Thanks, I thought dot was us only, but what is TC? I also read abou Pi markings somewhere? What do I need to show to fields on bottles in UK nowadays? Thanks
Dot is the US standard (department of transport)
TC is Canada (transport Canada)
Pi is the symbol for TPED (Transportable Pressure Equipment Directive - European standard
UNISO is a more recent international standard.
Cylinders may be marked with multiple standards. In the UK can use a multi marked DOT/TC/Pi cylinder but not if it’s just DOT/TC
Buy from a reputable UK retailer and you know it will be good for the UK
You would need to show your cylinder at sites before you can fill, to check that it’s UK legal, in date, and that is free from damage.
Have a look at the UKPSFs HPA1 air safety guide. It’s now out of date with regard to newer standards, but remains valid for key air safety.
Noting that you asked about a budget cylinder, do consider an aluminium 3000psi. They give best value for money of air to £, and though ‘heavier’ than fibre wrapped a ‘standard’ 48ci 3000 has a similar weight to a ‘standard’ 68ci 4500.
You don’t get the wider range of shapes and sizes or the benefit of a curved base* to roll in your shoulder, but you do save money and may find that many sites only do 3000psi fills anyway.
It’s personal preference and experience as to whether the difference between types is worth >£100 extra (and then hydro testing every 5 years)
* if you shop around there was a 3000psi aluminium with the curved base and may still be available in some retailers