Diving BCD
FUNCTIONS
In Module 4 – The Autonomous Scaffolding, it was addressed that the diving vest brings together two functions:
- Attach the bottle to the diver’s back
- Control your buoyancy
It was then explained how the vest could be used to attach the bottle to the diver’s back, but in reality this is a secondary utility. In fact, the true and main function of the vest is to allow the control of the diver’s buoyancy during immersion and provide positive buoyancy to the surface, giving greater comfort and safety in both situations.
THE USE OF THE DIVING VEST IS MANDATORY BY LAW
JACKET
It is currently the most widely used in amateur diving. The air is distributed from the back, shoulders and flanks to the ventral area. It is practical to use and there are adjustable models.
DORSAL VEST (ASA/WING)
Usually used by technical divers, for having a large capacity of drive. As the air is distributed only on the back, the harness is released to the front, allowing the attachment of various accessories, including complementary bottles.
COLLAR VEST (BIB)
Little used nowadays. It does not support the bottle, which requires a fixing harness. The vest is placed by the head and the air is distributed around the neck and in the pectoral area. It is fixed with a subcutal strap and a waist strap.
FEATURES
It is formed by a bag of resistant fabric (nylon or other material), which can be filled with air coming from the bottle through the first floor of the regulator (air in intermediate pressure), with air coming from a small auxiliary bottle (air at high pressure) or the mouth which is frankly not advised.
Some models have a double bag, i.e. a polyurethane inner tube, protected by an outer casing in nylon fabric resistant to abrasion and cuts and perforations.
All models of vest have pockets, where can be packed the second emergency floor and the console, delicate pieces of equipment, which are protected and stop dragging around the bottom.
REGARDLESS OF TYPE AND MODEL, THE DESIGN AND CONSTRUCTION OF THE VEST MUST BE TAKEN INTO ACCOUNT THE QUALITY OF THE MATERIALS AND THE SAFETY OF THE USER
FILLING TRACHEA
The vest has a trachea, to which is connected a mechanical air injection system (Direct System) that has a filling valve, a discharge valve and a nozzle. This filling mechanism is powered by a hose connected to an LP (intermediate pressure air) outlet on the first floor of the regulator. The air injection valve must be progressive to allow smooth and controlled filling of the vest.
Air discharge is done through the trachea and nozzle, which also allows you to fill the vest to the mouth (not advised). The trachea must be of large diameter to allow a quick purge of the vest.
In some vests it is possible to opt for a second emergency floor incorporated into the filling system. This second floor is served by the hose that feeds the air injection mechanism into the vest which reduces the number of hoses connected to the first floor of the regulator.
SAFETY VALVES AND QUICK PURGE
To prevent overfilling and allow rapid air release, the vest has safety and quick purge valves. Usually these valves are located on top, next to the shoulder, and at the bottom, behind, next to the lower edge of the vest. Shoulder valves, including filling trachea valve, are used when the diver swims horizontally or upside up. The bottom valves are used when the diver is upside down.
THE HANDLING OF THE SAFETY VALVES MUST BE PERFECTLY AUTOMATED, SO THAT ITS ACTIVATION IS IMMEDIATE, IN CASE OF NEED
CHOOSE AND ADJUST
The vest must adapt correctly to the diver’s body so that the diver feels comfortable, even when it is completely full. The vest should be chosen depending on the weight of the diver and his equipment, not forgetting the size of the trunk: if it is too wide, it can rotate around the body, if it gets too tight, it becomes uncomfortable.
The diver must make a first adjustment of the straps with the empty vest and then fill it, to make sure that it does not hinder him/her movements after being completely full.
During the dive, due to the compression of the suit, it is necessary to make further adjustments of the straps so that the vest becomes tight to the body again (but not tight). Usually when the vest is full, on arrival at the surface, it is necessary to relieve the straps again so that the diver does not feel too tight.
The bottle attachment strap is wide and robust, with a lever buckle, which allows a strong and efficient grip, not letting the bottle slip from the holder. It is preferable to make the grip with the wet strap.
THE VEST IS A RELATIVELY FRAGILE PIECE, WHICH REQUIRES A CAREFUL PACKAGING
MAINTENANCE
After use should be passed through fresh and dry water in the shade with some air inside.
To wash the inside of the vest, it fills with water through the trachea nozzle up to 1/3 of its capacity, then stirring so that the water rinses the entire interior. At the end it pours back through the filling trachea.
There should be very special care with the air injection system buttons. These buttons should always be in perfect working condition, so they are never stuck when pressed. If the open jamfilling knob can lead to an untimely ascent, with very serious consequences for the diver, especially if the diver is not trained to act quickly on the safety valves.
Periodically, the filling system should be reviewed by qualified technicians.
BUOYANCY CONTROL
The control of buoyancy is one of the most important skills that the diver must have skills. The control of buoyancy is the ability that allows the diver to control his descent, ascent, the course during the dive without accidental contacts such as the bottom, with the fauna and flora.