How To Measure A Flange?

How To Measure A Flange?

Flanges are protruding rims that connect pipes, valves, and other equipment to increase the strength of the joint. Flanges are used to create piping systems and can be easily removed for inspection or modification.

What Are The Most Common Flange Types?

Weld Neck Flange:

Weld neck flanges perform exceptionally well in high pressure systems. They are one of the most common types of flanges. Their long neck allows for seamless butt welds to be made directly onto the pipe, resulting in a smooth connection. They are therefore ideal for use in industries such as oil and gas, where high pressure is critical. This type of flange connection is almost exclusively used for larger diameters and higher pressure classes.

Slip-on Flange:

Slip-on flanges are easy to install, making them popular with fabricators and manufacturers. Because slip-on flanges have no welded bevels and allow for pipe length adjustment based on the flange position, they are a simple and excellent alternative to welded necks. The matching pipe has sufficient space in the slip-on’s bore. This extra room gives fabricator and welder sufficient workspace to make connections. They are often used in industries such as shipbuilding and construction that require fast and efficient installation. This type of flange is widely used in low pressure applications.

Socket-weld Flange:

Socket weld flanges are resistant to high pressures and temperatures, which benefits the power generation and chemical processing industries. With a counterbore in the middle to enable a clean pipe weld into the socket, socket weld flanges are less popular but no less effective connection for flanges that require less total available space than a typical weld neck flange. 

They are generally available in smaller nominal pipe sizes and are an excellent alternative to slip-on and weld necks when necessary. If the fluid is non-corrosive and the pressure is relatively low, a socket weld may be chosen for an assembly with limited space or extremely high-temperature duty.

Blind Flange: 

Blind flanges are essential for closing off certain parts of a piping system. Blind flanges are dependable barriers in petrochemical and other hazardous material-related industries, keeping workers safe and stopping leaks during emergencies or maintenance. Raised blind flanges typically have a slight indentation in the middle and other industry standard cast steel requirements dating back decades. This recess allowed the pipe end to mate with the connecting flange and for a seal to form between the blind and the connecting flange.  In most cases, blind flanges are not produced in these shapes because early cast iron specifications are somewhat outdated. Instead, choose modern blind flanges with or without a hub.

Threaded Flange:

Threaded flanges are easy to install and work well in low-pressure applications. They are an vital component in piping systems and other environments where a lot of welding is not required to maintain a tight seal. The threaded flange has a female NPT thread in the middle for connection to the male NPT pipe. They are also sometimes called companion flanges, screw flanges, or NPT flanges. Threaded flanges are often used to create reduced connections.

Lap Joint Flange:

Lap joint flanges are one of the other common flange types. They are also known as Backup flanges, Loose Ring flanges, Loose Hub flanges, and Van Stone flanges. Lap joint flanges are easy to remove and offer flexibility, making them ideal for industries such as food and beverage that require adjustments or regular maintenance. The hubs can be adjusted to your specifications and are typically taller than slip-on designs. Higher-pressure class slip-ons are typically designed with a lap joint height for improved attachment. Industrial flanges are used in a variety of industries such as structural and piping applications. Rolled angle rings and lap joint flanges are two essential components in many processes. The main difference between rolled angle rings and lap joint flanges is that the latter are only available in a butt welded arrangement.

How To Measure A Flange?

Getting the right flange is very important. Use the guide below to measure your flanges and check the measurements using the flange identification chart to see which flange is right for your application. One of the most important measurements is the Pitch Circle Diameter (PCD), which determines whether the bolt holes in the flange match up with each other.

A: Inside Diameter

Measure from one side of the inner hole to the center of the other side of the hole. This will tell you what size pipe or tube you need.

B: Outside Diameter

Measure across the centre from the external edge to the other external edge of the flange.

C: Pitch Circle Diameter (PCD)

Measure the distance from the center of the bolt hole to the center of the opposite bolt hole. This can also be measured from the external edge of the bolt hole to the internal edge of the opposite bolt hole. This measurement will tell you the distance between bolt holes so you can match the same flanges together.

D: Hole Size

Measure from edge to edge, across the center of the bolt hole. This will usually be slightly larger than the metric bolt being used.

E: Thickness

Measure from one edge of the flat face to the other.

C&N Hongcheng specialises in the manufacture of various types of flange products. We use cross-linked polyolefin substrates and proprietary adhesives to ensure long-term corrosion protection. Our liquid coatings are high performance protective solutions designed for the oil, gas, water, transportation, power, mining and construction industries. These coatings provide lasting protection for buildings, structures and equipment operating in industrial and harsh environments. Please contact us for more information.