PEM 3 KNOWLEDGE SHARING PRESENTATION

1. PEM 3 KNOWLEDGE SHARING PRESENTATION FUNDAMENTALS OF MECHANICAL SEAL Presented by Emmanuel Raphael Essen (MNIMechE, MNIM, ISMN) October, 2014 PEM 3 Knowledge sharing Presentation, October 2014

2. Tables of content. • Historical development of a Mechanical seal • What is Mechanical Seal • Reason for using Mechanical seal • Advantages of Using cartridge seal. • Types of seals: • Essential elements of a mechanical seal • Mechanical seal Components • Essential requirements for proper operation of a mechanical seal • The fluid in the pump and seal area, Leakage, Seal failures and Leakage Rate. • Effective forces in a mechanical sealPower consumption of a liquid lubricated mechanical seal • Seal Face Material • Power Consumption • Classification of Mechanical Seal • Many factors need to be considered in the application of a mechanical seal • Mechanical seal application limit • Seal faces loading devices • Flush arrangement • Selecting a Mechanical seal • Mechanical seal piping plan PEM 3 Knowledge sharing Presentation, October 2014

3. Historical Development of a Mechanical seal At the beginning of the nineteenth century, many endeavours were made to develop a replacement for the conventional, braided packing used for piston pumps and rotating shafts. A more reliable system for different kinds of liquid-conveying rotating machinery was desired. By the 1930’s, the James Walker Group came up with a mechanical shaft seal for refrigeration compressors. At the same time, the John Crane company invented the first automotive mechanical shaft seal. In the early 1940’s, the company developed and introduced the patented elastomer bellows axial shaft seal, today known as “Type 1”. After this breakthrough in sealing technology, other types of mechanical shaft seals were developed. With several types of mechanical shaft seals, the John Crane company adopted the tagline, “The right seal for the right application”. Today, John Crane is still a leading seal manufacturer along with Grundfos, Burgmann, Flowserve, etc. PEM 3 Knowledge sharing Presentation, October 2014

4. What is Mechanical Seal Mechanical seal is a sealing device for any rotating equipment which prevents the inner fluid from leaking through the clearance between the rotating shaft and the housing case. There are various types of mechanical seals for each application and operating condition of the equipment but in principle, mechanical seal is a face type seal, which performs sealing by two sealing faces vertical to the shaft. Mechanical Seal incorporates various components such as the spring giving contact force and the packing which eliminates intrusion of the fluid from the outside. The seal face is an accurately flat face, and so if it is worn, it does not cause the leakage of the sealant as far as wear is within the maximum allowable amount. Therefore it can be used for a long time free of maintenance, and is very effective and efficient in terms of reliability and economy Mechanical seals are used not only in pumps but also in other various equipment such as mixers, agitators, compressors, rotary unions, submersible motors, etc. PEM 3 Knowledge sharing Presentation, October 2014

5. Reasons for using Mechanical seal: • To minimize leakage • To prevent toxic fluids escaping to atmosphere • To reduce power loss. • Advantages of Using cartridge seal. • By using cartridge seals the following can be achieved: • Reduced skill base • Increased Reliability • Fits multiple types of pumps • Reduced downtime • Increased operating profits. • Types of seals: Static Seals & Dynamic Seals • STATIC SEALS: Sealing takes place between two parts that don’t move in relation to each other. • Application - Pipe flanges ,vessel /Tower nozzles, pump casing joint. - Fan /Blower casing joint , Compressor casing joint. - Turbine casing joint, Heat exchanger joints PEM 3 Knowledge sharing Presentation, October 2014

6. Types: Gaskets , O-rings etc GASKET: Packing designed to go between two rigid parts in stationary conditions May be in form of sheet , strip , bulk. Properties: Impermeability, Ability to flow into joints, Corrosion resistance DYNAMIC SEALS: Used for sealing fluid between parts that move in relation with each other. Application: Centrifugal pump gland, valve gland , bearing housing Turbine/compressor inter stage and end sealing , Reciprocating compressors cylinder sealing TYPES: Gland packings, Mechanical contact seals, Labyrinth seal, Oil seal, Oil film seals PEM 3 Knowledge sharing Presentation, October 2014

7. Essential elements of a mechanical seal The basic design of the Mechanical seal consists of the following elements: Flexibly mounted seal face, Rigidly mounted seal face, Compression device and Secondary seal • Mechanical seal Components • Rotary seal face • Stationary seal face • Springs • Retainer • Sealing /flushing media • O-rings PEM 3 Knowledge sharing Presentation, October 2014

8. Essential Requirements for Proper Operation of a Mechanical Seal • These are the essential requirements: • Seal faces must be flat and polished. • Seal faces must be installed perpendicular to the shaft. • Spring force must be sufficient to maintain contact of the faces The Fluid in the Pump and Seal Area Key Point: The fluid contacts the seal faces and other parts in wide open areas, in very small gaps and at the exit of the seal faces. Pressure and temperature of the fluid will depend on its location and determine its respective state, i.e. liquid, gaseous, solid or a mixture. PEM 3 Knowledge sharing Presentation, October 2014

9. Leakage: A few facts about the leakage (and wear) behavior of contacting mechanical seals: It is essential for proper lubrication and wear of the faces. Normal leak rates range between immeasurably small to steady drips or temporary to even small steams. Some seals leak some of the time, some seals never leak (measurably), and some leak all the time. Leakage patterns can be constant, progressive or erratic in nature. It can be in liquid, gaseous and/or solid state. Successful contacting seals tend to have very low wear rates and low leakage rates. Some forms of contact is necessary for low leakage rates. Non-contacting or “full lift off” seals (hydrostatic or hydrodynamic tend to have visible, sizeably larger leakage rates. PEM 3 Knowledge sharing Presentation, October 2014

10. The large majority of mechanical seals never wear out and are removed from service for some other reason. • Seal failures • Seal failure occur for a wide range of reasons. Type of seal failures • Lubrication failures: Dry running and poor lubrication • Contamination failures: Clogging, Hang-up, Particles deposits, Sticking and seizure. • Chemical, physical degrading and wear: Ageing and swollen rubber parts, Corrosion, wear, Explosive decompression • Installation failures: Shaft misalignment, seats not mounted perpendicular to the shaft, axially moving shaft and wrong assembly length. • System failures: The pressure in the seal chamber, the temperature around the shaft seal in the seal chamber, the pumped medium, the speed, the shaft seal dimensions. PEM 3 Knowledge sharing Presentation, October 2014

11. Leakage rate: • The leakage rate of a mechanical shaft seal depends of a number of factors such as: • Surface roughness of seal faces • Flatness of seal faces • Vibration and stability of pump • Speed of rotation • Temperature, Viscosity and Type of pumped medium • Pump pressure • Seal and pump assembly. • . PEM 3 Knowledge sharing Presentation, October 2014

12. Effective forces in a Mechanical Seal • These are the forces operating in mechanical seals: • Axial and radial forces • Closing and opening forces • Hydrostatic and hydrodynamic forces • Seal Face Materials: Few materials are suitable for seal faces. To keep leakage as low as possible, the seal gap must be very small. As a result, the lubricating film is very thin. • Consequently, the seal face materials must be able to withstand rubbing against each other at high load and speed. • The best seal face materials have low friction, high hardness, good corrosion resistance and high heat conductivity. • Examples of seal face materials: Carbon graphite, Aluminium Oxide (Alumina), Tungsten carbide, Silicon carbide, Diamond coatings PEM 3 Knowledge sharing Presentation, October 2014

13. Power Consumption of a liquid lubricated mechanical seal Important Points: Face friction, churning and soak in heat. Flush to dissipate the heat in order to control the gap temperature. Coefficient of friction can swing considerably during operational transients. The key is to maintain the gap profile as parallel as possible, i.e.minimize distortions. PEM 3 Knowledge sharing Presentation, October 2014

14. Interesting, right? This is just a sneak preview of the full presentation. We hope you like it! To see the rest of it, just click here to view it in full on PowerShow.com. Then, if you’d like, you can also log in to PowerShow.com to download the entire presentation for free.