Cylinder valve technology - Perfect Playground for a Design Engineer

In 2009, the 31st annual seminar of the All-India Industrial Gas Manufacturers Association (AIIGMA) in New Delhi was inaugurated by Dr A P J Abul Kalam, former President of India.

In his keynote speech, Dr Kalam observed that to judge the impact of the gas industry correctly, it is essential to consider not only its contribution to the GDP but to what extent it helps leverage the other manufacturing sectors it serves.

Compressed gases are the essential raw material for industries related to chemicals, power, mining, steelmaking, metals, medicine, firefighting, automobiles, refrigeration, biotechnology, food, water, fertilizers and electronics; in short, necessary for sustaining the modern way of life.

While the significance of compressed gases is easy to establish, the importance of gas equipment like cylinders and cylinder valves cannot be less emphasized.

Gas cylinders and valves handle high-pressure gases with varying oxidation, fire, toxicity and corrosive properties in the harshest conditions, at extreme temperatures.

The designer of cylinder valve needs to be knowledgeable in several different fields, each requiring specialization in its own right.

Let's start with materials, and for convenience, we divide them into metallic and non-metallic components.

Brass is the most commonly used metallic material for cylinder valve. Still, several applications require the cylinder valve body and components to be manufactured from Carbon steel, Stainless steel, Aluminium and Nickel alloys (e.g. Monel, Hastelloy).

Non-metallic materials are used to provide efficient sealing of the gas boundaries. A variety of non-metallic materials like elastomers and plastics are used in cylinder valves.

Commonly used elastomers are EPDM, Nitrile, Neoprene and FKM, while the most popular plastics used are Polyamide, PTFE, PEEK, PVDF and PCTFE. Fluid lubricants are used to reduce the friction of parts inside the cylinder valves. The most commonly used greases are Fluorocarbon, or Hydrocarbon based, and every brand/grade come with a different temperature, pressure and gas compatibility rating.

Are you overwhelmed already? Hang on; we are just getting started.

Selecting the appropriate material needs knowledge of mechanical and chemical properties of different materials, availability, and price points. Other considerations include ease of fabrication (Forgeability, machining, pressing), which is discussed below.

The next area of expertise that the cylinder valve designer must possess is manufacturing technology, mainly related to metalworking.

Cylinder valves bodies are hot forged and then machined. The designer must ensure maximum material savings in the design and ease of manufacturing, considering the capability and technology level of the workshop at the valve manufacturers disposal.

Handwheels are usually pressured diecast, pressure relief devices require sheet metalworking and lower spindle assembly are crimped. Each of these manufacturing processes is sufficiently diverse, thereby challenging the designer to learn and learn fast.

Different valve body material needs specific heat treatment processes not limited to stress-relieving, normalizing and solution annealing. The valve designer is expected to specify not only the heat treatment but also surface treatment like blasting, plating, electropolishing, painting, and coating required for each part in the drawings.

Do you still envy the work of the cylinder valve designer?

Once the appropriate material and manufacturing process and valve design are decided, the designer must specify dimension and tolerances to enable the valve parts to be interchangeable and assembled seamlessly. The trick is to ensure the tolerances are close enough for consistency in manufacturing but not unnecessary close to make the design difficult and expensive to manufacture. Knowledge of leak rate computation, spring rate calculation, and determination of squeeze of an elastomer are crucial for the valve design as the strength of material for calculating the factor of safety.

Finally, a good cylinder valve designer must be fully aware of material compatibility, gauging methodology, and design & type testing standards required for the appropriate certification and statutory compliance of a cylinder valve.

To say that a cylinder valve designer needs to be an allrounder is an understatement of epic proportions.

Designing a perfect cylinder valve is as much work of art as it is a science!!

Reach me at rb@teknovalves.com