Tag Archives: Fluid Sealing Association

Custom Rubber Expansion Joints

Keeping aging facilities and equipment maintained is an everchanging task that can jeopardize the goal of maximizing uptime. Years of thermal cycling, vibration or foundation settling can disorient piping or pumps. Piping engineers will use rubber expansion joints to account for these types of challenges in a rigid piping system. Permanent misalignment can set
in after years of operation. The original size expansion joint could no longer be the best fit when it comes time to replace.

Replacing a permanently misaligned expansion joint connection with the original part could lead to reduced service life and/or missed expectations of the new expansion joint. Determining the best way to accommodate this when it comes time to replace the existing expansion joint can have long-term effects on reliability.

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Sealing High-Speed Shafts in Turbomachinery

Rotating liquid pump shafts that are originally sealed with soft packings mostly use contacting face seals, also known as mechanical seals. Typical rotational speeds are roughly between 1,000 and 3,600 revolutions per minute (rpm). In turbomachinery — such as compressors and expanders—the rotational speeds are higher and mechanical seals would not
immediately appear to be an option, due to greater rubbing speeds along with a lack of liquid cooling and lubrication.
Nevertheless, from the late 1970s when they were first marketed, noncontacting mechanical seals, known as dry gas seals in cartridge form, have been used in most gas turbomachinery.

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API 622: Valve Packing for Fugitive Emissions

The American Petroleum Institute (API) has developed two commonly used standards designed specifically for the petroleum industry. They include API 622 “Type Testing of Process Valve Packing for Fugitive Emissions,” and API 624 “Type Testing
of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions.” API 622 and API 624 may be specified by an end-user. Valve OEMs must use API 622-approved packing for any valve on test for API 624.

Since the introduction of the U.S. Clean Air Act in 1963, the U.S. Environmental Protection Agency (EPA), as well as individual states, have set increasingly stringent restrictions regulating fugitive emissions from industrial facilities.

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Across the broad spectrum of process industry applications today, fluid handling sealing systems perform a vital role in plant safety, maintaining pump efficiency, reliability, energy consumption, water usage and control of emissions to the environment. Often well hidden within the visible pumping equipment structure, mechanical seals operate 24/7 performing the critical function of static and dynamic sealing between the fixed pump housing and rotational drive shaft. From aqueous solutions to very abrasive slurries to highly volatile and hazardous fluids, mechanical seal technology continues to advance meeting the increasingly demanding application conditions and emission control standards required of users today.

Mechanical Seal Design
The most basic mechanical seal is comprised of a primary wear ring element fixed to the rotating shaft and a stationary opposing wear ring element that is fixed within the pump housing. Having precisely machined surfaces, these two wear components or seal faces are axially spring loaded together creating a seal interface. Dynamically, the wear faces operate on an extremely thin, highly engineered fluid film creating a stable, controlled operating environment between rubbing surfaces of the seal faces.

Maximum Sealing Safety and Reliability
Seal education and operator safety awareness training is of the highest priorities that the Fluid Sealing Association member companies promote. The FSA KnowledgeBase (fsaknowledgebase.org) shares design tools, best operating practices, and guidelines to meet government regulations using best available control technology, which emphasizes the importance of applying the right seal design for each given set of operating conditions. Seal selection based on all working conditions, fluid properties, equipment operating procedures and proven performance to industry standards like API-682 all must be considered and applied to achieve maximizing mean time between planned maintenance.

Environmental Responsibility
Recent advances in mechanical seal technology are playing a significant role in our collective responsibility to promote and achieve fluid control systems that meet the highest levels of environmental responsibility. The development of engineered seal face materials is lowering the coefficient of friction on seal faces thereby reducing power consumption, heat generation, and the associated the volume of cooling water required. Gas lubricated dry running dual seals that further minimize power consumption and fully isolate the process fluid from atmosphere are achieving near zero emissions to the atmosphere and the utilization of fluid dynamics modeling tools providing highly predictive behavior of seal interface conditions is optimizing performance on highly critical applications.

Fluid Sealing Association Releases Latest “Compression Packing Technical Manual”

The Fluid Sealing Association (FSA) has released the fourth edition of the “Compression Packing Technical Manual.” This update represents a four-year intensive joint effort of FSA and the European Sealing Association’s (ESA) compression packing technical committee’s new technical learnings. These learnings can help inform end users on industry best practices and performance characteristics of compression packings.

New sections to the manual have been added including:
- environmental controls
- compression packing vs. mechanical seals – leakage rates
- pump packing power consumption
- determining stuffing box dimensions

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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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A User’s Guide to Expansion Joint Control Units

It is no secret that one of the greatest demands for an expansion joint is the expectation to serve a long, leak-free life with little to no maintenance. Once installed, these flexible rubber connectors should require little attention. The preservation of this investment (and one’s sanity) can be maximized with an in-depth overview of how control units can prevent a new expansion joint from being overstressed.

The purpose of a control unit is to act as a safety device against excessive movement resulting from pressure thrust. A typical control unit assembly is comprised of threaded rods, steel gusset plates, nuts and washers.

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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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How to Investigate Compression Packing Failure Modes

In many respects, troubleshooting and failure analysis of packing materials is similar to the investigation of a crime scene. A good investigator knows how to gather clues from many different sources and put them together to understand what has happened. A good troubleshooter uses the same information gathering method, familiarizing themselves with the sealing materials, the process equipment and the systems where they are used.

The troubleshooter should seek information from the people who work with the equipment on a regular basis. Seal installers, maintenance personnel, operators, process engineers and others can all shed light on potential causes of failure.

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