The Dennis Pump is a two-stage back-to-back high-pressure Turbine made entirely of gunmetal, and is very simple in construction. It is driven through a Hardy disc joint which allows a certain amount of universal action.
The water enters the pump through the suction direct into the eye of the first impeller and from there through passages in the diffuser ring to the eye of the second impeller, and then through the diffuser ring again to the deliveries.
Two grease cups are provided for lubrication; one is on the back cover of the pump underneath the suction adaptor, the other on the front cover between the air pumps. Both of these are for the purpose of lubricating the pump spindle. The only other lubrication that is required, but it is very important, is a small amount of engine oil and grease for the air pump clutch which is poured into clutch operating box by unscrewing the four cap nuts and removing the lid. Also there are two inspection covers on the air pump crank cases. These should be kept full of engine oil up to the baffle. The big ends of the connecting rods are kept lubricated by this means, and the pistons and cylinder walls by splash.
Instructions for Getting the Pump to Work
First see that the suction is screwed tight after having made sure that the leather washer is in position.
See that the copper, strainer is well under the water. On no account should the pump be run unless the strainer is screwed on to the last length of suction, as there is a possibility of stones, etc., being drawn up into the pump and so choking the water passages.
Connect up the delivery hose and open up whichever outlet is first going to be used.
Start up the engine and run it quite slowly. See that the rotary three-way valve on the back of the pump cover has the arrows in this (T) position, namely, one pointing downwards to the suction, the other two across the pump pointing to each of the air pumps.
Then pull the small lever between the air pumps towards you. This actuates the air pump clutch and the air pumps will then start exhausting. (The air pumps should not be run at a higher speed than 250 to 300 revolutions per minute.) Hold the clutch lever in until the pump has picked up its water. Then push the lever away from you and turn the rotary valve half a turn, bringing the arrows into a _|_ position cutting out all connections between the air pumps and the turbine.
Work on your throttle to speed the engine up to give the required pump pressure. Always run with the ignition lever fully advanced when pumping, but never more than half advanced when starting up the engine.
After the engine has been running a short time and has got thoroughly warmed up the temperature can be controlled by the small cock on the pump which allows cold water to enter the radiator from the pump head and run out at the overflow pipe. The correct temperature should be about 150deg to 170 F.
If it is required to stop pumping for a short time there is no need to shut down the whole plant. Simply reduce the engine speed until it gives about 20 to 30 lb. pressure on the Pump gauge, and then screw down your delivery valve. This will not damage the pump in any way, and for this reason control branches can be used with a Turbine Pump.
If the Pump is to be got to work direct from a street hydrant, there will, of course, be no need to use the exhauster pumps.
The Air Pumps can be tested separately by means of the rotary valve. Simply turn the rotary valve with one arrow pointing to the pump to be tested and the other pointing to the suction as <-| or |->.