CHAPTER I

PIPE FITTINGS

The Pipe.-Somewhere in the extension issue of Aesop's Fables, there is a little story where clever grandpa is trying to explain to his grandson how iron pipe is made. Says he: "It is very simple, my boy; all they do when making pipe is to take a hole and put iron around it. Small hole, small pipe; large hole, large pipe."

"But tell me, grandpa," asked the boy, "where do they get their different sizes of holes from?"

The moral of the above is that any subject seems to be simple until one asks questions about it and the subject of pipe and fittings for railway rolling stock is one on which many perplexing questions may be raised and which to answer, either in part or as a whole, is the purpose of this book.

Manufacture of Pipe.-The manufacture of wrought iron tubes which we call pipes originated in England in the early part of the last century. About the year 1834 the firm of Morris, Tasker and Morris began to make the first wrought iron pipe in the United States at Philadelphia, Pa. Later, it started a tube mill known as the Pascal Iron Works. About 15 years after, a tube plant was erected at Malden, Mass. The principal owners of this plant were the firm of Walworth and Nason of Boston, Mass.

From these early beginnings, the manufacture of pipe increased with each year to a large extent. As the price of high grade pig iron increased (this being the material from which wrought iron pipe is made) and the demand for pipe became still greater, inventive geniuses set to work to produce cheaper pipe by other methods of manufacture.

Steel Pipe. This resulted, in the year of 1886, in the manufacture of mild or soft steel pipe. The difficulties previously experienced in welding steel skelp or plate from which steel pipe is made, had gradually been overcome by improvements and thereupon the manufacture of steel pipe was started on a large scale. However, at first the pipes were hard in spots and the pipe fitters had trouble in threading them, partly due to the old-fashioned pipe threading dies then in use in many places. Since then much progress has been made, both in the quality of the material and in the processes of manufacture.

There is much high grade steel pipe made today that is soft and tough, easy to bend, and there is no trouble to cut good clean threads on it. This is true provided improved cutting dies, or so-called chasers are used. These must be kept sharp and have proper lip angle and clearance, as will be more fully explained later. It is also important that sufficient and good lubricating oil is used. This is necessary because of the higher friction encountered in threading steel pipe as compared with wrought iron pipe. Dies suitable for steel pipe can also be used on iron pipe; but blunt dies that will still cut a good thread on iron pipe will tear the thread on steel pipe, owing to the softness and toughness of the metal. It must also be observed that steel pipe cannot be cut quite as fast as iron pipe, and that the pipe and dies must

be kept reasonably cool to prevent excessive friction and expansion of the metal; therefore, the need of good thread cutting oil. Fig. 1 illustrates the difference between iron and steel pipe chips.

Iron

Steel

Fig. 1. The wrought iron threading chips break up like wood turnings; the steel chips are long and curl up inside the chip space, increasing friction on the dies

From an examination of these chips, it can easily be understood why more chip space and a greater lip angle of chaser is necessary when cutting Bessemer steel or Open Hearth steel pipe.

As steel pipe costs less to manufacture than good iron pipe and is therefore correspondingly lower in price, its production now greatly exceeds that of iron pipe. When new, it has a higher tensile strength than wrought iron. That is, if a piece of pipe of each kind of a given size of same weight were subjected to a stretching test, the power to pull the steel pipe apart would be higher. Such a test is referred to as a pipe's tensile strength.

On the other hand, it is reliably claimed that after a few years' service steel pipe loses much of its tensile

strength and is known at times to crystallize as a result of vibration, causing "fatigue."

Because pipe used on engines and cars, especially air brake, signal and steam train line pipe, is subject to very severe service due to vibration, shocks, expansion and contraction, sometimes in rapid succession, exposure and drippings from cars, wrought iron pipe has been favored by some railroads. The principal reason is that it is much less affected by rust or corrosion than steel, and therefore iron pipe lasts much longer and renewals are less frequent.

How to Distinguish Iron from Steel Pipe. It is not easy to determine from its appearance whether pipe is iron or steel. Iron pipe is rough and has small fibrous ridges running lengthwise and the scale on it is heavy, whereas the scale on steel pipe is very light and shows small bubbles or blisters, underneath which the surface is smooth and white. On a flattening test, iron pipe usually breaks before steel. On the other hand, steel pipe will open more readily in the weld than iron under a test. Upon fracturing steel pipe, it will be noted that the grain is much finer than that of iron pipe.

Test of Pipe by Filing.-A quick and easy test for determining the material from which pipe is made is to file a bright smooth surface about 2 inches square on the pieces of pipe to be inspected. If the bright surface shows fine hair lines running parallel to the length of the pipe, it is wrought iron pipe, because those hair lines are the fibres of siliceous slag. It is for the presence of this silicate-phosphate of iron which envelopes and protects the pure grains of iron, that gives to good wrought iron pipe its rust resisting properties.

If the surface does not show any of these fine threads or ribbons, the material is steel.

Acid Test of Pipe to Ascertain if Iron or Steel.Cut off a short piece of pipe and file the end smooth to remove the marks of the cutting tool. Then suspend the piece of pipe in a solution of nine parts of water, three parts sulphuric acid and one part muriatic acid. Place the water in a glass dish. Add the sulphuric and then the muriatic acid. Next suspend the pipe in such a way that the end will not touch the bottom of the dish. After two hours' immersion, remove the piece of pipe and wash off the acid. If the pipe is iron, it will show faint ridges or rings, displaying the different layers of iron and streaks

Fig. 2. Test sample of wrought iron and steel pipe

of silicate slag or cinder. If the pipe is steel, the end will present a bright, solid, unbroken surface much finer in appearance than iron. When making this test, care must be taken not to mistake the file marks for the hair like circular ridges of iron pipe.

Fig. 2 shows a test sample of both kind of pipes. Galvanized iron pipe of smaller sizes is the regular wrought pipe, coated inside and outside with a covering of zinc. The dimensions are the same as those for black or plain pipe given in Table 1.

The use of galvanized pipe is preferable for purposes where excessive corrosion shortens the life of common black pipe, such as on refrigerator cars and other cars