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Unformatted text preview: his standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties to agreement based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated in Annex A. pressure + 0.1 N/mmz, for working upto 1 N/mmz, and pressure + 0.2 N/mmz, for working above 1 N/mm* . 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. 3 TERMINOLOGY For the purpose of this standard, the following definitions shall apply. 4 MATERIALS 3.1 Prestressed Concrete CyIinder 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. The cement used in the manufacture of prestressed concrete pipes and specials shall be one of the following: 4.1 Cement a) 43 grade ordhmry Portland cement conforming to IS 8112. b) 53 grade ordinary Portland cement conforming to IS 12269, c) Rapid hardening Portland cement conforming to IS 8041. d) Portland slag cement conforming to IS 455 with slag not more than 50 percent. e) Sulphate resisting Portland cement conforming to IS 12330. 3.2 Prestressed Concrete Non-Cylinder Pipe — A suitably compacted concrete core longitudinally prestressed with pretensioned high tensile steel wire embedded in the concrete, circumferentially prestressed and coated with cement mortar or concrete to protect the circumferential prestressing wire, to withstand internal pressure and external design loads. NOTE — Sulphate misting Portland cement shsll be used where sulphate is predominant. 3.3 Specials — All items in the pipeline other than straight pipes of standard length, such as bendi, air valves and scour valve tees, etc, are classified as specials. 4.2 Aggregates The aggregates shall conform to IS 383. The provision of4 (Grading) of IS 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 3.4 Working Pressure — The maximum sustained internal pressure excluding surge to which each portion of the pipeline maybe subjected when installed. 1 — ,.. IS 784:2001 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. Following composition of natural rubber is recommended for sealing rings: Natural rubber content as compound Ash Total sulphur Acetone extract Sulphur in acetone extract...
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This document was uploaded on 10/01/2013.

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