SOUTH AFRICAN NATIONAL STANDARD

Transcription

1 ISBN SANS 1689:2015 DRAFT SOUTH AFRICAN NATIONAL STANDARD Corrugated stainless steel piping systems for hot and cold water supplies Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: Fax: SABS

2 Table of changes Change No. Date Scope Foreword This South African standard was approved by National Committee SABS TC 138/SC 04, Water and sanitation Equipment and systems Metallic pipes and fittings, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This document was published in xxxx 2015.

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4 Contents Page Foreword 1 Scope Normative references Definitions Requirements Performance requirements Marking and method of marking Annex A (informative) Exterior application Annex B (normative) Friction loss curves Annex C (informative) Quality verification of Corrugated stainless steel piping systems for hot and cold water supplies...17 Bibliography

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6 Corrugated stainless steel piping systems for hot and cold water supplies 1 Scope 1.1 This Standard specifies the minimum requirements for the design, manufacture, testing and installation of stainless annular corrugated metal tube and fittings. 1.2 Components within this system comprise of sleeved/unsleeved corrugated stainless steel pipe and metallic fittings intended for 1000 kpa water service up to and including a maximum working temperature of 100 C, for nominal pipe sizes 15 mm to 28 mm and.fitting sizes 15 mm to 35 mm. 2 Normative references The following referenced documents are indispensible for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. Information on currently valid national and international standards can be obtained from the SABS Standards Division. ASTM A 240/A 240M, Standard specification for chromium and chromium nickel stainless steel plate, sheet and strip for pressure vessels and for general applications. ASTM A 312/A 312M, Standard specification for seamless welded and heavily cold worked austenitic stainless steel pipes. ASTM A 268/A 268M, Standard specification for seemless and welded ferritic and martensitic stainless steel tubing for general services ASTM A 790/A 790M,Standard specification for seemless and welded ferritic/austenitic stainless steel pipe. SANS , Copper-based fittings for copper tubes Part 1: Compression fittings. SANS , Pipe threads where pressure-tight joints are made on the threads Part 1: Dimensions, tolerances and designation SANS 6509, Corrosion of metals and alloys - Determination of dezincification resistance of brass. EN , Stainless steels Part2: Technical delivery conditions for sheet/plate and strip of corrosion resisting steels for general purposes. 3 Definitions For the purposes of this document, the following definitions apply. 3.1 Corrugation A corrugated pipe is a tube with a series of parallel ridges and grooves on its surface. This pipe can be manufactured of steel or plastic. It can be coated or lined. Corrugated pipe is used in 3

7 applications such as hot and cold water supplies where flexibility, durability, and strength are important attributes. 3.2 Chloride corrosion Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment (typically one with high chloride levels). It can lead to unexpected sudden failure of normally ductile stainless steel that is subjected to a tensile stress. SCC is more likely to occur at elevated temperatures (> 60 o C) and is subjective to the grade of stainless steel selected. 3.3 Pitting corrosion is a localized form of corrosion of the stainless steel surface, by which cavities or pits are produced in the material. Pitting corrosion often remains undiscovered until it causes perforation and leakage and can be severely detrimental to thin sheets or tubes. 4 Requirements 4.1 Materials. Stainless steel material shall be minimum types 304, 304L and 316L complying with the requirements of ASTM A 240 or ASTM A 312/312M. Other grades of stainless steel are permissible as long as the corrosion resistance is equal to or higher than 304, Ferritic and Martensitic stainless steel complying with ASTM A 268/A 268M or ASTM A 790/790M. The user shall confirm with the manufacturer whether the type of stainless steel to be used is suitable for the intended application Weld and passivation Weld shall be fusion welds done by the seaming process or by any other welding process that produces a weld having mechanical properties and corrosion properties and corrosion resistance of at least the same order as those of the parent metal. When tested in accordance with clause 5, the strength of the welded point, shall be similar to the strength of parent material. The weld shall be passivated using nitric acid and proper rinsing thereafter. 4.2 Corrosion All materials that come in contact with potable water shall be intrinsically non corrosive and copper alloy material shall be tested in accordance with SANS 6509 and the maximum penetration shall not exceed 250 µm Chloride corrosion To avoid chloride based corrosion the material shall be selected in accordance with table 1. Table 1 Chloride ion concentration 1 2 Resistivity (Soil) Chloride ion concentration (ppm) Ω.cm ,000 > /304L /316L/ <1000 Super duplex 4

8 Stainless steel of grades 304/304L and 316/316L should be used within the following range: Cl- < 500 ppm, Resistivity > 1,000 Ω.cm, ph > 4.5 <8.5 When it is necessary to handle hot water or when more conservative guidelines are necessary, then upper chloride limits of 50 ppm for (304L) and 250 ppm for (316L) may be appropriate Pitting corrosion To avoid pitting based corrosion the material shall be selected in accordance with table 2. Table 2 Pitting corrosion Type Stainless Steel Grade AISI EN number (EN ) Pitting resistance Equivalent (PRE) Austenitic 304/304L Austenitic 316 /316L This table is based on the following formula: PRE = % Cr x % Mo + 16 x % N Where: Cr is Chromium; Mo is Molybdenum and N is Nitrogen. Pitting resistance (PRE) of selected material shall be a minimum of Galvanic reaction Compliance with the installation requirements of this standard will ensure that galvanic corrosion due to direct contact with dissimilar metals is avoided. Therefore these instructions shall be complied with. 4.3 Piping. Corrugated piping dimensions and tolerances shall comply with table 3. Table 3 - Dimensional requirements of tubing Nominal Diameter DN Inner diameter mm Outer diameter mm Std. Tol. Std. Tol. Thickness mm Corrugations/ 100 mm Min Installation Centreline Radius mm Volume ml/m Of tube ± ± min min min min

9 Figure 1 - Annular Type Corrugation Tube 4.4 Fittings Dielectric waterway fittings shall comply with the requirements in accordance with SANS and drawing figure 2. Where: A) Inner guide (PTFE) B) Silicone O ring C) Outer grommet (PTFE) D) Brass nut for fitting E) Corrugated stainless steel tube F) DZR brass fitting G) Inner depth of fitting H) Inner diameter of fitting I) Width of brass nut Figure 2 Typical dielectric tube fitting 6

10 4.4.2 Threaded ends shall comply with the requirements in SANS Fittings shall be compatible with copper tube on the end suitable for copper made to the requirements of SANS and for stainless steel for the end suitable for stainless steel made to the requirements of this standard The socket bore of the fittings shall comply with table 4. Table 4 Socket bore diameters of fittings Dimensions in millimetres Nominal size of individual ends Socket bore Max. 22,305 28,305 35,370 42,370 54,370 Min. 22,155 28,155 35,170 42,170 54, The minimum wall thickness of the tube fittings shall comply with the requirements of table 5. Table 5 Minimum wall thickness Dimensions in millimetres Nominal size of fitting end Wall thickness of body shell, min. Fittings made from rod, drawn tube, extrusions, pressing or hot stampings 1,2 1,4 1,5 1,6 1,8 1,9 Fittings made from castings 1,4 1,6 1,8 1,9 2,2 2,3 Wall thickness measured from root of thread, min. 1,3 1,5 1,6 1,8 2,0 2, The length of thread on the nut and on the body for a compression outlet shall be such that, when the fitting is assembled to a tube a) after all clearance between the tube and the fitting has been eliminated, and before the application of further torque necessary to effect a seal, the number of full threads engaged is not less than the relevant number given in table 3, and b) after the application of the appropriate torque given in table E.1, there is still sufficient thread left for a further ½ turn of the nut. The number of threads engaged shall comply with the requirements of table 6. 7

11 Table 6 Number of threads engaged 1 2 Nominal size mm 15 and and 32 Number of full threads engaged, min. 2½ 3½ 4.5 Threads Threads for threaded connections Threaded ends of fittings for direct connection to threaded steel pipes shall comply with the requirements of SANS Threads at compression outlets (nut/body thread) The threads at compression outlets of fittings shall be of acceptable size and form, except for outlets of fittings of nominal assembly diameters 15 mm, 22 mm and 28 mm, which shall be as follows: a) for nominal assembly diameter of copper pipes 15 mm, a 15 mm pipe thread in accordance with SANS ; b) for nominal assembly diameter of dielectric side for stainless steel corrugated tube 22 mm, a 28,57 mm diameter, mm pitch, medium class, British Standard Whitworth form (55 ); and c) for nominal assembly diameter of 28 mm, a 34,92 mm diameter, mm pitch, medium class, British Standard Whitworth form (55 ) Thread chamfers Each external and internal thread shall be chamfered at the face of the fitting to an included angle of (90 ± 10). The diameter of the chamfer shall be at least equal to the minor or major diameter of the thread, as appropriate 4.6 Outer cover (sleeve) If the pipe is sleeved, the outer cover shall be of suitable grade of flexible PVC and if intended for outside use it shall be UV stabilized in accordance with (4.6.2) The UV stabilization shall be tested and evaluated in accordance with SANS Installation Methodology (Fixing methods) Fixing clamps Clips, holderbats or saddles shall be stainless steel or plastic (UV stabilized for outside use), unless the pipe is sleeved in which case any appropriate materials can be used Fixing distances (spacing) 8

12 Horizontal runs shall be supported at a minimum of 30 cm to 50 cm intervals, vertical runs should be supported at a minimum of 50 cm to 60 cm, all fixed to the structure. NOTE: As a general rule avoid pipe sagging in order to improve aesthetics and avoid reduction in velocity and collection debris Fixing at valves and terminal fittings Fix on both sides of valve or fittings within a maximum distance of 5 cm, and on formed bends within 5 cm of each side of the bend. Terminal fittings shall be securely fixed to the structure using wall plates before connecting the pipe Connections The end connecting to the pipe on tee pieces, reducers, elbows, stop-ends and straight connectors etc shall be in accordance with the design and dimensions in figure 2. Connections to other piping systems shall be in accordance with the relevant standards for the particular material and the connectors or adaptors shall be suitable Installation underground and within walls and structure Only PVC sleeved pipes shall be used underground, unless it is coated with zinc-rich epoxy primer or coated with thermally sprayed aluminium (TSA) in accordance with the coating manufacturer s instructions, when stress corrosion cracking is a concern, especially at temperatures above ambient. The installation shall comply with the requirements of SANS Freeze Protection Freeze protection shall be in accordance with SANS Performance requirements 5.1 Sampling. A sufficient quantity of tubing or fittings, as agreed upon by the purchaser and the seller, shall be selected and tested to determine conformance with this standard. In the case of no prior agreement, random samples selected by the testing laboratory shall be deemed adequate. Individual tests shall be carried out on different samples of the same tube and different fittings of the same type. 5.2 Hydrostatic tube Test. Test specimen at least 500 mm in length, from randomly selected specimens and two suitable test fittings assembled per the manufacturer s testing instructions. The test specimen shall be filled with water and the internal pressure increased to 8 MPa for a period of 1 min, at a temperature of 20 C ± 3 C. No signs of leakage or failure shall occur. 5.3 Hydrostatic Burst test Test at 20 C. Test specimen at least 500 mm in length, randomly selected specimens assembled per the manufacturer s instructions. The test specimen shall be filled with water and the internal pressure increased to 4000 kpa ± 50 kpa or 4 times the manufacturer s rated pressure, whichever is greater, at a temperature of 20 C ± 3 C for a period of 5 minutes. No signs of crack or leakage or failure shall occur. 9

13 5.4 Hydraulic Shock (Water Hammer) Test A specimen at least 600 mm in length shall be fabricated containing a fitting joint. The fitting shall be assembled in accordance with the manufacturer s installation instructions. The specimen shall be mounted in a system with water at atmospheric pressure. The specimen shall be subjected to a hydraulic shock for 2,000 cycles at 20 C ± 3 C. The hydraulic shock shall consist of a sudden increase in pressure from 350 kpa to 2000 kpa lasting 1 second. No signs of leakage or failure shall occur. 5.5 Vibration Test. Two specimens at least 600 mm in length shall be fabricated in accordance with the manufacturer s installation instructions and subjected to a hydrostatic pressure of 100 kpa. Each sample is to be fitted with pipe plugs, filled with water in such a manner as to exclude all air, and connected to a hydrostatic source. The samples are to be extended to their intermediate position, locked, filled with water, and mounted in the pendant position on a test fixture attached to the table of a vibration machine. The amplitude of the vibration is to be 5 mm, and the frequency is to be 25 Hz for 3 hours. No signs of leakage or failure shall occur. 5.6 Flattening Test. A specimen of piping at least 600 mm shall be prepared. One end of a sample assembly shall be securely attached to a fixture to which a pressure equivalent to 20 kpa is obtained and manometer is connected. The other end shall be plugged closed. Insert the specimen into two flat plates with the welded end set to 90 degrees opposite of the pressing direction (See Figure 3). The tube shall be pressed to 2/3 D height of the outer diameter until the tube is flat. No signs of cracks or leakage shall be found. Figure 3 - Flattening Test 10

14 5.7. Steel Ball Impact Test. A specimen at least 300 mm in length, from randomly selected specimens shall be assembled per the manufacturer s instructions. One end of a sample assembly shall be securely attached to a fixture to which a pressure equivalent to 20 kpa is obtained and manometer is connected. The other end shall be plugged closed. The specimen shall be secured on a concrete cement plate, and a 2 kg steel ball shall be dropped onto the centre of specimen from 1 m height (See Figure 4). No sign of leakage shall occur. Figure 4 - Steel Ball Impact Test 5.8 Impact Test. A specimen is fabricated from randomly selected specimen assembled per the manufacturer s installation instructions. One end of a sample assembly shall be securely attached to a fixture to which a pressure equivalent to 20 kpa is obtained and manometer is connected. The other end shall be closed with fitting plug. Apply an impact force in accordance with Table 7 to the fitting using a hammer as shown in Figure 5. No signs of cracks or leakage shall occur. Table 7 - Impact Forces for Impact Test 11

15 Nominal Diameter in mm Impact Force N*m Figure 5 - Impact Test 5.9 Pliability Requirements A corrugated metal hose shall be capable of being bent 10 times to a small radius in accordance with Table 8 without leakage Test 12

16 The sample shall be subjected to a bend test as shown in Figures 6 and 7. With one tube end rigidly fixed, the other shall be moved in a circular arc around a mandrel whose radius is calculated from the bend radius, r (pliability test), as given in Table 8, until the tube is in intimate contact with the former through an arc of 90. Table 8 Bend radii for pliability test 1 2 DN Pliability test Bend radius (r) mm Figure 6 - Bending Test for Fitting/Tubing Combination 13

17 Figure 7 Pliability test Determination of radius 6. Markings and identification All tubes shall bear the following markings. The marking on the tubing shall be at intervals of not more than 1 m, engraved or etched directly onto the pipe itself or printed indelibly on the PVC sleeve: (a) SANS 1689 (b) Manufacturer's name or trademark; (c) Nominal size; (d) Pressure rating at 100 C; (e) Manufacturing date. f) stainless steel grade (AISI) g) UV stabilized sleeved tubing (refer to 4.6.2) shall be marked UV. 14

18 Annex A (informative) Exterior applications Corrosion has been proved to be influenced by the distance of the structure from the sea, or from a chemical or a process plant. In South Africa, grade AA25 should be used in the following areas: a) Western Cape (i.e. west of Hermanus): within 25 km of the sea; b) Southern and Eastern Cape: within 20 km of the sea; c) Natal South Coast (i.e. south of Amanzimtoti): within 15 km of the sea; and d) Durban area and Natal North Coast: within 25 km of the sea. In addition, any site within 5 km of a chemical or related process plant complies with the criteria for the use of grade AA25. Examples of such plants are pulp-and-paper mills, oil refineries, petrol-from coal plants, steel mills and metallurgical process plants. 15

19 Annex B (informative) Friction loss curves Figure B.1- Friction loss curves Friction loss (hydraulic gradient) versus flow rate (flow velocity) graph. NOTE 1: Friction factor of corrugated stainless steel tubes varies according to diameter and the profile of the corrugation and the factor on this graph varies between a k value of 1.2 to NOTE 2 : The friction loss of stainless steel corrugated tubes is higher than that of smooth bore pipes 16

20 Annex C (informative) Quality verification of Corrugated stainless steel piping systems for hot and cold water supplies When a purchaser requires ongoing verification of the quality of Corrugated stainless steel piping systems for hot and cold water supplies, it is suggested that instead of concentrating solely on evaluation of the final product, he also direct his attention to the manufacturer's quality system. In this connection it should be noted that SANS 9001 covers the provision of an integrated quality systems. 17

21 Bibliography Standards ISO/TR 10217, Solar energy Water heating systems Guide to material selection with regard to internal corrosion. SANS 9001/ISO 9001, Quality management systems Requirements. Other publications Callaghan, B G. Corrosion of solar water heating systems. British Corrosion Journal, Vol. 14, No. 2, 1979, p. 78. SABS 18