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Unrestrained Joint Pipe

Mechanical Joint Pipe

The AMERICAN mechanical joint, furnished in pipe sizes 4” to 12” and in fitting sizes 4” to 48”, is a flexible stuffing box type connection used primarily in underground service.

The AMERICAN mechanical joint was developed by the American Cast Iron Pipe Company and first marketed in 1929. Since that time, millions of feet of AMERICAN pipe equipped with this joint have been installed to give dependable service across the nation and in many foreign countries. The joint is designed with a stuffing box into which a rubber gasket is compressed by a ductile iron gland drawn up with low-alloy steel bolts. It affords liberal deflection before joint compression and allows expansion and contraction of the line without leakage. It is rated for a water working pressure of up to 350 psi.

Originally designed to meet the rigid requirements of the gas industry for a pressure-tight joint, the AMERICAN mechanical joint was instrumental in starting a nationwide trend toward rubber-packed joints for water service as well as gas service. Its design was widely accepted and it soon became the standard joint of the iron pipe industry.

The popularity of the AMERICAN mechanical joint among utility officials, contractors and engineers steadily increased until the majority of cast iron piping furnished for gas, water, sewage and other services was equipped with this joint. However, push-on joint pipes, which are less labor intensive and compatible with push-on or mechanical joint fittings, currently make up the vast majority of ductile iron pipelines being installed for underground service. Mechanical joint pipe is now used to a much lesser extent.

The AMERICAN mechanical joint meets the requirements of ANSI/AWWA C110/A21.10 and ANSI/AWWA C111/A21.11.

AMERICAN ductile iron mechanical joint pipe is centrifugally cast in nominal 20’ laying lengths under rigid production and quality control procedures in accordance with ANSI/AWWA Standards. AMERICAN mechanical joint ductile iron pipe is produced in 4”-12” sizes and in special thickness class 53 only.

The AMERICAN mechanical joint provides easy installation under the most adverse conditions. Plain rubber gaskets of SBR are normally used for water and domestic sewage service. Fabric tipped plain rubber gaskets are available, as well as other special gaskets such as oil-resistant rubber. Plain rubber gaskets or tipped gaskets are used for air or liquid temperatures up to 120°F. For applications involving temperatures in excess of 120°F, or for other special service applications, and for installations in contaminated soils where permeation through gaskets might be a concern, consult AMERICAN for recommendations. See Table No. 2-6.

Standard joint accessories furnished with mechanical joint pipe and fittings include ductile iron glands, low-alloy steel tee head bolts with hex nuts and plain rubber gaskets.

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Maximum Depths of Cover

for American Mechanical Joint Pipe ANSI/AWWA C151/A21.51

This table tabulates the maximum depth of cover for the five types of laying conditions, along with corresponding nominal wall thickness and maximum rated working pressure, all for special thickness class 53 ductile iron pipe. AMERICAN mechanical joint pipe is available only in special thickness class 53.

Minimum allowable depth of cover is 3’.
For depths less than 3’, consult AMERICAN.

Size (in.)

Thickness (in.)

Laying Conditions –
Maximum Depth of Cover (ft.)1

Type 1

Type 2

Type 3

Type 4

Type 5

4

0.32

1002

1002

1002

1002

1002

6

0.34

78

89

1002

1002

1002

8

0.36

55

63

71

88

1002

10

0.38

40

46

53

66

87

12

0.40

33

39

45

57

76

1 An allowance for single H-20 truck with 1.5 impact factor is included for all sizes and all depths of cover.

2 Calculated maximum depth of cover exceeds 100’.

Standard Laying Conditions

ANSI/AWWA C150/A21.50 ANSI/AWWA C151/A21.51

Flat-bottom trench.1 Loose backfill. (Not recommended for 14" and larger pipe.)
Flat-bottom trench.1 Backfill lightly consolidated to centerline of pipe.
Pipe bedded in 4” minimum loose soil.2 Backfill lightly consolidated to top of pipe.
Pipe bedded in sand, gravel or crushed stone to depth of 1/8 pipe diameter, 4” minimum. Backfill compacted to top of pipe. (Approximately 80% Standard Proctor, AASHTO T-99.)
Pipe bedded to its centerline in compacted granular3 material, 4” minimum under pipe. Compacted granular or select material2 to top of pipe. (Approximately 90% Standard Proctor, AASHTO T-99.)

1 “Flat-bottom” is defined as undisturbed earth.

2 “Loose soil” or “select material” is defined as native soil excavated from the trench, free of rocks, foreign material and frozen earth.

3 Granular materials are defined per the AASHTO Soil Classification System (ASTMD3282) or the Unified Soil Classification System (ASTM D2487), with the exception that gravel bedding/backfill adjacent to the pipe is limited to 2" maximum particle size per ANSI/AWWA C600.

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