ASME B16.36 orifice flanges are supplied in pairs to hold an orifice plate for flow measurement. Each flange has radial pressure tappings drilled through the flange ring so that a differential pressure transmitter can measure the pressure drop across the plate, and jack screws to spread the flanges for plate changes. B16.36 covers orifice flanges in Class 300 and higher, based on the dimensions of ASME B16.5 weld neck, slip on and threaded flanges.
Raaj Fittings manufactures orifice flange unions to ASME B16.36 at our two plants in India, complete with taps, jack screws and plugs, in carbon, low-temperature, alloy and stainless steel for oil, gas and process metering.
Flange taps are located a fixed distance from each face of the orifice plate, which is why B16.36 controls the tap location, flange thickness and bore. Weld neck orifice flanges are bored to the pipe inside diameter so that there is no step at the plate, which would disturb the flow profile. Metering runs are usually built with straight lengths of pipe upstream and downstream, as required by the flow measurement standard used.
B16.36 orifice flanges are made in Class 300 to 2500. Lower-pressure systems normally use Class 300 orifice flanges as the minimum. Raised face and ring type joint facings are available. Materials include ASTM A105, A350 LF2, A182 F11 / F22, stainless steel F304/304L and F316/316L, and duplex.
Every orifice flange is made from PMI-verified material, dimensionally inspected against the ordered standard and marked with material, size, rating and heat number. Orders are supplied with EN 10204 3.1 certificates; EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request.
ASME B16.36 covers orifice flanges from Class 300 upwards. Systems designed for Class 150 normally use Class 300 orifice flanges at the metering point.
Tappings are normally ½" NPT, two per flange. Socket weld tappings or other configurations can be supplied to order.
The flange ring must be thick enough to drill the radial pressure tappings at the required distance from the orifice plate faces.
Yes, orifice flange unions are normally supplied with jack screws so the flanges can be spread to remove the orifice plate.