ORIGINAL: seanreit
Matt, you make in intersting point that my experiance seems to suggest differently.
My line hanging in my airplane is under "case pressure" coming back to the check valve. My guess is this is around 30 to 40 psi and hot coming back to the check valve.
Are you suggesting that without the solenoid valve inline with the check that "that" is the hot pressurized gas that came loose in your experiance?
I have run the line straight to the engine, started it and not installed the check valve. This expelled hot engine gasses inside the fuse with no ill effects other than a couple of times the festo fitting inside the engine case, the blue part of it melted. Replaced the festo fitting and kept a check installed on the propane line and never had an issue after that.
FWIW.
I think we are talking about 2 different things. Again, I think you are talking about an OFFBOARD system (correct me if I am wrong), where the pressurized starting gas is not held in the model. I am not commenting on the safety of that system with propane, other than I think it works based on my RAM experience.
What I am talking about (in terms of pressure and heat) is the ONBOARD system, where the pressurized gas system stays in the plane. I have attached a table of the vapor pressure of propane. When the onboard tank's temperature rises (nothing to do with the turbine running, I have seen this happen with planes just sitting in the pits in the sun) the propane pressure gets to almost 200 PSI when the temperature in the plane gets to 110 F. The lines cannot take the pressure and pop off of nipples or rupture.
JetCat offers a couple of features to help mitigate this. The first is starting gas dump, whereby the onboard tank is slowly dumped into the running turbine after it has started. This helps minimize the time that the lines are exposed to this high pressure.
The second feature is kerosene start, and all of this starting gas stuff is moot.