GB/T 29038-2024Technical specification for light gauge stainless steel piping (English PDF)

1 Scope

The document lays down the technical specification for the materials, design, construction and acceptance of light gauge stainless steel piping.

It applies to the design, construction and acceptance of light gauge stainless steel piping for water supply (the medium being piped direct-drinking water, domestic hot water, cold water and the like) and for boiled-water supply in industrial and civil buildings, at a nominal pressure not greater than PN 25, a nominal size not greater than DN 300 and a temperature not greater than 80 °C.

2 Normative references

The documents cited are GB 5749 (drinking water hygiene), GB/T 12771 (welded stainless steel pipes for fluid transport), GB/T 19228.1, GB/T 19228.2 and GB/T 19228.3 (stainless steel press-fit fitting assemblies: fittings, light gauge pipes for connection, and O-ring rubber seals), GB/T 21359 (stainless steel threaded joints for the food and water supply industry), GB/T 21472 (stainless steel elbows and tees for the food industry), GB/T 33926 (stainless steel ring-compression fittings), GB 50015 (building water supply and drainage design), GB 50981 (seismic design of building mechanical and electrical works) and CJ/T 151 (light gauge stainless steel pipes).

Dated references apply only in the edition quoted; undated references apply in their latest edition, including all amendments.

3 Terms and definitions

3.1 Light gauge stainless steel pipes - stainless steel pipes whose ratio of wall thickness to outside diameter is not greater than 6 % and whose wall thickness is 0.6 mm to 4.0 mm.

3.2 Light gauge stainless steel pipes wrapped in plastic - light gauge stainless steel pipes with a plastic covering layer on the outer wall.

3.3 Press jointing - a jointing method in which the pipe is connected by a socket fitting carrying a special sealing ring, the pipe mouth being pressed with a dedicated tool so as to seal and secure the joint; according to the end structure, press jointing is divided into the S type and the D type.

3.4 D-type socket jointing (single-press extrusion jointing) - press jointing in which the socket end of the fitting has no extended straight section.

3.5 S-type socket jointing (double-press extrusion jointing) - press jointing in which the socket end of the fitting has an extended straight section.

3.6 Ring (annular) compressing jointing - an extrusion jointing method in which a wide-band sealing ring is placed at the spigot and socket and the socket is crimped with a dedicated ring-compression tool so that it is tightened and sealed in an annular compressed form.

3.7 Plug-in TIG welding jointing - a jointing method in which the stainless steel pipe is inserted into the socket of the fitting and the two are fused into one body by tungsten inert gas (TIG) welding.

3.8 Balanced TIG welding jointing (butt TIG welding jointing) - a jointing method, described in the document as a jointing without a joint, in which stainless steel pipes are butted directly against each other, or a pipe is butted against a fitting, and welded by tungsten inert gas (TIG) welding.

3.9 Clip cover jointing - an extrusion jointing method in which tightening a nut deforms a drum-shaped stainless steel ring inside the fitting so that it secures and closes the gap at the pipe connection.

3.10 Press jointing with clamp ring - a jointing method in which the pipe is connected by a socket fitting carrying a pull-out resisting clamp ring and an O-ring rubber seal, the pipe mouth being pressed with a dedicated tool so as to seal and secure the joint.

3.11 Compression jointing - a jointing method in which a nut is tightened so that the sleeve at the pipe mouth compresses the sealing ring and thereby seals the joint.

3.12 Clasp flange jointing - a flared-ring jointing method in which a raised ring of right-triangular or circular-arc section is expanded at the pipe end with a dedicated tool, the seal being made on the end face and an anti-slip rubber ring being fitted at the thread.

3.13 Grooved coupling jointing (trench type jointing) - a jointing method forming a quickly assembled joint, in which an annular groove is machined (by roll grooving or by cutting) at the joint area of the plain end of the pipe or fitting, the joint then being made up of a split clamp, a C-shaped rubber sealing ring and fasteners.

3.14 Threaded coupling jointing - a jointing method in which a 90° flanged face is expanded at the pipe end with a dedicated tool, two such flanged faces then being pressed against a sealing ring with a limiting structure and tightened.

3.15 Flanged jointing (flange joint) - a jointing method in which fasteners are tightened to secure the flanges on adjacent pipe ends.

3.16 Circular water supply for branch pipe - a supply arrangement in which double-socket bends serve the water fittings inside a building and the supply pipework is laid out as a ring, so that water standing in the pipe is set in motion whenever any one draw-off point is used.

4 Pipes and fittings

4.1 to 4.2 Pipes and fittings shall carry a test report from a nationally recognised product testing body and a works quality certificate; those used for drinking water shall also carry the hygiene licence documents for water-contact products issued by the health authority. They shall meet GB/T 12771, GB/T 19228.1, GB/T 19228.2, GB/T 19228.3, GB/T 21359, GB/T 21472, GB/T 33926 and CJ/T 151.

4.3 Table 1 lists seven designations with their service conditions. The austenitic types are S30408 (06Cr19Ni10) and S30403 (022Cr19Ni10), both for water supply (piped direct-drinking water, domestic hot water, cold water and the like) and boiled-water supply; S31608 (06Cr17Ni12Mo2) where higher corrosion resistance than S30403 is required; and S31603 (022Cr17Ni12Mo2) for high-chloride media or where higher corrosion resistance than S31608 is required. The ferritic types are S11972 (019Cr19Mo2NbTi) for high-chloride media and fire-fighting supply, S12362 (019Cr23MoTi) where higher chloride-ion resistance than S11972 is required, and S12361 (019Cr23Mo2Ti) where higher chloride-ion resistance than S12362 is required.

4.4 Table 2 sets the permitted chloride content of the water conveyed for the same seven designations. For cold water (temperature not above 40 °C) the limit is 200 mg/L for S30408 and S30403 and 1 000 mg/L for S31608, S31603, S11972, S12362 and S12361. For hot water (temperature above 40 °C) the limit is 50 mg/L for S30408 and S30403 and 250 mg/L for the other five.

4.5 to 4.8 Joints shall use matching stainless steel fittings, preferably of the same designation as the pipe; dimensions and tolerances shall meet the national or industry standards in force; chemical composition and mechanical properties shall meet Annex A. Fitting structures include press-fit, ring-compression, welded, clip-cover, clamp-ring press, compression, threaded, grooved and flanged types.

4.9 After the forming and welding process, austenitic stainless steel fittings shall be given a bright solution treatment under a protective gas (pure hydrogen or an AX gas mixture) at 1 000 °C to 1 100 °C. Ferritic stainless steel shall be annealed at 850 °C to 1 050 °C.

4.10 to 4.11 Sealing rings shall match the jointing method; rubber is preferred, the choice being made from the jointing method, the medium temperature, the sealing requirement and the service life. Sealing rings for press-type joints shall meet GB/T 19228.3, and those for other jointing methods shall meet the relevant national or industry standards in form, dimensions and material.

5 Design

5.1 Layout and installation. The piping shall be made up throughout of light gauge stainless steel pipes, fittings and accessories, and measures against galvanic corrosion shall be taken where it meets other materials. Buried piping should be of a designation not lower than 022Cr17Ni12Mo2 (S31603), with external corrosion protection that should be free of chloride ions; plastic-wrapped pipe is preferred where the pipe is embedded in a wall or in a screed. Buried pipe should not pass through building foundations, and shall be run in a sleeve where it passes through a wall, a hole being left in the wall and building settlement taken into account. Wall-embedded pipe shall not use clip-cover or other threaded joints and its diameter should not exceed 20 mm; it shall be run horizontally or vertically in a preformed or cut chase and fixed with clips. The pipe shall not be cast into reinforced concrete structural layers, should not cross settlement, expansion or movement joints without a device to take up expansion and shear, and shall not be run in switch rooms, power or communication risers, flues, air ducts or drainage channels. Piping to be drained should fall towards the drain point at a gradient of 0.002 to 0.003.

5.1.9 Bathroom distribution pipework should use branch pipe circular water supply: the ring should not exceed 15 m in length, and where a branched layout is used instead the water volume in the pipework should not exceed 0.003 m3.

5.1.10 to 5.1.13 Threaded adaptors or flanges shall be used at the service entry, at the entry angle fitting, at branch take-offs and at instrument connections, and threaded or flanged joints shall be used at connections to sanitary fittings, water supply units and equipment. Press-fit, ring-compression, clip-cover, clasp-flange, clamp-ring press, compression, threaded, welded and adaptor joints suit small-bore pipe of DN 100 and below; grooved, flanged, welded and ring-compression joints suit large-bore pipe above DN 100.

5.2 Compensation and insulation. Where a straight run carrying domestic hot water exceeds 15 m, compensation shall be provided; above DN 40 a stainless steel bellows expansion joint or a linear temperature compensator should be fitted, the compensation being calculated at 1.21 mm/m for a supply temperature not above 60 °C. Connections between horizontal mains and branches, between mains and risers, and between risers and the hot water branch at each floor shall be arranged so that expansion of one does not act on the other. Exposed piping shall be protected against condensation, insulation shall be of non-corrosive material and its thickness shall be calculated.

5.2.3 Table 3 gives the minimum insulation thickness in millimetres for anti-condensation duty and for hot water pipes at not more than 60 °C, where foamed polytetrafluoroethylene, phenolic foam or similar material is used. The anti-condensation and hot water values by nominal size are: DN 10, DN 15, DN 20 and DN 25 - 5 and 20; DN 32 - 10 and 20; DN 40, DN 50, DN 65, DN 80, DN 100 and DN 125 - 10 and 25; DN 150 and DN 200 - 10 and 30.

5.3 Hydraulic calculation. Design flow shall follow GB 50015. Water velocity should not exceed 1.8 m/s; at DN 25 and above a velocity of 1.0 m/s to 1.5 m/s should be used, and below DN 25 a velocity of 0.8 m/s to 1.0 m/s. Friction head loss may be taken from Annex B or calculated from formula (1), a Hazen-Williams expression whose symbols are: head loss per unit length of supply pipe, in kilopascals per metre; the Hazen-Williams velocity coefficient C, taken as 130 for stainless steel pipe; the calculated internal diameter of the pipe, in metres; and the design supply flow, in cubic metres per second. Local head losses should be taken as 25 % to 30 % of the friction head loss.

5.3.4 Where the medium is above 10 °C the friction head loss shall be multiplied by the temperature correction factor of Table 4: 10 °C - 1.0; 20 °C - 0.94; 30 °C - 0.90; 40 °C - 0.86; 50 °C - 0.82; 60 °C - 0.79; 70 °C - 0.77; 80 °C - 0.75.

6 Construction

6.1 Preparation. Work may start once the drawings and technical documents are complete and have been reviewed, the method statement has been explained to the workforce, materials, labour and plant are in place, site water, power and storage are adequate, and the pipes and fittings supplied match their documents and carry an instruction sheet and certificate of conformity. Installers shall have been trained in pipework installation, and the appearance and joint areas of pipes and fittings shall be inspected and cleaned before work starts.

6.2 General rules. Pipes and fittings should not touch cement grout, cement, mortar or wet concrete; open ends shall be capped during breaks in work. Holes and chases formed with the builder's work should be 50 mm to 100 mm larger than the pipe outside diameter for holes, the pipe outside diameter plus 20 mm deep and plus 40 mm to 50 mm wide for wall chases, with a clear space above exposed pipes of not less than 100 mm. Waterproofing shall be provided where the pipe passes through a basement or underground structure wall. Adaptors shall be used at valves, meters and taps, and threads shall not be cut on the pipe itself. Installed mains shall show no marked undulation or bending and no damage to the outer wall. Drinking water piping shall be disinfected after a successful pressure test, using a potassium permanganate solution at a mass concentration of 0.03 %, the pipe being filled and left standing for 24 h and then flushed with mains water until the flushing water meets GB 5749. Pipes and fittings shall be handled with care and kept free of oil, and the piping shall not be climbed on or used to tie safety lines, support scaffolding or act as a support.

6.2.7 Table 5 gives the permitted deviation of coordinates and level in millimetres. For coordinates: outdoor buried +/-50, outdoor overhead or in trench +/-20, indoor buried +/-15, indoor overhead or in trench +/-10. For level: outdoor buried +/-15, outdoor overhead or in trench +/-10, indoor buried +/-10, indoor overhead or in trench +/-5.

6.2.8 Table 6 gives the permitted deviation of pipe and valve position in millimetres. Longitudinal and lateral bending of horizontal pipe: not more than 5 per 1 m, not more than 10 per 10 m, and not more than 15 per 10 m for outdoor overhead, trench and buried pipe. Verticality of risers: not more than 3 per 1 m, not more than 10 for heights over 5 m, and not more than 10 per 10 m for heights over 10 m. Spacing of parallel pipes and of valves in a row set on the same line: not more than 3.

6.3 Installation. Exposed piping shall be installed after the builder's finishes are complete, the position of preformed holes being checked first. Fixed supports should be spaced at not more than 15 m, the spacing for hot water pipes being set from the thermal expansion of the line and the compensation allowed by the expansion joint; fixed supports should be placed at reducers, branches, joints and both sides of load-bearing walls and floors. Plastic clips may be used up to DN 25; metal clips or hangers shall be separated from the pipe by plastic tape, rubber or another soft packing. Metal clips or hangers shall be used at draw-off and distribution points, and should be placed 40 mm to 80 mm from the fitting. For exposed piping the outer wall of the pipe shall stand 40 mm from the finished wall face at DN 10 to DN 25 and 50 mm at DN 32 to DN 65. Sleeves shall be fitted where the pipe passes through a load-bearing wall or floor: in bathrooms and kitchens the sleeve shall stand 50 mm above the finished floor, elsewhere 20 mm, the bottom shall be flush with the floor soffit, sleeves in walls shall be flush at both ends, and the gap between sleeve and pipe shall be filled with flame-retardant material and waterproof mastic and left smooth. Concealed pipe shall be protected against corrosion on the outer wall, shall be pressure tested and recorded before it is closed in, and may then be made good with M7.5 cement mortar. Pipe shall not be bent or twisted about its axis during installation and shall not be forced into line where it passes a wall or floor; the clear distance from other services should be not less than 100 mm where the design is silent, and in a duct the light gauge stainless steel pipe should be placed inside the galvanised steel pipe. Seismic design shall follow GB 50981.

6.3.3 Table 7 gives the maximum spacing of movable supports in metres, for horizontal pipe and for risers: DN 10 and DN 15 - 1.0 and 1.5; DN 20 and DN 25 - 1.5 and 2.0; DN 32 and DN 40 - 2.0 and 2.5; DN 50 and DN 65 - 2.5 and 3.0; DN 80, DN 100 and DN 125 - 3.0 and 3.5; DN 150 and DN 200 - 3.5 and 4.0.

6.4 Jointing. Work follows three steps: drawing an as-measured installation drawing from the coordinates and levels on the design drawings, setting out the pipework from it, and planning the assembly order with a trial assembly. Cutting shall use a powered pipe cutting machine or a hand cutter, the cut face shall be flat and square to the pipe axis, and internal and external burrs should be removed with a dedicated tool. Each jointing method is then carried out to its own annex: press-fit to Annexes C and D, ring-compression to Annex E, clasp-flange to Annex F, clamp-ring press to Annex G, compression to Annex H, plug-in TIG welding to Annex I, butt TIG welding to Annex J, flexible threaded to Annex K and grooved to Annex L.

7 Acceptance

7.1 to 7.2 Intermediate and final acceptance shall be carried out according to the nature of the works, the contractor having first inspected its own work. Intermediate acceptance is carried out by the contractor together with the supervising engineer, and final acceptance by the client or by a supervisor appointed by it, with the designer joining a combined acceptance where needed. Acceptance of concealed and embedded pipework before it is closed in shall concentrate on supports, sleeves and expansion compensation, and shall include a flow capacity check and a hydrostatic test; the mains water used for the test shall meet GB 5749.

7.3 to 7.4 The test pressure is 1.5 times the working pressure of the piping and not less than 0.6 MPa. Concealed and embedded pipework shall be checked against the installation requirements before testing; the fixing and protection of the pipework under test shall be verified beforehand and the test joints left exposed; builder's work may follow only after a successful test, which the supervising engineer shall witness, record and report in writing. The test is run by capping the end of the section, filling slowly while venting air, checking for water-tightness once full, raising the pressure slowly with a hand pump over not less than 10 min, holding at the test pressure for 10 min during which the pressure shall not fall by more than 0.02 MPa, then dropping to working pressure for a visual check, which is passed if there is no leakage. Where leakage or an excessive pressure drop is found the piping shall be examined and the test repeated after the cause has been removed. Below an ambient temperature of 5 °C, frost protection shall be provided during the pressure and flow capacity tests and the pipework drained afterwards.

7.5 After a successful test the piping shall be disinfected and flushed as required by 6.2.9; instruments shall be protected beforehand, and throttle valves, check valves and other accessories that obstruct flushing shall be removed, kept safe and refitted afterwards.

7.6 to 7.7 The handover file shall contain the installation and record drawings and design change documents, the quality certificates for pipes, fittings and main accessories, the records of concealed work acceptance and intermediate tests, the flow capacity and pressure test records, the cleaning and disinfection records, the records of any quality incidents, and the quality assessment records. Final acceptance shall concentrate on the correctness of pipe position, diameter, level, gradient and verticality; the cleanliness, soundness and tightness of joints; the position and fixing of compensation devices, supports and clips; the flow capacity check, made by opening the largest number of draw-off points required by the design and confirming that each reaches its rated flow, which may be done floor by floor or section by section in special buildings; and the freedom of movement of valves and the sensitivity of instruments.

A Annex A (normative) Chemical composition and mechanical properties of light gauge stainless steel pipes and fittings

A.1 The annex applies to welded light gauge stainless steel pipes and fittings.

A.2 Table A.1 fixes the chemical composition, expressed as mass fraction in per cent, for the seven designations. Carbon: not more than 0.08 for S30408 and S31608, not more than 0.030 for S30403 and S31603, and not more than 0.025 for S11972, S12362 and S12361. Nickel: 8.00 to 11.00 for S30408, 8.00 to 12.00 for S30403, 10.00 to 14.00 for S31608 and S31603, 1.00 for S11972, and not specified for S12362 and S12361. Chromium: 18.00 to 20.00 for S30408 and S30403, 16.00 to 18.00 for S31608 and S31603, 17.50 to 19.50 for S11972, and 21.0 to 24.0 for S12362 and S12361. Molybdenum: not specified for S30408 and S30403, 2.00 to 3.00 for S31608 and S31603, 1.75 to 2.50 for S11972, 0.70 to 1.50 for S12362 and 1.50 to 2.50 for S12361. Copper: not specified for the first five designations and 0.60 for S12362 and S12361; the copper row is printed in the document with the symbol Gu. Nitrogen: not specified for the four austenitic designations, not more than 0.035 for S11972 and not more than 0.025 for S12362 and S12361. Other elements are specified only for the ferritic designations: titanium plus niobium in the range 0.20 plus four times the sum of carbon and nitrogen, up to 0.80, for S11972; and titanium, niobium, zirconium or another combination in the range eight times the sum of carbon and nitrogen, up to 0.80, for S12362 and S12361.

The same table also limits silicon, manganese, phosphorus and sulfur, but those four rows are printed with cells merged across several designations and the merging cannot be resolved from the extracted text, so their values are not reproduced here.

A.3 Table A.2 fixes the mechanical properties. Proof strength at non-proportional extension, in megapascals: not less than 210 for S30408 and S31608, not less than 180 for S30403 and S31603, not less than 275 for S11972, and not less than 245 for S12362 and S12361. Tensile strength, in megapascals: not less than 520 for S30408 and S31608, not less than 480 for S30403 and S31603, not less than 415 for S11972, and not less than 410 for S12362 and S12361. The table also fixes the elongation after fracture in the heat-treated and in the non-heat-treated condition, but those cells are merged across the austenitic and the ferritic group and the pairing cannot be settled from the extracted text, so those figures are not reproduced here.

B Annex B (informative) Calculation of friction head loss in light gauge stainless steel piping

B.1 to B.2 The annex carries Table B.1, a friction head loss calculation table that runs from page 12 to page 26 of the document. Its symbols are: supply flow, in cubic metres per hour or litres per second; calculated internal diameter of the pipe, in metres; friction head loss per unit length of supply pipe, in kilopascals per metre; water velocity at a temperature of 10 °C, in metres per second; and nominal size of the pipe.

Table B.1 is arranged by nominal size, from DN 10 upwards, and within each size by the pipe series and the calculated internal diameter, giving the velocity and the head loss against each flow step. The individual figures are not reproduced in this description.

C Annex C (normative) Stainless steel press-fit D-type socket jointing

C.1 The socket end of a D-type press fitting carries an annular U-shaped groove holding an O-ring rubber seal. On installation a dedicated pressing tool reduces the diameter of the raised part of the U-groove and the socket area of pipe and fitting is pressed into a hexagon. Figure C.1 identifies the pipe, the double-socket short coupling, the O-ring rubber seal and the stainless steel ring.

C.2 Before installation a line is marked right round the pipe end with a dedicated marker to set the insertion length, which shall not be less than the reference values of Table C.1: DN 10 - 18 mm; DN 15 - 21 mm; DN 20 - 24 mm; DN 25 - 24 mm; DN 32 - 39 mm; DN 40 - 47 mm; DN 50 - 52 mm; DN 65 - 64 mm. The socket end shall be machined with the annular U-groove, the O-ring seal shall be fitted in the groove and its position confirmed.

C.3 The joint is made by inserting the pipe squarely into the fitting without tilting it and without cutting or dislodging the seal; checking after insertion that the marked line stands 3 mm from the end at DN 10 to DN 25 and 5 mm at DN 32 to DN 65; pressing with the dedicated tool, the recess of the jaw held tight against the raised part of the fitting, the fitting gripped and the jaw square to the pipe axis; continuing until a slight vibration is felt; confirming that the pressed area of pipe and fitting has formed a hexagon and checking it with a hexagon gauge; using no lubricating oil during pressing; and, where a threaded adaptor is used, pressing only after the thread has been tightened.

D Annex D (normative) Stainless steel press-fit S-type socket jointing

D.1 Figure D.1 shows the S-type socket joint and identifies the fitting, the pipe, the O-ring rubber seal and the pressed area.

D.2 The joint is made by marking the insertion depth on the pipe end with a marker, checking the O-ring seal in the fitting, inserting the pipe to the depth shown by the mark with an adjustment of not more than 3 mm and without damaging the seal, pressing a locking recess on each side of the O-ring with a dedicated tool, and confirming the locked shape and position with a dedicated gauge.

D.3 The pipe mouth is sawn with a hacksaw and deburred, the mouth left smooth and the bore clean; clean water may be used as a lubricant when the pipe is inserted; the tools shall be checked as sound and working before the shift; and the installation steps shall be followed in the order set by the operating procedure.

E Annex E (normative) Stainless steel ring-compression jointing

E.1 Figure E.1 shows the joint before and after ring compression and the socket of the fitting, identifying the fitting, the pipe, the sealing ring, the sealing section and the stabilising section.

E.2 With either hand or powered tools the joint is made by selecting the hydraulic tool matching the fitting and checking that the sliding blocks of the compression assembly move freely and that the assembly is clean; inserting the pipe to the bottom of the socket and marking the pipe along the edge of the fitting; sliding the sealing ring onto the pipe, pushing it to the bottom of the socket with the depth mark aligned to the edge of the fitting and then pushing it into the gap between fitting and pipe; and placing the area to be pressed between the upper and lower blocks with the pipe aligned to the colour mark on the jaw, fitting and pipe square to the jaw, then pumping until the blocks close without a gap, holding for 3 s and releasing.

E.3 to E.4 Dies shall be used and replaced as a set, and the colour marks of die, slide block and pipe run shall agree. After compression the pressed area shall show an even indentation right round through 360°, the end face of the fitting shall meet the pipe closely with no gap, and any excess of the sealing ring squeezed out at the seam shall break off by itself or come away easily. Where the compression is incomplete the blocks shall be replaced in pairs or the tool sent for repair, and the area may be compressed again with a sound tool and rechecked. Where a threaded adaptor is used, a further compression shall follow the tightening of the thread. Pipe and fittings of DN 60 to DN 100 need a second compression, made with the block close to the root of the sealing section of the fitting at the second ring from the end of the socket and pressed until the blocks close without a gap; DN 125 to DN 150 need a third compression made in the same way.

F Annex F (normative) Stainless steel clasp-flange jointing

F.1 Figure F.1 shows the joint in its locking-nut form, identifying the pipe, the plain male thread, the plain female thread, the male-threaded straight coupling, the sealing ring, the locking nut and the raised ring; and in its locking-flange form, identifying the pipe, the locking flange, the threaded hole, the bolt, the sealing ring, the flanged fitting and the raised ring.

F.2 Before jointing, a ring shall be expanded at the pipe mouth: a dedicated tool shall be used to expand the ring; the push nut or loose flange shall be slipped on beforehand; the rolling speed shall not be too high and the roundness of the ring shall be even; and the height of the raised curved face of the ring shall meet the requirement without over-rolling.

F.3 to F.5 Rubber sealing rings of triangular section should not be used for this joint and no lubricating oil shall be used. The pipe shall be inserted fully home, after which the push nut or the loose flange bolts shall be tightened with a spanner until the sealing ring and the raised ring close completely. The finished joint shall be examined and shall show no cracks or splits.

G Annex G (normative) Stainless steel clamp-ring press jointing

G.1 Figure G.1 shows the parts and the basic form of the clamp-ring press fitting, identifying the body, the O-ring rubber seal and the pull-out resisting device. Table G.1 gives, for each nominal size, the pipe outside diameter in millimetres, the socket length in millimetres with a tolerance of plus 5 and minus 0.5, and the insertion depth in millimetres: DN 15 - 16.0, 15.7, 16; DN 20 - 20.0, 16.5, 17; DN 25 - 25.4, 22.5, 23; DN 32 - 32.0, 25, 26; DN 40 - 40.0, 29, 30; DN 50 - 50.8, 37, 38; DN 60 - 60.3, 44, 45; DN 65 - 76.1, 52.7, 53; DN 80 - 88.9, 55.3, 56; DN 100 - 101.6, 60.6, 61.

G.2 A dedicated pressing tool shall be used: the jaw model shall match the size of pipe and fitting; jaws shall be protected against rust at intervals, shall never be struck against metal, shall be kept sound at every part and shall be overhauled after twelve months of use; powered pressing tools shall be kept out of the rain and not used in damp conditions; powered tools shall be under the care of a named person and used for this purpose only; and the press gun, jaws, arms and ring dies shall be operated by trained personnel.

G.3 The joint requires trained installers familiar with the pipe and fittings; the pipe length is calculated from the run, the cutting length confirmed and the pipe cut; burrs are removed so that they cannot cut the seal; the pipe is inserted without tilting and without cutting, twisting or dislodging the seal; the pipe is inserted to the bottom of the socket to the required depth, marked with a dark oil-based pen; the joint is pressed with the dedicated tool, the pressing position below the jaw and the jaw held tight against and square to the fitting or pipe; no lubricating oil is used; and ring dies are used as a set with the press arms.

G.4 After jointing the indentation right round shall be even and tight and the pressed shape shall be circular. Where the pipe is found not to be inserted fully home the joint area shall be cut out and remade. Where the pressing is found to be incomplete the tool shall first be checked and repaired if damaged, and a new joint shall then be fitted and pressed again.

H Annex H (normative) Stainless steel compression jointing

H.1 The end of a compression fitting carries a screwed nut and an O-ring rubber seal. On installation the connecting end of the pipe is expanded from inside into a raised ridge with a dedicated tool, or a retaining ring is added; the O-ring seal is then placed in the end of the fitting, the pipe is inserted and the nut is tightened. Figure H.1 identifies the pipe, the O-ring silicone rubber seal, the equal straight coupling, the split stainless steel snap ring, the male thread, the locking nut and the stainless steel inner sleeve.

H.2 Preparation follows in order: cutting the pipe with an abrasive cut-off machine, the cut square and the internal and external burrs cleaned off; unscrewing the nut from the end of the fitting and slipping it onto the pipe; expanding the pipe from inside into a raised ridge with the expanding tool, or adding a retaining ring; placing the O-ring seal in the end of the fitting; inserting the pipe, with the nut already on it, into the fitting; and tightening the nut by hand and then with a spanner.

H.3 When jointing, the nut at the end of the fitting shall be unscrewed and slipped onto the pipe before expanding. The expander carries dies for the different diameters, an expanding-collar type die, which forms a single raised ridge, being used from DN 15 to DN 50, with a wooden mallet to help fit and remove the die halves. The pipe locates itself on the die during expansion, the lever being worked up and down to a hand force of about 30 kg to 50 kg, and the position of the collar or expanding ring shall meet Table H.1, which gives the outside diameter at the expanded position in millimetres: DN 15 - 16.85; DN 20 - 22.85; DN 25 - 28.85; DN 32 - 37.70; DN 40 - 42.80; DN 50 - 53.80.

I Annex I (normative) Stainless steel plug-in TIG welded jointing

I.1 Figure I.1 shows the plug-in TIG welded joint and identifies the double-socket straight coupling, the stainless steel pipe and the TIG weld.

I.2 to I.3 The joint is made by inserting the pipe into the socket until it meets the internal shoulder and then withdrawing it 0.5 mm to 2 mm, running an annular weld right round the end of the socket with tungsten inert gas welding, and polishing the weld. Filler wire may be added where the end of the fitting has no extended edge; where it has an extended edge the joint may be welded without filler, the extended edge taking its place.

I.4 Tungsten inert gas welding calls for a low current and a fast travel speed. Table I.1 gives the welding parameters against pipe wall thicknesses of 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm and 1.5 mm. Without pulsing, the tungsten electrode diameter is 1.0 mm, then 1.0 mm to 1.5 mm for the next three thicknesses, then 1.0 mm to 2.0 mm; the welding current is 8 A to 12 A, 12 A to 18 A, 25 A to 38 A, 35 A to 48 A and 45 A to 60 A; the travel speed is 50 mm/min to 85 mm/min, 60 mm/min to 180 mm/min, 150 mm/min to 300 mm/min, 260 mm/min to 450 mm/min and 400 mm/min to 550 mm/min; the gas flow is 4 L/min to 5 L/min, 4 L/min to 5 L/min, 5 L/min to 6 L/min, 6 L/min to 8 L/min and 8 L/min to 10 L/min. With pulsing, the electrode diameter is 1.0 mm to 1.5 mm, then 1.5 mm to 2.0 mm for the next three thicknesses, then 2.0 mm to 2.5 mm; the welding current is 10 A to 16 A, 18 A to 25 A, 25 A to 42 A, 38 A to 50 A and 45 A to 60 A; the pulse frequency is 8 Hz to 10 Hz for the first three thicknesses and 10 Hz to 12 Hz for the last two; the travel speed is 60 mm/min to 130 mm/min, 100 mm/min to 140 mm/min, 130 mm/min to 260 mm/min, 220 mm/min to 400 mm/min and 360 mm/min to 500 mm/min; and the gas flow is 5 L/min to 6 L/min, 5 L/min to 6 L/min, 6 L/min to 8 L/min, 8 L/min to 10 L/min and 10 L/min to 12 L/min.

I.5 to I.6 A portable inverter machine able to do both TIG and manual arc welding should be used, and both the inner and the outer wall of the stainless steel pipe shall be protected by inert gas during welding.

J Annex J (normative) Stainless steel butt TIG welded jointing

J.1 to J.2 Figure J.1 shows the butt TIG welded joint and identifies the pipe, the weld and the TIG weld. The joint is made by running an annular weld right round the bevel with tungsten inert gas welding; where several passes are needed the root pass shall also be TIG, the remaining layers being allowed in manual metal arc welding. Inert gas should be used to protect the inner face of the weld, or a filler wire that protects it should be chosen, so that the inner face is left flat and free of gaps. The weld shall be polished.

J.3 Table J.1 gives the bevel parameters: bevel angle 60° to 70°, gap 0 mm to 2 mm, root face 0 mm to 1 mm. Where the wall thickness of pipe and fitting is less than 3 mm a square edge or a slight chamfer may take the place of a bevel.

J.4 Filler wire is chosen from the material of the pipe and fitting and from the tungsten inert gas welding process: austenitic H08Cr21Ni10 may be used for 06Cr19Ni10 (S30408); austenitic H06Cr19Ni12Mo2 for 06Cr17Ni12Mo2 (S31608); and austenitic H03Cr19Ni12Mo2 for 022Cr17Ni12Mo2 (S31603).

K Annex K (normative) Stainless steel flexible threaded jointing

K.1 On installation a 90° flanged face is formed at the pipe end with a dedicated tool, and two such faces are pressed against a sealing ring with a limiting structure and tightened. Figure K.1 identifies the union female-threaded fitting, the O-ring seal, the sealing ring with limiting structure, the union male-threaded fitting, the flanged stainless steel pipe, the ready-made flanged short coupling, the TIG weld and the parallel thread G.

K.2 Before installation a line is marked right round the pipe with a dedicated marker to set the width of the flanged face, which shall follow the reference values of Table K.1, in millimetres: DN 15 - 4.0; DN 20 - 4.0; DN 25 - 5.2; DN 32 - 6.4; DN 40 - 6.6; DN 50 - 7.1; DN 60 - 8.6; DN 65 - 9.3; DN 80 - 10.6; DN 100 - 12.0. The end of the fitting shall be fitted over the 90° flanged form, the sealing ring with limiting structure shall be placed in the groove and its position confirmed.

K.3 The joint is made by cutting the pipe with an abrasive cut-off machine where cutting is needed, the cut square and the internal and external burrs cleaned off; unscrewing the nut from the end of the fitting and slipping it onto the pipe; forming the 90° flange at the pipe end with a hydraulic flanging machine; placing the sealing ring with limiting structure in the end of the fitting; and tightening with a spanner.

K.4 to K.6 The instruction manual for the flexible threaded system shall be read carefully before installation and followed. After jointing the width of the flanged face shall be confirmed with a dedicated vernier caliper; where the flange is incomplete the fitting shall be cut off and the work redone. Where the measured size is wrong the hydraulic flanging die shall first be checked and sent for repair if damaged; the flange may then be reformed with the machine and rechecked with the caliper. When jointing, the nut shall be unscrewed and slipped onto the pipe before flanging; the hydraulic flanging machine carries dies for nominal sizes DN 15 to DN 100; the pipe locates itself on the die during flanging; the sealing ring with limiting structure shall lie flat in the end of the fitting and no lubricating oil shall be used; the flanged pipe shall be pressed into the threaded fitting without damaging the seal or disturbing its flatness; and at connections to valves, taps and other line accessories the thread of the ordinary fitting shall be wrapped with sealing tape or coated with metal sealant.

L Annex L (normative) Stainless steel grooved jointing

L.1 Figure L.1 shows the grooved joint and identifies the groove, the clamp, the saddle-shaped sealing ring, the roll-grooved pipe, the bolt and the nut.

L.2 The cut face of the pipe shall be flat and free of cracks, dents and necking and shall be ground smooth; the pipe mouth at the grooving area shall be rounded and slag, oxides and other dirt removed from the surface. The groove shall be machined with a dedicated roll grooving machine fitted with a limiting device.

L.3 During grooving a level shall be used to check that the pipe lies horizontal; the end face of the pipe shall be held against the stop of the grooving machine and the pipe axis shall be square to that stop; the pipe shall not move axially or angularly while the groove is rolled; the time taken to machine one groove shall meet Table L.1, in minutes - DN 50 - 2; DN 65 - 2; DN 80 - 2.5; DN 100 - 2.5; DN 125 - 3; DN 150 - 3; DN 200 - 4; DN 250 - 5; DN 300 - 6; and the depth and width of the groove shall be measured with a vernier caliper, the fitting being removed only once the groove is confirmed correct.

L.4 The rolled groove shall meet the following: the surface from the pipe end to the groove shall be true, without dents or roll marks; the groove shall be concentric with the pipe wall and its width and depth shall meet the relevant standards; and the outside diameter at the groove shall not exceed the specified value.