Ball and Socket Joints, Universal Pipe Joints, Compression Sleeve Joints on Pipe Systems

Let us continue again with All about Piping, Fabrication, Welding, etc. only at Piping & Fabrication, and now let us know more about Ball and Socket Joints, Universal Pipe Joints and Compression Sleeve Joints. and here the rest of them.

Ball-and-Socket Joints

FIGURE A2.31 Ball-and-socket mechanical joints

For river crossings, submarine lines, or other places where great flexibility is necessary, ductile cast-iron pipe can be obtained with ball-and-socket joints of the mechanical-gland types, as shown in Fig. A2.31. Provision is made for longitudinal expansion and contraction, and a positive stop against disengagement of the joint is a feature of the design. As much as 15_ angular deflection can be accommodated without leakage. This pipe is heavy enough to remain underwater where laid without requiring river clamps or anchorage devices. The pipe may be pulled across streams with a cable, since the joints are positively locked against separating, or it may be laid directly from a barge, bridge, or pontoons, without the services of a diver. The mechanical ball-and-socket joint is suitable for use with water, sewage, air, gas, oil, and other fluids at considerable pressure. Either bell-and-spigot or mechanical (gland-type) fittings can be used with this line of pipe, although the integral ball present on the spigot end of some designs has to be cut off before the pipe can be inserted in a regular bell.

Universal Pipe Joints

FIGURE A2.32 Universal cast-iron pipe joint

This type of cast-iron pipe joint (shown in Fig. A2.32) has a machined taper seat which obviates the need for caulking or for a compression gasket. The joint is pulled up snugly with two bolts, after which the nuts are backed off slightly, thus enabling the lock washers to give enough to avoid overstressing the socket or lugs. Pipe is made in 12- to 20-ft (3.5- to 6-m) lengths to the usual pressure classes and can be bought as Type III under Federal Specification WW-P-421. Universal-joint fittings are available for use with the pipe. This type of joint is used to some extent in pipe diameters of NPS 4 (DN 100) to NPS 24 (DN 600) for underground water supply systems; but it is not considered suitable for gas service, and it does not permit much angular displacement or expansive movement.

Compression-Sleeve Coupling

FIGURE A2.33 Compression sleeve (Dresser) coupling for plain-end
cast-iron or steel pipe

The type of joint shown in Fig. A2.33 is used with plain-end pipe of either cast iron or steel. It is widely known under the trade names of Dresser coupling and Dayton coupling. Compression sleeve couplings are used extensively for air, gas, oil, water, and other services above- or underground. With a joint of this type, it is necessary to anchor or brace solidly at dead ends or turns to prevent the line from pulling apart. Compression couplings and fittings with screwed packing glands are available for use with small-size cast-iron or steel pipe. In welded transmission lines for oil or gas where any significant change in temperature is expected, a certain percentage of the joints may be made up with compression couplings instead of welding in order to allow for expansion.