The Rees Roturbo Pump
With the introduction of electric motors and steam turbines high efficiencies became possible and for high lifts the old arrangement of impellers in series was revised and the centrifugal pump became a strong competitor of the plunger pump for conditions which used to be looked upon as only suitable for reciprocating pumps. These conditions were well known and it was attempted to overcome them by designing the impeller with blades bent rearwards so as to reduce the brake effect. This necessitates increase in the speed of the impeller to compensate for the slip of the water and beyond a certain amount of recurvature the capacity of the pump is very greatly reduced and the internal friction of the impeller increased with consequent loss of head at anything but a restricted range of service. The problem of varying heads has been completely solved by the invention known as the Rees pressure-chamber impeller, which was introduced in Europe in 1907 by the Rees Roturbo Manufacturing Company, of Wolverhampton, England. The invention has been protected by patents in every country in the world by the parent company, the Rees Roturbo Development Syndicate, Ltd., Wolverhampton, England. Pumps are being sold under license in most of the European countries; among these may be mentioned Messrs. Krupp, of Essen, Germany. Since introducing this new type of pump many installations for all kinds of services have been installed abroad and in many instances where no other type of centrifugal pump could be used, these have given excellent service and satisfaction to the users. The pump illustrated herewith constitutes an entirely new departure; the name “Roturbo” has been registered to denote the type. The right to manufacture it in this country and Canada has recently been obtained from the Rees Roturbo Development Syndicate, Ltd., by the Manistee Iron Works Company, of Manistee, Mich. The characteristic feature of this pump is that it is a true turbine pump—that is to say, the “rotor” has a strong “turbine” effect, due to the water passing, hence the name “Roturbo.” The turbine effect is secured by making the rotor of large capacity for storing water, which is maintained by rotation at a constant maximum internal pressure with the minimum amount of loss; consequently, instead of throwing away the surplus speed energy of the water discharged when the head of delivery is reduced, the energy is extracted from the water before it leaves the pump casing. In a pump constructed as described above, it is found that the power absorbed when running at a constant speed remains practically constant for all heads of discharge and heights of suction possible and never appreciably exceeds that required for the total head for which the pump is designed. Thus, such a pump is self-regulating. It being impossible by any variation of head or suction to throw any excessive load or strain on the driving motor. There are no moving on parts in contact except at the bearings. The internal arrangement is such that the whole pump is in hydraulic balance, without end or lateral pressure on the shaft. In the characteristic curve of the Roturbo pump it will he noticed that the power rises to a maximum at about normal head and volume, but the head can be reduced to any extent without affecting the powercurve, and the discharge can be reduced below the atmospheric line, into vacuum, without any effect except reducing the power required for the motor. If we now superpose a Roturbo characteristic curve on that of an ordinary volute centrifugal pump, when drawn to the same scale, Fig. 1, the vertical distance between the two poser curves will represent the turbine effect extracted in this Roturbo from the water at any head and volume. The inner portion of the impeller between the eye and the largest section of the pressure chamber may he looked upon as a centrifugal pump proper and the blades of this portion are designed similarly to those of an ordinary centrifugal pump. The rim portion, beyond the pressure chamber, is designed as a reaction turbine, having rearwardly directed nozzles discharging from the pressure chamber. The . pump is, therefore, always discharging with a constant pressure, which is the ideal condition for a centrifugal pump, and the turbine is always discharging from a constant pressure, which is the ideal condition for a turbine. The result of a combination of a pump and turbine, with a pressurechamber between them, is that the self-regulation is complete, and at any heads lower than normal duty the power taken from the motor is prevented from rising. As the speed of the water in passing through the pressurechamber is reduced, internal friction is reduced to a minimum and a high efficiency is secured without the necessity of machining or polishing blades or surfaces. The internal wear is also minimized. In practise it is found with this type of pump that the highest efficiency point is at a duty in which the speed of the water issuing from the turbine blades is about half the periphery speed of the impellers. Consequently, the resulting speed in relation to the fixed casing is greatly reduced; as a result of this the diffusers may be removed some considerable distance from the periphery of the impeller and there is nothing in the path of the water after leaving the impeller and the speed of the water being also low, it has been shown from all results that there is no tendency to wear at this point, even when pumping gritty water. The illustrations show examples of these pumps for wide range of duties with their respective curves showing the actual power absorbed and the efficiency, and it is worthy of note that the efficiencies procured from Roturbo pumps are permanent efficiencies, as the results depend much less upon diffuser effect in the casing than on the ordinary turbine pump, which is liable to considerable loss of efficiency when wear takes place. In this type of Roturbo, Fig. 2, all the diffusers in the fixed casings are eliminated so that any suspended matter which passes through the pressure-chamber of the impeller has a clear flow through the fixed casing. The style, which is a stock type, meets all usual requirements for low heads, although embodying the simplest parts and construction, requires no special care in machining, so forming a cheap type of pump. Owing to the low velocity of water through the pressurechamber of the impeller, the efficiency is very much higher than the ordinary volute pump in this class, and this is secured without the use of diffusers. The efficiency is not only high, but is also permanent. Fig. 3 shows a steam-driven Roturbo pump of 400,000 gallons capacity per hour that was installed in Nova Scotia, and was driven by a direct-connected steam engine of 300 B.H.P., running at 400 r.p.m. The pump delivered water against a head of 150 feet. The test at the works gave an efficiency of 84 per cent at the duty point. Fig. 4 represents the ’atest type of the Rees Roturbo boiler feed pump, direct coupled to an enclosed ventilated, directcurrent motor. The pump impeller consists of a series of pressure-chambers, which are mounted upon a central shaft supported upon bearings throughout the whole length except that portion passing through the chambers. The general appearance of these pressure-chambers is shown in Fig. 5. The whole pump is in perfect hydraulic balance. This feed pump on test delivered 18.000 gallons per hour against a boiler pressure of 220 pounds per square inch and took 50 B.H.P. to drive same. showing a pump efficiency of 76.5 per cent. Fig. 6 shows the characteristic curve and efficiency of the above
An interesting example of a comparatively low speed Roturbo pump running at 925 R.P.M. gave the high efficiency of 84 per cent. The duty of this pump is 150 feet lift and a delivery of 158,406 gallons per hour at the above speed, the diameter of the discharge pipe being 12 inches The curve shown in Fig. 7 gives the performance of the pump under test to meet stringent contract conditions. The overall efficiency of the pump and motor was shown to be 7.5 per cent. When this pump was tested the following results were procured: Starting from the duty point, viz., 158,400 gallons at 150 feet head, the power is reduced from 120 H.P. to less than 40 H.P. as the discharge valve is closed. To the right of the curve when the discharge valve is opened, so as to reduce the head against which the pump is working, the volume with minimum pressure is increased to double of that at the duty, showing that there is no throttling in the pump and no reduction of capacity. The characteristic of the pump is shown in the power curve which, instead of rising at the lower head, is actually reduced from 135 H.P. to 105 H.P, due to the turbine effect of the impeller. Therefore, the Roturbo type of pump gaging selfregulation and high and permanent efficiency at constant speed, coupled with the modern high speed prime movers in the shape of electric motors, steam turbines, gasoline engines, etc., finally removes the limitations of the centrifugal pumps entirely and the. above illustration shows that there are few conditions of pumping that the Roturbo type of pump is not fitted for. They arc used for pumping sewage, mines, coal mines, boiler feeds, pressure augmentors for city service, fire protection, dock pumping, cooling towers and condensing plants. They are also being used with exceptional advantage for fire engine service, big. 8 shows an application of the Rees Roturbo pump for this service driven by a gasoline engine.
This machine is equioped with a 50 H.P. engine adapted to drive either the machine or the pump, as required. The outfit attains a speed of 46 miles per hour when running on good roads The efficiency obtained at the pump, viz., B. H. P. to W. H.P., was 74 per cent. when working at the duty and against a pressure of 120 pounds per square inch. Due to the self-regulating characteristic of this pump the streams can be delivered through any number of hose pipes without overloading the engine when the head is reduced. Consequently, the maximum power of the engine can be utilized at all times, no matter what head may be, since it runs at constant speed.
A fire that did considerable damage in the mill of the Clark County Box & Lumber Co., Vancouver. Wash., started in the sawdust which had been allowed to accumulate. There was no insurance.