Conversion of the old LPG Bunsen burners to use natural gas (NG) may be possible, but it may be safer and more economical to simply purchase new Bunsen burners. If you are requiring several class sets, your school may be able to negotiate with a science supplier to get a very competitive pricing for a bulk purchase.
For safety reasons, it is vitally important to use the correct Bunsen for the type of gas being used. The difference between LPG and NG burners is related to the design of the jet. Whilst there are a number of differences between the actual gases, the two most relevant factors relate to the pressure at which the gas is delivered and the air-to-gas ratio required for proper combustion. Natural gas operates at a lower pressure than LPG and also requires less oxygen than LPG.
To see if it is possible to obtain a replacement jet for your existing burners, it would first be necessary to approach the manufacturer or supplier of the Bunsen burner. Some Bunsen burners have a screw-in jet, and for these it may be possible to arange for a competent person to replace the jet. Some manufacturers may refuse liability on their products, if their burners have been modified. In addition, the name of the burner's preferred fuel is usually cast into the metal base, so, if the jets are changed, it may cause confusion and potentially the incorrect burner fuel being used, with unpredictable consequences.
From a cost point of view: if it is possible to replace the jet, the expense of the spare part and the time taken to replace these may be similar to the cost of a new Bunsen burner, so any savings may be minimal. By purchasing new Bunsen burners, you can be assured of the safety of staff and students by having the correct burner, for the relevant gas.
Therefore, it is the opinion of Science ASSIST that, the benefits of purchasing good-quality, new, natural gas Bunsen burners outweigh any possible savings of converting the old LPG burners.
‘Burners’, R&L Enterprises website, http://www.rexaloy.co.uk/manufacturing-catalog-bunsen-burners.html (Accessed March 2016)
‘LPG Gas Blog Converting LPG & Natural Gas Appliances’, Elgas website. https://www.elgas.com.au/blog/474-converting-lpg-and-natural-gas-appliances (Accessed March 2016)
‘LPG Gas Blog Difference Between LPG & Natural Gas’, Elgas website. https://www.elgas.com.au/blog/486-comparison-lpg-natural-gas-propane-butane-methane-lng-cng (Accessed March 2016)