If you’ve ever gone Scuba diving at any point in your life, then you know there’s a lot of extra weight between the scuba tank, all the pressure gauges, the tank bangers, and the regulators. All this weight affects your tendency to float, which is why you need equipment that balances all this out and improves your positive buoyancy. It is for this precise reason that the scuba diving Buoyancy Compensator Device (BCD) was invented.
Source: Buoyancy Compensators | SCUBA 101
A Buoyancy Compensation Devices, or a BC, as it is commonly abbreviated, is a piece of diving equipment that features inflatable bladders worn by divers that balances your buoyancy levels depending on where you are during the diving process. The idea is to neutralize the gravity pull, especially when you’re underwater by manually adjusting the volume of air in these inflatable bladders.
The main idea behind this process is to maintain a neutral buoyancy when you are underwater, preventing you from sinking to the bottom of the ocean due to the average weight of your Scuba gear.
These bladders are filled with air from the diver’s main oxygen cylinder (air tank) using a low-pressure hose that is regulated by a regulator attached to the air tank. The placement of the BC is mostly around the torso and behind the diver, which is primarily due to ergonomic movement and mostly to maximize the safety of the unit. This piece of equipment, although crucial, requires a lot of operational knowledge and attention to detail, not just because the adjustment process is predominantly manual, but also due to the fact that buoyancy varies depending on depth.
Source: BCD Myths Fact Or Fiction
History of the BCD/BC
The Buoyancy Compensation Device actually dates back to the 1950s, a period when cave diving was becoming popular. Cave divers at the time were intent on improving their bottom times, so they began to add more equipment to their scuba gear in an attempt to increase the period of time they could spend underwater. The problem came in when instead of being able to hover over the exploration area, all the extra gear just made them sink to the sea bed.
Source: Vintage Scuba: BCD Evolution, From Lifevest to Fenzy – S06E02
Necessity being the mother of invention, these cave divers came up with an ingenious way to maintain neutral buoyancy by adding two empty jerry cans to the now heavy equipment.
So in addition to the two steel tanks, line reels and external battery, the two empty jerry cans were hooked to their dive harnesses, at which point the divers added air from regulators till the cans became buoyant enough to let them to hover, as opposed to sinking. This marked the birth of the Buoyancy Compensator Device.
Fast forward almost 70 years later and the craft has been refined to a point where abrasion resistant air bladders are now the material of choice, allowing divers to tune their hovering at any depth. The BCs are still manually operated though, so that’s still some what of a drawback.
How it works
The tendency to sink or float is significantly reliant on weight. Think about it this way, if you have two 1 liter water bottles, and you fill one out with stones, and the other with foam, which one sinks? The stones sink, of course. The idea here is, buoyancy has more to do with relative weight as opposed to size.
If something happens to be heavier in comparison to the water it displaces, it sinks, and the reverse. Case in point, if you put a rock in a scuba BC, it will sink, but if you put some air into it, while the rock is still in it, then the BC becomes larger due to air volumn without any relative increase in weight. At this point, the rock in the BC becomes irrelevant, and the weight of water displaced by the compensator is less, so it floats!
Source: Diving tutorial UCPA #5 – How to use your BCD (jacket)
Additionally, neoprene wetsuits, although buoyant on the surface, become less so as the diver goes deeper. The rules change every 60 feet or so, which is why the Buoyancy Compensator comes in handy. You manually add air into the BC and you are able to regain buoyancy as you go deeper.
Another illustration is one pair of 2-liter soda bottles. Fill one with steel ball-bearings and fill the other one will contain Styrofoam. When immersed in water the one that is filled with ball-bearings will definitely sink while the other one will float.
Most people might attribute this phenomenon to the fact that there’s air inside the foam. However, the scuba air tank also contains air and as a matter of fact, most scuba tanks will sink when full. The idea is not to struggle to maintain neutral bouyancy, the BC will ensure you can hover horizontally with as little effort as possible, which will help conserve oxygen provided by the air tank and prolong your scuba dive.
Types of BCs
The kind of scuba BC you pick depends on your level of diving expertise. The Back Floatation BC for instance, is nifty if your main aim is effortless horizontal hovering. The air bladder here is positioned between you and your scuba tank. It is popular because of its size and relative convenience when maneuvering in confined spaces. It also doesn’t squeeze in your sides while you dive, which makes it great as a dry suit accessory.
It’s one notable drawback is it doesn’t float you face up if you’re unconscious, which means it’s not really a good option for armature diving, and all its features are pretty much for cave and shipwreck divers.
Next on the list is the Horse Collar BC. This concentrates the bulk of floatation on your neck and chest. It’s mainly used by recreational divers simply because it floats you face up on the surface in case you are injured or exhausted while diving. A drawback is you have to learn how to ride the buoyancy bubble as the horse collar could roll your face underwater as well. If you don’t learn this skill before you use it you’ll have a tough time trying to hover with your face up.
Source: BCD Guide
The Front Adjustable BC came in much later as a variation of the Jacket Style BC. This nifty piece of equipment is quite popular by virtue of the fact that you can custom fit it, and fine tune it to the specific diver. This ensures that it stays comfortable, doesn’t wobble around and doesn’t feel like a burden as you swim.
Buoyancy Compensator Devices are actually very sensitive. You need to know when and how to keep them clean and fully operational before you consider buying one. The salty sea water may damage the bladder if you don’t take constant care of it.
BCs require constant rinsing after every diving session. This needs to be done with clean, fresh water. You also need to drain the water in the bladder after each session prior to rinsing. It is also crucial to ensure the inside of the bladder is dry when you store it.
Source: Rinsing a BC
The bladder sides have a tendency to stick together, which is why it is recommended to store it with some air. Heat is one among the main things that reduce the scuba BCs life span, so you need to keep away from anything that discharges any type of heat. This includes direct sunlight, heaters, furnaces or even kitchen cookers.
When should you consider buying a BC
If you haven’t already begun diving, and you still have no clue as to what kind of diving you wish to pursue, then the best thing is to wait until you can get a professional dive instructor to help you find the right BC and proper fit. Remember that Buoyancy Compensators are manually operated, so it is important to know how to use one before you buy one.
On the other hand, if you know what type of diving you’re into, and you’ve signed up to an open-water diving class, then you can always visit a pro-diving center and purchase your BC with your regulator equipment. They work closely together.
What to look for
It’s not just about functionality, any diver will tell you that comfort and safety are just as crucial. So what exactly should you look for?
Source: Choosing A BCD
First, in terms of utility value, your BC should have surface floatation capabilities. This means it should be able to hold a sufficient amount of air, enough to allow you to swim with minimal effort and be as comfortable as possible.
Neutral buoyancy is also key. The increase in pressure as you go deeper into the ocean will cause your BC to compress. It should be easy enough to add or expel air from your compensator to ensure you maintain neutral buoyancy. This will ensure you don’t sink to the bottom and you provide you with the ability maintain nuetral bouyancy at any depth.
Lastly, and perhaps the most important feature, is your ability to maintain how you control your descent. Being able to release air effortlessly and have a smooth descent is key. It’s all about safety here. Going down too fast could make you panic, and you possibly react incorrectly with dangerous consequences. Also, the air contained in your BC should be enough to help you comfortably keep your head above water while on the surface.
Many divers end up with dysfunctional BCs because they have no idea what to look for when purchasing one. If you don’t do your due diligence and find out what scuba diving compensation devices are and how to use them, then you could end up buying a BC that is not functional for your style of scuba diving.