Re: Lost in the Imperial system!!!
Posted: Thu May 23, 2013 10:44 pm
Hayden,
Yes, your injector will have a nominal 'size', a '1/2" Injector' for example refers to is being 1/2" OD pipework required to pipe it up. Whatever size your injector is will give you your pipe size.
The supply pipe will see boiler pressure or just above, one great thing about injectors is their inability to overpressure, unlike a feed pump.
At 80psi your boiler will be at around 160deg.C.
To work out the safe working pressure of tube use;
P = 2T x t / D
Where T= Wall thickness
P= Working pressure
D internal diameter of tube
t= safe working stress of copper, 25,000psi divided by a safety margin of 8 gives us 3125psi
So for a 1/2" injector and 16swg tube;
P = 2 x 0.064 = .128
x 3125 = 400
/ .372 = 1075psi
This is, of course, at cold- as copper's strength decreases proportionally to it's working temperature, then it's maximum working pressure is going to be lower, but as we have already used a safety factor of 8, and as 1075psi is 13 times the maximum pressure of your application, then 1/2" 16swg tube would be suitable for you.
Greg
Yes, your injector will have a nominal 'size', a '1/2" Injector' for example refers to is being 1/2" OD pipework required to pipe it up. Whatever size your injector is will give you your pipe size.
The supply pipe will see boiler pressure or just above, one great thing about injectors is their inability to overpressure, unlike a feed pump.
At 80psi your boiler will be at around 160deg.C.
To work out the safe working pressure of tube use;
P = 2T x t / D
Where T= Wall thickness
P= Working pressure
D internal diameter of tube
t= safe working stress of copper, 25,000psi divided by a safety margin of 8 gives us 3125psi
So for a 1/2" injector and 16swg tube;
P = 2 x 0.064 = .128
x 3125 = 400
/ .372 = 1075psi
This is, of course, at cold- as copper's strength decreases proportionally to it's working temperature, then it's maximum working pressure is going to be lower, but as we have already used a safety factor of 8, and as 1075psi is 13 times the maximum pressure of your application, then 1/2" 16swg tube would be suitable for you.
Greg