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. ISBN 978-0-626-22858-3 SANS 10268-1:2009Edition 1.3SOUTH AFRICAN NATIONAL STANDARD Welding of thermoplastics Welding processes Part 1: Heated-tool weldin
4、g Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 10268-1:2009 Edition 1.3 Table of changes Change No. Date Scope 1 2002 Amended to be aligned with international specifications for poly
5、ethylene pipes, to update referenced standards, and to replace withdrawn referenced standards. 2 2007 Amended to change the designation of SABS standards to SANS standards, with no technical changes. 3 2009 Amended to update referenced standards. Acknowledgement The SABS Standards Division wishes to
6、 acknowledge the valuable assistance derived from publications of the Deutscher Verband fr Schweisstechnik (German Welding Engineering Association). Foreword This South African standard was approved by SABS TC 1041, Welding of thermoplastics, in accordance with procedures of the SABS Standards Divis
7、ion, in compliance with annex 3 of the WTO/TBT agreement. This document was published in August 2009. This document supersedes SANS 10268-1:2007 (edition 1.2). A vertical line in the margin indicates where the text has been technically modified by amendment No. 3. SANS 10268 consists of the followin
8、g parts under the general title, Welding of thermoplastics Welding processes: Part 1: Heated-tool welding. Part 2: Electrofusion welding. Part 3: Hot-gas welding. Part 4: Hot-gas extrusion welding. Part 5: Solvent welding. Part 10: Weld defects. Annex A is for information only. SANS 10268-1:2009 Edi
9、tion 1.3 1 Contents Page Acknowledgement Foreword 1 Scope . 3 2 Normative references . 3 3 Definitions 4 4 General requirements 5 5 Heated-tool butt welding 5 6 Testing and approval . 14 7 Heated-tool socket welding 14 Annex A (informative) Bibliography 19 SANS 10268-1:2009 Edition 1.3 2 This page i
10、s intentionally left blank SANS 10268-1:2009 Edition 1.3 3 Welding of thermoplastics Welding processes Part 1: Heated-tool welding 1 Scope This part of SANS 10268 covers the welding of thermoplastics using the heated-tool butt welding (HS) and heated-tool socket welding (HD) processes. It refers spe
11、cifically to polypropylene homopolymer (PP-H), polypropylene block copolymer (PP-B), polypropylene random copolymer (PP-R), polyvinylidene fluoride (PVDF) and high-density polyethylene (PE-HD). 2 Normative references The following standards contain provisions which, through reference in this text, c
12、onstitute provisions of this part of SANS 10268. All standards are subject to revision and, since any reference to a standard is deemed to be a reference to the latest edition of that standard, parties to agreements based on this part of SANS 10268 are encouraged to take steps to ensure the use of t
13、he most recent editions of the standards indicated below. Information on currently valid national and international standards can be obtained from the SABS Standards Division. ISO 8085-1, Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels Metric series Specificatio
14、ns Part 1: Fittings for socket fusion using heated tools. Amdt 1 ISO 8085-2, Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels Metric series Specifications Part 2: Spigot fittings for butt fusion, for socket fusion using heated tools and for use with electrofusion
15、 fittings. Amdt 1 SANS 4427-2/ISO 4427-2, Plastics piping systems Polyethylene (PE) pipes and fittings for water supply Part 2: Pipes. Amdt 3 SANS 6269, Welding of thermoplastics Test methods for welded joints. SANS 10269, Welding of thermoplastics Testing and approval of welders. SANS 10270, Weldin
16、g of thermoplastics Approval of welding procedures and welds. SANS 15874-2/ISO 15874-2, Plastics piping systems for hot and cold water installations Polypropylene (PP) Part 2: Pipes. Amdt 3 SANS 10268-1:2009 Edition 1.3 4 3 Definitions For the purposes of this part of SANS 10268, the following defin
17、itions apply: 3.1 bead-forming the process of initial heating of the joint faces under pressure which results in the formation of a molten bead of plastics around the inside and outside circumferences of the joint NOTE This process is also known as adapting or equalization. 3.2 bead-forming pressure
18、 the pressure required to ensure the correct formation of the beads on the inside and outside circumferences of the joint 3.3 bead-forming time the time that the bead-forming pressure has to be sustained to ensure correct formation of the beads on the inside and outside circumferences of the joint 3
19、.4 changeover time the time required to remove the heating plate and bring the joint components together under joining pressure NOTE The changeover time has to be kept to an absolute minimum to prevent cooling of the molten plastics. 3.5 heating time the time required to ensure that the plastics in
20、the joint components have been melted to a sufficient depth to ensure a homogeneous joint NOTE This time is also known as soaking time. 3.6 joining pressure the pressure required to ensure complete fusion of the molten plastics in the joint components 3.7 joining time the time taken to increase the
21、joining pressure gradually on joining to the final pressure required plus the time that this pressure is maintained while the joint cools 3.8 peeling diameter the diameter to which the pipe end is machined before the joint is made 3.9 weld bead the portion of molten plastics that is pressed out of t
22、he joint by the bead-forming and joining pressures 3.10 welding the process of fusing two or more metal or plastics components with the aid of heat, or (in the case of plastics only) with the aid of a solvent, to form a homogeneous, permanent whole that is characterized by the welding method used. I
23、n both cases pressure may be applied to assist the welding process SANS 10268-1:2009 Edition 1.3 5 3.11 weld zone the area of the parent material in which material flow will occur between the components of the weld owing to the effect of heat, pressure or solvents, or a combination of any of these,
24、on the material 4 General requirements As humidity, strong sunlight (heat), wind and temperatures below 5 C can cause serious problems and result in bad weld joints, the weld zone shall be protected from these conditions by means that will provide an environment conducive to good weld joints. Shelte
25、rs can be erected over the weld zone and, in cold weather, pre-heating of the pipe to ensure a uniform wall temperature around the entire circumference of the pipe is of great benefit. If the welding conditions are suspect, trial welds shall be carried out before full-scale production proceeds. Join
26、t faces shall be clean and undamaged before welding takes place. 5 Heated-tool butt welding 5.1 Heating plate preparation and care At the start of any welding session, the heating plate shall be cleaned with clean, lint-free paper and a suitable non-oil-base cleaning solvent. Such solvents include,
27、but are not limited to, trichloroethane, acetone, methylene chloride, ethanol-propanol mixture and ethanol. The heating plate shall then be switched on and heated until the surface temperature, measured with the help of a fast-indicating thermometer or thermal crayon, attains the correct value as ta
28、ken from the appropriate graph in figure 1. To prevent contamination of the heating face with the thermal crayon, care shall be taken to use only the edge of the heating plate for temperature measurement. To prevent contamination and surface damage, the heating plate shall be kept in a protective de
29、vice while not in use. Bead-forming shall not take place sooner than 5 min after the heating plate has reached the required temperature. To ensure defect-free welds, the heating plate shall be cleaned as described above before and after every weld. 5.2 Joint preparation Heated-tool butt welding is a
30、lways undertaken with the help of pipe-welding machines that can be set up to provide the necessary pressures in relation to the time required for the specific weld. After the pipe components have been clamped in the welding machine with sufficient space having been left for the insertion of the fac
31、e machining attachment and the heating element, the pipes are axially aligned. The offset of the pipe components shall not exceed 10 % of the pipe wall thickness. The welding procedure continues with the preparation of the joint faces. This is achieved by means of the face machining attachment which
32、, depending on the type of welding machine, is swung or put into place and used to machine the faces of the two components so that they are clean and squarely trimmed. The shaving thickness shall be kept to a minimum but be sufficient to ensure a smooth joint face and to prevent uneven heat build-up
33、, which could cause problems during the welding process. This machining shall take place immediately before welding since oxidation could take place on the joint faces if they are left too long after preparation, which will result in a poor weld. After machining, the joint faces and the weld zone sh
34、all be wiped clean with lint-free paper and a suitable cleaning solvent (see 5.1). The joint faces shall not be touched with bare hands, since contamination by skin-oil deposits will necessitate re-cleaning or even re-machining. The machined faces are then brought into contact and checked for plane-
35、parallelism. The maximum gap between the prepared pipe components shall not exceed those given in table 1 at any point on the circumference of the pipe. (See figure 2 for a schematic of face machining.) Pipe offset shall be checked after machining to ascertain whether it is still within limits. If t
36、he pipe offset is no longer within limits, re-machining could be required. SANS 10268-1:2009 Edition 1.3 6 a) Heated-tool temperature as a function of pipe wall thickness for polypropylene (PP) b) Heated-tool temperature as a function of pipe wall thickness for polyethylene (PE-HD) Figure 1 Heated-t
37、ool temperature as a function of pipe wall thickness for polypropylene (PP) (top) and polyethylene (PE-HD) (bottom) NOTE For polyvinylidene fluoride (PVDF) the lower and upper limits of the welding range are between 232 C and 248 C. SANS 10268-1:2009 Edition 1.3 7 Figure 2 Machine preparation of pip
38、e-joint faces Table 1 Maximum width of gap between machined faces Dimensions in millimetres1 2 Pipe outside diameter Maximum width of gap(d) (a) 1 000 2,0 5.3 Machine set-up and pressure calculations The setting force (or pressure) of the machine is the sum of the force (or pressure) required to mov
39、e the workpiece into position for welding, plus the force (or pressure) required for bead-forming or joining, as follows: a) for equipment with force measurement, the setting force Fsis given by Fs= Fw+ Fbwhere Fwis the workpiece moving force; and Fbis the bead-forming (or joining) force. SANS 10268
40、-1:2009 Edition 1.3 8 b) For equipment with pressure measurement, the setting pressure Psis given by Ps= Pw+ Pbwhere Pwis the workpiece moving pressure; and Pbis the bead-forming (or joining) pressure. Depending on the material to be welded, the machine is now set up for time and pressure in accorda
41、nce with tables 2, 3 or 4, or in accordance with the tables supplied by the welding machine manufacturer. Tables 2, 3 and 4 use standard values of contact pressure (), which is the pressure required to be produced at the welding face during bead-forming and joining. The actual values of Fband Pbcan
42、be calculated on the basis of the welding area and the contact pressure () values given in tables 2, 3 or 4, as follows: a) for equipment with force measurement, the bead-forming or joining force Fbis given by Fb= A1 where A1is pipe cross-sectional area, in square millimetres; and is the contact pre
43、ssure (from tables 2, 3 or 4). b) for hydraulically operated machines, the bead-forming or joining pressure Pbcan be calculated as follows: =AP A1b2 where A1is the pipe cross-sectional area, in square millimetres; A2is the welding machine piston area, in square millimetres; and is the contact pressu
44、re (from tables 2, 3 or 4). A1and A2can be calculated as follows: A1= dmt A2= r2where dmis the mean pipe diameter, in millimetres; t is the pipe wall thickness, in millimetres; and r is the radius of the piston, in millimetres. SANS 10268-1:2009 Edition 1.3 9 Example: PE-HD pipe lengths (see table 2
45、) of outside diameter 250 mm and of wall thickness 16 mm are to be butt-welded using a welding machine that has a piston diameter of 75 mm. Mean pipe diameter = 250 16 = 234 mm A1= 234 16 = 11 764 mm2A2= 37,52= 4 418 mm2 = 0,15 N/mm2(from table 2) Hydraulic pressure required, =AP A1b2 =117640,154418
46、Pb = 0,40 N/mm2The workpiece moving pressure Pw, or force Fw, shall not exceed 20 % of the joining pressure (or force) given in the equipment of the manufacturers tables. The workpiece moving pressure is read off the pressure gauge once the workpiece has been mounted and moved up to the heating plat
47、e. Tables of dimensions for high-density polyethylene (PE-HD), for PE-HD PE 80 pressure pipes and for polypropylene (PP) can be obtained from SANS 15874-2 and SANS 4427-2. Amdt 1; amdt 3 The correct ratio between pipe weld area, temperature and pressure is very important because, as the pipe wall th
48、ickness increases, so do the pressure and the temperature-exposure time required. SANS 10268-1:2009 Edition 1.3 10 Table 2 Recommended values for the heated-tool welding of high-density polyethylene (PE-HD), determined at an ambient temperature of 20 C and at moderate airflow 1 2 3 4 5 6 Bead-formin
49、g Heating Joining = 0,15 N/mm2 0,02 N/mm2Changeover = 0,15 to 0,20 N/mm2Height of bead prior to heating period Nominal wall thickness (min. values) Heating timeaMaximum time Time to complete pressure build-up Total cooling time while under joining pressure mm mm s s s min Up to 4,5 0,5 45 5 5 6 4,5 to 7 1,0 45 to 70 5 to 6 5 to 6 6 to 107 to 12 1,5 70 to 120 6 to 8 6 to 8 10 to 1612 to 19 2,0 120 to 190 8 to 10 8 to 11 16 to 2419 to 26 2,5 190 to 260 10 to 12 11 to 14 24 to 3226 to 37 3,0 260 t
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