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FAQ's
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Can I use a water pump to pump air? No. Water pumps are designed to pump water (an incompressible fluid). Air compressors are designed to pump air (a compressible fluid). Water pumps have passageways matched to the piping inlet flow area that permit optimum volumetric flow rate through the pump. Air compressors have passageways that maximize compression ratio. This is what allows the air compressors to reach output air pressures within ~5 psi of the steam inlet pressure.
Do I need a lubricator? Yes, an inline displacement style lubricator is required when operating these water pumps and air compressors to lubricate the steam cylinder. Since a displacement lubricator functions the same regardless of its size, select the largest possible to aesthetically fit within the spacing your application permits to maximize the oil reserve you can carry.
Can I regulate the water pump so that it will pump just what I need back into the boiler? Not really. The pumps, just like their full size cousins, operate properly under full boiler pressure. Restricting the flow rate of steam to the pump as boiler pressure fluctuates under operating conditions, could cause the pump to cycle inconsistently and slowly. Slow or stalled operation allows the steam in the line and inside the pump to stagnate, cool, and therefore condense. Restarting could take a few moments longer as the new live steam works to purge condensate from all of the chambers inside the pump. It is best to turn the pump on full and shut it off completely when finished, like it were an injector.
What size piping should I use? Match the pipe size on the pump with the piping coming out of the valve turret. There is no advantage to use large diameter piping from the turret, only to reduce it down at the pump to accommodate the inlet pipe size. Using a larger than necessary pipe diameter will cause excessive condensate in the line since the extra volume of steam in the pipe will start to cool as soon as it leaves the boiler from the turret.
Why is it important to plumb a bleed valve on the water pump? The bleed valve, plumbed on the discharge side of the water pump enables one to 1) Purge trapped air in the water supply line. 2) Verify that the pump has water (primed) and is pumping correctly, 3) Serves as a drain point when winterizing the system.
What do I need to do to protect the pump from freeze damage? To winterize, the pump should be thoroughly cycled on compressed air to purge condensate from the steam cylinder and water cylinder. Be sure to also drain your displacement lubricator. If possible, disconnect the union between the pump discharge and the boiler check valve. If you included a bleed valve on the discharge side of the plumbing, open it as this also prevents forcing the trapped water back into the boiler for winter storage. Blow compressed air into the water supply line until no moisture escapes from the bleed valve. If possible, open the steam supply union going into the pump and squirt some cylinder oil into the line and cycle the pump a few moments more to work the oil thoroughly inside.
On start-up, my packing glands sometimes leak, why is this? O –rings will take a “compression set” over time. This may require tightening the packing gland lightly with a small screwdriver. Also try applying some steam oil on the piston rod to that it can work into the gland seat. Usually, the gland needs moisture and oil to remain soft and flexible.
How long will the O-ring seals last? On average, 5 years life of regular service is expected. The best elastomers have been selected and applied to each pump and compressor design to maximize the service life. Rings need changed when there is excessive blow by such that the pump lacks power and cannot cycle under load. O-rings can be replaced by the owner or sent back to KSP for a thorough inspection and cleaning.
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What size pump do I need? Order based upon what the prototype you are modeling would have used. A single cylinder water pump in 1.5” scale will supply enough water to keep a 1.5” scale 4-8-4 locomotive operating, although the 2-cylinder water pump (that has a larger displacement volume) does a much better job. You should always have more than one way to feed water into a boiler, especially if your steam pressure is low since injectors and steam pumps will not be able to function.
How do I specify left side or right side mount for the pump? Since a pump can be manufactured for mounting and plumbing on either side of a locomotive, it is important that your pump is ordered with the correct inlet / outlet configuration needed. The left and right sides of a locomotive are defined by point of view of an engine crew sitting in the cab looking forward down the track. It is not appropriate to define left and right side of a locomotive as an observer facing the smokebox and looking toward the cab. A Left side mount pump will have “right side” admission steam / water or air connection lines. Likewise a Right side mount pump will have “left side” admission steam / water or air connections. See photo.
Can I order a pump / compressor with unique inlet side connection for the steam cylinder and have an opposite direction inlet for the water / air cylinder? Yes, each pump can be manufactured to suit your specific need. This is a common request for tank or logging locomotives where the inlet connections are more conveniently transposed to access water supply and check valve placement.
