Category Archives: rotary seals

The Advantages of Crimped Can Seals

A combination of crimped can seals will handle a variety of applications when a rubber lip seal is not your solution.

Rotary seals are often secured in sealing hardware by crimping the sealing element in a metal can. One of the most common rotary seals is a molded rubber lip seal in a can. 

While not crimped, the can retains the sealing element, and stops the seal from rotating in the gland. Rotary sealing elements for low pressure (under 15 psi), are often nitrile or Viton rubber sealing elements.

This style of seal comes in many cross sections, and may include garter springs to help the seal stay engaged with the shaft. These seals are typically low in cost, and produced in high volume.

These seals are found in many low-pressure applications. However, as the pressures begin to climb over 10 psi and speeds run over 500 ft/min, friction generates heat, which accelerates wear on the rubber element and in turn begins to wear the mating shaft material.crimped can seal

Overcoming Friction

Friction or the resultant heat is the largest concern in rotary service.

The crimped can seal with PTFE (Teflon) elements can run with pressures in excess of 500 Psi and PV (pressure- velocity) reaching over 350,000psi-ft/ min. The crimped can allows these elements to remain secure.

The crimped case seal causes all the relative motion to remain at the sealing lip interface. With the crimped can, we have the opportunity to install multiple lips or seal cross sections to handle a variety of loads. This allows us to control leakage, and keep friction to a minimum.

We can seal most any fluid or run dry sealing gases with little or no lubrication. With widely varying temperatures, we can include springs to maintain seal contact, offset some eccentricity of shafts, keep dirt out or keep very light loads.

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The Perfect Wave; The Gerromatic Rotary Seal

Gear motors, pumps and stirring units keep process material in constant motion in the process industry’s production facilities. A large number of shaft seals are used at drive shafts to keep liquids securely within the equipment. But leaks may be more likely to occur if the pressure acting on the seals becomes too great. Freudenberg Sealing Technologies has developed a new rotary seal, the Gerromatic, which has a wave-shaped sealing lip. This increases the maximum amount of pressure that can be applied. The sinusoidal contact path also reduces friction and provides self-cleaning, which extends operating life.

In the process industry, including the food and beverage sector, shaft seals used in equipment mostly have a rotation-symmetrical seal lip, which abuts the rotating shaft with a groove-like contact pattern. During wet-running, this can cause the medium to be displaced at the contact surface. The seal then runs in a more or less dry condition, leading to increased friction and higher temperatures. The increased friction increases wear and reduces the efficiency of the equipment. The accompanying rise in temperature is not desirable, especially when the process media are temperature-sensitive. If the seal lip is also exposed to high temperatures at high rotational speeds – for example, due to a process material that applies pressure to the seal lip in a vessel with a stirring unit below it – the lip can fold down on the low-pressure side, which would result in immediate leakage and the seal’s failure.

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[VIDEO] NEW! Rubber Energized Seals Webinar

Rubber Energized SealsGallagher recently recorded the Rubber Energized Seals webinar, discussing rubber energized rod or piston seals, and the advantages and disadvantages to using some of the most common seal profiles.  This webinar is presented in conjunction with one of our trusted partners, Eclipse Engineering, Inc.

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Preliminary Considerations for Spring-Energized Seals

springsealsToday we’ll continue our look at spring-energized seals by exploring some of the preliminary considerations to made when working with these seals.

A spring energized PTFE seal is selected to fit an exact set of service conditions found in your application.

Gallagher Fluid Seals recommends conducting a review of the entire sealing environment. You should use the Engineering Action Request (EAR) form before selecting a seal design.

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PTFE Radial Lip Seal Applications

dieselToday we’ll conclude our series of blog posts on PTFE by discussing some PTFE radial lip seal applications, as well as a brief look at wear sleeves.

PTFE has superior mechanical and physical properties and chemical resistance, which means the areas where PTFE radial lip seals are used is growing. These areas include:

Diesel Engine Applications

These consist of the front and rear crankshaft, accessory drive, and blower and thermostat seals. PTFE seals are used and tested in these areas because they can meet the performance and life requirements of modern engines.

Minimum wear, performance at high temperatures with limited lubrication, resistance to abrasive contaminants and fluid compatibility are the main factors for PTFE’s use in these applications.

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PTFE Rotary Seals: Housing, Pressure and Shaft Run-Out

rotary7Today we’ll continue our look at PTFE rotary seals by focusing on three areas: housing/bore considerations, pressure and shaft velocity and shaft misalignment and runout.

Housing/Bore Considerations

Typical PTFE rotary lip seals are pressed into the bore to assure proper OD sealing and seal retention in the housing. Most seal and housings are made from steel and cast iron. Take care when softer materials – aluminum, bronze, plastic – are used for the housing. Aluminum has a thermal expansion rate almost double that of steel. Metal case designs can lose the required press fit in an aluminum housing when they go through thermal cycles due to the higher rate of thermal expansion of aluminum.

A finish range of 32 to 63 μin Ra (0.8 to 1.6 μin Ra) is recommended for service pressures up to 3 psi (0.20 bar). For thicker fluids such as grease, a 125 μin Ra (3.17 μin Ra) finish would be acceptable with no system pressure.

A lead in chamfer is strongly recommended for all seal housings. The chamfer aligns the seal during installation and helps keep the seal from cocking. Both corners of the chamfer should be free of burrs or sharp edges. For pressurized rotary applications, take additional precautions to ensure the seal isn’t pushed from the housing.

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PTFE Rotary Seal Shaft Considerations

shaft table 3As we continue this blog’s PTFE series, we’re going to take a closer look at PTFE rotary seal shaft considerations.

In rotating applications, proper surface finish is crucial for getting positive sealing and the longest seal life possible. Rotating surfaces that are too rough could create leak paths and can also be very abrasive. Unlike elastomer contact seals, PTFE lips can run on very smooth surfaces regardless of lubrication.

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PTFE Rotary Lip Seals: Definitions

rotaryseal2Over the past few weeks, we’ve gone into a lot of detail about how PTFE rotary lip seals work.

Today we’ll offer up a short glossary of some of the terms used when discussing these seals. We’ll also break down some of the factors affecting PTFE rotary lip seal design.

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PTFE Radial Lip Seal Design Principles

Over the past few weeks, we’ve been discussing the basics of PTFE rotary seals. In today’s entry, we’ll take a look at PTFE radial lip seal design principles.

PTFE radial lip seals generally incorporate a uniformly thin element cross section, made to compensate for the high flexural modulus of PTFE, especially in cases of severe shaft run-out. The thin sections also minimize thermal expansion and compressive “creep” and their effects on maintaining a controlled contact pattern on the shaft surface.

Most PTFE seal constructions have the “body” portion of the element clamped between the two metal cases. To maintain proper retention pressure on the element, a thin element keeps compression set and “creep” at a minimum.

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PTFE Radial Lip Seal Design

rotarydesignIn the newest installment of our series of blog posts on PTFE rotary seals, we’re going to take a closer look at PTFE radial lip seal design.

Before selecting a seal type and the filled PTFE compound to be used in a proposal, it’s important to have a thorough understanding of operating conditions and how they affect the seal performance.

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