Connecting Safely

Connecting cylinders and equipment safely is vital

Connecting Safely

Valve operation

  • open cylinder valves slowly using the correct spindle key or the handwheel fitted on some cylinders
  • soft seat, spindle key operated cylinder valves should not be subjected to excessive torque
  • an opened valve should never be left against the backstop but should be turned back half a turn to avoid seizure in an open position
  • to shut the valve turn it clockwise just enough to stop the gas completely - never use force
  • if you stop work for more than a few moments, close the cylinder valve

Non-flammable gases such as oxygen, nitrogen, argon and air all have conventional right-hand threads.

Flammable gases such as acetylene, hydrogen, propane and mixtures containing fuel gas all have left-hand threads.

The only exceptions are special cylinders of dissolved acetylene, specified for purposes other than welding and cutting and some propane cylinders used on fork lift trucks: these cylinders have right-hand thread valve outlets. Buy Spindle Keys online

Acetylene cylinders

If an acetylene cylinder has been transported horizontally, it should be placed in an upright position for a minimum of 12 hours prior to use.

Non-standard keys

To avoid damaging the valve seat or spindle square:

  • never use anything but the recommended cylinder valve keys
  • never increase the leverage of keys or use longer ones
  • never use spanners with long handles; or even the correct key if it is badly worn
If the valve spindle is too stiff to open by hand with the spindle key, return the cylinder to the supplier.

Broken spindles

If you think your cylinder valve has a broken or damaged spindle, do not try to use it.

Do not attempt to remove the gland nut as the broken spindle could be ejected or unwound at great risk to the operator.

Contact BOC Gases Directline: 1800 355 255.

Gas pressure – correct equipment

The gas cylinder and outlet valve are designed to supply gas through an approved pressure regulator.

The pressure regulator screws directly into the valve outlet.

  • never install additional piping or fittings between regulators and the outlet valves of MCPs
  • when individual cylinders of the same gas are manifolded together to a common outlet, the pressure regulator should be screwed into this outlet
  • use needle or fine adjustment valves downstream of the pressure regulator only, never upstream

Pressure regulators

  • the pressure regulator must correspond to the pressure in the cylinder
  • the threads must be the same as the valve outlet
  • never force any connection
  • regulators should be maintained regularly in accordance with the manufacturer's instructions
  • do not attempt to repair or modify the regulator
Buy pressure regulators online

Fitting a pressure regulator

Before fitting a pressure regulator to a full cylinder always screw out the pressure adjusting screw to stop flow through the regulator when the cylinder valve is opened.

Pressure regulator connection

This advice applies to ALL gas cylinders and regulators:

  • never try to ease any regulator threads with oil
  • never use PTFE tape
  • never 'pack-out' a connection
  • never use any connection that appears worn when tightening or loose when fully screwed home

Correct regulator

Never interchange left-hand threaded pressure regulators between gases. They are designed for use with a specific gas and to interchange them could be hazardous.

Never use left-hand to right-hand adaptors.

Remember: cylinder pressure and properties are different for each gas.

Fit flashback arrestors

Flashback arrestors prevent flames travelling back into cylinders.

They should be fitted downstream of pressure regulators in oxygen, acetylene, propane and hydrogen systems. Buy flashback arrestors online

Manifold - regulators and flashback arrestors

  • cylinders connected to a manifold or header system must be properly designed for the task and installed by a specialist engineer
  • it must be fitted with one or more pressure regulators
  • acetylene manifolds must also be fitted with a flashback arrestor

Use a non-return valve with mains gas

When using mains gas, the law states that a British Gas (BG) approved non-return valve must be fitted.

BCGA website