4. ;Oxygen cylinders should not be exposed to temperatures exceeding 100° F.

5. ;Take care not to lay hot welded or cut material on or alongside oxygen cylinders, and great care must be taken never to allow the blowpipe flame or the heat from same to impinge upon the oxygen cylinder. No cylinders should be in immediate proximity to the cutting blow-pipe when the latter is in use or alight.

6. ;Carefully avoid the use of oil or grease, or lubricants in any form upon the cylinder valves or fittings, and keep same dry and free from grit.

7. ;Never use keys of long leverage to close cylinder valves. They give undue power which is injurious to the valves and frequently result in broken valve spindles. If the valve leaks when closed with the ordinary lever key, it is often due to grit. To remove this, open the valve slowly and then close it sharply.

8. ;After disconnecting a cylinder before it is empty it is desirable to test for leakage by pouring some water into the valve socket. If no bubbles appear in the water, it proves that the valve is gas-tight. The valve-gland can be tested in the same way at any time when the valve is open, and a regulator attached, by pouring water into the recessed part of gland nut round the spindle. The gland nut must be tightened up, if necessary, to prevent leakage.

9. ;See that all socket and nipple ends are in good order and free from grit before fixing regulators or other fittings into valves.

A good way of ensuring this is to snift a little oxygen through the valve before inserting the regulator or other fitting.

10. ;Never open the cylinder valve suddenly when the regulator is attached. The valve should be opened by tapping the key gently with the hand.

Always shut the cylinder valve when cylinder is empty, or not in use.

11. Store cylinders under cover in an outhouse or in a portion of the premises most remote from any source of fire risk. Avoid as much as possible exposing cylinders to conditions which promote oxidation and return empty cylinders to the oxygen factory as quickly as possible, always with the valves closed. A quick turnover, and reasonable care of cylinders and their valves, on the part of users, helps materially to cheapen the price of oxygen.

Instructions and Precautions for operating Metal Cutting Blowpipes.

-We have dealt separately with the various components of a complete oxy-acetylene metal cutting unit. Here we shall indicate the Instructions and Precautions which should be observed in starting up and operating the metal cutting process.

1. ;Oxygen Cylinder.-Read carefully through the notes under the heading of li Oxygen Cylinders," page 88.

2. ;The oxygen cylinder should be fixed, preferably in a vertical or inclined position, sufficiently distant from the cutting job to ensure that the cutting blowpipe flame cannot by any mischance impinge upon it.

3. ;Open the cylinder valve sharply and snift a little gas through the valve socket to remove any dirt before attaching the regulator (Fig. 52) ; also examine the socket to make sure that it is clean and free from traces of oil.

4. ;Regulator.-Couple up the oxygen regulator to the cylinders after making sure that it conforms with the conditions specified under the heading " Endurance Pressure Regulator," page 82.

5. ;Open the regulator outlet valve.

6. ;Open the oxygen cylinder valve slowly by tapping the extended lever key with the hand, and allow a flow of gas to escape.

7. ;Close the regulator outlet valve and watch the pressure gauges. The high pressure gauge should register about 120 atmospheres on a cylinder which has not been previously used.

8. ;To ascertain that a tight connection has been made between the cylinder valve and the regulator, close the cylinder valve, thus retaining the pressure in the regulator. If the high pressure gauge finger remains stationary, the joint between the valve and the regulator is tight. If, on the other hand, the finger of this gauge falls, the joint is leaky and must be tightened up by screwing the fly-nut down until a sound joint is obtained.

Tubing between the Regulator Outlet Valve and Metal Cutting Blowpipe.-For the regulator, used when cutting metal up to about 4in. thick, canvas and rubber tubing |in. bore should be used.

For the regulator used when cutting steel from 4in. to 15in. thick, and for cast iron cutting, canvas and rubber tubing 7/16in. bore should be used for both oxygen and acetylene supplies.

For outdoor work, or in any place where the tubing is liable to be chafed or ill-used, armoured tubing is recommended.

We recommend that a clip should always be used for attaching the tubing to a blowpipe or regulator ; this makes a better and easier joint than wire and does not damage the tube.

Before using, always blow through the tubing by means of high pressure air.

The importance of removing all fine particles of dust from the tubing will be appreciated when it is remembered that the oxygen used in conjunction with acetylene has to pass through the fine injector nozzle z (Figs. 49 and 50) of the cutting blowpipe.