《03PIPE amp; VALVE》.pdf

CITY UNIVERSITY OF HONG KONG DIVISION OF BUILDING SCIENCE AND TECHNOLOGY Course: BST21541 Piped Services Chapter 3 Pipes Valves 1. Pipes Pipes are used for the transport of liquids or high pressure gases. By far, the most common is the circular section which has several outstanding advantages which account for this preference: a) The circular section gives maximum cross sectional area-to-perimeter ratio and hence minimum flow loss for a given fluid discharge. Note: This assumes the pipe is running full (under pressure). If the pipe is not full (flowing under gravity), a circular section does not give the lowest flow loss. b) The circular section has maximum strength for a given area and wall thickness (due to absence of corners). c) The circular section lends itself readily to mass production techniques and hence is usually the most economical section to produce. 1.1 Materials for Pipe Pipes and fittings shall conform to Schedule 2 of the Waterworks Regulations. From time to time the Water Authority may approve other pipe materials for use in cold water, hot water or salt water inside service. The following pipe materials may be used in cold water, hot water or salt water inside service as appropriate: 1.1.1 cast iron pipe to BS EN 416, BS EN 437, BS 4622; 1.1.2 ductile iron pipe to BS EN 545: 1.1.3 copper pipe to BSEN 1257 and BSEN12449; 1.1.4 unplasticized polyvinyl chloride (uPVC) pipe to BS EN 1452; 1.1.5 chlorinated polyvinyl chlori