SANS 10120-3 L-1983 Code of practice for use with standardized specifications for civil engineering construction and contract documents Part 3 Guidance for design Section L Medium-.pdf
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1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. SABS 0120 : Part 3 Section L-1983 Medium-pressure pipelines PART 3 : GUIDANCE FOR DESIGN SECTION L CONTENTS Clause 1 . 1.1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.5
4、1.2 1.2.1 1.3 1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 1.3.6 1.3.7 1.3.8 1.3.9 1.3.10 2 . 2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.3 2.3.1 2.3.2 2.4 2.4.1 2.4.2 2.4.3 2.5 2.5.1 2.5.2 2.6 2.6.1 2.7 2.7.1 2.7.2 2.7.3 3 . 3.1 4 . 4.1 5 . 5.1 5.2 Page Number PRE-TENDER CONSIDERATIONS 1 Inves
5、tigations 1 Type of pipe and corrosion protection 1 AC pipes. COD type . 1 Protection against electrolytic corrosion 1 Laying. depths. and cover 1 Brickwork 1 . Administration 1 Payment for trench excavation 1 Documentation 1 General 1 Protection of steel pipes l . Specifying and selection l . Excav
6、ation 1 . Valve chambers 1 Clearances inside chambers and manholes 1 Brickwork for manholes and chambers 1 Disinfection of potable water pipelines 1 Test pressures . 1 Measurement and scheduling of excavation quantities 1 DESIGN CONSIDERATIONS 2 Design criteria . 2 General 2 Design of bedding for pi
7、pes . 2 . Detail on drawings 2 Intersecting services 2 Materials 2 Flexible pipes . 2 AC pipes 2 Steel pipe wall thickness 2 . Flexible couplings 2 Protection of bolts. etc 2 Depths and Covers 2 . Depth of water mains in reticulation and wrks layouts 2 Measurement and payment considerations 3 Valves
8、 . 3 Bypass valves 3 Air valves . 3 Fire hydrants 3 Ancillaries 3 Concrete encasing 3 Thrust blocks 3 Tolerances . 5 Tolerances in manholes and other structures 5 Testing 5 Test pressures . 5 Test requirements 5 Leakage rates 5 APPLICABILITY OF OTHER CODES . 5 General . 5 TEST PROCEDURES 5 General 5
9、 OIJALITY CONTROL b) certain plate thicknesses are to be preferred because they are stock sizes and more readily available than other thicknesses. Non-standard thicknesses require special rolling6 and even though the mass of steel involved is lower than for pipes of standard thickness, the pipes may
10、 be more expensive. The use of non-standard thicknesses may also lead to expensive delays on the works because of supply problems. Flexible Couplings (Subclause 3.8.2) The coupling arrangement shown on Drawing 13.1 is expensive and is not intended for use where long lenqths of pipe are coupled toget
11、her. It is specifically meant for use in positions where it is desirable to be able to uncouple a joint relatively quickly and without complications, either to gain access to the pipeline or to replace a valve or special during make-and-break maintenance operations. Under these conditions it pays to
12、 have a machined collar onto which the coupling can seal. Because only relatively few such couplings are used, the additional expense is warranted. Do not use machined collars as shown on Drawing L-3.1 where standard (flexible) couplings with centre register are scheduled. Where RC pipes and steel s
13、pecials are used, a machined collar is essential because the AC triplex coupling cannot tolerate ovality. Use (and schedule separately) pipes with machined collars and slip-on couplings without a centre register but with centre locating studs as shown on Drawing L-3.1, at the entry to each pump stat
14、ism, on one side of each important in-line valve, and in other locations where relatively frequent make an9 break maintenance operations are likely to occur. Use (and schedule separately) slip-on type couplings without a centre reqister and conforning to Drawing L-3.1 (except that the collars do not
15、 have to he machined) where closure pieces are required. Protection of bolts, ekc. (Subclause 3.9.6). Specify suitable painting procedures (or stainless steel) for bolts, etc., to be used inside pumpstations and the like. Protection of bolts and nuts against corrosion in all areas facilitates mainte
16、nance. DEPTHS AND COVERS Depth of Water Mains in Reticulation and Works Lay_uw (Subclause 5.1.4). Because the depths of cover .- over water mains, elect.rica1 service ducts, and stormwater pipes are normally kept to a minimum, and because these services frequently cross one another, conflict between
17、 specified covers an3 other requirements is common in reticulation and similar projects. Anticipate these problem areas and prepare detail drawings and project specification clauses to dispose of the problems. A typical example of a solution tn such a problem is set out in Subclauses 3.2.6 and 3.2.7
18、 of Section I. of Part 2 of the code. (See also 2.4.3 below and Subclause 3.2.5 of Sect-ion L of Part 5 of the code.) 3) In course of preparation for the Uepartmet of Communsty Develupmrnt. 4) GLASS WL, Bactella in steel plpellnes, Thr rlvil englneer sn South hfrica, Vol. 23, No. 9 September 1981. P
19、- 5) Bedding pipes). 6) Electric welded low carbon steel plpes for aqueous flusds (ordinary duties). SABS 0120 : Part 3 Section L-1983 Medium-pressure pipelines Measurement and Payment Considerations. Determine and schedule a minimum depth of excavation that slightly exceeds the depth needed for the
20、 bulk of the route of the pipeline after allowing for the specified depth of bedding and outside diameter of the pipe. By so doing, the payment of the next incremental rate for minor increases in trench depth can be avoided. VALVES Bypass Valves (Subclause 5.3). Consider the fitting of a separate by
21、pass valve (of cross-sectional area about 10-15 % of that of the main valve) to each valve of nominal diameter over 300 mm. This should be standard practice as the bypass not only helps to equalize the pressure on the valve faces but also helps to reduce water hammer, provided that first the main va
22、lve and then the bypass valve are closed. Air Valves. Where an air valve is so located that it may be subject to inundation by ground or surface water, ensure (if possible) that the air valve cover is above ground level. This is necessary to prevent dirty water from beinq drawn into the pipeline sho
23、uld it empty. Fire Hydrants. Consider the merits of the design of fire hydrants using concrete pillars as shown on Drawing L-3.0 to overcome depth and other problems. ANCILIARIES Concrete Encasing. Concrete encasing of AC, concrete, and plastics pressure pipes is generally not advisable. The pipelin
24、e is liable to shear failure as the inherent flexibility of the pipe is lost. Stabilizing of the subsoil or the use of a protective sleeve or a stronger type of pipe is preferable. Thrust Blocks (Subclause 5.5). Because thrust blocks for bends, reducers, tees, valves, offsets. hydrants, and end caps
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