Creation of standards for the assembly of flange connections

Creation of standards for the assembly of flange connections

Experience, mainly from refineries, shows that increased reliability and safety of flange connections can be achieved by categorising them. In relation to these categories, standards with set assembly procedures and requirements for materials, fitters, equipment, etc. should then be developed.

Determining the criteria that influence the classification of a flange connection into each category is individual for each company. The common denominator may be, for example, whether the joint and its leakage will affect production or operational safety if the joint has had repeated leaks in the past.

The first stage is therefore to establish the criteria on the basis of which specific categories will be defined. These criteria are most often determined with respect to the combination of operating temperature and pressure.

The division into three categories, which we will describe in the following lines, has been the most successful.

Příklad rozdělení přírubových spojů do kategorií

Critical flange connections - category I.

Most often these are flange connections of apparatuses, e.g.: heat exchangers, reactors, columns, boilers, etc. Many years of experience have shown that recurring leaks of important flange connections falling into category I have been sealed reliably and in the long term by implementing so-called complex solutions. 

The comprehensive service includes:

• design of flange joint leakage solution
• calculation of tightening torques according to EN 1591-1 with proof of tightness
• supply of designed seals and fasteners including lubrication system
• controlled tightening by assembly personnel trained to EN 1591-4 

In a comprehensive solution, one supplier controls the entire process described above and is responsible for the tightness of the flange connection.

Critical flange connections - categories II. and III.

The criteria for these categories may vary. These are mainly DN PN standardised connections. These connections are most often made as part of routine installation and maintenance activities. However, we would also recommend having calculated tightening torques and set standards for their installation. 

This approach to flange connection solutions is nowadays increasingly applied in other industries such as energy, paper, pharmaceuticals, etc.
For more than 30 years, we have been helping our customers with critical flange joint leakage solutions.

We mostly cooperate with our customers on complex solutions of flange connections in category I. However, we also deal to a considerable extent with calculations of tightening moments and e.g. supervision of flange connections in categories II and III. 

The resulting reliability of these connections has clearly proven its validity and inspired many customers to change their thinking.

Our experience is at your disposal in determining the criteria that lead to the categorization of flange connections.

On the pages Frequent solutions, we show with examples that a reliable flange joint leakage solution is a matter of interacting factors.