Strainer and separator run on the hot-water skid, joined by bolted flanges

Strainer and separator — Inzonex Modular Insulation, hot-water skid

Flanged joints / Standards

Flange standards: PN, ANSI class and DIN

Two flanges of the same bore, from two standards, will not meet.

European plant is dimensioned to EN 1092-1 and rated by nominal pressure in bar: PN6, PN10, PN16, PN25, PN40. North American plant is dimensioned to ASME B16.5 and rated by class: 150, 300, 600. The numbers are not the same kind of number, the bolt circles differ, and the bolt counts differ. There is no adaptor between them - where two standards meet, one flange gets changed.

The numbers

What PN and class actually mean

PN is a pressure, roughly

PN16 is a nominal 16 bar, and the pressure a flange will actually hold falls as the temperature rises. On a hot-water circuit at 60 to 90 degrees that derating is small. It is still the reason the standard prints a temperature-pressure table rather than a single figure.

Class is not a pressure

Class 150 does not mean 150 psi. It is an index into a table: a carbon steel class 150 flange is rated near 285 psi cold and drops away steeply with temperature. Reading the class as a pressure is one of the more common ways a joint gets specified wrong.

DIN

Where the DIN numbers went

Superseded, not abolished

DIN 2632, 2633, 2634 and the rest were withdrawn in favour of EN 1092-1, which carries the same dimensions for the same PN and DN. A drawing calling for a DIN 2633 DN50 PN16 is asking for what EN 1092-1 now calls a Type 11 DN50 PN16. The part that arrives will fit.

The conversion people mean

A search for a DIN to ANSI conversion is almost never asking about DIN against EN. It is asking whether a European flange will bolt to an American one. It will not. What is needed is the DN and the PN of what is installed, and then the correct flange ordered to that.

The check

What to measure before ordering

Four numbers settle it

Outside diameter of the flange, diameter of the bolt circle, number of bolts, and bore of the pipe. Those four identify the standard and the rating between them. A tape measure across the bolt circle is worth more than the label on the box.

The same DN is not the same flange

DN50 in EN 1092-1 PN16 is 165 mm across with four M16 bolts on a 125 mm circle. Two inch in ASME B16.5 class 150 is 152.4 mm across with four five-eighths bolts on a 120.7 mm circle. Same bore, neither the rim nor the holes in the same place.

Reference

EN 1092-1 PN16, Type 11

Size	Flange OD mm	Bolt circle mm	Bolts
DN15	95	65	4 x M12
DN20	105	75	4 x M12
DN25	115	85	4 x M12
DN32	140	100	4 x M16
DN40	150	110	4 x M16
DN50	165	125	4 x M16
DN65	185	145	8 x M16
DN80	200	160	8 x M16
DN100	220	180	8 x M16
DN125	250	210	8 x M16
DN150	285	240	8 x M20
DN200	340	295	12 x M20

Size · Flange OD mm · Bolt circle mm · Bolts. From EN 1092-1; confirm against the current standard before ordering.

Asked about flange standards: pn, ansi class and din

Questions.

Answers distinguish modelled heat-loss estimates from equipment selection and service guidance.

What is the difference between PN and ANSI flanges?

PN is the European series in EN 1092-1, indexed by nominal pressure in bar. ANSI, properly ASME B16.5, is the American series indexed by class. They use different flange diameters, different bolt circles and different bolt counts. Two flanges of the same bore from the two standards cannot be bolted together.

Is PN16 the same as class 150?

No, and they are close enough in rating to cause trouble. A PN16 DN50 flange is 165 mm across, with four M16 bolts on a 125 mm circle. A class 150 two-inch flange is 152.4 mm across, with four five-eighths bolts on a 120.7 mm circle. Neither the rim nor the holes line up.

What replaced DIN 2633?

EN 1092-1. The DIN flange standards were withdrawn and their dimensions carried over. A DIN 2633 DN50 PN16 and an EN 1092-1 Type 11 DN50 PN16 are the same part. Old drawings still call for the DIN number, and what arrives will fit.

How do I identify an existing flange?

Measure the outside diameter, the bolt circle and the pipe bore, and count the bolts. Those four numbers identify the standard and the rating without relying on a stamp that may be painted over or facing the wall.