A common question fielded by Parker O-ring Application Engineers is “will a (insert polymer family) O-ring work with (insert chemical mixture).” Not a day goes by where I do not field this question in some way, shape, or form. Which, honestly, makes perfect sense, because chemical compatibility is one of the two most important factors in designing a seal, the other being size. Choosing the right compound can literally make or break your seal and to the general designer, this can be a massive undertaking. There are so many rubber compound families out there and hundreds and hundreds of chemicals, so how can you know whether your seal is going to hold up? Well, today, I hope to give you a simple, and quantitative way to figure that out.
Much like elastomeric expansion joints, metal expansion joints are used to preserve the integrity of a piping system where the piping is subject to changes in temperature, pressure, vibration, compression, extension, cyclical movements or movements required by usage.
Oftentimes, metal expansion joints are used when an elastomeric joint simply cannot handle the extreme conditions – generally high temperature, large temperature range, or high pressure exists in your application. Generally, metal expansion joints can be used from -450°F to +2000°F, depending on the metallurgy, and can also handle pressures from full vacuum to 3,000psi.
Anyone who has ever enjoyed a fruit tea out of a mug that previously contained coffee knows the problem: taste transfer. It is an undesirable phenomenon during product changeovers in the food industry.
With Fluoroprene XP, a line of premium seal materials, Freudenberg has brought out an all-purpose weapon to handle steam sterilization, aggressive media used for cleaning in place (CIP) and sterilization in place (SIP), and high-fat concentrations. Until now, production processes in the food industry, in particular, have required the use of an extremely wide range of material options. Depending on the fat, flavor or acid concentrations in the food, and the specifications of the CIP/SIP processes and steam sterilization, seals made from EPDM, VMQ or FKM are used.
Probably the most common cause of O-ring failure is compression set. An effective O-ring seal requires a continuous “seal line” between the sealed surfaces. The establishment of this “seal line” is a function of gland design and seal cross section which determines the correct amount of squeeze (compression) on the O-ring to maintain seal integrity without excessive deformation of the seal element.
Non-metallic bearings may not be the best answer in every case but have been an excellent choice for many applications worldwide. In general, these product-lubricated bearings preclude additional contaminants (oils, greases) infiltrating the pumped fluid.
Non-metallic bearing materials include rubbers, synthetic rubbers (elastomers), plastics, graphite based materials, ceramics and lignum vitae. Thordon XL, Thordon SXL and Thordon Composite (GM2401) are elastomeric grades that offer exceptional wear life, low friction, reduced starting torque and dry start-up capability (SXL only). The inconvenience of pre-lubricating with water and the failures that can result if the flow of liquid is interrupted are eliminated. These elastomeric grades perform particularly well in dirty water and in applications where shock loading is a factor. These grades have high resilience, readily restoring to original shape from impact or localized deflection caused by passing minor particulate. In addition, the high toughness of the material enhances the natural resistance to abrasion damage.
ThorPlas is a proprietary, engineered thermoplastic bearing material. While the range of high performance elastomer bearing grades clearly offers superior performance in the applications in which they can be specified, there are technical limits, such as maximum temperatures and pressures beyond which they cannot be used. To address these limitations, this new grade significantly expands the range of applications where bearings can be specified while still maintaining many recognized elastomeric performance advantages.
Gallagher Fluid Seals is the trusted supplier of MRO sealing materials – including gasketing, packing, expansion joints, etc. – to all kinds of plants and manufacturers throughout the northeast and mid-Atlantic. At Gallagher, we take the time to specify the right gasket for every application, and we do our best to keep our customers well-informed about industry best practices and sealing safety.
The following is an article recently published in Pumps & Systems Magazine, which discusses why you should NEVER reuse a gasket.
by Jim Drago & Ron Frisard
Safety is a concern at any industrial site. An Occupational Safety and Health Administration compliance specialist has stated that safety should be more than a priority: “Priorities in an organization can and usually do change. Safety and health need to be a core value of the organization.”1
Thanks to their high elasticity and their very good resistance to wear and abrasion, elastomers made of rubber are generally superbly suited to seals. But they also have disadvantages: Due to their limited Shore hardness (a maximum of 90 SH A), they are not suited to applications at all levels of pressure. Dynamic applications are only achievable with the use of lubricants. Freudenberg Sealing Technologies polyurethane materials offer an alternative in cases where rubber elastomers cannot be used or where highly specialized elastomers are out of the question for cost-related reasons.
In 1937, a research group at I.G. Farben led by Dr. Otto Bayer (1902–1982) produced polyurethane (PU) synthetically for the first time, and the material made its triumphant march around the world. The industrial production of PU began in 1940. The first foam material based on PU was developed between 1952 and 1954. Many additional developments based on PU followed over the course of decades. As early as 1960, the production of PU foam material came to 45,000 tons. Global demand has greatly increased since then. At present, more than 12 million tons are processed annually. Today it is difficult to imagine our everyday lives without polyurethanes. They are actually one of the most multifaceted categories of plastic. We encounter them as soft polyester foams, as thermal insulating materials, in the soles of our shoes and in the steering wheels of our cars. Polyurethanes above all owe their wide distribution to two special attributes: They can be produced by mixing liquid feed materials. This can even be done in small processing operations. And since innumerable feed materials are available, it is possible to manufacture made-to-order materials in consistencies ranging from soft to hard or from foamed to compact, for a broad range of applications.
O-rings are a universal seal throughout the world. However, some axial applications may benefit from a different sealing solution called Press-in-Place seals, or PIP seals.
First, let’s define axial seal. “Axial” implies the seal is being compressed from top to bottom. In other words, the seal is pressed between two flat surfaces. One flat surface has a groove cut into it to retain the O-ring and limit compression. This may also be called a face seal.
Some face seal applications may not lend themselves ideally to an O-ring. One example is a face seal groove that is oriented vertically or upside-down. The O-ring may fall out of the groove, adding to assembly time, or even resulting in a pinched or damaged O-ring.
Seals and molded rubber technical parts are mostly given their form in closed molds. The rubber mixture is heated inside them so that vulcanization and solidification can take place. After a very precisely defined heating time, the degree of cross-linking reaches its maximum level. Then the mold can be opened and the component removed.
There are many different molding processes. The most important of them – and the ones most frequently used at Freudenberg Sealing Technologies (FST) – are listed here.
Compression Molding Compression molding is one of the oldest ways to manufacture technical elastomer components. First, a blank is manufactured that is large enough to fill out the form of the component being produced. It is inserted into the component mold in the tool (tool cavity). The component is given its form by closing the tool in the press. Due to the heat of the heating plate in the press, high pressure builds up inside the tool due to thermal expansion, and the vulcanization process is initiated.