The Pumping Engine; Its Many Points, Faults and Peculiarities.
ERNEST W. NAYLOR,
Member American Association Mechanical Engineers; Cleveland Association Civil Engineers.
The simple word pump is really too general, as it may mean a little hand pump or the mighty 100,000,000 gallon pumping engine; therefore, any pump driven by any power other than manual should be called a pumping engine, as it is really not a pump, in the sense of the pump in the village green, where the ossips congregate with valid excuses for getting water, so that _____y may air their grievances, both real and fancied, and truly, t kind of air is much more easily gotten rid of than the air a pump barrel, a point that is often overlooked in the signing of pumping engine plants ; but of that, more here.ter.
One of the first and most important conditions of any engine dant is the location and foundation. Location, in many istances, is a mere item, but foundation is always a serious eality and of the utmost importance. I have known thouands of dollars to be thrown away, caused by the niggardly id pigheaded policy of some municipal crank who thought he lew all about building, because he probably superintended e erection of a hog pen.
The first duty of any engineer is to ascertain the nature of the ground upon which he is going to build, which, in most instances, is very easily found out.
Opinions vary greatly as to the best materials for foundations ; some engineers thinking stone the only thing fora foundation, while others say brick, and yet others think concrete the best. We have tried all kinds of material and unhesitatingly say that concrete, if properly mixed and rammed, is the best for all foundations. It is solid, homogeneous and capable of being held together and strengthened in many ways at little cost. Twisted iron or plain bolts with wall plates are easily built in as the structure progresses, and a foundation built in such a way is practically one solid lump, and when the, part above the floor is trowelled, there is no finer looking foundation. We have seen some erectors, after they have lined up their bed plate, fill it up with liquid cement. This is a bad practice, for if hot water, along with the oily cylinder discharges get to the cement, it is liable to swell and crack the bed plate. We have seen several such broken bed plates. Of course, if the cylinders are properly drained and piped, such a thing should not occur, but a careless attendant can easily forget and cause his employer many dollars by such forgetfulness. When the bed plate is in position on its foundation it should then be carefully wedged up with thin iron wedges, doubled so that a parallel packing bearing on all the surface is formed, and not simply a point. Wood should never be used for many reasons. It is easily crushed, and is liable to change with the weather, both being fatal to its use. I have seen bed plates lined up with wood wedges, and when the erection was complete and the engine tried, the erector has been surprised to find something out of line, and it is a mighty big job to get that something back into line, as any one knows who has been there. Iron wedges may cost a little more at first, but an immense amount of trouble is saved afterward. It is a good plan to have small “ tits ” cast on the bed plate at convenient places, so that when planing they can be tooled over at the same time. Then one always has a datum, so to speak, where a straight edge and level can be placed at any time. There are many pumping engines that work badly, simply because they are out of line, and because of the difficulty of getting a straight edge or a line. When no provision has been made for the same, the engineer is prevented from attending to this important point, and he just lets her go until something goes to pieces, and then it has got to be done.
I have known a case where in a vertical cross compound engine the shaft was found three-quarters out of the square, and the attendant wondered why she would “ run hot.” He never thought of trying for lines as she had only been running somewhat over a month. This was a case of bad work on the erector’s part and no provision had been made for trying line after erection. The consequence was the necessity of lifting a fifteen-ton fly wheel and a seven-ton crank shaft, which was no easy matter, owing to the design of the engine. It pays well to constantly watch for sinking or getting out of line during erection. Foundation or holding down bolts should never be “ built in,” as in case of a defective bolt or a hole in a bed plate being a little off, it is considerable of a job to make it right. The better way is to build in the wall plates, having square holes in them for the end of foundation or holding down bolts, and after placing the bed plate, the bolts can be dropped down from the top and secured by a wing cottar at the bottom, which is accessible by a hand hole left open when building the foundation. All such bolts should be placed so that they can be removed without disturbing any other part.
The form of the bed plate naturally differs with the design of the engine and individual ideas of the designer, but it is always a good plan to have a little extra weight in a bed plate, especially in the depth, as it is comparatively easy to spring any bed plate, however strong it may appear, and the fewer pieces it is in the better it is for it.
Fig. 1 is a holding down bolt made when material is highpriced and labor cheap. Fig. 2 is the same bolt made when labor is high-priced and material at average rates. In No. 1 case we have smiths at a cheap rate, and not at any high-class machine tools; whereas in No. 2 a square bar of mild steel or merchant iron is taken and cut down and shreaded in a powerful machine at one operation, and the cottar slot then punched in by the smith. No. 3 shows a section of foundation for a 10,000,000 gallon pump.