The Mechanical Joint (MJ) Coupled Joint offers a method of providing joint restraint with a standard mechanical joint socket of a pipe, fitting, valve or other product. It is available in sizes 4" through 12" with a pressure rating of 350 psi and deflection capability up to 2 1⁄2°, and in 14" through 54" with a pressure rating of 250 psi intended for installation in essentially straight alignment. Check AMERICAN if larger sizes or greater deflections are desired. The MJ Coupled Joint is commonly used as a method of joint restraint for mechanical joint all-bell fittings and especially to restrain MJ valves.
The joint material consists of a standard mechanical joint gasket and a standard ductile iron joint gland. The restraint gland1 is ductile iron and is factory assembled on the pipe behind a welded-on 1⁄2" square alloy steel retaining ring. All MJ Coupled Joint restraining hardware is recommended to be Type 304 stainless steel. Tee-head bolts are special-length bolts.
Note: It is sometimes possible to provide for field-cutting and positive, even “drop-in” field-adaptable restraint in restrained piping areas by using modified MJ Coupled joints where the weld ring and restraint gland are intentionally moved farther away from the joint, and the standard short studs of the joint are replaced by longer threaded rods in the field. Threaded rods, of course, can also be cut to suit in the field. Similar effect can also be accomplished utilizing standard fabricated, stuffing-box couplings and similarly modified “Coupling Gland Ends.” Contact AMERICAN for additional information on this.
1.) The restraint gland for 30"-54" sizes is a substantially rectangular cross-section ductile iron gland.
Pressure classes are defined as the hydrostatic water working pressure of the pipe in psi. The thicknesses shown are adequate for the rated hydrostatic working pressure plus a surge allowance of 100 psi with a safety factor of 2.0 for that sum. Calculations result in net thicknesses and are based on a minimum yield strength in tension of 42,000 psi and 2.0 safety factor times the sum of working pressure and 100 psi surge allowance.
Thickness can be calculated for rated hydrostatic working pressure and surges other than the above by use of equation 1 in ANSI/AWWA C150/A21.50.
AMERICAN ductile iron pipe is available for hydrostatic working pressures greater than 350 psi – for special applications, contact AMERICAN.
These are standard pressure classes as given in AWWA C150 and C151. AMERICAN can furnish any thickness in between these standard thicknesses if deemed desirable for major projects.
Size | OD | Pressure Class | ||||
|---|---|---|---|---|---|---|
150 | 200 | 250 | 300 | 350 | ||
Nominal Thickness in Inches | ||||||
4 | 4.8 | - | - | - | - | 0.25 |
6 | 6.9 | - | - | - | - | 0.25 |
8 | 9.05 | - | - | - | - | 0.25 |
10 | 11.1 | - | - | - | - | 0.26 |
12 | 13.2 | - | - | - | - | 0.28 |
14 | 15.3 | - | - | 0.28 | 0.3 | 0.31 |
16 | 17.4 | - | - | 0.3 | 0.32 | 0.34 |
18 | 19.5 | - | - | 0.31 | 0.34 | 0.36 |
20 | 21.6 | - | - | 0.33 | 0.36 | 0.38 |
24 | 25.8 | - | 0.33 | 0.37 | 0.4 | 0.43 |
30 | 32 | 0.34 | 0.38 | 0.42 | 0.45 | 0.49 |
36 | 38.3 | 0.38 | 0.42 | 0.47 | 0.51 | 0.56 |
42 | 44.5 | 0.41 | 0.47 | 0.52 | 0.57 | 0.63 |
48 | 50.8 | 0.46 | 0.52 | 0.58 | 0.64 | 0.7 |
54 | 57.56 | 0.51 | 0.58 | 0.65 | 0.72 | 0.79 |
60 | 61.61 | 0.54 | 0.61 | 0.68 | 0.76 | 0.83 |
64 | 65.67 | 0.56 | 0.64 | 0.72 | 0.8 | 0.87 |
