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September, 1912 lv have been considered impossible on a centrifugal pump before the advent of this new type. In the Roturbo pump the design dif- fers from the ordinary impeller or flat disc runner, which is formed with the main object of securing velocity of the water in the expanding channels of the fixed casing. With the Roturbo pressure-chamber, the water, after being picked up at the £i 110 LBS FET SQUIRE SINC 5000 10000 La THE MARINE REVIEW is at' a duty in which the speed of the water issuing from the turbine blades is about half the periphery speed of the impeller. 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 periph- ery of the impeller, and there is noth- ing in the path of the water after leav- ing the impeller and the speed of the 3 LFFICIENCY 50 BAF 2700 O 000 GALLONS PrR Hour Fic. 6--ReEEs Roturro Pump, Norma Duty, 220 Les. Heap, 18,000 Gattons PER Hour eye, becomes practically stationary, water being also low, it has been shown relatively to the pressure-chamber itself, from all results that there is no tend- thus eliminating friction losses, and ency to wear at this point, even when generating a pressure by centrifugal pumping gritty water. This forms a force. marked contrast to the usual centrifu- The inner portion of the impeller gal pumps, whose facilities have to be between the eye and the largest sec- tion of the pressure-chamber may be 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, hav- ing rearwardly directed nozzles, dis- charging from the pressure chamber. The pump is, therefore, always dis- charging with a constant pressure, which is the ideal condition for a_ centri- fugal pump, and the turbine is always discharging from a constant pressure, which is the ideal conditon for a tur- bine. The result of a combination of a pump and turbine, with a pressure- chamber between them, is that the self- regulation is perfect, 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 pressure-chamber is reduced, internal friction is reduced to a minimum and a high efficiency is secured without the necessity of ma- chining or polishing blades or surfaces. The internal wear is also minimized. In practice it is found with this type of pump that the highest efficiency point provided for the renewal of blade tips and other parts, due to the excessive erosion. With much wear, of course the pump efficiency falls rapidly. The illustrations show examples of these pumps for wide range of duties with their respective curves showing the actual power absorbed and the ef- ficiency, ard 't is wo-thy of note that [50 SLL. fh) nt . 779200 158400 289 the efficiencies procured from Roturbo pumps are permanent efficiencies as the results depend much less upon dif- fusers effect in the casing than on the ordinary turbine pump, which is liable to considerable loss of efficiency when wear takes place. This is well illus- trated in the efficiency procured from the Roturbo irrigation type of pump, which is especially designed for large volumes and medium and low heads such as are required in irrigation, sew- age, and circulation pumps for con- densers. In this type of Roturbo, Fig. 2, all the diffusers in the fixed casings are eliminated so that any suspended mat- - ter which passes through the pressure- chamber of the mipelier has 4 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 ana con- struction, require no special] care m machining, so forming a cheap type of © pump. Owing to the low velocity of water through the pressure-chamber of the impeller, the efficiency is very much higher than the ordinary volute pump in this class, and this is secured with- out the use of diffusers. The efficiency is not only high but 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 revolutions per minute. The pump delivered water against a head of 150 ft. The test at the works gave an efficiency of 84 per cent at the duty point. Fig. 4 represents the latest type of the Rees Roturbo boiler feed pump, di- rect coupled to an enclosed ventilated, direct current motor. The pump im- peller consists of a series of pressure- Vs LIFICIENCY fo sox C3G600 W800 GHLLONS FEF, HOU Fic. 7--Rers Rotrursa Pump. NorMAL Dury, 150 Fr. Heap, 158,400 GaLtons PER Hour