What are flange bolts

Flange Bolts

Flange bolts are identifiable by a ridge below the bolt head. This built-in washer distributes the clamping load over a greater area. Commonly used by assembly line workers in the automotive industry, these bolts are designed to provide the same holding power as a washer.

Flange bolts are also know as frame bolts and are designed to provide the holding power as if a washer was installed. The skirt is the distributing agent of the entire clamping load. Pipe flange bolts are widely used in various applications, especially pipe fittings and plumbing. With their multi-feature function, they help make jobs easier and faster. Flange bolts are made from a variety of types and grades to suffice for the various applications flange bolts are used.

Materials used:

  • Carbon
  • Alloy steel
  • Stainless steel
  • Carbon steel
  • Copper
  • Aluminum
  • Cast iron
  • Brass
  • Bronze etc.

How to tighten pipe flange bolts?
Final torque for the pipe flange bolts is dependent on the type of gasket used. This torque provides the clamp load on the gasket needed for proper sealing. Metallic and spiral type gaskets require greater clamping force than flat rubber gasket material. Higher system pressures lead to increased fastener torques. Pipe flange gaskets are never be used to pull the piping up to the pump. This can stretch the bolt, bend a pipe flange, break the pump casting or bend a suction plate. Rather, pipe flange bolts can fill the gap between the pump and spool piece by using the correct tightening sequence. Pipe flange bolts should be tightened in the correct sequences as illustrated below.

flange bolt - What are flange bolts
There should be a sufficient number of steps to bring the flanges together and achieve the torque required by the gasket. Four and eight pipe bolt flanges are tightened in a cross manner. For large flanges with 12 or more fasteners, it is suggested that two workers tighten the bolts at the same time, working 180 degree apart. Each worker tightens bolt number one in quadrant A, then bolt number one in quadrant B, then move to bolt number two. This process is repeated till the required torque is achieved on all the fasteners. Thus, pipe flange bolts reduces excess localized loading on the flange components and gasket.

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