Carbon Steel Orifice Flange - ANSI B16.36

Introduction to Orifice Flange
An Orifice Flange is used in combination with orifice meters to measure the flow rate of oil, gas and other liquids conveyed by the pipeline. Orifice flanges are manufactured to ASME B16.36 in multiple sizes and, material grades.

WHAT IS AN ORIFICE FLANGE?
An orifice flange is used to measure the flow of the fluid conveyed by the pipeline via a flow nozzle positioned on the flange itself. Pairs of pressure tappings are machined onto the orifice flange, making separate tappings on the pipe wall unnecessary.

The traditional orifice flange assembly consists of a pair of flanges, orifice plate, bolts, nuts, gaskets, jacking screws and plugs. Jacking screws ensure the easy removal of the primary flow element.

Orifice flanges are available in all ASTM forged grades (ASTM A105, ASTM A350, ASTM A694, ASTM 182 respectively for carbon, alloy and, stainless steel flanges), dimensions (combinations of nominal sizes and pressure ratings) and, in socket weld, threaded or weld neck shape (WN is the most used).


Orifice flanges are basically the same as standard weld neck, slip-on and screwed flanges except for the provision of radial, tapped holes in the flange ring for meter connections and additional bolts to act as jack screws to facilitate separating the flanges for inspection or replacement of the orifice plate.
In choosing the type of orifice flange, the considerations affecting the choice of weld neck, slip-on and screwed standard flanges apply with equal force. They are made in pressure classes 300#, 600#, 900#, 1500# and 2500#; in carbon steel, stainless steel and alloy materials; and raised faced or ring joint.
They are not available in 150# sizes because the thickness of 150# flanges are not enough to allow for drilling pressure taps.
Orifice flanges are installed in a straight run of pipe in order to avoid turbulence at the plate. As a rule of thumb, an orifice flange has ten diameters of straight pipe upstream and five diameters of pipe downstream. There are guidelines set out in (American Gas Association) AGA Report #3 which is the Orifice Metering of Natural gas.
When installing the orifice plate flange the pressure taps need to be at the same elevation to each other. The assumption when making the calculation for the orifice plate is that static head of the tubes is the same on both sides of the orifice plate. Pressure taps should not be installed facing down as the taps could become plugged with debris in the line.
 

DN15-DN3000
Maximum weight 6tons
25,000tons production annual year

ANSI B16.5,ANSI B16.47 Series A&B,ANSI B16.48,ANSI B16.36
API 605,API 16D,API 17D
BS4504,BS3293
DIN
AS
EN1092-1
GOST
EEMUA145