Feature Seals & gaskets Selecting the right gasket for the job


ERIKS outlines the issues that need to be considered when specifying gaskets in order to prevent premature failure and the associated leakage, product loss and downtime that can occur as a result


G


askets are often the forgotten heroes in manufacturing and process operations, providing a vital interface and seal between


mating surfaces. It is only when they start to fail that their importance is recognised.


The difficulty can be that gaskets often fail over a period of time, with deterioration and the slow build-up of leaks being difficult to detect. In many instances, failure arises because gasket material, shape or thickness has been incorrectly specified – often because basic criteria such as chemical, tem- perature or mechanical compatibility have been overlooked. It is estimated that across Europe, more than 300,000 tonnes of product loss through leakage could be prevented simply by better gasket selection. To avoid unnecessary gasket failure and maintenance, pro- duction engineers need to consider a set of principal criteria when specify- ing gaskets.


Chemical compatibility


Gasket materials must be compatible with any process chemicals employed in a given application. For example, manufacturing processes in the food and pharmaceutical industries can contain hazardous materials and if the gasket materials are not compatible with the application, a serious failure can follow, with resulting wastage and downtime. However, appropriate materials for a range of applications are available; good chemical compati-


In chemical processing, gaskets must often function under extreme conditions where aggressive media and/or high temperatures may be pre- sent. Relatively fragile flanges require gaskets that seal with low surface pres- sure and this need can be addressed by PTFE gasket materials that are chemi- cal resistant, while graphite suits high temperature applications.


Cutting systems


It may be necessary also to specify chemical inertness in synthetic gasket materials to prevent chemicals from leaching into process fluids. Also, any tools used for cutting custom-sized gaskets must be free from contami- nants that could transfer to the gasket. This can be achieved using modern cutting systems, the best of which operate on a CAD/CAM interface and require no fixed tooling. These sys- tems can deliver fast results to a range of specifications and with good dimensional replication.


bility with a variety of process chemi- cals is offered by, for example, the syn- thetic rubber material EPDM (ethylene propylene diene monomer). In addition to process chemicals, there is also thermal stability to con- sider. The higher the process tempera- ture, the smaller the range of specifications available and, likewise, low temperatures demand careful specification if the gasket is to with- stand the cold without cracking. Extremes of temperature can damage poorly specified gaskets; for example, a gasket can become brittle at low tem- perature and, without the ability to offer a flexible seal, may allow the ingress of unwanted materials.


The range includes spiral wound gaskets


Emission demands such as those imposed by the TA-Luft regulations are also relevant, as the application may require that the gasket complies with tighter restrictions on emissions. This means TA-Luft approved gasket materials must be used.


Careful consideration of issues such as those listed above can prevent prob- lems before they occur, and there is assistance available from suppliers such as ERIKS.


Avoiding over-specification In some cases, consulting with an expert supplier may result in a planned reduction of gasket quality if current components have been over- specified, because while over-specifi- cation is not as costly as the potential results of under-specification, it remains an unnecessary expense. A different gasket design or material that is possibly not so complex and thus less costly to manufacture, may never- theless be more than adequate for the application, resulting in savings on supply costs.


ERIKS can create a complete sealing solutions package tailored to suit each application, keeping your assets run- ning longer and more efficiently to improve productivity and reduce main- tenance downtime. ERIKS’ product groups cover non-metallic, semi-metal- lic and metallic gaskets, with valve stem and stuffing box seals available in a range of materials.


ERIKS can design sealing solutions tailored to suit indi- vidual applications


Process & Control JULY 2012


ERIKS T: 0121 508 6219 www.eriks.co.uk


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