Diving cylinder

A diving cylinder, also known as a scuba tank, is a gas cylinder used to store and transport the high-pressure breathing gas required by a scuba diver. These cylinders are essential components of scuba diving equipment, providing the diver with a portable supply of breathing gas, typically air or enriched air nitrox.

Diving cylinders in various sizes and configurations

Design and Construction

Diving cylinders are typically made from either steel or aluminium. The choice of material affects the cylinder's buoyancy characteristics, weight, and durability.

Steel Cylinders

Steel diving cylinders are known for their strength and durability. They are less buoyant than aluminium cylinders, which means they require less additional weight to be carried by the diver. Steel cylinders are often used in technical diving due to their robustness and ability to withstand higher pressures.

Aluminium Cylinders

Aluminium cylinders are lighter and more buoyant than steel cylinders. They are commonly used in recreational diving. The manufacturing process involves the extrusion of aluminium billets, as shown in the image below.

Aluminium cylinder extrusion process

Components

A diving cylinder consists of several key components:

Cylinder Body

The main part of the diving cylinder is the body, which is a hollow tube that holds the compressed gas. The body is designed to withstand high internal pressures.

Neck and Valve

The neck of the cylinder is threaded to accept a valve, which controls the flow of gas from the cylinder. The valve is a critical component, allowing the diver to regulate the supply of breathing gas.

Cylinder with machined neck detail

Manifold

In twin-set configurations, a manifold is used to connect two cylinders, allowing them to be used as a single unit. This setup is common in technical diving.

Manifolded twin 12L steel cylinder set

Testing and Maintenance

Diving cylinders are subject to rigorous testing and maintenance to ensure safety. This includes regular visual inspections and hydrostatic testing.

Hydrostatic Testing

Hydrostatic testing involves filling the cylinder with water and pressurizing it to test its integrity. This process ensures that the cylinder can safely hold the required pressure without risk of failure.

Hydrostatic test of a diving cylinder

Usage

Diving cylinders are used in various types of diving, including recreational, technical, and commercial diving. The choice of cylinder depends on the type of dive, the depth, and the duration of the dive.

Recreational Diving

In recreational diving, single aluminium cylinders are commonly used due to their lightweight and ease of handling.

Technical Diving

Technical divers often use multiple steel cylinders, sometimes manifolded together, to carry different gas mixtures for deep or extended dives.

Related Pages

• Scuba diving
• Technical diving
• Breathing gas
• Scuba set