Oil and gas plants are large, complex environments with thousands of miles of interconnected piping. The Pipeline and Hazardous Materials Safety Organization estimates that there are 160,521 miles of liquid petroleum pipeline and 1,585,672 miles of natural gas pipeline in the United States. Pipe flanges are a critical part of the piping systems, interconnecting pipe fittings to other equipment.
Flanges come in various standard dimensions, according to different publications from organizations such as ASME, API, MSS, and others. Projects in the oil and gas sector are unique, necessitating specific pipe flanges to perform the job.
Nearly all flanges are round discs that interconnect valves, pipes, strainers, and fittings. Different shapes such as rectangles, squares, or oval are specific to speciality equipment such as hydraulics. Knowing the different types and standard dimensions can assist you in ordering the correct flanges for your piping systems. Here are some steps to take to pick out the right pipe flanges for your project.
1. Define Your Standard or Specification
Originally, pipe flanges came in standard weld neck, threaded, or blind configurations. As fittings came into the oilfield, standard dimensions became necessary for functional interchangeability. The late 1930s saw the American Petroleum Institute (API) adopt the ASA B16.
Over the years, more standards, sizes, definitions, and pressure classes were added. Most of the standards represent the dimensions, tolerances, and chemistry of the materials. Details of the standard dimensions include the number, size, and diameter of bolt holes, as well as the flange face.
Standard dimensions are the same for all materials used. However, the specifications are regularly revised, broadened, and updated. Standard classifications often used in the oil and gas industries include:
- 150#
- 300#
- 600#
- 900#
Each of these standards classifies flanges by pressure class, facing, pipe size, and connection.
2. Figure Out the Flange Facing
Defining the facing of your flanges is one of the first steps to ordering the industrial pipe fittings. The face of the flange is the sealing surface. The most common types of flange faces include:
- Raised face
- Lap joint
- Large male and female
- Ring-type face
- Flat face
- Full face
The raised face is the most common industrial flange facing. The standard dimensions may vary depending on the classification. Class 150# and 300# have a 1/16-inch raised face. Class 400# to 2500# have a 1/4-inch raised face. Lap joint types have flat faces and are used together with a stub end. Flat face flanges utilize the whole face for sealing and are popular for low-pressure applications. The ring-type face uses a metal ring gasket that fits into the groove in the flange. You can modify your flange faces as long as the minimum standard dimensions are maintained.
3. Pick Out the Correct Pressure Class
The pressure class of a flange standard determines its dimensions. The pressure class rating may fall within 125 to 900 psi. Four factors that influence the pressure limits of the flanges within the oil and gas industry include:
- Dimensions, thickness, number, and size of bolts
- Internal and external temperatures
- Material used
- Flange sizes
You may need to consult your fitting distributor to determine the right flange pressure class for your project.
Flanges are critical fittings for oil and gas industrial piping. For more information on how to source the right flanges for your project, reach out to Lynco Flange and Fitting.