Turbine versus Reciprocating Pumps.
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We have received a long letter from one of our readers, commenting upon, and criticising, the report of the Executive Committee presented at the recent Congress of Professional Fire-Brigade Officers, and the discussion which followed it. Pressure on our space has prevented our dealing with this matter before the present issue. The Executive Committee had been instructed carefully to consider and prepare a report upon the subject of turbine versus reciprocating. pumps for fire-engines, a subject which had been raised by Firemaster Inkster, of Aberdeen, in a very able and instructive paper read by him a year ago at the Guildhall, Westminster. The Executive Committee did not agree with Mr. Inkster that any difficulty or risk attached to the "changing from one delivery to two with a reciprocating pump," but, in this connection, our correspondent suggests that the committee was evading the point raised by Mr. Inkster, which was rather that risk attached to changing from two deliveries to one delivery with a reciprocating pump, an operation which only a trained engine-driver could effect with safety, unless he quite stopped his engine and ceased pumping, thus causing what might prove to be a costly delay.
On the question of coupling up additional lengths of hose, the committee stated that "all chief officers know that in this operation the additional length of hose proposed to be added is first made ready, and so placed that nothing remains to be done but to break the joint and then re-make it with the added piece in series with the hose previously in use, the pump, of course. being stopped during the actual operation. A similar delay would surely be required with any kind of pump." Again, our correspondent disagrees with the committee, and rightly so, because it is not necessary to stop a turbine pump or the engine by which it is driven during the operation, as the delivery may be interrupted without the slightest danger of causing damage to the pump casing or the engine. This is not so with a reciprocating mime, as with such a Blimp the simply cannot. he cut off—the pump itself must be thrown out of operation for the time.
On the third point raised by the committee, viz., that of efficiency. the committee agreed that the turbine pump showed some slight advantage over the reeinroestine type, bet rinsed its high speed as the objection to its use, and suewested that, until the turbine tenof pump has seen several years of actual ser
vice, it would be premature to offer any definite opinion upon its value as compared with a reciprocating type of pump. Evidently the coranauttee has entirely overlooked the fact that reciprocating pumps have been practically superseded on all the ships of His Majesty's fleet, their place being taken by pumps of the rotary type. In other branches of engineering, too, wherever high efficiency is required for pumping plant, the turbine type has been adopted.
One of the objections raised against the use of reciprocating pumps is that of vibration, but on this point the committee has thought fit to defend it, and to assert that vibration depends upon the kind of reciprocating pump employed, the kind of gear by which it is driven, and many other points. It urges that the pump should be geared down so that the operating crankshaft does not make more than 260 to 270 a n.m. With such an arrangement, the mechanical loss, due to the reducing gear, must be added to the internal friction of the pump plungers, valves, etc., which losses are entirely absent with the turbine type of pump.
"Why," asks the committee, "should 500 gallons be laid down as the limit of output for a reciprocating pump, whilst 1,000 gallons is given for the turbine ? " "Surely," comments our correspondent, "the committee ought to know its own business better than to ask such a question. The question of output is limited to a large extent by traffic conditions, and, therefore, a fire engine must not he made of such unwieldly proportions that it cannot safely be driven or hauled along the streets in congested areas, or along the public highway."
The committee, too, urged that the charging or priming arrangement which is necessary for all turbine pumns is a distinct disadvantage, but it evidently forgets that a large number of auxiliary devices are used on steam-driven pumps to effect the same, or some similar purpose. The attitude of the committee appears to have been that of "sitting on the fence," but with a
leaning towards the reciprocating pump. Our correspondent, who has closely studied the relative efficiencies of turbine and reciprocating pumps, is rather bitter against the committee for its valueless report, and in his letter to us he quotes an extract from Firemaster lnkster's contribution to the discussion which followed the presentation of the report. Firemaster Inkster said he could not conceive for one moment why gentlemen of a mechanical mind should still hang on to a reciprocating machine, when they had a machine that was superior and which, even yet, was not at its best, but clearly was sufficiently at a stage of efficiency to warrant him in taking up the attitude he had done, and he was still more convinced of the superiority of the turbine than he was when he presented his paper at Westminster 12 months ago. Chief Officer Dane, of Croydon, who also contributed to the discussion, thought that the turbine had a. much greater range of usefulness than the reciprocating pump, and he proceeded to argue that when taking water from the town mains, a reciprocating pump not only fails to utilize the pressure in the mains, but actually loses it, whereas the turbine pump takes in the water at the centre of the impeller, and that "the pressure of water in the water main introduced into the pump is not lost. but added to:'
Chief Officer Waddell, of Glasgow, was also in entire agreement with Firemaster Inkster. He said that the turbine pump was a very much easier machine to deal with, both in pumping and in driving to fire. The turbine pump was as steady as a rock, whereas, in the reciprocating pump, they got vibration. He had tested both machines thoroughly, and in his opinion the efficiency and utility of the turbine pump exceeded the reciprocating pump by far.
Another contributor to the discussion, Councillor Harvey, of Leith, said that Mr. Inkster, last year, stood up as the champion of the turbine pump, and, not only had Mr. Inkster's arguments not been proved incorrect, but they had at once put the reciprocating pump upon its defence, and it had remained there ever since. He added that they all knew that any mechanical contrivance increased in value an it became more simple, and the simplicity of the turbine pump was its recommendation.
Our correspondent would like to know on what evidence the committee had reached its unsatisfactory conclusions. We, also, should like to be enlightened on this point