5 steps to a leak-free bolted flanged joint

In all parts of industry, bolted flanged joints are necessary for many purposes. With increased performance demands in mind – both economically and ecologically – correct function (i.e. tightness & integrity during entire period of operation) of flanged joints is necessary, especially to minimize emissions. The best way to achieve tightness & integrity is through analysis of the bolted flanged joint.

For over 25 years, has provided bolted flanged joint services across a wide array industries. Using this experience, we have developed a procedure to ensure reliably “leak-free” joints in 5 steps.

Following this procedure, even challenging requirements regarding bolted flanged joint tightness can be met. Cost of repair and forced outages as well as the effort pertaining to control of emissions can be reduced to a minimum.

Boundary Conditions

First and foremost, the real boundary conditions i.e. medium, tightness requirements, material stress limitations and the loads acting on the joint (e.g. temperature, internal pressure and external loads) for a particular application have to be determined.

The loads (including transient loads) have to be considered in detail during assembly as well as in every state of operation and for each and every load condition. Reliable analysis needs realistic and detailed load input.

If necessary, measures the occurrent loading characteristics on site.

Design

During the design phase, a suitable configuration and appropriate materials of flange, bolts and gasket are selected and dimensions are determined.

In a flanged joint, the gasket plays the lead role in the overall performance. Therefore, detailed knowledge about the gasket characteristics and performance under different conditions is necessary; this includes data on long term behavior, deformation characteristics and tightness characteristics.

has developed a universal test rig capable of determining every gasket factor need to select the correct gasket for a given application. is the first choice in gasket testing services.

Calculation

One major task of the analysis of a flanged joint is the calculation. In any case and application, the assembly / mounting personnel need a target torque (pre-stress value) for the nuts/studs of the joint. Additionally, the structural integrity of the joint must be demonstrated by stress analysis and - if there are frequent load transients – fatigue analysis. Finally, a tightness analysis has to be performed. Because of the complexity of the behavior of bolted flanged joints, only an iterative calculation procedure that relates the state of assembly to the operation states can lead to reliable results.

With 's state of the art software tool TEMES_fl.cal, a reliable calculation of bolted flanged joints based on this iterative approach is possible. The software includes all current, relevant analytic calculation procedures accepted across industry. As a service, Finite Element Analysis is offered, too.

Assembly

Another critical step in the procedure is the actual assembly of the joint. Quality assembly / mounting by qualified personnel is one of the essential steps to guarantee integrity and tightness of flanged joints. The effort applied during this step has to be on par with the demands – this is true regarding the tools and applied procedure as well as the qualification of personnel.

The necessary assembly pre-stress value (tightening torque) must be applied reliably. Hydraulic tensioners are ideal tools for this type of tightening because all bolts can be tightened simultaneously, thus creating a homogeneous deformation (seating) of the gasket and a uniform gasket stress.

offers tightening tools; compact tensioners are designed to fit virtually every flanged construction. Additionally, especially in critical cases, the bolt loads applied can be controlled using special elongation measurement devices or ultrasonic equipment.

Assembly / mounting must also be regarded as a critical part of quality control. Actually, this step starts with disassembly; feedback has to be given if there is anything remarkable when checking the flanged joint components. Only qualified personnel are able to reliably perform this task. provides training to flange assembly personnel according to industry standards.

Experience

A controlled feedback of experience is the last but not least step of the procedure to achieve correct function of flanged joints. With this feedback, potential leakers can be identified. Experience is gained on site, primarily. Especially the comments of the assembly staff have to be considered; they are in “contact” with the joints during assembly and – arguably more importantly – during disassembly.