140 The Drainage of Fens and Low Lands* 



suction pipes of the air-pumps should get choked with weeds, an 

 extra injection cock is provided, connected with the casing of the 

 centrifugal pump, so that the air-pump may still obtain its supply of 

 water for condensing. This cock can also be used to form a vacuum 

 in the cases of the centrifugal pumps, should the ejectors get out of 

 order. The small donkey engine for feeding the boilers draws water 

 from the condenser when the engines are working or from the canal 

 when they are at rest. 



The two large centrifugal pumps are coupled to the main shaft of 

 each engine. The outer casing of these pumps is 7 feet 7 inches in 

 diameter, and cast in two pieces, the lower part being fixed to one 

 side of the bed-plate of the engine, and has a large flange on the 

 upper side, on to which the upper half is bolted. The lateral suction 

 pipes are also bolted to the sides of this casing by flanges, which 

 admit of their being easily dismounted to examine the disc inside, 

 remove weeds, &c. The suction pipes have no foot valves, and the 

 discharge pipe a hinged valve, which remains closed when the 

 pumps are not at work. The discs are 3 feet i x\ inches diameter, 

 with a central web having six long and six short blades on each side. 

 The spindle of the pump is of Bessemer steel, with a brass casing 

 and lignum-vitse bearings. Each pump is supplied with an ejector 

 for forming the vacuum in the suction pipes before starting. 



The following experiments were made in December 1882 in the 

 presence of the Itahan Government engineers appointed to inspect 

 the machinery, and to ascertain if it fulfilled the conditions of the 

 contract. At the two trials both engines were set in motion with 

 steam supplied from one boiler, and were kept running for twelve 

 hours. On the first occasion the pumps ran at 130 revolutions per 

 minute, the pressure of steam in the boilers was 70 lb. per square 

 inch, cut off at o'i75 of stroke, the vacuum was 24^ inches, and 

 24,700 gallons of water were raised per minute, the lift being 6 feet 

 6| inches, and the consumption of coal 2f cwts. per hour. On 

 the next trial the experiment was continued with a lift of 5 feet 

 8 inches, when, with the same number of revolutions, the pumps 

 raised 27,300 gallons of water per minute, with a consumption 

 of 2 J cwts. of coal per hour. The horse-power in water raised was 

 on an average 47^ per cent of the indicated horse-power, with a 

 mean consumption of 6* 12 lb. of coal per horse-power per hour. 



[Extracted from a paper by Mr. T. R. Guppy in the * Minutes of 

 the Proceedings ' of the Institution of Civil Engineers.] 



