Phew they are some sort of questions you have there now let me see if I can answer them in a manner you will understand.
1. BTU Heating value of the gas the initials relate to the term Bristish Thermal Units and is the amount of gas required to raise 1lb of water through 1 degree F
2. The Specific Gravity of gas simply means the “weight of gas in relationship to air” i.e. Natural Gas is approximately .69 and is therefore lighter than air so any leak will rise, on the other hand LPG gas has a specific gravity of 1.5 or thereabouts so it is heavier than air and any spillage or leakage will effect a puddle of vapour kinda like a petrol spill if you will.
3. Diversity Factor is a calculation which is applied to a carcase pipeline than has bends, elbows, tees joints etc as well as a different number of gas appliances connected to the same pipeline – this factor figure is used to determine the correct size of pipe to carcass out and installation that will allow for all appliances working and takes into account the resistance to gas flow caused by bends tees etc.
I hope this explaination is understandable to you and that you now at least understand the silly terms we use in our Trade.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians