Prestressed Concrete Cylinder Pipe Freshwater and Treated Sewage Lines
Prestressed Concrete Cylinder Pipe Sewer Force Main
Prestressed Concrete Cylinder Pipe Gravity Sewer Line
Option--Intakes and Outfalls

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Prestressed Concrete Cylinder Pipe Sewer Force Main

• Scope
• Specials, Fittings, and Accessories
• Markings
• Design Data and Shop Drawings
• Restained Joints
• Pipe Installation
• Making the Joint
• Finishing the Joint
• Backfilling
• Hydrostatic Test of Completed Line

SCOPE
All concrete pressure pipe furnished under this specification shall be prestressed concrete cylinder pipe, manufactured in accordance with the AWWA Standard C301­92 for Prestressed Concrete Pressure Pipe, Steel Cylinder Type, for Water and Other Liquids. The pipe shall be furnished complete with gaskets, grout bands, and lubricant as required for proper installation and completion of the line. Pipe shall be designed for an internal working pressure of _______ pounds per square inch, a surge pressure allowance of 40 percent of the internal working pressure, and an earth cover as shown on the plans with an AASHTO HS-20 truck live load, all in accordance with the AWWA Standard C304­92 for Design of Prestressed Concrete Cylinder Pipe. The external loading shall be based on a soil density of 120 pounds per cubic foot and a bedding type R___. In addition, the pipe and any restraint system shall be suitable for a field test to a pressure equal to 120 percent of the internal working pressure.

SPECIALS, FITTINGS, AND ACCESSORIES
All specials and fittings required for bends, branches, closures, and connections shall be capable of withstanding the pressures and loads as described above. Fittings and specials shall be as described in AWWA C301­92. Outlets and other connections shall be capable of withstanding the pressures and loads as described above and shall be suitably reinforced. Long radius curves or small angular changes in the pipeline can be formed by deflecting joints of straight pipe or by using pipe sections with one end beveled not more than 4-1/2 degrees to the axis of the pipe. Flange outlets with blind flange covers shall be furnished complete with flange gaskets, nuts, and bolts. The pipe supplier shall furnish all accessories needed when restrained joints are required.

MARKINGS
Each standard pipe shall be marked to designate its strength classification. Bevel pipe and elbows shall be marked to indicate the point of maximum length. Each fitting or special shall be sufficiently marked to indicate its position in the pipeline. Pipe sections with steel cylinders thicker than standard shall also be clearly marked.

DESIGN DATA AND SHOP DRAWINGS
The pipe supplier shall make available to the contractor and/or the engineer basic design data on the prestressed pipe and shop drawings of the specials and fittings. The supplier will also make available to the contractor a pipe installation schedule indicating the sequence for installing pipe, fittings, and specials, as well as the elevations and stationing of the line at key points such as outlets, bends, and change in grade.

RESTRAINED JOINTS
As shown on the plans, pipe joints shall be mechanically restrained (harnessed) near bends, tees, bulkheads, wyes, and valves for the distances shown. The maximum longitudinal stress in the steel cylinder of harnessed pipe sections shall not exceed 13,500 pounds per square inch based on the internal working pressure or 17,000 pounds per square inch based on the test pressure and deflection angle. The steel cylinder thickness in pipe sections between the location of the maximum thrust force and the end of the harnessed section can be prorated on the basis of zero longitudinal thrust at the end of the harnessed section.

Two acceptable types of harnessed or restrained joints are the harness clamp and Snap Ring® types of flexible restrained joints. The clamp type consists of two semicircular steel clamps which fit over steel lugs that are factory welded or rolled into the steel bell and spigot sections. The semicircular clamps are drawn together by bolts at the springline on both sides of the pipe to form a flexible restrained joint.

The Snap Ring type of flexible restrained joint consists of a split steel ring which is recessed in the steel bell section of the pipe until the joint is made. Once the joint is made, the split steel ring is drawn down into position to form a lock between the bell and spigot by tightening a single steel bolt. The split steel ring, when tightened down, will provide a flexible restrained joint that will transmit longitudinal thrusts across the joint.

Both joint types shall be encased in grout after the joint has been completed using special grout bands supplied by the pipe manufacturer.

PIPE INSTALLATION
The pipe shall, at all times, be handled with equipment designed to prevent damage to the joints, or to the inside or outside surfaces of the pipe. The bottom of the trench shall be excavated to proper line and grade, shall be free of rocks, and shall provide a uniform bearing for the full length of the pipe barrel. A suitable excavation should be made at each end of the pipe to allow for the larger bell and to permit installation of the grout band.

Both the bell and spigot of the pipe sections to be joined shall be cleaned just prior to joining. A thin layer of the lubricant supplied by the pipe manufacturer shall be applied to the surfaces of the bell, spigot, and gasket. After lubrication, the gasket shall be installed in the spigot groove. The stretch in the gasket should be equalized by inserting a smooth rod under the gasket and moving the rod completely around the full circumference of the spigot.

All safety procedures for installation and testing operations shall be followed as required by federal, state, and local regulations.

MAKING THE JOINT
During joint make-up, the pipe being lowered into the trench should be supported so the jointing effort is a straight pull-in motion. The jointing effort can be aided with come-alongs, winches, dead man, or backhoe. The position of the gasket should be checked with a feeler gauge as supplied by the pipe manufacturer. If the gasket is not in place, the joint must be taken apart and relaid using a new gasket. When the gasket is found to be in the proper position with the feeler gauge, the joint can be finished as described below.

When a joint opening is needed to make a grade or alignment adjustment, the joint should be laid home first, then opened as required on one side. All joint openings must be within the recommended limits of the pipe supplier.

FINISHING THE JOINT
A grout band shall be strapped to the outside of the completed joint so that it encompasses the external joint recess. A grout consisting of one part portland cement, three parts sand, and sufficient water shall be mixed to produce a grout free of lumps and with a consistency of heavy cream. The grout shall be poured into the opening at the top of the grout band so that it completely fills the external joint recess. The grout should be rodded or puddled to ensure complete filling of the joint recess. A stiffer mix can be used to trowel over the opening at the top of the grout band.

For sanitary sewer lines, the interior, exposed surfaces of the steel joint rings shall be protected in one of the following ways:

A) The pipe supplier shall paint the portions of the joint rings that will be in contact with sewage with 8 mils of coal tar epoxy. (See Figure 1)

B) The contractor shall mortar the interior joint recess using a stiff 1:3 portland cement/sand mortar.

C) The contractor shall apply a butyl rubber mastic joint filler to the spigot end or bell socket prior to joining the pipe such that the mastic squeezes out and fills the interior joint recess.

BACKFILLING
Backfill material adjacent to the pipe shall be free from rocks, tree stumps, broken pavement, or other solid, unyielding objects. Backfill can be placed with front-end loaders or other equipment, taking care to keep the material uniform on both sides of the pipe in order to prevent shifting of the pipe. Care shall be taken to place backfill material under the haunches of the pipe for the lower one-sixth of the pipe circumference. Densification of the backfill material over the pipe shall be in accordance with the restoration requirements at grade. Heavy equipment will not be permitted over the pipe until a cover of at least 2 feet is achieved.

HYDROSTATIC TEST OF COMPLETED LINE
The completed pipeline (or completed sections of the pipeline) shall be bulkheaded, filled with water, and pressure tested to 120 percent of the internal working pressure. After the line is filled, and prior to pressure testing, it shall be allowed to soak under low pressure to allow the pipe walls to absorb water and for temperature stabilization. While filling the line, the contractor shall be responsible for properly bleeding off trapped air to avoid adversely affecting the leakage test results.

During the hydrostatic test, the contractor shall use a meter or other device to accurately measure the quantity of water necessary to maintain the test pressure on the gauge. The line will not be accepted until this measured quantity is less than 10 gallons per inch of diameter per mile of pipe per 24 hours. All visible leaks must be repaired regardless of the measured leakage.

Figure 1 - Interior joint protection with coal tar epoxy

Non-restrained and harness joint pipe

Snap Ring® restrained joint pipe