SAE Flange PCD
The PCD of a flange is regarded as one of the most critical dimensions in valves and flow control. PCD stands for Pitch Circle Diameter. It is defined as the diameter of a circle that goes through each of the wheel bolts, studs, wheel rim holes or bolt holes. Flanges are regarded as the perfect example to describe and calculate the Pitch circle diameter. This is because a flange has multiple holes.
1. What is an SAE Flange ?
An SAE Flange is defined as a method of connecting valves, pipes, pumps, or other equipment to form a piping system. An SAE Flange also provides easy access for inspection, cleaning, and modification. Most SAE flanges are either screwed or welded. The joints present in SAE flanges are made by bolting together two flanges with an elastomer o-ring in between the groove and the flat side to produce a seal.
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There are various types of flanges but the most common ones especially in the Petro-chemical industry are Slip-on Flange, Blind Flange, Welding Neck Flange, Threaded Flange, Socket Weld Flange, and Lap Joint Flange. However, SAE Flange is the most common flange to be used in high pressure hydraulics applications.
2. What is SAE Flange PCD ?
The PCD (also known as Pitch Circle Diameter) is defined as the diameter of the circle that passes through the centre of all the studs, wheel rim holes, or wheel bolts. There are different ways to calculate the pitch circle diameter, but the easiest way involves two steps. The first step involves measuring the distance between the two adjacent studs from the centre of each of the holes. The second step involves using the formula to calculate the pitch circle diameter. The formula depends on the value of the measurement derived from the first step.
3. What are the important definitions to know when calculating the PCD of an SAE flange?
To successfully calculate the pitch circle diameter of a flange, it is important to know some important definitions that will be used as parameters. They are discussed below:
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Pitch Circle: The pitch circle is defined as the transverse section of the pitch cylinder in the flange normal to the axis.
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Pitch Circular: The pitch circular is defined as the distance that is measured along the pitch circle between the centres of two adjacent holes (or teeth). It is usually on a plane that is at a right angle to the axis of rotation.
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Studs: A stud is defined as a large-headed piece of metal that pierces and also projects out from a surface. It is mainly used as a form of decoration. There are different forms of stud arrangement which include 3 studs (meaning three holes), 4 studs (meaning four holes), 5 studs (meaning five holes), and so on.
4. How to measure the Pitch Circle Diameter (PCD) of an SAE Flange?
The Pitch Circle Diameter is regarded as one of the most critical dimensions for measuring a flange. The Pitch Circle Diameter of an SAE Flange is the diameter of the circle that goes through each of the bolt holes. It might be difficult to measure the pitch circle diameter of some flange. The common tools used to measure PCD are electronic caliper or plastic ruler sliding gauge caliper.
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PCD is important when comes to assembly complete set of SAE Flange. 4 socket head cap screws and spring washers need to insert inside the bolt hole to tighten up. Please refer to the correct way of measuring SAE Flange PCD.
Please refer to the common mistake of measuring SAE Flange PCD below:
To get accurate SAE Flange PCD measurement, please ensure you put the caliper in the right place. The wrong measurement PCD dimension may cause inaccurate dimension and affect assembly installation.
The actual measurement of pitch circle diameter as below:
5. Can the SAE Flange body size different from the connection?
Each SAE flange has two different dimension identities: SAE Flange body and SAE Flange connection. The common SAE Flange comes with the same SAE Flange body and connection. Example: SAE Flange code 61 with PCD of 52.37 and 26.19 has a 1-inch flange body and it can use to 1” nominal bore pipe size. If the SAE Flange body dimension is not equal to the SAE Flange connection, the flange needs to be customized by machining accordingly.
SAE Flange PCD dimension, 3000# Code 61:
SAE Flange PCD dimension, 6000# Code 62: