Here are some additional natural gas thoughts.
At the Minneapolis Community & Technical College we moved several
years ago into a new larger facility. It was going from the second
floor of the building to the fifth floor. Plenty of northern window
light (probably the finest skyline view of downtown Minneapolis in
the building), plenty of venting and plenty of power. One problem,
low natural gas pressure. We measured under one pound coming out of
the line. Hooking up 38 Hoke jewelers torches was not a pressure
problem. All the torches work fine for general bench work. We put
about 20 pounds of pressure into the oxygen line and again everything
works fine. The casting area however was different. We couldn't run
the large casting torch. We re-hooked up the old Smith NE250 I used
as a student in 1977 and it solved the problem. They don't even make
this torch any more. Even with a rosebud tip it takes us longer to
melt larger quantities. We even melt with two torches on an open
pour. So what I am saying is that minimum natural gas pressure is not
a problem in the jewelry lab where I teach.
When I had natural gas in my home workshop, I just put a gas ball
valve on a "T" section of pipe going to the furnace and had all the
pressure I needed. For general bench pressure whatever the gas line
produces should be adequate for general bench work. For bench oxygen
pressure use about 5 pounds.
Melting has a different set up. I do prefer propane for casting
silver, gold and platinum. A camper pressure regulator is preset at
about 3 or 4 pounds. You can use one directly on top of a disposable
propane tank and be code compliant in most areas. Casting pressure on
oxygen is 20 pounds.