Boiler Pressure Test

[fredrosse]

Getting ready for the 2014 steaming season. Hydrostatic test to 300 PSIG (20.7 Bar) with a pump put together with use of a small double acting hydraulic cylinder and some scraps making up a pumping handle.

The hydraulic cylinder has a 1/2 inch piston rod diameter, with a 7/8 inch diameter piston, and is rated for 2500 PSI. Two small check valves are made from Swagelok compression fittings, 1/4 inch diameter stainless balls, stainless springs wound on the lathe from 0.023 MIG welding wire, and ordinary 1/4 inch pipe couplings. The arrangement of the attached tubing allows three displacement conditions: effective bore of the piston rod only, @ 1/2 inch = 0.196 square inches, effective bore of the main cylinder, @ 7/8 inch = 0.601 square inches, or effective bore @ 7/8 inch minus 1/2 inch = 0.405 square inches.

[Dhutch]

Very nice, simple. Whats the coil for, to give some effective volume change, or because its what you had available?

Daniel

[fredrosse]

The coil gives flexibility so I can attach the compression fittings to various boilers or pressure vessels without the need to make a special bend of tubing. I could have used a flex hose, but sometimes I want to run pressures up to 2500 PSI, and that is an expensive hose which I do not have.

I bought several hundred feet of 1/4 inch OD stainless tubing, and made a coiling tool to wind the coils of a monotube boiler for a previous project. My first steamboat project, a 15 ft long Coleman Scanoe, used about 80 feet of this tubing for the boiler. Thus it was an easy task to wind that testing coil for the hydro-pump. At the time the stainless tubing was selling for $1.50 US per pound, a good bargain.

I also have a couple of thousand feet of 1/16 inch OD stainless tubing, but have not yet tried to make a compact steam generator with that stuff. I understand Volvo was investigating a steam powered automobile back in the 1970s with a boiler about the size of an automobile battery, so that must have used very small diameter tubing to get enough heat transfer surface area. Some day, maybe I will retire from my day job and try to make something very compact.

[Dhutch]

The coil gives flexibility so I can attach the compression fittings to various boilers or pressure vessels without the need to make a special bend of tubing. I could have used a flex hose, but sometimes I want to run pressures up to 2500 PSI, and that is an expensive hose which I do not have.

Sounds fair.