Flange connections according to protocol

Posted September 2026

What is meant by that?

Leaking flange connections in refineries or chemical plants are unfortunately a common occurrence, partly because a flange fitter does not properly know how to establish a leak-free flange connection.

To prevent this, protocols have been established that describe exactly how flange connections must be correctly and controllably assembled, disassembled, aligned, and maintained. Each refinery uses its own procedures and protocols, and this article describes only the basics of a flange protocol.

Protocols vs Guidelines

Please note! Until the flange protocols are described in more detail below, the following applies:
When working on a flange connection according to a protocol, strict, documented steps must be followed and data recorded.
Working without a protocol, on the other hand, means relying on assumptions and long-standing habits.

the Protocol

In the past, working on flange connections received relatively little attention in practice, in contrast to, for example, welding flanges, and the lack of information regarding working on flange connections led to unnecessary leaks.

Working on flange connections according to a protocol applies to simple work on flange connections using standard hand tools. Because some systems place very high demands, they often require special equipment and special procedures and are, moreover, often carried out by specialized companies.

Working on flange connections according to a protocol depends on the type of piping system; whether it involves low-pressure or high-pressure flanges; working on flange connections without a protocol applies only to low-pressure flanges.

Differences between working on flange connections with and without a protocol

Working with a protocol

..involves clear steps: Workers follow a written instruction (such as ASME PCC-1 or EN 1591) that specify the exact tightening order, like a star pattern.
..controlled pressure must be applied to the gasket, and assembly must be carried out using a torque wrench
..tools like torque wrenches or bolt tensioners are checked and calibrated before use
..flange fitters record data by writing down the exact force or pressure applied to each bolt
..the people performing the work are certified, have completed official training, and have proven that they know how to perform the work safely
...traceability offers the advantage that the documentation can be reviewed to demonstrate that the work was carried out properly if, for example, a leak occurs later

Dimensions Nonmetallic Full Face Gaskets

Working without a protocol

..here is no record available, and officially no one can record the final tightening torques or the tightening sequence
..unchecked standard wrenches are used without knowing if they measure force correctly
..the workers tighten the bolts on personal memory or what feels right, because there are no written instructions
...there is no documentation, and NO official proof or label on the flange indicating who did the work and on what date
.assembly and tightening are performed with standard ring wrenches (tensioners), and not with torque wrenches.
...a higher risk because the likelihood of uneven pressure, damaged gaskets, and dangerous gas or liquid leaks increases significantly

Remark(s) of the Author...

This article refers to the so-called flange fitter, who, with the right training, would be able to make a leak free flange connection.

I cannot entirely agree with this, because everyone has a different mindset and approaches and solves things in a different way.

Moreover, some people, despite their certificate, will probably never learn it; just compare it to a driver's license

Point: good training will certainly help to become a good flange fitter.

This article is currently still in the draft phase and will be finalized later, upon receipt of any comments.