The Art of projection and complete magic lantern ... - Yesterday Image

—70obstruction and consequent unevenness of flow. You can easily verifythis by holding your hand on the mouth of cylinder valve."STRENGTH OF CYLINDERS FOR COMPRESSED GAS.By Keith S.Murray.(Extract from Engineering Revieiv.)" There are two kinds of steel bottles generally in use for the transportof gases at high pressure. They are known in the trade as lapweldedand solid drawn. Both are made of mild wrought steel, with thedifference that the lapwelded bottles are rolled and welded up likeordinary tubes, whilst the solid drawnbottles are formed from a circularslab, or a circular block of steel, which by repeated heating and pressingin suitable dies is moulded into a tube with a spherically closed end.The process of solid drawing acts beneficially on the strength and rigidityof the metal, it has been found from tests made that the ultimate tensilestrength of this metal is about 66,000 lbs. per square inch, as comparedwith about 54,000 per square inch in the case of welded bottles.The solid drawn bottles are consequently lighter, neater, and perhapsmore reliable than the lapwelded, and although rather more expensive,are slowly but surely superseding the older lapwelded type, moreespecially in the smaller sizes. All bottles, or at any rate all theseemployed for non-liquified gases, are made to contain a certain easilymeasurable quantity of gas at a pressure of 120 atmospheres, which isthe recognised standard pressure.Both classes of bottles are now made of three common externaldiameters, viz., 4in., 5|in. and yin. and they vary in length according tothe quantity of gas they are required to contain at the standard pressure.The thickness of these bottles is as follows :External diameter, 4