Industrial Flange Sealing
Reliable flange sealing is essential for the safe and efficient operation of refineries, petrochemical plants, chemical facilities, power generation plants and other industrial processing units.
A bolted flange connection must maintain sufficient contact pressure on the gasket throughout its service life. When bolt preload or gasket stress decreases, the risk of leakage increases.
Industrial flange leakage can result in fugitive emissions, product loss, safety risks, unplanned shutdowns, additional maintenance and regulatory concerns.
What Is Flange Sealing?
Flange sealing is the process of preventing fluid or gas from escaping through the interface between two bolted flanges. A gasket is compressed between the flange faces to create a sealing barrier and accommodate surface imperfections.
The effectiveness of a flange connection depends on maintaining sufficient gasket contact stress under operating conditions. The initial bolt preload, gasket properties, flange stiffness, temperature, pressure, vibration and operating cycles all influence long-term sealing performance.
For critical industrial applications, flange sealing should therefore be considered as a complete mechanical system rather than simply a choice of gasket material.
How Does a Bolted Flange Seal?
When flange bolts are tightened, they generate a preload that compresses the gasket between the flange faces. This compression creates the contact pressure required to prevent the process fluid from passing through the joint.
The sealing performance of the connection depends on maintaining sufficient gasket stress during operation.
Bolt Preload
Bolt preload provides the mechanical force that clamps the flange assembly together. If preload is lost, the compression available to the gasket can decrease.
Gasket Contact Stress
The gasket must maintain sufficient contact stress to provide an effective sealing barrier. As gasket stress decreases, the potential for leakage can increase.
Operating Conditions
Temperature changes, internal pressure, vibration and mechanical loads can affect the behaviour of the bolted joint over time.
Why Do Industrial Flanges Leak?
Flange leakage can have several causes. In many cases, leakage develops gradually as the mechanical conditions of the joint change during service.
Gasket Creep and Stress Relaxation
Compressible gasket materials can undergo creep and stress relaxation under sustained compression and temperature. As gasket thickness or compression changes, bolt preload and gasket contact stress can decrease.
This phenomenon is particularly relevant for soft gasket materials such as PTFE, expanded graphite and certain composite gasket systems.
Bolt Relaxation and Loss of Preload
Bolt preload can decrease over time because of gasket relaxation, embedment, thermal effects and other changes within the joint. Loss of preload can reduce the sealing force available at the gasket interface.
Thermal Cycling
Repeated heating and cooling can cause differential thermal expansion between bolts, flanges and gasket materials. These changes can alter the load distribution within the joint and contribute to sealing degradation.
Vibration and Mechanical Loads
Equipment vibration, pipe movement and mechanical loads can affect bolted flange connections. In critical applications, maintaining stable gasket compression is important for long-term joint reliability.
Installation and Tightening Errors
Incorrect tightening procedures, uneven bolt loading, inadequate surface preparation or unsuitable gasket installation can compromise flange sealing from the beginning of the joint's service life.
Flange Leak Prevention
Effective flange leak prevention starts with proper joint design and continues throughout installation, operation and maintenance.
Key practices include selecting an appropriate gasket, controlling bolt preload, following a suitable tightening procedure, considering operating conditions and monitoring critical flange connections.
For high-consequence applications, preventing loss of gasket compression can be as important as achieving the correct initial tightening load.
Maintaining Sealing Force Over Time
Achieving the required bolt load during installation does not necessarily guarantee that the same sealing force will remain available throughout the operating life of the joint.
Gasket creep, stress relaxation, thermal cycling and other mechanical effects can progressively reduce the load acting on the gasket.
This creates an important engineering challenge: how can sufficient sealing force be maintained after the initial installation?
Load-Maintaining Technology for Flange Connections
LitoZen's GasketForce™ is a load-maintaining device designed for critical bolted flange assemblies.
GasketForce is designed to compensate for changes in gasket compression and help maintain the mechanical load applied to the joint over time. It is intended to reduce the effect of gasket creep, relaxation and load loss on sealing performance.
The device is installed as part of the bolted flange assembly and is designed to work with common industrial gasket systems and critical flange connections.
Flange Sealing and Fugitive Emissions
Flange connections are among the potential sources of fugitive emissions in process facilities. A loss of sealing performance can allow process fluids or gases to escape into the environment.
For facilities operating under emissions management and leak detection programs, improving flange sealing reliability can contribute to the reduction of leakage events and associated maintenance activities.
Learn more about fugitive emissions and flange leakage.
Industrial Applications
Reliable flange sealing is relevant across a wide range of industrial applications, particularly where leakage can result in product loss, environmental emissions, safety concerns or costly maintenance.
- Oil & Gas Production Facilities
- Refineries
- Petrochemical Plants
- Chemical Processing Facilities
- Power Generation Plants
- Fertilizer Plants
- Pharmaceutical and Specialty Chemical Manufacturing
- Mining and Metallurgical Processing Plants
- Water Treatment and Desalination Facilities
- Hydrogen Production and Energy Transition Projects
Flange Sealing Standards and Engineering Practices
Industrial flange design and sealing performance are addressed by several international standards and engineering practices. Depending on the application, relevant references may include EN 1092-1, EN 1591-1, EN 13555, ASME B16.5, ASME B16.47 and ASME PCC-1.
Leakage management practices can also involve requirements and guidance such as TA-Luft, VDI 2290 and related fugitive-emission frameworks.
These standards address different aspects of flange design, gasket testing, bolted joint assembly and leakage performance. Their applicability should always be evaluated according to the specific equipment, service conditions and regulatory requirements.
Technical Resources
Explore LitoZen's technical resources on flange sealing, leakage prevention and industrial sealing reliability.
/pages/flange-leak-prevention">Flange Leak Prevention in Industrial Facilities
/pages/fugitive-emissions">Fugitive Emissions Reduction in Industrial Facilities
/products/gasket">GasketForce™ Load-Maintaining Technology
pages/industrial-flange-roi-calculator">Industrial Flange ROI Calculator
Industrial Flange Sealing: Key Takeaways
Reliable flange sealing depends not only on the initial installation of the gasket and bolts, but also on the ability of the joint to maintain sufficient sealing force throughout its service life.
Gasket creep, stress relaxation, bolt load loss, thermal cycling and vibration can all affect long-term flange integrity. Understanding these mechanisms is an important part of preventing leakage and improving the reliability of critical flange connections.
LitoZen develops technologies designed to address these challenges and improve the long-term reliability of industrial sealing systems.