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Maximum Depths of Cover

for Minimum Pressure Classes of Ductile Iron Pipe
ANSI/AWWA C151/A21.51

2 1 2 2 5 Fr Max Depths Of Cover Print

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 minimum pressure classes of ductile iron pipe. Taken from the table that follows, it is offered as a convenience for quickly checking the capabilities of minimum pressure classes of ductile iron pipe under a given set of conditions.

For the majority of internal pressure and external loading conditions, minimum pressure classes are more than adequate and possess substantial safety factors.

Size (in.) Pressure Class Thickness (in.) Laying Conditions Maximum Depth of Cover in Feet1
Type 1 Type 2 Type 3 Type 4 Type 5
60 150 0.54 see3 52 9 13 20
64 150 0.56 see3 52 9 13 20
1.) An allowance for single H-20 truck with 1.5 impact factor is included for all sizes and all depths of cover.
2.) Minimum allowable depth of cover is 3’. For depths less than 3’, consult AMERICAN.
3.) Laying condition Type 1 is limited to 12" and smaller pipe. For 14" and larger pipe, laying condition Type 1 should not be used.
4.) Calculated maximum depth of cover exceeds 100’.

Maximum Depths of Cover

for All Pressure Classes of Ductile Iron Pipe
ANSI/AWWA C151/A21.51

This table lists maximum depths of cover for the five types of laying conditions for all standard pressure classes; also tabulated are the corresponding nominal wall thickness and maximum rated working pressure. (Note: Although not listed in the following table, ductile iron pipe for working pressures higher than 350 psi is available. Consult AMERICAN regarding specific conditions involved.)

Size (in.) Pressure Class psi1 Nominal Thickness (in.) Laying Conditions
Maximum Depth of Cover in Feet6
Type 1 Type 2 Type 3 Type 4 Type 5
60 150 0.54 see9 57 9 13 20
60 200 0.61 see9 8 11 14 22
60 250 0.68 see9 10 13 16 24
60 300 0.76 see9 13 15 19 26
60 350 0.83 see9 15 18 22 30
64 150 0.56 see9 27 9 13 20
64 200 0.64 see9 8 11 14 21
64 250 0.72 see9 10 13 16 24
64 300 0.8 see9 12 15 19 26
64 350 0.87 see9 15 17 21 29
5.) These pipes are adequate for the rated working pressure indicated for each nominal size plus a surge allowance of 100 psi. Calculations are based on a 2.0 safety factor times the sum of working pressure and 100 psi surge allowance. Ductile iron pipe for working pressures higher than 350 psi is available.
6.) An allowance for a single H-20 truck with 1.5 impact factor is included for all sizes and all depths of cover.
7.) Minimum allowable depth of cover is 3’. For depths less than 3’, consult AMERICAN.
8.) Calculated maximum depth of cover exceeds 100’.
9.) Laying condition Type 1 is limited to 12" and smaller pipe. For 14" and larger pipe, laying condition Type 1 should not be used.

For other conditions not covered in these tables see AWWA C150 or consult AMERICAN for design of pipe thickness. Special thickness classes may be appropriate in such cases.

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