When tightening the bolts on a pipe flange, what is the correct method?

The sequential criss-cross method of tightening is the correct approach when dealing with pipe flanges. This technique ensures that the load is distributed evenly across the flange, preventing warping or deformation that could compromise the integrity of the seal. By tightening bolts in a criss-cross pattern, you minimize the risk of uneven pressure on the gasket, which is crucial for achieving a reliable seal and preventing leakage.

Using this method is particularly important in situations where flanges may not initially be perfectly flat or when working with larger flanges where the potential for distortion is higher. Tightening bolts in a uniform sequence allows for better control over how the flange comes together, ultimately ensuring that the gasket is adequately compressed and performs effectively.

Other methods, such as tightening the top bolts first or using gasket glue to hold the gasket in place, can lead to uneven pressure distribution and potential gasket failure. Tightening every second bolt first also does not provide the same level of uniformity in force application across the flange, making the criss-cross approach the ideal practice in these situations.