EN 1092-1 Type 11 PN 25 Weld Neck Flange — Dimensions, Weights & Bolting

It is a weld neck flange made to the European standard EN 1092-1 in nominal pressure class PN 25. In EN 1092-1, “Type 11” is the designation for the weld neck (welding neck) flange — a flange with a long tapered hub that is butt-welded to the pipe. PN 25 is rated for roughly 25 bar at room temperature, and the chart on this page covers DN 10 to DN 2000.

PN stands for “Pression Nominale” — the nominal pressure class. A PN 25 flange is rated for a maximum working pressure of about 25 bar at room temperature, with the exact allowable pressure depending on the material group and falling as temperature rises, per the pressure-temperature tables in EN 1092-1. The PN series runs 2.5, 6, 10, 16, 25, 40, 63, 100, 160, 250, 320 and 400.

PN 25 is specified where PN 16 runs out: district-heating flow lines, hot water and thermal-oil circuits, moderate-pressure steam and condensate, and general process duty in the 16–25 bar band. From DN 200 upward it saves real weight against PN 40, which is why big moderate-pressure headers are ordered in PN 25 rather than jumping a class.

EN 1092-1 gives each flange construction a type number — plate (01), loose (02/04), blind (05), hubbed slip-on and threaded (12/13), integral (21) and collars (32/34) — but the chart on this page is edited down to the weld neck alone. It lists the D, K and L mating dimensions with bolting, which are shared by every type of the class, plus the Type 11 columns: neck OD A, thickness C2, lengths H2 and H3, neck diameter N1, radius R and neck wall S.

PN 25 sits between ASME Class 150 (roughly 20 bar cold for A105) and Class 300 (roughly 51 bar) in duty. The systems are dimensionally unrelated: EN 1092-1 uses DN sizes, metric bolting and its own facings, ASME B16.5 uses NPS sizes and imperial bolting — the two never bolt together at the same nominal size.

The Type 11 weld neck series in PN 25 runs from DN 10 to DN 1000 (DN 10–150 per the PN 40 dimensions; the dedicated PN 25 series begins at DN 200). The chart also lists rows up to DN 2000, but the weld-neck-specific columns end at DN 1000 — larger sizes are quoted case-by-case as special forgings.

From the weight columns in our chart: A DN 200 about 18 kg (40 lbs), a DN 300 about 33 kg (74 lbs), a DN 600 about 145 kg (319 lbs), a DN 1000 about 323 kg (711 lbs). These are approximate carbon-steel weights calculated from the standard dimensions with a standard bore — actual weight varies with the bore and material.

Form A flat face, Form B1 raised face (standard), Form B2 smooth raised face; tongue/groove and spigot/recess (Forms C–F) on request. State the form required — and the gasket it must suit — on your enquiry.

The bore is machined to match the inside diameter of the mating pipe so the joint has a smooth, unrestricted flow path and a clean butt weld. State the pipe wall thickness or internal diameter (or the pipe standard and series) with your order — the chart's S column gives the preferred neck wall thickness for each size.

We manufacture them in carbon steel A105/P250GH and low-temperature A350 LF2, stainless steel 304/L (1.4301/1.4307), 316/L (1.4401/1.4404), 321 (1.4541), 310, 347 and 410, 254 SMO (1.4547), 904L (1.4539), duplex 2205 (1.4462), super duplex 2507 (1.4410), alloy steel F1–F91, Monel 400/K500, Inconel 600/625/825, Hastelloy C276/C22, titanium Gr. 2/5, copper nickel 90/10 and 70/30, and bimetal/clad — all with EN 10204 3.1 certificates.

It rises with size — the chart's bolting columns give the exact count and metric thread per DN: a DN 200 takes 12 × M24, a DN 450 takes 20 × M33, a DN 1000 takes 28 × M52 and a DN 2000 takes 48 × M64. Bolt holes (column L) and the bolt circle (column K) are also tabulated, so gasket and fastener take-offs can be made straight from this page.

EN 1514-1 sheet or spiral wound gaskets sized for PN 25; full-face gaskets for Form A flat face. Always match the gasket to the facing form and PN class of both flanges.

The tapered hub and full-penetration butt weld make the joint as strong and fatigue-resistant as the pipe itself, the weld is easy to examine by radiography or UT, and the matched bore eliminates turbulence and crevice corrosion at the joint. Cheaper constructions have their place in undemanding services, but Type 11 is the engineering choice for process lines, temperature cycling and critical media.

When the line's design pressure (at design temperature, for your material group) exceeds the PN 25 rating of roughly 25 bar — remembering that the allowable pressure derates at elevated temperature, so a 22-bar line at 250 °C may already need PN 40. Surge, water hammer and test pressures should be included in the check. See the PN 40 Type 11 chart linked on this page.

Every batch is dimensionally inspected against EN 1092-1, marked with size, PN class, material grade and heat number, and supplied with EN 10204 3.1 mill test certificates. PMI verification, ultrasonic and magnetic-particle examination, impact testing for low-temperature grades, NACE MR0175 compliance and third-party witness inspection by LR, BV, DNV, SGS, TÜV or IBR are available on request.

Yes. Besides standard EN 1092-1 dimensions we machine special bores, extended hubs and long weld neck versions, special facings and drilling, and flanges to customer drawings — including sizes outside the standard series as special forgings, quoted case-by-case. Send the drawing or datasheet and we will quote to it.

District-heating utilities, chemical and food plants, power-station auxiliary systems, thermal-oil and hot-water system builders, and any European-specification project in the 16–25 bar band. EPC contractors ordering to EN piping classes specify PN 25 Type 11 flanges on the moderate-pressure units of the plant.

Size (DN) and quantity, standard and type (EN 1092-1 Type 11), PN class, facing form, pipe wall thickness or bore, material grade, any impact-test or NACE requirement, and the certification and inspection you need. Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer and exporter in Mumbai, India, shipping worldwide with sea-worthy packing.