media have to be planned, blended, labeled, analyzed and then used at the appropriate time and depth during and according to the dive plan. Depending on the environment dived and the planned bottom times stage tank size and material are of consideration to the diver, while most divers prefer aluminum stages because of their lesser weight and lift requirements.

In ocean drift diving and wreck diving scenarios the decompression stage bottles are usually carried by and with the diver throughout the whole dive, even if that means that the breathing mixture is carried below safe breathing depth. In cave diving scenarios the decompression stage bottles are clipped to the line in a way that not to much stress is exerted onto the line and left at a depth where the breathing gas can be safely breathed, eliminating the potential danger of breathing the wrong mix at the wrong depth.

Extended Penetration
Stage diving must be well thought out. Staging allows the diver to extend the distance of safe exploration. Due to being further into the system it may also produce additional time pressure stress. Training and gradual build up in penetration distances will help offset this stress. In addition stage diving is similar to flying a airplane in that the diver must think well ahead of their position. By thinking ahead and being familiar with stage techniques the diver avoids delays during stage drops and retrievals and the diver will also avoid sudden changes in buoyancy.

Stage and multi-stage diving are other techniques used to further penetration into the caves or wrecks but allows as well longer bottom times during technical dives. When a diver reaches his turnaround pressure but wishes to further penetrate the cave or wreck then a stage or extra tank becomes a necessity. A stage tank can be worn on either side or all on the left hand side depending on configuration preferences. The dive is generally started on the stage tank and when the pre-established turn pressure is reached the diver switches over to another stage or the primary tanks either back mounted or sidemounted. When turn pressure on the primary tanks is reached the diver will turn around and will find his or her stage that was clipped to the line, then change over to the stage tank and exiting the cave or wreck breathing of the stage tank or tanks. Stage diving has a potential high impact on the cave and wreck environment and damage can be extended far into the cave or wreck. Care should be taken not to harm the cave or wreck. Special training is needed to use stage tanks safely in the cave or wreck environment.

Gas and Stage Switching Procedures
How you and your team will switch between your cylinders during the dive needs to be preplanned and practiced in open water situations prior to attempting them in the overhead environment or in real decompression situations.  There are a few common and ¨accepted¨ ways that this can be accomplished.  However your team decides to accomplish gas switches it needs to be remembered that there are many things that can go wrong when switching gases and going to and from regulators.  The end result of an improper switch can end in loss of gas, loss of a way to deliver gas, hypoxic and hyperoxic situations.  Gas switches no matter how done need to have the entire teams attention at 100%.  This is true if you are doing a switch to a bottom gas, travel gas, or a decompression gas.  In addition to verifying your own gas supply and system you must also verify that the other members of your team have made a proper switch as well.

Entire team switching gas and stages
One way that teams prefer to switch gases is the entire team switching at once.  This means that at one point, after the signal has been given and confirmed by the entire team, every member of the team will initiate and switch gases at the same time.  The sequence for this is:

One team member gives signal to switch gases upon arrival at the correct depth or point of dive

1. Team confirms the need and place to switch
2. Every diver locates proper cylinder
3. Divers read labels and check depth vs. MOD
4. Everyone turns on the correct stage cylinder
5. Divers deploy regulator of stage and get it into position to breathe
6. Purge regulator you are planning to breathe from, confirm it will supply gas
7. Switch to new regulator and breathe prior to storing previous gas (you may need to go back to it)
8. Store hose that is no longer needed
9. Trace regulator back from your mouth to the stage bottle and check mix and MOD vs. your actual depth
10. Check other team members to verify they are doing switches and to proper tank and breathing gas
11. Once all team members have switched and confirm okay, continue dive or decompression

This type of switch is best accomplished with all the team members facing each other.  While you are completing each of your steps you are as well going to be keeping up to date with what the rest of the team is doing.  How is their buoyancy, are they at the correct depth, are they switching to the correct tank, is the tank on, is somebody out of gas?  The ability for every member of the team to be able to see each other and the cylinder that each member switches to is critical.  A wrong switch to a wrong tank and breathing gas is a life-threatening event for every member of the team.  Every team member must stay in complete control of the procedures during this time of task loading.

Individual Gas Switches
The second style of gas switching is very similar to the first in the stops but has a different team strategy.  Some teams prefer to switch with one person always acting as observer.  This means that one person will delay their switch and act as an observer until the rest of the team has confirmed their switch.  Upon confirmation of the gas switch of the rest of the team this diver will then switch gases with the rest of the team observing them.  This second way will take a longer time to get the entire team switched but gives you the added benefit of always having one diver less task loaded and paying attention to confirm the switch of the other team members and can respond in case of any failures.

Team member gives signal to switch gases upon arrival at the correct depth or point of dive

1. Rest of team confirms the need and place to switch
2. Rest of team locates proper cylinder (leader does not switch)
3. Team read labels and check depth vs. mod (leader observes)
4. Team turns on the correct stage cylinder (leader observes)
5. Team deploy regulator of stage and get it into position to breath (leader observes)
6. Team purges planned next regulator, confirming it will supply gas (leader observes)
7. Switch to new regulator and breath prior to storing previous gas (leader observes)
8. Store hose that is no longer needed (leader observes)
9. Team traces regulators back to the stage bottle and check mix and mod vs. actual depth (leader observes)
10. Team members verify they are done with switch and to proper tank (leader confirms or makes any adjustments needed)
11. Upon completion and confirmation of the entire teams successful switch the team leader will then start at the top of the list and complete theirs with the rest of the team acting as observers.

Tanks
Configurations vary but easy deployment, easy location and identification has to be of paramount importance. Double tanks with isolator manifold are commonly used, however in recreational diving independent tanks are used. A sufficient quantity of gas must be carried by the diver to allow completion of the planned bottom time, utilizing the minimum gas management rule for the type of diving enrolled in. Furthermore, this gas supply must allow for gas matching between divers.

The first item that needs to be addressed in tank selection for a specific dive is the needed gas supply and with it tank size resulting from factors such as body size, gas consumption, planned depth and duration. Experience has taught that the most logical approach to the question of gas supply can be best summed up by the statement in why there is a need for gas supply requirements. The first step in planning a dive involves computing the amount of gas needed for the dive. This includes primary mixes and decompression mixes. Decompression systems should provide a sufficient volume of gas to complete all appropriate stops with a minimum reserve supply. Each decompression gas cylinder must be appropriately marked as to its use, breathing gas and M.O.D. It’s also suggested that regulators be color coded or coded for easy identification. Mouthpieces should be protected to prevent from accidentally being used with the wrong mix during your decompression at the wrong depth.

The choice between tank materials will be dedicated by the environment and thermal considerations. The diver should be balanced in a way that he or she is neutrally buoyant with empty tanks at 10 feet / 3 Meter, comfortable for prolonged periods of time. In order to archive this diver must balance and trim their rig carefully for the environment one is diving in. Ample emergency gas volumes must be carried for the type of diving engaged in plus a redundant buoyancy device such as a dry suit or back up BCD must be worn on deeper dives.

Steel Tanks
While steel tanks are a great choice for cold water, wreck or cave diving due to their larger volume 104 or 121 cft / 15 or 18 ltr where the weight of the tanks is partially offset by the thermal protection due to dry suit sworn by most divers. Helium based breathing gases do affect weight and buoyancy underwater and must be taken into account.

Aluminum Tanks
Warm water, wet suit ocean diving is best done with aluminum 80 cft / 12 ltr tanks due to their lesser weight and with it lesser negative buoyancy at the bottom phase of the dive. If more gas is needed a aluminum stage tank should be added to fulfill breathing gas requirements.

Harness and Backplate / Softpack
While many dive gear manufacturers offering traditional BCD’s for recreational diving most wreck, technical or cave divers prefer the harness and backplate / softpack combination. Most recreational BCD’s can not be adapted for advanced forms of diving such as cave, technical and wreck diving and when a diver is ready to proceed to higher levels of training a new set of gear has to be purchased. Harness and backplate / softpack combinations eliminate that problem since they can be easily adapted for single tank recreational diving or technical and cave diving activities that may lay n the future.

Harness
A harness is used to attach the tanks to the diver sandwiching the wing style BCD between the tanks and the harness. The harness is attached to a backplate or a soft pack, which is then attached to the single or double tanks. A wing style buoyancy compensator has to be worn, attached to it a low pressure power inflator. The webbing attached to the backplate should be of the all through type with no connections, easy clips, rings or fast buckles intersecting the webbing. Such fasteners who make it easier to get into and out of the diving rig are potential failure points with disastrous potential to loose all of the equipment during the dive and in the long run it is more economic to change a basic webbing when it is worn out.

The crotch strap that has to be worn in order to prevent the unit from “riding up” should be without a clip but made from the closed loop type in order to prevent breaking clips during or prior to a dive. Crotch straps can be used as we for gear storage when a d-ring is attached to it at the back, or to attach a scooter to a d-ring in the front. The all one through webbing allows as well the placement of d-rings at any location throughout the harness to accommodate backup lights, stage tanks on the chest d-rings and gauges or reels on the waist d-ring.

Backplate
Backplate’s are made out of ABS plastic, aluminum or stainless steel. The stainless steel backplate is the most popular one since it is a little heavier and compensates for some of the weight a diver may needs to carry when diving with positive tanks or a dry suit.

Soft packs
The softpack harness systems on the market have the advantage of being well adaptable for the type of diving one is involved in ranging from recreational single tank diving to technical, wreck or cave diving to advanced forms of cave diving such as sidemount diving. The potential downside is the fast clips on the chest that could a dive fast out of the rig but could fail before or during a dive and be difficult or impossible to repair.

Buoyancy device
Back mounted wing style wing’s are known for superior trim characteristics in recreational openwater diving and advanced diving while openwater style BCD’s are not recommended due to limited lift capabilities, buoyancy characteristics, tank attachments and d-ring placement specially in advanced forms of diving such as technical, wreck or cave diving. The lift of the wing needed is depending on equipment weight, tank weight full and empty,  scooters and stages if worn. Oversized wings and tight bungeed wings do have a tendency to create more drag in the water resulting in more energy spend and potential exhaustion of divers. All wing inflator and dry suit inflators if used should have the same connector to insure interchangeability of hoses and gas supply.

Wing style BCD
Wings are coming in a variety of lift capacities, styles and some sport a choice of features. The chosen wing should have the right amount of lift for the equipment, tanks and environment dived in. The corrugated hoses should be not as long as to touch the floor when diving close to the bottom and stirring up silt, damaging the environment or entangling the diver. Shorter size corrugated hoses are available to change the log size hose. In demanding environments such as inside wrecks or caves it is a good idea to have the inner bladder protected against puncture. Dump valves in the corrugated hose assembly can fail and present a potential problem. Dump valves on the bottom of the wing should be streamlined by cutting of the plastic knob to prevent entanglement.

Back up wings are recommended in deep dive applications or a dry suit can be used as a back up buoyancy device however dual bagged bladders are potentially creating added drag and degrade performance, this will in the end may slightly increase in gas consumption. The advantage of a dual bladder in the event of a BC failure is that the diver may still function normally and make a safe ascent. Diving with a single bagged bladder provides less drag and maximizes performance. Given a choice, most divers would prefer a configuration that reduces drag. But, if there’s a chance the single bladder could fail and this failure could be life threatening, it makes good sense to sacrifice being streamlined by increasing redundancy. By opting for greater redundancy, divers need to recognize this will increase their gas consumption. They must also realize it’s going to slow them down a little. Keep in mind dry suits can be used as a backup buoyancy control device.