The Steamboating Forum

I currently have a small Penberthy injector in use on my launch that works fine but requires a minimum of 80 psi to work. In discussions with a few fellow steamboaters it was mentioned that injectors were offered that would function at a lower minimum pressure. Does anyone out there know if I can modify my injector to function correctly at a lower minimum pressure?
I should say that I normally operate my boat in the 100-130 psi range and my safety lifts at 150psi.....Earle

Injectors are very precise things. If you can calculate the correct jet sizes and positions, then obviously you can alter its characteristics.

You may find that the lower pressure injectors have larger jet holes, so complete new jet assemblies would need to be made.

Personally I would find building a duplex pump easier and less stressful than attempting to make new jets for an injector.

Beckman Boatshop offers these injectors and the working ranges are quite wide, the lower pressure version is 25- 140psi. They can sell you a new set of jets too.
http://www.steamboating.net/page21.html

I sometimes drive a steam roller and at the end of the day the pressure is allowed to drop and the injector is turned on till the boiler is completely full then it knocks off. It is working at a very low pressure to be able to do this, I think it is a Penberthy.
Hope this may help, best regards, John

torpedostern wrote:I currently have a small Penberthy injector in use on my launch that works fine but requires a minimum of 80 psi to work. In discussions with a few fellow steamboaters it was mentioned that injectors were offered that would function at a lower minimum pressure. Does anyone out there know if I can modify my injector to function correctly at a lower minimum pressure?
I should say that I normally operate my boat in the 100-130 psi range and my safety lifts at 150psi.....Earle

Hi Earle. Penberthy injectors come in two operating ranges: 40 to 140 psi (might work at as low as 25 psi with positive head) and 50 to 200 psi. Rather than buy parts - the three jets used could cost as much as $600 - you might want try all of the following first:
1. Keep the suction run and "lift" as short/low as possible and the suction line AT LEAST one size larger than the discharge line. Easy test is to raise the water supply above the injector - if it functions better you probably have a suction problem;
2. Make sure there are NO air leaks in the suction line. It doesn't take much;
3. dis-assemble the injector and check all the parts for wear and "crud". If dirty, soak in a solution that will remove scale, etc. Re-assemble and try again;
4. Check to make sure all the parts match. Many live steam hobbyists think the parts are interchangeable - THEY AREN'T, that's why Penberthy asks for the injector serial number when ordering replacement parts;
5. As John suggests, talk with Lloyd at Beckmann Boatshop (you should know them by now). They can supply you with the parts and probably give some help troubleshooting.

A Penberthy injector is a wonderful product; but if its not provided with an adequate leak tight water supply (free of debris - use a strainer) and is clean and adjusted, it won't function well. Yours works, but requires almost double the normal starting pressure so I'd guess that the problem is in the suction line. That's where most steam boaters mess up. Short and straight is the best. If you must have an elbow, use a "sweep elbow".

Ron

P.S. International Steamboat Society http://www.steamboating.org has a reprint of a nice booklet from Penberthy with maintenance instructions in their "booklocker" area. The maintenance portion was reprinted in the Mar/Apr 2009 Steamboating Magazine.

Might I suggest this http://www.lindsaybks.com/bks11/inj/index.html

Been buying books from these guys for years , lots of great steam stuff there and a wealth of other info.