MS PSC Pipe Mould

This standard covers the requirements of prestressed concrete pipes (including specials) with nominal internal diameter in the range of 200 mm to 2 500 mm (see Note under Table 1), in which permanent internal stresses are deliberately introduced by tensioned steel to the desired degree to counteract the stresses caused in pipe under service.

Materials

For the purpose of this standard, the following definitions shall apply.

3.1 Prestressed Concrete Cylinder Pipe - A welded sheet steel cylinder with steel socket and spigot rings welded to its ends, lined with concrete suitably compacted and circumferentially prestressed to withstand internal pressure and external design loads and subsequently coated with cement mortar or concrete to protect the steel cylinder and prestressing wires.

3.2 Prestressed Concrete Non - Cylinder Pipe -A suitably compacted concrete I core longitudinally prestressed with pretensioned high tensile steel wire embedded in the concrete, circumferentially pre- stressed and coated with cement mortar or concrete to protect the circumferential prestressing wire, to withstand internal pressure and external design loads.

3.3 Specials - All items in the pipeline other than straight pipes of standard length, such as bends, air valves and scour valve tees, etc, are classified as specials. 3.4 Working Pressure - The maximum sustained internal pressure excluding surge to which each portion of the pipeline may be subjected when installed.

3.5 Site Test Pressure - 1.5 times working pressure pertaining to the section or 1.1 times static pressure, whichever is more (surge pressure is to be controlled within 25 percent of pump head in case of pumping main).

3.6 Factory Test Pressure - a) Site test pressure + 0.1 N/mm2, for working pressure upto 1 N/mm2, and b) Site test pressure + 0.2 Nzmm", for working pressure above 1 N/mm1

3.7 Surge (Water Hammer) Pressure - It is a pressure which is produced by a change of velocity of the moving stream and becomes maximum when there is sudden stoppage which may be caused by the closing of a valve or by shutting down a pump station. Surge pressure is to be controlled within 25 percent of pump head.

Materials

4.1 Cement

4.2 Aggregates- The aggregates shall conform to IS 383. The provision of N (Grading) ofIS 383 shall not apply. Manufacturer shall furnish the grading curve for coarse and fine aggregates which he proposes to use. The variation in fineness modulus during manufacture shall not be more than ±5 percent. Silt content in fine aggregates shall be less than 3 percent. The fineness modulus of the aggregates for coating shall be between 2.6 to 3.2.

4.3 Water- Water used for concrete, cement mortar and for curing the pipes shall be free from injurious amounts of oil, acid, strong alkaline scales and vegetable matter and shall be able to make concrete of satisfactory strength requirements

4.4 Admixtures- Admixtures may be used with the approval of the purchaser. However, use of any admixture containing chlorides in any form shall be prohibited. The admixtures shall conform to IS 9103.

4.5 Steel for Reinforcement

4.5.1 Prestressing Steel- Prestressing steel wire shall conform to IS 1785 (Part 1) or IS 1785 (Part 2) or IS 6003 or IS 6006. For longitudinal prestressing, wire having tensile strength, less upto 15 percent of ultimate tensile strength, may be used, if required. This is to avoid excessive wear of rollers for threading, or cracking of wire during button heading for end anchors.

4.5.2 Untensioned Reinforcement - Un tensioned reinforcement may consist of mild steel conforming to IS 432 (Part 1) or IS 432 (Part 2) or high strength deformed bars conforming to IS 1786 or plain hard drawn steel wire conforming to IS 1785 (Part 1) and IS 1785(Part 2) or welded wire fabric conforming to IS 1566.

4.6 Steel for Cylinders and Specials- Steel plates for cylinders and specials shall conform to IS 2062.

4.7 Rubber Sealing Rings

4.7.1 Rubber sealing rings shall comply with IS 5382. The manufacturer of pipe shall examine each sealing ring visually for defects, particularly at the joints.

4.7.2 Every sealing ring shall be clearly marked. The marking shall indicate the chord diameter, internal diameter of the ring and name of the manufacturer of rubber sealing rings.

4.7.3 In case of splices, each splice shall be thoroughly visually checked by twisting the ring through 360°. Splices showing visible separation or cracks shall be rejected. Not more than two splices in each ring shall be permitted. All sealing rings shall be protected from direct rays of the sun and stored in dry place.

4.7.3 In case of splices, each splice shall be thoroughly visually checked by twisting the ring through 360°. Splices showing visible separation or cracks shall be rejected. Not more than two splices in each ring shall be permitted. All sealing rings shall be protected from direct rays of the sun and stored in dry place.