How do i stand legaly working on an industrial gas boiler without gas safe qualifications?

The jobs I am asked to do are change ironizing probes, glow plugs,jackets and coils. I donot break into gas lines only isolate at stop tap nor do i alter any settings. Pipework is checked with leak detecter when it is reembled and any leaks found or gas supply needing to be adjusted we get in a qualified gas fitter.. All boilers are connected on flexi hose. I have onc,hnc in engineering and my boss says I am compitant to do the job so they say I am ok to carry out the repair