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How are gas regulators manufactured?

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Four different single stage gas regulators Gas regulator bodies and bonnets are made either by die casting or forging. The plastic handles and levers are made by injection moulding, while connecting nuts are forged.

Die casting

Nine identical die cast gas regulator bonnets Die casting is a way of producing objects on a mass scale using moulds, also known as dies. Although the moulds may be expensive to make initially, they can be used over and over again, making it possible to mass produce thousands of identical complex shapes.

In the long run this brings manufacturing costs right down. The bodies and bonnets of most low cost single stage gas regulators are made in this way.

Diagram of die casting process

Step 1 – Melt metal

The metal, usually a zinc alloy, is melted in the furnace of a die casting chamber.

Die casting diagram showing molten metal entering mould

Step 2 – Inject mixture

The molten mixture, known as a casting, is then forced by a plunger through a nozzle into two dies, or moulds, which have been clamped together.

Because the process of die casting is so flexible, the moulds can be designed in a whole range of intricate shapes which can be replicated thousands of times.

Die casting diagram showing casting being ejected from mould

Step 3 – Eject casting

When the the die has been filled the molten metal begins to cool down and solidify, taking on the final shape of the casting. The two halves of the die then open up and eject it.

Trimming regulator body on grinding machine

Step 4 – Trim edges

When the casting has cooled completely it is trimmed to remove any rough edges. This process is either carried out by hand using cutting tools, or automatically in a trimming press.

Forging

Metal being hammered on a forge Forging is the process of using heat and mechanical energy to change the shape of metal. The most common metals used to make regulators in this way are brass, stainless steel and aluminium.

Regulators can be forged using two methods:

  • Drop forging
  • Bar stock forging
Molten brass in a drop forge showing moulds and ram

Drop forging

Many high pressure regulator bodies are made by drop forging, which produces a stronger product than one made by die casting. The process involves compressing molten metal into the shape of a mould using a hammer-like tool called a ram.

As the metal is shaped, its internal grain structure changes. Instead of flowing in many different directions, the grain begins to follow the general shape of the part. This makes it stronger.

Block of steel

Bar stock forging

Bar stock forged regulators are made by machining the body out of a single piece of metal. However, other components such as the bonnet (the top outer part) and spigot will probably be die cast as they are too complex to make out of a solid bar.

Bar stock forged metal has a much tighter grain structure than drop forged. This leaves less room for contaminants to get into the regulator and interfere with gases passing through. The quality is higher, but of course so are the costs.

Three stages of shaping for POL connector

Cold forging

Brass or stainless steel parts, such as nuts and POL connectors, are usually made by the process of cold forging. This involves shaping the metal at room temperature, or below, in several stages by forcing it through various moulds at high pressure.

Injection moulding

Plastic blocks The handles and levers of gas regulators are made out of plastic using the technique of injection moulding. This allows a large number of identical parts to be manufactured quite cheaply.
Plastic injection moulding machine Plastic granules are poured into a hopper leading to a heated barrel which turns them into a molten liquid. A rotating screw moves the mixture along, which is then forced into two mould halves which are pressed together.
Mould opens to eject solid plastic handle The molten plastic fills the mould and takes on its precise shape. As the mixture cools it solidifies and is then ejected from the mould. The process then starts all over again until hundreds, or maybe thousands, of identical parts have been produced.