eptfe

Fiber Reinforced Plastic (FRP) pipes and flanges are increasingly used in the oil and gas industry where metal is simply too heavy and expensive. In addition to cost pressure, the need for lightweight chemically resistant materials are also driving the use of fiberglass pipes  and flanges. Innovations in FRP flange design coupled with improvements in manufacturing technology have allowed FRP piping to be used in even more demanding applications. However, these demanding applications have added challenges for sealing the bolted flange connections.

More aggressive media and higher internal pressures have pushed the limits of the commonly used rubber gasketing materials, such as Nitrile Butadiene Rubber (NBR), Ethylene Propylene Diene Monomer (EPDM), or neoprene. Obtaining a reliable seal in FRP flanges using conventional gasketing materials has become more difficult.

Fiberglass pipes are generally known to have strength limits and a lower pressure resistance, making sealing fiberglass flanges difficult. Gore solved this problem with its patented expanded polytetrafluoroethylene (ePTFE) gasket, specifically designed to seal flanges at low stresses. This solution was successfully demonstrated in a multistage testing procedure conducted in cooperation with a globally leading manufacturer of anti-corrosive fiberglass pipe systems.

ePTFE Gasket Tapes for High Chemical Resistance

The connections to shell and tube heat exchangers pose immense challenges for the seals that are used because of both the chemically aggressive media and the frequent temperature load changes. Despite its excellent chemical resistance,polytetrafluoroethylene (PTFE) is not typically suitable as a sealing material in this case because the creep tendency of this material jeopardizes a reliable seal.

Shell and tube bundle heat exchangers generally include not only several connection pieces but also a shell cover flange with a significantly larger nominal diameter.The shell cover flange creates the seal to the tube bundle flange, which then seals the shell flange. These connections are subjected to the full operating pres-sure and test pressure of dozens of bar and seal it from the environment. Oftentimes the tube bundles are arranged in several passes that are channeled by the use of partition plates. This requires a seal at

A newly developed gasket tape made by Gore - of expanded polytetrafluorethylene (ePTFE) is specifically designed to address the challenges of creating reliable seals in large glass-lined steel equipment.

Equipment made of glass-lined steel is used when manufacturing  or processing aggressive chemicals such as aniline derivatives and sulphuric or hydrochloric acid. The Achilles heel of such systems is the gaskets needed to seal the joints between components. Exposure to aggressive media causes the seals to degrade overtime, resulting in damage to equipment and posing a health risk to operators. Replacing the seals costs a great deal of time and effort, with a corresponding drop in production output.

A newly developed gasket tape made of ePTFE (expanded polytetrafluorethylene) is specifically designed to address the challenges of creating reliable seals in large glass-lined steel equipment.

Operators of chemical plants choose sealing materials according to a wide range of criteria such as process medium, flange type, sealing performance, pressure and heat resistance, cost and longevity. Other important selection criteria include time required for installation and inventory management. And, of course, a plant operations prior gasket experience weighs in as well. Gaskets for glass-lined-steel equipment are safety-relevant parts because their failure can endanger human lives and/or harm the environment, but they are often treated for administrative purposes as C-class items, that is, parts of minor significance.

This classification doesn’t reflect the true importance of these sealants. There is a need for more explicit regulations to supplement the general legislation pertaining to occupational health and safety and the handling of hazardous substances. The introduction of a European-wide regulatory basis for establishing detailed, standard processes would be welcome, for instance with respect to approval procedures and safety. As things stand today, companies are obliged to find their own compromise between varying sets of requirements. These include compliance with EU-wide and national directives concerning environmental protection and occupational health and safety. At the same time, companies are making efforts to augment the reliability of their products, simplify inventory management and installation processes, and reduce downtime and overall costs. An added factor in both cases is specific process requirements with respect to temperature, pressure and media.

SEALING CHALLENGES

One particular challenge is that of choosing the right sealant for glass-lined steel systems, because these involve the use of aggressive media such as aniline derivatives and sulphuric or hydrochloric acid under demanding conditions. Glass-lined steel presents the advantage of being highly resistant to corrosive and/or abrasive media. Other characteristic features of this material are its smooth surface, which is easy to clean due to its low adhesion properties, and its biologic and catalytic inert behaviour. Nonetheless, it can be difficult to achieve reliable seals in glass-lined steel equipment. This is because the glass lining is more brittle than the metal, and can therefore split or splinter if handled incorrectly. As a result, the gasket load that can be applied to the seal is lower than that for an all-steel flange. Consequently, care must be taken to limit the pressure applied when installing gaskets between interconnecting parts of the system.

Another problem is that of achieving a reliable seal if the flange surface is uneven or has surface deviations. Once the glass lining has fused, its surface cannot be reworked. The challenges posed by these characteristics of glass-lined steel, combined with the exposure to aggressive chemicals and high temperatures, must be met by the chosen sealant. In practice, these difficult conditions often lead to premature sealing failure and a greater risk of corrosion. The further consequences of sealing failure include leaks and uncontrolled emissions, damage to equipment, high replacement and repair costs, production losses, unplanned maintenance and downtime, and potential risks to employees’ health and safety.

GORE® Gasket Tape is a 100% ePTFE form-in-place gasket that delivers worry-free sealing performance for large steel flanges (Series 500) and large glass-lined steel equipment (Series 1000). While this product has a number of advantages, GORE® has now made their gasket tape line even easier to use.

Improved installation-aid adhesive.

GORE® has upgraded the removable adhesive backer on GORE® Gasket Tape Series 500 and Series 1000 to a new higher strength material. This ensures that when the backer is removed at installation, it peels away in one easy-to-remove piece.