5 steps to a leak-free bolted flanged joint

In all parts of industry, bolted flanged joints still are necessary for many purposes. On the background of increased demands – both economically and ecologically – a 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 a consequent analysis of the bolted flanged joint.

For more than 25 years now, amtec provides services to industry regarding bolted flanged joints. 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 regarding control of emissions can be reduced to a minimum.

5 steps to a tight flange connection


Boundary conditions

In a first step, the real boundary conditions like medium, tightness requirements (depending on medium), requirements regarding stress limitations and the loads acting on the joint (e.g. temperature, internal pressure and external loads), have to be determined.

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

If necessary, amtec measures the occurrent loading characteristics on site.


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

In a flanged joint, the gasket plays a center role. Therefore detailed knowledge about the gasket characteristics (gasket factors) is necessary; this includes data about long term behavior, deformation characteristics and tightness characteristics.

amtec manufactures gasket testing equipment – amtec is the first choice in gasket testing services.


One major task of the analysis of flanged joints is a calculation. In any case, the assembly / mounting staff needs a tightening torque (pre-stress value). Additionally, the integrity of the joint has to 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 the amtec software TEMESfl.cal  a reliable tool for the calculation of bolted flanged joints based on the state of the art is available. It includes all actually relevant analytic calculation procedures. As a service, Finite Element Analysis are provided, too.


The next step in the procedure is assembly. Qualified assembly / mounting is one of the essential steps to guarantee integrity and tightness of flanged joints. The effort applied during this state has to meet the demands – this is true regarding the tools and applied procedure as well as regarding the qualification of personnel.

The necessary assembly pre-stress value (tightening torque) has to be applied, reliably. Hydraulic tensioners are ideal tools for this type of tightening because
  – ideally – all bolts can be tightened at the same time and a homogeneous deformation (seating) of the gasket and thus a uniform gasket stress is created.

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

Assembly / mounting has to be regarded as step of quality control, too. Actually, this step starts with disassembly; feedback has to be given if there is anything remarkable when checking the parts. Only qualified personnel are able to perform this task, reliably. amtec provides training to flange assembly personnel.


A controlled feedback of experience is the last but not least step of the procedure to achieve correct function of flanged joints. Thus 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 – almost more important – during disassembly.

As there are a lot of flanged joints in an industrial site, usually, data collection and evaluation using a database is practically. amtec provides a comprehensive database tool for Life Cycle Management of flanged joints.