Gas Safety Training in the UK

Pressure
Chemical/ Material Compatability
Working Conditions
Tubing Perfomance in Emergency
Internal Diameter
Hose Barbs
Push Fit Connectors
Compression Fittings

The working pressure of the tubing must match or exceed the maximum outlet pressure of the regulator to which it will be connected.

Ensure that the tubing material will not react/age/degrade/etc. with intended service gas.

Assess the area where the tubing will be installed. Will, for example, the tubing be subjected to harsh conditions? (heat/cold/external chemical or mechanical attack).

Consider how the tubing material will behave in the event of [say] fire. If the tube were to fail/melt/burst then will ensuing gas release enhance the impact of the fire? Metallic or metal armoured tubing may offer greater resistance to fire. Also, by fitting a re-settable flashback arrestor, fitted with a thermal cut-off valve, would stop the supply of gas at an ambient temperature of approximately 100° C.

Unless it is required to, the tubing should be so sized as to not restrict flow rate at the required working pressure. In most cases, a first approximation can be had from compressed air flow tables or nomograms. Hydrogen and helium will, however, tend to flow at greater rates for a given diameter than more 'air-like' gases.

Ensure that the tubing is properly fitted. Joints and connections, as a rule of thumb, should be kept to an absolute minimum; they're mechanical weaknesses and potential leak paths - joints or connections in tubing should always be kept well away from open sources of ignition, etc. Consider the options available and remember DO NOT MODIFY THE REGULATOR OUTLET:

For soft-walled plastic tubing (inerts/non-flammable/non-corrosive and [relatively] low pressure service), simply select a 3/8" BSP nut and a barb of suitable outside diameter to fit the inside diameter of the tubing to be used. See illustration below. We can supply brass hose barbs for 5mm, 6mm, 8mm and 10mm i.d. plastic tubing - these are £1.50 + VAT each including the 3/8" BSP nut. Tubing should, of course, be secured using a hose clip once it has been pushed [fully] onto the hose barb. If required, we can supply 'O' clip pliers and 'O' clips in a wide range of sizes - confusingly, it's the outside diameter of a hose that would be quoted when sizing a suitable clip!

For hard-walled plastic tubing. In this case (as is normally always the case) tubing size is specified in terms of outside diameter - it's pipe that specified in terms of it's i.d. and pipes are considerably bigger than tubes; but let's not worry about that now! The best way to do this with the less reactive gases at higher pressures is to use a push fit connector in conjunction with our EasiDaptor©. Firstly, measure the outside diameter of your hard-walled tubing and let us know. We can then, secondly, fit a suitable push fit/quick release coupling for most metric AND imperial tubing sizes.

NOTE: Great care must be taken when setting up rigs or experiments with push fit, quick release couplings, as the mechanism for mis-connection (right cf. left handed threads) is quite effectively defeated! Anti-confusion techniques like colour banding for matching hoses to correct connectors may be employed.

These are, perhaps, the most obvious solution for metallic tubing. Metallic (or some very hard walled plastics) may be chosen for corrosive/toxic/flammable service &/or for high pressure &/or small bore instrument lines (e.g. hydrogen and helium supplies to chromatographs). For direct connection to your gas regulators we would, unsurprisingly, recommend that via an EasiDaptor© a suitable compression fitting can be selected with relative ease - whether in brass or stainless and for a range of sizes from 1/8" OD to 6mm OD - again metric of imperial, just let me know and we should be able to get the appropriate tube fitting you need.