Usage point template
Usage point templates , also known as flashback arrestors or safety devices according to the DIN EN ISO 5175-1 standard , prevent a flame from the torch's mouthpiece from flashing back through the hose line into the gas cylinder or the distribution line during oxy- fuel welding or flame cutting , thereby causing an explosion. The use of these devices is essential for safe handling of oxy-fuel welding, cutting and heating processes.
function
In Germany and many other countries around the world, protection with a point of use template on the pressure reducer is required by law. In addition, protection can also be provided in the hose line or on the handle of the implement. Safety devices according to the DIN EN ISO 5175-1 standard (formerly EN 730-1) are equipped with at least two safety elements (functions).
Usage point templates reliably prevent:
- Entry of air or oxygen into the distribution line or single bottle
- Flashback
- The further gas supply in case of an afterburn
A point of use template has at least the following two security elements:
- a non-return valve (NV)
- reliably prevents mixture formation
- only allows gas to flow in one direction
- a flame arrester (FA)
- prevents flame transmission
- cools the impinging flame front below the ignition temperature
In addition, the point of use templates are usually equipped with a thermal leakage flow barrier (TV) as standard :
- triggers before reaching a predetermined temperature and interrupts the further flow of gas
- prevents impermissible heating of the safety device
With resettable, pressure-controlled point of use templates, there is another safety element, the pressure-controlled post-flow barrier (PV):
- interrupts the further gas supply in the event of pressure surges
- the gas supply can be released again manually.
In many common models, a dirt filter protects the point of use and in particular the gas non-return valve from dirt particles that may be introduced from the gas inlet side.
There are different types of flashback arrestors:
- Fuses that are connected to the pressure reducers (there is an internal thread at the input of the fuse, an external thread at the output)
- Fuses that are connected to the handle (an external thread at the fuse inlet, an internal thread at the outlet)
- Fuses that are connected between the hoses (inlet and outlet: e.g. oxygen = 6 mm nozzle; gas = 9 mm nozzle - note flow direction)
Mandatory review
Usage point templates are to be submitted at certain time intervals, but in Germany at least once a year ( TRBS 1201, Table 2- tried and tested test periods for recurring tests) or ( DGUV -R 500, chap. 2.26 point 3.27) by a trained and authorized person for tightness, gas flow and safety to be checked against gas backflow and to be marked accordingly.
history
In 1945 Paul Witt brought the dry usage point template onto the German market. The usage point template revolutionized welding safety and was also established worldwide in the years that followed. The handy, dry use point template largely replaced the previously common wet use point template which, with water, prevented gas rejection and flashback and was much more complex to install, maintain and handle.