Category Archives: Pump & Valve Packings Blog

How to Prevent Galvanic Corrosion of Valve Stems

Valve packing is a necessity for plants trying to contain product and meet the latest emission requirements However, finding a sealing product that works and has longevity can be a challenge. Graphite-based packing can be a good choice for stem sealing when elevated temperature requirements are necessary. This is due to graphite’s ability to maintain its sealing properties at temperatures that cause polytetrafluoroethylene (PTFE) to break down and allow leaks to occur. However, graphite is not an electrical insulator like PTFE; graphite will act as a metal and undergo galvanic corrosion if the environment is right.

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What to Understand About Chemistry to Make the Best Materials Choices

In chemistry, a strong oxidizer is a substance (like chromic acid) that can cause other substances (like seals and gaskets) to lose electrons. So, an oxidizer is a chemical species that undergoes a reaction that removes one or more electrons from another atom. This causes a change in mass. Metals will turn into their respective heavier oxides, and the carbon in graphite will oxidize into carbon dioxide – which, although molecularly heavier, is a gas at room temperature. This happens in pumps, valves, pipelines or any other equipment that have seals and gaskets carrying a strong oxidizer. It will cause pitting or rust and, depending on your choice of seal material, may require shorter service intervals.

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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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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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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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Compression Packing: A Look Beyond the Standard Stuffing Box

Stem packing is a familiar product. The most common type is braided compression packing. Braided packing is used in a wide range of applications. Depending on the service, construction materials can be as diverse as plants or animal derivatives, mineral fibers or synthetic plastics and even metal. The process of cutting rings from rope packing, inserting them into a stuffing box and torquing them to the right density is common, but it is not always the best choice. Another widely used manufacturing method is die-molding. It is the process of wrapping a material around a mandrel, placing it in a die and preforming it to make a seal. Using these and other manufacturing technologies, packing is found to work in applications as different as aerospace, heavy trucking and power generation. A review of some unusual applications demonstrates the versatility of compression packing as a selaing solution.

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Valve Packing Friction: the Hidden Factor for Better Plant Performance

In many processes, valves are used as a way to control flow – but they also must seal leakage from the stuffing box and operate freely to keep the plant running properly. Packing success and valve operability need accurate gland loading to perform correctly. Packing friction is a byproduct of tightening packing that needs to be compressed. If left unattended, issues can arise.

On September 9, 2010, a 30-inch diameter natural gas pipeline ruptured in San Bruno, California causing a massive fire that killed eight people. The accident released 47.6 million cubic feet of natural gas and also destroyed 38 homes in the residential area. Many small missteps occurred that resulted in this accident and caused loss of life. One misstep that does not get much attention is packing friction that created problems with control valves.

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Compensating for Oxygen Concentration

The air we breathe contains by volume 78% nitrogen, 21% oxygen and approximately 1% argon. Oxygen concentrations as high as 23% are considered acceptable by OSHA. However, in many areas of industry and medicine where technical or high-purity oxygen is used, oxygen concentrations can exceed 23% and create what is known as “flammable atmosphere,” leading to serious accidents and the inability for workers to self-rescue from hazardous situations when proper care is not taken.

Oxygen is non-flammable, but it is a fire promoter and can accelerate combustion and thus is a hazardous substance. Ignition may be caused by sparking, welding or using electric tools when concentrations rise above 23%. Materials of construction, education and testing go far to prevent these hazards in industrial settings.

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Factors for Successful Emissions-Compliant Valve Stem Seals

Valve seal performance is an important issue with today’s restrictions on emissions of volatile organic compounds (VOCs) from valves. Refineries and chemical processing plants, valve manufacturers, seal manufacturers, valve repair companies and outage service companies have a vested interest in ensuring that valves operate within emissions-compliance levels. Careful treatment from each of these parties is required to deliver successful, emissions-compliant valve performance.

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Back to Basics: Compression Packing

You have probably heard the old saying, “If you don’t have time to do it right, then you’ll need to make time to do it over.” Understanding basic compression packing installation steps is key to getting the job done right the first time.

The goal of this article is to provide an overview of the critical steps necessary to ensure outstanding packing performance.

The first step is to remember the “5 Ps of Packing Installation.”

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