The Steamboating Forum

A thought on using piston rings in this application.

Unlike in an internal combustion engine where one leaves a fair amount of end gap in the ring for large temperature changes in the ring, relative to the cylinder bore, these rings can be set up with essentially no end gap.

Any steam leaking through the end gap will need to escape somewhere. By condensation to some degree, I suppose. I'd be tempted to make my own ring with no gap. It's just cast iron.

Automotive machine shops who do dry sleeves often throw away the cut off ends. Cast iron pipe is better stuff than you might think. Just part off the bit you need with a lathe and lap it flat on a flat surface with 400 grit sand paper and oil. I put the sand paper grit side up on my drill press or band saw table. Elbow grease!

Fun to recommend hard work to someone else. Eh, Bart?

Mike

Fun to recommend hard work to someone else. Eh, Bart?

Yup... I'm busy reorganizing my metal storage in the garage, and designing the engine for the big boat I'm going to build.

- Bart

I somehow missed the piston ring bit. Thank you for pointing that out Bart, and thanks for the suggestion Mike!

87gn@tahoe wrote: Now, porting through on the LP so that it sees vacuum is a given, but on the HP? should I make a small hole (in the centre of valve travel) through the valve cover (don't worry they're nothing special, just a flat cast plate with no builders marks) so the valve sees atmospheric pressure, or through the valve like the LP so that it sees the LP receiver pressure (20+ PSI above atmosphere)? I'm thinking the lower pressure the better, as well as the hole through the cover would be a good indicator for when the o-ring needs replacing.

Any thoughts?

Now, porting through on the LP so that it sees vacuum is a given, but on the HP? should I make a small hole (in the centre of valve travel) through the valve cover (don't worry they're nothing special, just a flat cast plate with no builders marks) so the valve sees atmospheric pressure, or through the valve like the LP so that it sees the LP receiver pressure (20+ PSI above atmosphere)? I'm thinking the lower pressure the better, as well as the hole through the cover would be a good indicator for when the o-ring needs replacing.

Actually, I'd just do the usual thing - make it like the LP. If you have a simpling valve, you may have problems getting the valve to seat with that valve open otherwise, since your exhaust and intake will be of similar pressures.

- Bart

Bart,

Are you referring to the pressure differentials being similar between the steam chest side and "exhaust" side of the HP and LP valves?

87gn@tahoe wrote:Bart,

Are you referring to the pressure differentials being similar between the steam chest side and "exhaust" side of the HP and LP valves?

When the simpling valve is opened, the receiver gets HP steam directly from the boiler; this means the exhaust side of the HP is pressurized.
If the top of the HP valve is exposed to atmospheric pressure, the net pressure balance on the HP valve will want to lift it off the seat .

- Bart

barts wrote:

87gn@tahoe wrote:Bart,

Are you referring to the pressure differentials being similar between the steam chest side and "exhaust" side of the HP and LP valves?

When the simpling valve is opened, the receiver gets HP steam directly from the boiler; this means the exhaust side of the HP is pressurized.
If the top of the HP valve is exposed to atmospheric pressure, the net pressure balance on the HP valve will want to lift it off the seat .

- Bart

Okay, I understand what you were getting at now. Hp like the LP it is!

Thanks again professor.