President, INTEGRA Technologies Limited
Sarnia, Ontario, Canada
While other chapters of the Piping Handbook deal with the pressure integrity of
the piping system, this chapter deals with managing the leak integrity of bolted
flanged systems. It covers the main elements of a bolted joint system to provide
an understanding of the bolted joint connection and the science of joint sealing.
This chapter focuses exclusively on bolted joints subjected to internal pressures.
While integrity of mechanical (structural) joints are also critical, they are not covered
in this book.
Oil, gas, and power plants and other process industries are under constant
pressure to work their plants at maximum design limitations and for longer periods.
The bolted joint is often regarded as the weak link in the plant’s pressure envelope.
Whether a pipe flange, heat exchanger, reactor manway, or valve bonnet, the joint
integrity relies not only on the mechanical design of the flange and its components,
but also on its condition, maintenance, and assembly. Plant personnel are looking
for equipment to achieve leak-free joints with reduced shutdown periods while
increasing the time between shutdowns. Similarly, flanged joints in other piping
and distribution systems found throughout industrial, commercial, and residential
facilities are required to maintain their structural integrity and leak tightness.
Several standards have been written to enable designers to design bolted joints.
Compliance to the requirements of these standards ensures mechanical integrity
of bolted joints. However, these standards do not provide adequate and effective
requirements or guidelines to assure leak integrity of flanged joints.
To achieve leak integrity, a broader view of the bolted flange joint as a system
must be adopted. Ideally, a process is to be followed that manages the key elements
of the bolted system, which allows the design potential of the bolted joint to be
realized and helps in achieving continued l