The care and patience, the mental strain and not infrequently the physical torture incident to fitting up a complicated pipe system cannot adequately be set forth in words.

It is stated to be a fact, that in high pressure hot water heating the water frequently becomes red hot, pressures of 1000 to 1200 pounds per square inch being reached, and when the circulation of the system is defective the pipe becomes visibly red in the dark.

Pipes under work benches should be avoided, unless there is an opening at the back to permit the escape of the heated air, which would otherwise come out at the front.

When both exhaust and live steam are used for heating, many engineers prefer to use independent lines of pipe for each, rather than run the risk of interference and waste caused by admitting exhaust and live steam into the same system at the same time. Nevertheless, the advantages gained by being able to increase the heating power of a system in extremely cold weather by utilizing the entire radiating surface for high pressure steam, are so great that it is probably better so to arrange the system of pipes and connections that this can be done.

Double extra heavy pipe (XX) is used for ice and refrigerating machines (see page [246]), as a general rule, makers of this class of machinery obtain but little satisfaction in the use of the ordinary thread joining and use special dies with uniform taper—both for couplings, flanges and threading the pipe itself. They do this to protect their reputation and guarantees.

Welding boiler and other tubes.—The following is a good way in cases of emergency and can be done on a common forge:

Enlarge one end of the shortest piece, and one end of the long piece make smaller, then telescope the two about 3⁄4 of an inch. Next get an iron shaft as large as will go into the tube and lay across the forge with the tube slipped over it. Block the shaft up so that the tube will hang down from the top of the shaft. By such an arrangement the inside of the tube will be smooth for a scraper. When the tube gets to a welding heat strike on the end of the short piece first, with a heavy hammer, then with a light and broad-faced hammer make the weld. Borax can be used to good advantage, but it is not necessary. The next thing is to test the tube, which can be done in the following manner: Drive a plug in one end of the tube, stand it up on that end, and fill it with water, if it does not leak the job is well done, if a leak exists the welding must be again done.

Solid-drawn Iron Tubes: Calculated Bursting and Collapsing Pressures.

External
Diameter.		Thickness.Internal
Diameter.		Bursting Pressure.Collapsing Pressure.
Per Square
Inch of
Internal
Surface.		Per Square
Inch of
Section
of Metal.		Per Square
Inch of
External
Surface.		Per Square
Inch of
Section
of Metal.
Inches.Inch.Inches.Lbs.Tons.Lbs.Tons.
11⁄4.0831.084770022.4650021.7
13⁄8.0831.209690022.4580021.3
11⁄2.0831.334620022.4520021.0
13⁄4.0831.584530022.4430020.3
2.0831.834450022.4370019.7
21⁄4.0952.060460022.4360019.0
21⁄2.1092.282480022.4360018.3
23⁄4.1092.532440022.4310017.7
3.1202.760430022.4300017.0
31⁄2.1343.232420022.4270015.7
33⁄4.1343.482390022.4240015.0
4.1343.732360022.4210014.3
41⁄2.1344.232320022.4170013.0
43⁄4.1344.482300022.4160012.3
5.1344.732280022.4140011.7
51⁄2.148 5.204280022.4120010.3
6 5.704260022.41000 9.0