Start Up Issues and reversing issues

[JonRiley56]

Hey Ron,

Good advice on the blowdowns, I did that on Sunday, I will fire again in the dirveway and continue the process. My new safety arrives tomorrow.

jon

[Lopez Mike]

Mine came on the engine. I'm sure you can get them from Strath Steam in Australia. I'll look at them and see if there is any identification on them. I won't be near my boat until the weekend.

They are quite small. 3/8" hex on the outside and maybe an inch long. Probably a simple ball check with a spring that will lift at somewhere a bit more than your safety setting.

Mike

[DetroiTug]

The way I start the twin:

On each steam chest is a drain with a 1/4" line, these are manifolded together at a manual valve and then from there, a 1/4" drain line through the hull.

On fire up, I open the valve to the steam chest drains and crack the throttle open, put the Stephenson lever in forward. As steam builds it goes through the steam chests and heats each entire cylinder block. When the pressure gets to about 10 psi the engine will just start turning on it's own. I let it spin until the pressure is up around 30 - tapering the throttle back to maintain low RPM dockside. Then close the chest drains, I never open the cylinder drains.

As long as the cylinder(s) are hot when the steam starts going in and out, there is no condensing of steam and resulting condensate/water that can cause hydraulic locking.

When I take off again after sitting idle, I put my hand on the cylinder head, if I can hold it there, I open the chest drains again, if not, they are left closed.

I generally leave the engine spinning slowly (about 40 rpm) dockside which keeps the engine temp up as well.

-Ron

[fredrosse]

Cylinder relief valves can be had from Graingers, ASME rated for air, with metal to metal seat. 1/4 inch pipe thread, very small valves, about 1/2 inch diameter x 2 inches long, with no pipe connection for discharge. For a 150 PSI engine get 200 PSI relief setting, less than $10USD each. Cylinder relief valves should not be routinely used, clearing condensate thru the cylinder drain cocks during warmup, or after an idle period, is the proper method. On the cylinders you want a very small valve, and these work well in this application. I also have one of these on my engine driven feed pump discharge, and have lifted that one a few times when careless about valve lineups.

[JonRiley56]

Hi Fred,

Can I put a T fitting into the openings I have now and have this valve and a petcock connected to it ?

jon

[Lopez Mike]

Probably not a problem.

When designing engines one of the goals is to minimize the empty volume in the cylinder at the end of the stroke. "Out with the cold steam and in with the hot stuff!"

I don't think you could measure any efficiency loss from the extra volume on one of our small engines.

Mike

[Mjolnir]

I'm using steam operated drain cocks on my Leak compound. I built the engine with piston valves on both HP and LP, so it really needs good drains, and these work well. The principle is that there is a small piston sealed with an O ring that presses a valve down on its seat. The piston area is larger than the valve area so the steam pressure behind the little piston can hold the valve shut against normal cylinder pressure. If the steam supply to the little piston is turned off then the valve can open and allow water and steam out of the main cylinder. If the cylinder pressure gets too high then it can force the drain valve open. They are not hard to make and work well. I also have conventional releif valves in a separate tapping, which i guess is a bit belt and braces.

Our relatively small engines probably have plenty of excess strength in the cylinder covers, but with big engines it is possible for a slug of water entering a cylinder to break the cylinder cover. This can happen if the boiler is allowed to prime when the engine is running fast. The water enters the cylinder and then the engine tries to compress it. A slide valve may releive the pressure by lifting off the face, but of course a piston valve won't. So try not to let your boiler prime!

John