Category Archives: Mechanical Seals Blog

Unusual Mechanical Seal Applications

There are applications where the use of a mechanical seal would either not be considered or present major technical challenges. Here are some unusual examples of how mechanical seals can be applied to solve problematic sealing tasks.

LATEX
Liquid synthetic latex is an emulsion of polymer particles suspended in an aqueous solution. It is used in making coatings, glues and gloves and more.

Sealing latex has historically been a problem for mechanical seals because it solidifies when exposed to either heat or friction (shear). When latex is exposed to heat, water separates from the polymer particles leading to solidification or coagulation. A more challenging issue with sealing liquid latex is that when it enters the gap between the mechanical seal faces, it gets sheared which also leads to local coagulation.

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Using IoT to Improve Mechanical Seal Reliability

The Internet of Things (IoT) is a phrase in the limelight. The concept of IoT is extremely appealing, in all forms, to commercial industry. The technology of IoT has been implemented in various industries globally and it is finally approaching the rotating equipment industry.

To fully explain and understand how IoT technology can be implemented to increase mechanical seal reliability, a description of maintenance philosophies is needed. There are three main types of maintenance philosophies in industry today: reactive, preventative and predictive. Currently in the pump industry, and more specifically with mechanical seals, most of the maintenance is either in the reactive or preventative ideologies.

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A Guide to Elastomer Technology in Mechanical Seals

Elastomers (or rubbers) are a ubiquitous family of materials whose use stretches across nearly the entire range of mechanical seal designs. From plant-sourced natural rubber, so named by John Priestly in 1770 for its utility in rubbing away pencil graphite, to petroleum-sourced synthetic rubber first developed around the turn of the 20th century, elastomers and their properties are familiar but should not be overlooked – especially when dealing with mechanical seals.

Rubber seals come in a variety of profiles – O-rings, cup gaskets, bellows diaphragms, sealing/wiper lips and many others. They are classified as either static or dynamic and create positive pressure against surfaces to eliminate or control the leakage of liquids and/or gases while preventing the entrance of external contaminants such as dust and dirt.

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Controlling the Seal Chamber Environment

Reducing the temperature in the seal chamber offers many benefits to the performance and reliability of a mechanical seal operating in hot service. This is one of the most effective ways to increase the vapor pressure margin and prevent the pumped fluid form flashing in the seal chamber or at the interface of the mechanical seal’s faces. Additionally lowering the seal chamber temperature also increases the fluid’s viscosity, providing a more stable fluid film at the interface of the seal faces.

One method of achieving a reduction in temperature is to circulate fluid form the seal chamber through a heat exchanger and return the cooled fluid back into the seal chamber. The heat exchanger is often referred to as a “seal cooler” since it is not part of the process, but just an auxiliary system component.

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How Carbon Works in Mechanical Sealing

Mechanical face seals are a complex combination of materials and design that form a system whose prime objective is maintaining the integrity of the pumping system, keeping what is inside where it belongs and preventing contamination from the outside.

From the simplest design to the most complex, the system must operate across a multitude of conditions (and often beyond what the original design intended) in terms of speed, contact loads and environment. Every component in the system is a vital link contributing to the system’s success or failure.

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Overview of Multiple Lip Seals

Multiple lip seals are commonly used in centrifugal pumps and positive displacement pumps. There are many variations, but one version that has been particularly effective is a triple lip seal arrangement. The key feature is the third outboard lip seal element, which can be used for several functions.

Sealed media can be compartmentalized, providing the opportunity to apply any of the API piping plans based on the type of media being sealed. For instance, it can serve as an excluder or a secondary seal in a quench gland design for media that crystallizes or hardens with exposure to ambient temperature and pressure. Unlike a mechanical face seal, there are no rotating parts, and all internal components are not just replaceable, but replaceable on-site by in-house or field maintenance staff.

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FSA Introduces the KnowledgeBase Technical Reference

A key element of the mission statement for the Mechanical Seal division of the FSA states that we intend to be “…the primary source of technical information for our products and their application.” For many years, this objective was partially met through the publication and regular updating of the FSA Mechanical Seal Handbook.

For many who have relied on this FSA handbook for technical guidance on mechanical seals and support systems, changes in technology and user behaviors have caused their preferred source of reference material to shift from printed hardcopy materials to searchable online content. Therefore, we have spent the last few years converting FSA’s mechanical seal technical documentation into a format that is conducive to self-instruction by online users. This content has been developed, reviewed and vetted by representatives of the leading mechanical seals manufacturers and is considered to be representative of generally accepted best design practices for the industry.

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Back to Basics: Mechanical Seals

Mechanical seals touch nearly every aspect of industrialized society. Wherever a rotating shaft moves fluid, mechanical seals play a key role in sealing process fluids in, keeping contaminants out, or both.

A few basic components and principles in mechanical seal design contribute to a working seal at the interface of the rotating shaft and stationary pump/mixer/seal-chamber housing. Mechanical seals are usually end-face seals or rotating-face seals, but in some designs they can be circumferential or even a hybrid of lip-type seals.

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Analyzing Life-Cycle Costs to Select the Best Sealing Solution

Choosing the sealing solution that will be the most cost-effective option for a particular application is not as
simple as selecting the one that has the lowest one-time cost.

To assist users in choosing the best seals, the Fluid Sealing Association (FSA) created a life-cycle costs (LCC) calculation tool that enables end users to compare solutions to determine which offers the lowest cost over the life of the pump.

The FSA’s LCC calculation tool allows users to compare additional considerations, including the annual operating cost of each sealing solution. The tool calculates the traditional elements, such as spare parts and labor, plus parasitic losses that are often overlooked.

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Material Advances Improve Seal Reliability in Extreme Application Conditions

During the past 10 years, the industry has devoted extensive investment efforts to the research and development of advanced seal face materials capable of extending the application performance range and mean time between repairs (MTBR) of mechanical seals in pumps, compressors and other fluid-handling rotating equipment.

Much of this research involving universities, material development companies, laboratories and mechanical seal companies focused on diamond-like (DLC) and surface-grown diamond film coatings on conventional mechanical seal face material substrates. For today’s end users, diamond film and diamond-like film provide solutions that enhance reliability, promote safety and provide exceptionally low emission sealing of critical equipment across many difficult-to-seal fluids particular to the oil and gas industries. Diamond film combines the physical properties of diamond with the most advanced seal technologies available.

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