Understanding Gas Cylinder Valves

A gas cylinder valve is a crucial interface between your stored gases and your broader system. With this interface, you retain complete control over the system, applying the gas when it is required and shutting it off after use. To put it simply, your business needs cylinder valves.

In this article, we’re going to be looking at these valves in more detail, helping you to get a clearer picture of why they are so important, how they work, and what you should do when you use them within your facility. Read on to learn more.

What Is a Gas Cylinder Valve?

Chemicals are stored in cylinders at extremely high pressures. The exact pressure depends on the type of gas, the conditions of its storage, and its state, but the value will always be significantly higher than that of atmospheric pressure. For gases, compressed cylinders will contain chemicals with a pressure of 40 pounds per square inch (PSI) at 70 °F, or 104 PSI at 129.2 °F. For flammable liquid, a compressed cylinder contains chemicals with a vapor pressure of 40 PSI at 100.4 °F.

As a point of comparison, atmospheric pressure – i.e., the air pressure most of us experience on a daily basis – is around 14.7 PSI. Even the least pressurized canisters feature a PSI several orders of magnitude greater than that of the air that surrounds it. Open one of these cylinders in an uncontrolled way, and the contents flow rapidly down the concentration gradient and out into the space around the cylinder. At best, you lose the gas; at worst, public health and safety are put at severe risk.

This is where cylinder valves come in. These valves provide a safe and controlled way to open the gas cylinder and connect it to a broader system. When the valve is connected and opened, gas flows out of the cylinder and into the system. When required, the valve can be quickly shut off, stopping the flow of the gas through the system.

The Difference Between Valves and Regulators

While a cylinder valve does “regulate” the flow of gas out of the cylinder, the terms “valve” and “regulator” generally relate to the different things. The valve is designed to control the flow of gas into the system from where it leaves the cylinder. Opening and closing the valve does adjust the pressure but not with enough accuracy to provide reliable regulation.

The regulator sits within the system as a second stage. After the gas has passed through the cylinder valve, it may then pass through a regulator. Here, the pressure of the gas will be modified or controlled before it enters the equipment or apparatus that will be using it. Different types of equipment and apparatus have their own requirements when it comes to pressure, which makes a regulator very useful. However, the regulator can’t be deployed alone in the system without the valve.

Different Types of Gas Cylinder Valve

There are many types of gas cylinder valve, but most of these valves fit into several broader categories. These categories are largely based on the design of the valve and the gases they are built to handle.

Pressure Seal Valve

In a pressure seal cylinder valve, a seal is created between the two valve stems. This takes place when the handwheel is used to move the upper stem into place while the pressure of the gas is pushed up on the lower stem.

• The pressure seal valve is commonly used with inert noble gases, oxygen, and hydrogen cylinders.

O-Ring Valve

Within this type of valve, an o-ring component creates the seal around the upper stem. The valve is operated in the same way, with the handwheel controlling the movement of the upper stem and the pressure of the gas pushing up on the lower stem.

• The o-ring valve is commonly used with inert noble gases, oxygen, and hydrogen cylinders.

Packed Valve

Packed valves feature non-metal materials within the stem. This material – which may be a ring of fluoropolymer or another non-metal component – compresses against the interior of the packing nut, gripping tight against the surface to create a seal. Needle-type packed valves are also available, with a smaller diameter and lower flow rate compared to larger, sturdy stem-type packed valves.

• The packed valve is commonly used with gases labeled as corrosive or highly reactive.

Diaphragm Valve

A diaphragm valve is so-called because of the diaphragm between the stem or spindle and the valve seat itself, or between the upper and lower stems, depending on the design. It is this diaphragm that forms the seal when the valve is closed. This category of valve is available within a spring-loaded configuration, in which the lower stem is mounted on a spring and the diaphragm sits between the lower and upper stems. Alternatively, a static configuration is available, in which the lower stem connects to the upper and is pulled up and down along with this upper stem. This removes the need for the spring component.

• The diaphragm valve is commonly used with highly toxic gases that are non-corrosive, as well as high-purity, rate, and pyrophoric gas cylinders.

Cylinder Valve Safety and Considerations

There are a number of different considerations to make when deploying gas cylinder valves:

• Use a regular inspection schedule to ensure the valve remains in good condition and in full working order.
• Only use valves that are rated for the gas cylinder you will connect to the system.
• Use only the factory-approved method of opening and closing – for example, only use wrenches or pneumatic equipment if the valve is specifically designed for this purpose.
• Ensure that only trained personnel are permitted to operate the valves.
• Implement a clear shut-off procedure so that the flow of gas can be swiftly terminated in the event of a leak.
• Replace any damaged or worn valves without delay.
• Use a regulator to stay within the safe pressure range of the equipment or apparatus.

Explore Our Range of Sherwood Valve Products

Here at Chemtech, we provide a wide range of gas cylinder valves produced by the industry-leading Sherwood Valve organization. Take a look at our product pages and find what you need, or reach out directly to our team to learn more.