How to use mechanical seals in practical usage

EagleBurgmann Cartex Cassette Seals – Versatile, economical and efficient

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How to use mechanical seals in practical usageThe principle of the cartridge – reliable and affordable

EagleBurgmann Cartex Cassette Seals are fully pre-assembled and precisely installed component seals integrated into the bonnet and shaft sleeve. Seals are installed on pumps in many industries including chemicals, water, paper, food and many other applications. Cassette seals are easy to install and reduce operating costs.

Using Split Mechanical Seals – EagleBurgmann’s Splitex

What is a split mechanical seal?

How to use mechanical seals in practical usageSplitex – EagleBurgmann split gasket

A mechanical seal is a device used to store fluid in a vessel where a rotating shaft passes through the housing, or sometimes as the housing rotates around the shaft. These tanks are generally pumps, mixers, agitators, shredders, etc. The purpose of the mechanical seal is to allow the shaft to rotate freely without allowing large quantities of fluid to escape.

How is a split mechanical seal different from a component or cartridge seal?

The split seal is supplied in two separate parts. Unlike traditional cartridge mechanical seals, these two parts can be attached or removed from the shaft area without disassembling the equipment. Once connected, the sealing elements snap together to ensure a proper seal around the shaft.

When should a split mechanical seal be used?

Why are mechanical seals still the preferred choice in the process industry?

The challenges facing the processing industries have changed, although they continue to pump fluids, some dangerous or toxic. Safety and reliability remain paramount. However, operators increase the speed, pressure, flow rate, and even severity of the fluid properties (temperature, concentration, viscosity, etc.) when processing multiple batch operations. For operators in oil refineries, gas treatment plants, and petrochemical and chemical plants, safety means controlling and preventing loss or exposure to pumped fluids. Reliability means pumps that run efficiently and economically, while requiring less maintenance.

How to use mechanical seals in practical usageA properly designed mechanical seal offers the pump operator long-term, safe and reliable pump operation with proven technology. Mechanical seals have been shown to perform reliably under most operating conditions, including many rotating equipment and countless components.

Pumps & Seals—A Good Fit

It is hard to believe that nearly 30 years have passed since the mass promotion of sealless pump technology in the converting industry. The new technology has been promoted as a solution to all the perceived problems and limitations of mechanical seals. Some have suggested that this alternative would completely eliminate the use of mechanical seals.

However, shortly after this promotion, end users learned that mechanical seals could meet or exceed legal leak and leakage requirements. In addition, pump manufacturers have supported this technology by providing updated seal chambers that have replaced the old “stoppers” with compression seals.

Today’s seal chambers are designed specifically for mechanical seals, allowing for more robust technology to be used in the cassette platform, providing easier installation and creating an environment that allows the seals to function fully.

Design improvements

In the mid-1980s, new environmental regulations forced the industry not only to consider restrictions and emissions, but also the reliability of equipment. The Mean Time Between Repair (MTBR) of mechanical seals in a chemical plant was approximately 12 months. Today the average MTBR is 30 months. Currently the oil industry, subject to one of the most stringent emission levels, has an average MTBR of over 60 months.

Mechanical seals have maintained their reputation by demonstrating the ability to meet and even exceed the requirements of Best Available Control Technology (BACT). In addition, they did so while remaining a cost-effective and energy-efficient technology to meet emissions and environmental regulations.

Computer programs allow gaskets to be modeled and prototyped prior to production to confirm how they will handle specific operating conditions prior to field installation. The gasket design capabilities and gasket face material technology are advanced to the point where they can be developed to fit “one by one” for a process application.

Today’s computer modeling programs and technology allow the use of 3-D design review, finite element analysis (FEA), computational fluid dynamics (CFD), rigid body analysis and thermal imaging diagnostic programs that were not readily available in the past or were too costly for frequent use with earlier 2-D drafting. These advances in modeling techniques have increased the reliability of mechanical seal designs.

These programs and technologies have led to the design of standard cartridge seals with much more durable components. These included the removal of dynamic springs and O-rings from the process fluid and made flexible stator technology the choice.

Last updated: October 15, 2019 References

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The gauges are versatile for measuring straight pieces less than 19 cm in length, the outside and inside diameter of round pieces or the depth of the hole. [1] X Research Source Find out how to use gauges to conduct experiments in physics labs and use them correctly to get accurate results.

How to use mechanical seals in practical usage

Advice: Vernier calipers should be used when making the most accurate measurements possible, such as developing parts for manufacturing operations or collecting data for a physical experiment. Vernier calipers have an accuracy of 1/20 of a millimeter!

Course description

Mechanical seals

Course description

This course will focus on the working principle of conventional mechanical seals, seal designs and arrangements will be explained in this course. On the other hand the course will cover the seal selection, installation and operation as well as seal failure analysis & troubleshooting. The course covers both the fundamentals and current technologies for the operation and maintenance of mechanical seals. The course provides a comprehensive overview of the different types of mechanical seals and their properties and applications. In addition, due to the increasing size and speed of the shafts, as well as the increase in pressure, as well as the limited application of the principles of environmental protection and safety, all these requirements and requirements have prompted equipment manufacturers to use a special type of seal called dry gas seals. The principles of operation, construction, maintenance and troubleshooting of dry gas seals are explained in detail. È incluso anche un confronto tra guarnizioni a umido e a secco. Application examples are also provided. During the course participant’s discussion, comments, bringing up their own problems are welcomed and encouraged.

Course duration:Five days

Course objectives:

Upon successful completion of this course, the participant should be able to:

  • Describe the operating principle of a conventional mechanical seal (wet mechanical seal) and its components;
  • Describe the principle of operation of the dry gas seal and its components.
  • Familiarize the participants with the different types of seals
  • Explain the procedures for installing the gaskets
  • Define the items to consider when troubleshooting the mechanical seal, maintenance and installation
  • Describe the procedure required to specify a mechanical seal for your specific application.
  • Explore the mechanical design of mechanical seal and dry gas seals
  • Emphasize the importance of seals in rotating machines.
  • Learn mechanical seal and dry gas seal failure analysis and troubleshooting

Training methodology

The course will be conducted with formal lectures, case studies and interactive work examples. This training course covers the following training methods as a percentage of the total study hours: –

  • 50% lessons
  • 30 % Case Studies & Practical Exercises
  • 20% Videos and general discussions

The course instructor may change the above training methodology during the course for technical reasons.

Who Should Attend?

Mechanical maintenance engineers and design engineers involved in troubleshooting, selection, operation and maintenance of mechanical equipment. Entry level engineers through to senior engineers will benefit from the course structure. The course is aimed at engineers from the petrochemical, refining and energy industries.

Outlines of the course

Day 1

Initial test

  • introduction
  • Why do we need to seal?
  • Seal classification (static seal and dynamic seal)
  • Mechanical seal applications

Fundamentals of operation of a mechanical seal

  • Sealing requirements
  • Packaged gland
  • Simple mechanical seal – components of the mechanical seal
  • Sealing surface lubrication
  • Sealing points

Day 2

Basic sealing structures – classification of mechanical seals

  • Pusher seal / Pusherless seal
  • Sustainable and unbalanced seals
  • Single seal and double seal
  • Internal and external seals
  • Separate seals & cartridge seals
  • Special sealing designs
  • API sealing system

Sealing of constituent materials

  • The material of the sealing surfaces
  • Gasket materials
  • soft
  • Materials
  • Materials sprzętowe

Day 3

  • API 682 overview
  • API plans and seal placement
  • Temperature Control of Mechanical seals Sealing and Flushing Fluids

Environmental controls

  • Why is environmental control important?
  • Seal the flanged doors
  • Popular plans for washing gaskets – API plans
  • Elements of the environmental control system

Day 4

Dry gas seal

  • introduction
  • Operation and basic components
  • A spiral groove gasket and a gasket to protect the washer
  • Spiral groove seal
  • Loss
  • Safety
  • Maintenance
  • Unit design
  • Benefits
  • Application: seals for gas compressors
  • Replace the seals from wet to dry.

Day 5

Seal installation for dry seals & conventional mechanical seals

  • Pre-installation checks (hardware checkpoints)
  • Seal installation & seal setting in horizontal pumps
  • Seal installation & seal setting in vertical pumps
  • Seal failure analysis and troubleshooting
  • Mechanical seal repair and seal surface inspection (optical inspection system)
  • Topic of study
  • Glossary and definition of terms relating to seals
  • After the test

How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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How to use mechanical seals in practical usage

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What is an O-ring? The basics

How to use mechanical seals in practical usageTechnology is always evolving, but some things stand the test of time.

One of those things is the O-Ring, which was first patented in 1896. What is an O-ring? It’s a doughnut-shaped loop designed to prevent the passage of liquids or gases. It’s one of the simplest precision mechanical pieces ever produced, and continue to be one of the most widely-utilized sealing products.

O-rings can be made from plastic or metal, but for the purposes of our blog we will only focus on the rubber or elastomeric construction of the O-rings.

An O-ring, also known as a “bull”, works in tandem with the glands in which it is installed. The gland is usually cut from the metal hardware and works with an O-ring to seal. The stuffing box and o-ring must be designed together for best performance.

How do you seal an O-ring?

Seals prevent fluids from escaping through slots in equipment mating components. The O-Ring sits in the middle of a gland when it’s at rest, but as pressure begins to rise in the sealing system, the O-Ring shifts to the opposite side of the pressure.

Because the material is soft, the O-ring is mechanically squeezed to plug the opening between the two mating pieces of the fixture.

Restrictions on the use of O-rings

"Sebbene sia stato riscontrato che gli O-ring offrono un approccio ragionevole a una tenuta idraulica ideale, non dovrebbero essere considerati una soluzione immediata a tutti i problemi di tenuta".

It was the DR Pearl of United Aircraft Corp. in 1947, in a paper presented at the SAE Annual Meeting.

Pearl wrote these words nearly 70 years ago, but there are clear limitations to using O-rings as the primary seal. These restrictions include:

  • Rotational speeds greater than 1,500 feet per minute
  • Inappropriate design of associated equipment
  • Temperature, pressure and chemical compatibility of incompatible fluids

To find out more about where O-rings will work, download our detailed guide to O-rings. This 36-page document deals with O-Rings’ technical performance characteristics, materials, chemical and temperature compatibility, hardware considerations and failure modes.

  • Press
  • E-mail

Details

Today’s mechanical seal manufacturers are constantly working to design seals that are more durable, safer, easier to use, and low emissivity for the benefit of seal users, their products and the environment. Technology may be the key to making a mechanical seal reliable, but it is not the only key. Without knowing actual process conditions, understanding the effects associated with a larger system, and the proper functioning of the system, good poorly applied technology may not ultimately improve reliability.

Successful mechanical seal manufacturers today must apply key research skills in selecting the right technology for each application and then instill practical and operational knowledge of proper operation and maintenance techniques required to succeed. The close relationship between the gasket supplier and plant personnel increases the likelihood of achieving high reliability goals.

Extend the life cycle

To understand what manufacturers are doing to extend the life of the seals, look directly at the main mechanism of the mechanical seal: the small distance between the fixed and parallel sliding rotating sealing surfaces. Getting the right balance of load, heat generation, surface finish and parallelism will determine the amount of leakage that passes and the abrasive wear that limits life. Every component of a mechanical seal – from the stationary gland to the swivel bushing – must be designed to help maintain this fine parallel interface.

Heat generation due to frictional friction on the seal contact surface can reduce seal life if the mechanical seal is not suitable for these conditions. For example, seals designed for fluids rely on the fluid to provide cooling and lubrication. If this fluid is no longer available, for example if the valve unexpectedly closes, the absence of lubrication and cooling means high heat generation and rapid wear of the seal faces. There are many other ways to cause the seals to run dry and the special case is that the fluid itself evaporates at or near the sealing surfaces. Light hydrocarbons and hot water boil on sealing surfaces when vapor pressure is exceeded by temperature or absolute pressure.

If the sealing surfaces work without contact, the frictional heat can be eliminated. However, non-contact sealing surfaces allow for leaks which, depending on the type of fluid, can be an environmental or safety concern. If the fluid type is gas, having non-contact sealing surfaces is a good way to eliminate heat and frictional wear when gas leaks are acceptable. Again, the seal manufacturer’s goal is to manage the parallel-sliding interface appropriately for the service conditions. The challenge is to design a mechanical seal that functions reliably under ever-changing and often unknown conditions, where only micrometers (micrometers) define the difference between over-emission and heat generation problems.

New technologies

One of the most important areas where the technology is used today is optimizing the relationship between the two sealing surfaces by introducing very fine structures or patterns on the faces to create a special environment in a parallel sliding interface.

Surface features on the seal face or surface topography create support forces to counter the forces that seek to crush closed surfaces. These designed patterns and grooves create a locking profile that ranges from complete neutralization of all closing loads resulting in complete separation of the sealing surfaces, or a locking profile which reduces most of the closing loads resulting in light contact with the sealing surface. Le tenute a gas secco utilizzano una topografia che fornisce la separazione dell’intera superficie, mentre le tenute progettate per il funzionamento a umido o a umido leggero utilizzano una topografia che lavora per ridurre i carichi di contatto.

Some gaseous media topographies have a series of sharp-edged grooves that draw gas into a tapered area. This taper causes the internal pressure to rise to a level higher than that towards the outside of the sealing surface. The net result is that the increased contact pressure exceeds the pressures that act to close the sealing surfaces, and the sealing surfaces separate and remain open with a very thin layer of gas. At the point of separation of the sealing surfaces, the pressure at the interface of the surfaces decreases due to the lower separation efficiency and for the defined separation the balance of forces on the sealing surfaces is ensured. There are entire product lines for dry gas applications that use seal surface topography to generate lift and cause seal surface separation.

Another model is the smooth wave design, which includes a sinusoidal series of peaks and valleys that allow the process fluid to enter and then exit the same direction it entered. As the fluid is pushed back from the valley of the wave at the top of the wave, the pressure increases similar to a gas-tight topography. The waves are particularly useful for providing sufficient pressure on the contact surface to relieve the measured portion of the closing loads such that the net result is a reduced speed surface contact.

In addition to the grooved and wavy sealing surfaces, many different micro-surface features have been introduced to optimize reliability and performance for specific problems.

In various branches of the processing industry, and especially by type of fluid, zero emissions into the environment are allowed. Many volatile, toxic and hazardous fluids are subject to criminal penalties against the emitters, or the fluid may pose an intrinsic safety hazard. In these and other situations, double seals are usually used to prevent any process loss. As the name suggests, the two sets of mechanical seals are joined and filled with a liquid or gas that acts as a barrier against process leaks. The sealing surfaces therefore act on this barrier fluid instead of the process fluid, which alone or with the characteristics of the sealing surfaces can contribute to a further increase in reliability. Dual gas seals are good examples of the sealing surface technology used, and at the same time solve the problems of dry running, zero emissions, process contamination and energy consumption.

What is a pump shaft seal?

Shaft seals prevent fluid from leaking from a rotating or reciprocating shaft. This is important for all pumps and with centrifugal pumps there will be several sealing options available: seals, lip seals and all types of mechanical seals: single, double and tandem including cartridge seals. Positive displacement rotary pumps such as gear pumps and vane pumps are available with seals, lips and mechanical seals. Piston pumps have various sealing problems and usually rely on lip seals or gaskets. Some models, such as magnetic drive pumps, diaphragm pumps or peristaltic pumps, do not require shaft seals. These so-called ‘sealless’ pumps include stationary seals to prevent liquid leakage.

What are the main types of pump shaft seals?

Seal

Seal (also known as shaft packing or gland packing) consists of a soft material, which is often braided or formed into rings. It is pressed into a chamber around the propeller shaft called a gland to form a seal (Figure 1). Compression is normally exerted axially on the sealant, but can also be applied radially with a hydraulic means.

Traditionally, packaging was made of leather, rope or linen, but nowadays it is usually made up of inert materials such as expanded PTFE, compressed graphite and granular elastomers. Seal is economical and commonly used for thick, difficult-to-seal liquids such as resins, tar or adhesives. However, this is a poor sealing method for thin liquids, especially at higher pressures. Seal seldom fails catastrophically, and it can be replaced quickly during scheduled shutdowns.

Seal seals require lubrication to avoid the build-up of frictional heat. This is usually provided by the pumped liquid itself, which tends to leak slightly through the filling material. Może to powodować bałagan, a w przypadku cieczy żrących, łatwopalnych lub toksycznych jest często niedopuszczalne. In these cases, a safe external lubricant can be used. Seal is unsuitable for sealing pumps used for liquids containing abrasive particulates. Solids can stick to the packing material, damaging the pump shaft or packing box wall.

How to use mechanical seals in practical usageLip seals

Lip seals, znane również jako uszczelnienia promieniowe wału, to po prostu okrągłe elementy elastomerowe, które są utrzymywane w miejscu względem wału napędowego przez sztywną obudowę zewnętrzną (rysunek 2). The seal arises from the frictional contact between the ‘lip’ and shaft and this is often reinforced by a spring. Lip seals are common throughout the hydraulic industry and can be found on pumps, hydraulic motors, and actuators. They often provide a backup secondary seal for other sealing systems, such as mechanical seals. Lip seals are generally limited to low pressures and are also poor for thin, non-lubricating liquids. Many lip sealing systems have been successfully applied to a variety of viscous and non-abrasive liquids. Lip seals are not suitable for use with any abrasive liquids or fluids containing solids as they are susceptible to wear and any slight damage can lead to failure.

How to use mechanical seals in practical usage

Mechanical seals

Mechanical seals essentially consist of one or more pairs of optically flat, highly polished faces, one stationary in the housing and one rotating, connected to the drive shaft (Figure 3). The surfaces must be lubricated either with the pumped liquid itself or with a barrier fluid. Consequently, the sealing surfaces only come into contact when the pump is stopped. In use, the lubricating fluid forms a thin hydrodynamic layer between opposing sealing surfaces, reducing wear and facilitating heat dissipation.

How to use mechanical seals in practical usage

Mechanical seals can handle a wide range of liquids, viscosities, pressures, and temperatures. However, the mechanical seal must not run dry. A key advantage of mechanical seal systems is that the drive shaft and housing are not part of the sealing mechanism (as is the case with cable gland and lip seals) and therefore are not subject to wear.

Double seals

Double seals utilise two mechanical seals positioned back to back (Figure 4). The internal space between the two sets of sealing surfaces can be hydraulically pressurized with a barrier fluid such that the film on the sealing surfaces required for lubrication is a barrier fluid and not a pumped medium. The barrier fluid must also be compatible with the pumped fluid. Double seals are more complex to operate because of the need for pressurisation and are typically used only when it is necessary to protect personnel, external components and the surrounding environment from hazardous, toxic or flammable liquids.

How to use mechanical seals in practical usage

Tandem seals

Tandem seals are similar to double seals but the two sets of mechanical seals face in the same direction rather than back-to-back. Only the product-side seal rotates in the pumped fluid, but leaks through the seal surfaces eventually contaminate the barrier lubricant. This has consequences on the tightness of the lateral atmosphere and the surrounding environment.

Cassette seals

A cartridge seal is a pre-assembled package of mechanical seal components. The liner design eliminates installation problems such as the need to measure and set spring compression. The sealing surfaces are also protected against damage during assembly. In one design, a cartridge seal can have a single, double or twin configuration contained in the gland and mounted on the sleeve.

Gas barrier seals

They are double slot cartridge with faces designed to operate under pressure using an inert gas as a barrier to replace traditional lubricating fluid. The sealing surfaces can be separated or kept in free contact during operation by adjusting the gas pressure. A small amount of gas can escape into the product and into the atmosphere.

summary

Shaft seals prevent liquid escaping from a pump’s rotating or reciprocating shaft. Often several sealing options will be available: seals, lip seals and various types of mechanical seals: single, double and tandem, including cartridge seals.