Buoyancy Control Device - BCD

The buoyancy control device is a type of life jacket inflated by using air from the tank with a low pressure inflater. Air is released from it via a valve or hose. These actions assist your lungs in determining your level of suspension in the water. It can also be used on the surface for floating, resting, swimming or rescue. A standard BCD must accommodate you and all your diving equipment at the surface. Its large diameter inflation/deflation hose needs to maintain the function of releasing air quickly and easily when you need it.

It must have a pressure relief valve to prevent overexpansion upon rising as well as a low pressure inflation mechanism that connects it to the air in your tank. Ensure a snug fit so it does not cause any discomfort when you inflate it. All these added features can become rather bulky, so ensure that your purchase is a streamlined product. Think of it as a lifejacket with submersion ability. One of its primary design functions is to allow the diver to maintain neutral buoyancy with all the heavy equipment that is required for the dive.

Attributes

The typical BC consists of an inflation valve that pumps low pressure gas form the cylinder and regulator into its air pockets. Some BCD’s have integrated weight belt systems or pockets for the weights (as well as ones for storing decompression tables etc)

Two valves operate in order to regulate the air flow:

• A vent valve that facilitates air release
• An over pressurization valve that monitors drastic air influx

A harness fixes the jacket to the body safely and an inbuilt slider on the back plate cradles the tank.

Three common types of BC include:

1. Divers Lifejackets designed to float the diver face-up with a 15litre capacity are strapped to the chest, fastened around the waist and between the legs. Discomfort and separate requirement devices for breathing equipment prove disadvantageous.
2. Stabiliser jackets (stab jacket) 25litre buoyancy, alternate to wings which are located along the side of the torso and diver’s lifejacket type BC’s consist of wraparound inflate-ability. They are typically practical for recreational diving in that the standard D -rings for clipping gear, torches, cameras and integrated weight belts are present. Back-inflation options could prove dangerous as they force the diver into a face-down float during an emergency, the also have a tendency to inflate too tightly around the body due to the wide surface area of the internal air bladders.
3. A newer addition to the tech diving world consists of a BC with ‘wings’. The inflated areas on either side of the body allow for more tank space on the back plate. 30 litre ‘wing capacity ‘for extra buoyancy is not uncommon.