Pekos

You first need to check why the gas tips are clogging.
This means breaking one (or more) down for inspection.
The typical causes are

A - pipe scale from corroded piping
  A1 - clean the pipe internally by either steaming or pickling
  A2 - install strainers ahead of the gas nozzles no bigger that 2/3 of the smallest jet size

B - oil or tar from the gas (condensate)
  B1 - change the gas
  B2 - put knock out pots in the line(s)
  B3 - heat trace the piping

C - high sulphur content in the gas, when the gas expands as it leaves the jet, it drops out some solid sulphur which plugs the hole
  C1 - change the composition
  C2 - clean the nozzle frequently

D - corrosion of the jet by flame contact, if there is inufficient chrome in the nozzle it will scale from flame contact
  D1 - change the material

I'm sure others may have some thoughts but this should get your ideas flowing.
In any event, you should probably have a program of regularly inspecting the burners for progressive damage, both to the jets and the refractory blocks.


 

If I have to install stainers on fuel gas pipes, can you recommend a specific type of strainers
thanx

Pekos
You should check with your local piping and fittings supplier to see which manufacturers he carries.
Generally, a "Y" type strainer with a drain connection and a removable basket would be sufficient.  If the service is critical and cannot be interrupted, you may need a dual basket with change-over/diverter valve.