A line needs bends, tees, reducers, flanges and caps in the same material, the same wall thickness and the same batch as the pipe — otherwise the weld doesn't fit and the pressure rating doesn't match.
Typical ratios for a buried trunk main with 6 bends per kilometre of alignment change, one branch every 500 m and a valve chamber every 2 km. Use it to sanity-check a tender list — not as a substitute for the isometric.
| Item | Size range | Material | Standard | Availability |
|---|---|---|---|---|
| Seamless butt-weld elbow 90°/45° | DN15 – DN600 | A234 WPB · 20# | GB/T 12459 ASME B16.9 | Stock |
| Welded (plate) elbow, large bore | DN600 – DN2000 | A234 WPB · Q235B · Q355B | GB/T 13401 | Made to order, 7–15 d |
| Equal / reducing tee | DN15 – DN2000 | A234 WPB · 20# | GB/T 12459 B16.9 | Stock + made to order |
| Concentric / eccentric reducer | DN25 – DN2000 | A234 WPB · 20# | GB/T 12459 | Stock + made to order |
| Slip-on / weld-neck flange | DN15 – DN2000 | Q235B · 20# · 16Mn | GB/T 9119 B16.5 B16.47 | Stock |
| Dished head / cap | DN25 – DN2000 | Q235B · Q345B | GB/T 25198 | Made to order |
| Pipe support / saddle | Per drawing | Q235B + 聚氨酯 / 木托 | Per drawing | Made to order |
| Rubber-lined fittings | DN25 – DN1200 | 碳钢 + 天然橡胶 / 丁基胶 | HG/T 20677 | Made to order, 10–20 d |
Order says PN16, the valve on site is Class 150 — bolt holes line up, gasket face doesn't seal, and nobody notices until the pressure test.
Fix: state the valve make and model on the enquiry.Pipe is 12 mm, the bend supplied is 10 mm SCH — weld prep still fits, but the fitting becomes the weakest point in the section.
Fix: quote fittings by wall thickness, not by DN only.Horizontal liquid lines need flat-bottom (eccentric) to avoid air pockets; vertical lines take concentric. Swapping them traps gas or drains the wrong way.
Fix: mark eccentric/concentric on the isometric, with the flat side orientation.Fittings are made from the same heat as the pipe wherever possible, with the heat number transferred onto the fitting and printed on the certificate. That is what makes a weld procedure qualification hold on site.
Bevels protected with plastic caps, flanges faced with plywood discs, small fittings in wooden crates, large bends on saddles — not loose in a container where they grind against each other for six weeks.
Marks are stencilled in three languages on two sides, and the crate numbering follows the packing list so the site storeman can book items in without opening everything.
90° / 45° / 180°, R=1.5D or long radius, seamless up to DN600 and plate-welded above.
Equal and reducing tees, concentric and eccentric reducers, all with heat numbers.
Slip-on and weld-neck to GB/T 9119, B16.5, B16.47; dished heads to GB/T 25198.
Yes — that is the point of buying both here. Same heat where possible, same wall thickness series, one packing list, one shipment. It removes the classic argument about who supplied the mismatched bend.
No fixed minimum on stock items — mixed containers are normal. Made-to-order large bends, lined fittings and supports start from one piece because they are built to drawing anyway.
Yes — bends, tees and reducers DN25–DN1200 lined with natural or butyl rubber, 3–6 mm, spark-tested after lining. Common for slurry, flue-gas desulphurisation and acid service.
Technical proposal and quotation within one working day.
