This page describes the plumbing of the system that delivers water from the tank on the tender to the boiler via two separate pumps.
The axel pump is intended to be the primary way that water is injected into the boiler. The output of axel pump goes through a check valve and then through the feed water heater in the smoke box before entering the boiler through the front tube sheet. The bypass valve provides a way to adjust the axel pump output. Partially opening the bypass valve will allow some of the pump output flow to return to the input pipe. The test valve provides a way to bleed off air in the pump and also provides a way to verify that the axel pump is actually working.
The electric pump is the backup system used to immediately inject water into the boiler. The original plan was to use an injector for this function but the electric pump is cheaper and less hassle. The electric pump output goes through a piston type check valve next to the pump and then onto a ball check valve on the side of the boiler and then through a shutoff valve into the boiler.
This description starts with the electric pump because the water input pipe that feeds both pumps is attached to it. The pump is a SHURFLO Model 8000-543-290 typically The spec sheet is at http://www.depcopump.com/datasheets/shurflo/8000-543-290.pdf . The pump operates from 12 volts DC and will deliver about 1 gallon per minute at 100 psi pressure. The plan is to operate the pump with a momentary on push button switch --- see electrical section for details.
The pump has 3/8" NPT input and output ports. There is a 1/4" NPT port on the end for a pressure switch. This pump doesn't come with a pressure switch. The pump is hidden in the electrical compartment under the oil tank. The photo above shows the pump with some of the associated plumbing. The 1/8" pipe across the bottom is the water input. The input pipe is equipped with a coolant type quick connect on the right end. The hose from the tender will connect there using a right angle female quick connect fitting. These quick connects are identical to those used on the oil filter. The water enters the pump via the tee which has a male port in the middle that enters the pump via a 3/8" to 1/8" bushing. The left side of the tee has a 1/4" tube compression fitting which connects to the pipe that carries the input water to the axle pump. The hose clamp and spacer serve to secure the pipe to the motor so that forces on the hose from the tender won't be transferred to the plastic pump body.
The normal 3/8" output port at the top of the pump is plugged and the output taken instead from the 1/4" port out the end normally used for a pressure switch. The two elbows are 1/4" with one port male and the other port female. That is a piston type check valve between the two elbows.(McMaster-Carr #7768K56). A 1/4" tube compression fitting is connected to the lower elbow.
Photo above shows the input water pipe from the tender hose fitting on the right to where it goes up between the two oil feed lines just in front of the fuel valves. The pump sets between the frame bar and the outer frame channel, both which have been modified to accommodate the pump so that the top of the pump is no higher than the top of the battery.
The photo above shows the pump output pipe--- it goes through elbows and a union and follows the top of the frame toward the front of the boiler.
The photos above show the axel pump just after it was constructed several years ago. See Axel Pump Construction. There is a ball bearing in the aluminum rings on the right end. The pump is a Clippard cylinder. The fittings between the elbows and the hose barbs are check valves.
This shows the axel pump mounted on the front truck --- although you can't see much of it. The eccentric and surrounding bearing (now painted) are beside the gear case on the far axel. The pump cylinder is under the bolster. The blue hoses are from the pump, the lower one the input and the upper one the output. (The black hose is for the brake cylinder.) The elbow and check valves are reversed from the position shown in the previous photos.
This shows how the axel pump input pipe is routed along the lower frame bar to a fitting behind the frame stiffener plates. The return pipe from the pump output to the bypass valve is routed above the upper frame bar beside the electric pump output pipe.
This wraps up the water plumbing ---- on to plumbing the brakes and lubricator.