From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical discussion on the K.S. Sprengel pump, correction pumps, and issues with air and fuel vapor in pressure lines for gauges.
| Identifier | ExFiles\Box 19\3\ Scan381 | |
| Date | 19th May 1930 | |
| (10) The new K.S. Sprengel pump drawing pure air from outside the tank and discharging it inside the bell, is confirmed by Searight as making a vast difference. He thought it might render the hand pump unnecessary because of reducing the percentage of fuel vapor in the air within the tank unit. It works splendidly on non-pressure balance systems, but on the latter it is not applicable since it calls for a vent to atmosphere at the tank. In case of trouble with any of our gauges on Am. P.I it would be an almost certain cure. (The Sprengels would suck air from inside the tank vent). (11) The correction pump is not an essential part of either the pressure balance or open systems, but can be used with either. Since the new type Sprengels defeat the object of the pressure balance systems, the pump appears more necessary on the latter. Searight does not agree that it would be better to supply air from pump to the top of the tank unit as suggested by Bandemer and used on K.S. House gauges, because the pump would have to have a delivery valve of some sort, probably a tire valve and this would be a potential leak on the air-pressure line. Consequently trouble would be likely from slugs in the pressure line. See 12 below. The present pump has no valves. The inertia and friction of the fuel in the small bore delivery pipe makes a discharge valve unnecessary and the cup leather acts as an intake valve. The pump is therefore a simple syringe. (One would expect the English gauge to be much more satisfactory if it could be simplified to retain the present long scale with a longer back leg, no balance line, no hand pump, and the new type effective Sprengel pumps. But, as stated above, to arrange a central tank vent without fouling coachwork parts or spare wheel carrier appears almost impossible). (12) Searight points out that because the air in the pressure line and balance line is practically stagnant fuel vapor does not get up into either of these lines and form "slugs" unless there is a leak. The slightest leak particularly at the gauge end on either of these pipes will put the instrument wrong in a few hours, both from fuel vapor entering and condensing in the pipe and also from moisture out of the air condensing. A pipe left open for a few hours in humid weather will definitely have to be blown out before the gauge will work. Consequently, he provides some very good lead plugs for the ends of the pipes, which are not supposed to be disturbed till the gauge is finally coupled up for use. cont'd.{John DeLooze - Company Secretary} | ||