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
Glass-lined steel equipment is used by chemical processers to deal with aggressive media under demanding conditions. Yet the inherent demands of such systems – high temperatures, alternating system pressures, limited gasket loads and deviation of sealing surfaces – can make it challenging to maintain a tight, lasting seal.
While the Polytetrafluoroethylene (PTFE) material itself offers good chemical resistance, it does not readily conform to flange surface deviations, nor does it resist creep particularly well under low gasket loads. Incorporating compressible materials or fillers into common envelope gaskets or filled PTFE gaskets, offers only a partial solution.
Sealing challenges are even greater when gaskets for large flanges (≥DN 600/ASME 24") are fabricated offsite. This often results in long lead times, as well as shipping, handling and inventory challenges. These, along with time-consuming and
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.
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.
Over time, and for any number of reasons, flanges are prone to surface deviations. Damaged areas will tend to create a leak path that the gasket must try to seal.
Flange damage most commonly occurs when removing previously used gasket material from the sealing surface - tools such as chisels, or screw drivers, should be avoided. A brass wire brush is suggested.
The video below proves how well GORE® Gasket Tape Series 500 works on flanges with surface deviations versus a standard filled PTFE gasket.
[embed]https://www.youtube.com/watch?v=nwuxtiFbxH0[/embed]
A spool of GORE® Gasket Tape Series 500 provides an immediate, cost-effective solution to sealing challenges that demand reliable performance and extended durability. This advanced product, with its industry-leading creep resistance, is designed to maximize the operational reliability of large steel-flanged applications, especially those with thermal cycling.
It eliminates the lag time, costs and complexities associated with engineering, specifying, procuring, shipping, storing and installing traditional one-piece prefabricated gaskets. It also delivers exceptionally reliable sealing performance, while making multiple gasketing installations faster, more cost-effective and simpler.
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.
GORE® Universal Pipe Gasket (Style 800) provides a reliable seal for steel, glass-lined steel and fiber reinforced plastic (FRP) flanges, in the full spectrum of strong acid, alkali, and solvent process media, including the most challenging thermal cycling and elevated temperature applications.
This single gasket solution can reduce the process safety and production downtime risks caused by the use of an incorrect gasket material. Highly conformable 100% ePTFE reliably seals irregular surfaces.
What Makes the GORE Universal Pipe Gasket Unique?