Laporan Praktikum Teknik Perawatan

SEALING and BEARING

Dosen pembimbing : Bp. Gatot S.

Oleh :

Yolla Mahandani (08401062)

Rani Rahmawati (07401055)

JURUSAN TEKNIK KIMIA

POLITEKNIK NEGERI BANDUNG

BANDUNG

2010

Seal (mechanical)From Wikipedia, the free encyclopedia

Compression seal example

A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage (e.g., in a plumbing system), containing pressure, or excluding contamination. A seal may also be referred to as "packing."

Seal types;

Induction sealing or cap sealing Adhesive, sealant

Bodok seal , a specialized gas sealing washer for medical applications.

Bridgman seal , a piston sealing mechanism that creates a high pressure reservoir from a lower pressure source.

Bung

Coating

Compression seal fitting

Diaphragm seal

Ferrofluidic seal

Flange Gasket

Gasket

Glass-ceramic-to-metal seals

Hose coupling , various types of hose couplings

Hermetic seal

Hydrostatic seal

Hydrodynamic seal

Labyrinth seal A seal which creates a tortuous path for the liquid to flow through

Lid (container)

Rotating face mechanical seal

Face seal

O-ring

O-ring boss seal

Piston ring

Plug

Radial shaft seal

Trap (plumbing) (siphon trap)

Stuffing box , Gland (engineering) (mechanical packing)

Wiper seal

Dry gas seal

Exitex seal

Diaphragm sealFrom Wikipedia, the free encyclopedia

An example of a diaphragm seal (in green) used to protect a pressure sensor.

A diaphragm seal is a flexible membrane that seals and isolates an enclosure. The flexible nature of this seal allows pressure effects to cross the barrier but not the material being contained.

Common uses for diaphragm seals are to protect pressure sensors from the fluid whose pressure is being measured.

Materials

Since diaphragm seals need to be highly flexible, elastomers are commonly used, and include a wide variety of both general purpose and speciality rubbers.

Applications

Diaphragm seals (also known as chemical seals) are also used to protect a process fluid from the pressure sensor. Examples of this use are:

Sanitary processes (food, pharmaceuticals, etc.) where allowing process fluid to accumulate in the pressure port of the sensor would compromise the purity of the fluid (such as milk getting into the pressure port of a pressure gauge and spoiling)

Very pure process fluids, where the metal surface of the pressure sensor might contaminate the fluid (such as copper ions from brass leaching into ultra pure water.)

Pneumatic systems where small changes in pressures must be eliminated, such as those controlling air bearings.

Seal Failure

ESEM image of ozone cracks in NBR diaphragm seal formed at sharp corners in seal

Diaphragm seals are susceptible to failure via several mechanisms, including cracking. Ozone cracking can occur in many elastomers for example used in pneumatic systems. If the gas contaminates the air supply, then many rubber diaphragms are at risk from the problem.

Piston ringFrom Wikipedia, the free encyclopedia

A piston ring is an open-ended ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.

The three main functions of piston rings in reciprocating engines are:

1. Sealing the combustion/expansion chamber.2. Supporting heat transfer from the piston to the cylinder wall.

3. Regulating engine oil consumption.[1] [1]

The gap in the piston ring compresses to a few thousandths of an inch when inside the cylinder bore.

Automotive

Most automotive pistons have three rings: The top two while also controlling oil are primarily for compression sealing (compression rings); the lower ring is for controlling the supply of oil to the liner which lubricates the piston skirt and the compression rings (oil control rings). At least two piston rings are required for a piston and cylinder combination. Typical compression ring designs will have an essentially rectangular cross section or a keystone cross section. The periphery will then have either a barrel profile (top compression rings) or a taper napier form (second compression rings). There are some taper faced top rings and on some old engines simple plain faced rings were used.

Oil control rings typically are of three types:

1. single piece cast iron2. helical spring backed cast iron or steel

3. multipiece steel

The spring backed oil rings and the cast iron oil rings have essentially the same range of peripheral forms which consist of two scraping lands of various detailed form. The multipiece oil control rings usually consist of two rails or segments (these are thin steel rings) with a spacer expander spring which keeps the two rails apart and provides the radial load.

The piston might be a fairly loose fit in the cylinder. If it were a tight fit, it would expand as it got hot and might stick tight in the cylinder. If a piston sticks (seizes) it could cause serious damage to the engine. On the other hand, if there is too much clearance between the piston and cylinder walls, much of the pressure from the burning gasoline vapour will leak past the piston (a condition known as blow-by) and into the crankcase, and the push on the piston from combustion will be much less effective in delivering power.

Wear due to ring load on the bore

Piston rings are subject to wear as they move up and down the cylinder bore due to their own inherent load and due to the gas load acting on the ring. To minimize this, they are made of wear-resistant materials, such as cast iron and steel, and are coated or treated to enhance the wear resistance. Two-stroke port design is critical to ring life. Newer modern motorcycle manufacturers have many single function but serrated ports to retain the ring. Typically, top ring and oil control rings will be coated with Chromium [2] , or Nitrided [3], possibly plasma sprayed [4]

or have a PVD (physical vapour deposit)[5] ceramic coating. For enhanced scuff resistance and further improved wear, most modern diesel engines have top rings coated with a modified chromium coating known as CKS[2] or GDC [2], a patent coating from Goetze which has aluminium oxide or diamond particles respectively included in the chrome surface. The lower oil control ring is designed to leave a lubricating oil film, a few micrometres thick on the bore, as the piston descends. Three piece oil rings, i.e. with two rails and one spacer, are used for four-stroke gasoline engines.

Fitting new piston rings

When fitting new piston rings, or breaking them in within an engine, the end gap is a crucial measurement. In order that a ring may be fitted into the "grooves" of the piston, it is not continuous but is broken at one point on its circumference. The ring gap may be checked by putting the ring into the bore/liner (squared to bore) and measuring with a feeler gauge. End gap should be within recommended limits for size of bore and intended "load" of engine. Metals expand with a rise in temperature, so too small a gap may result in overlapping or bending when used under hot running conditions (racing, heavy loads, towing), and even at normal temperatures, a small ring gap may lead to ring gap closure, ring breakage, bore damage and possible seizure of the piston. Too large a gap may give unacceptable compression and levels of blow-by gasses or oil consumption. When being measured in a used bore it may indicate excessive bore wear or ring wear. (Radial wear on ring face reduces thickness of used/worn ring (face wear in bore) essentially decreasing face circumference of ring and thereby increasing size of ring end gap.)

It is considered good practice to build a new engine with the ring gaps staggered around the circumference of the bore. This means that any escaping gas must negotiate a labyrinth before escaping past the rings. However, when the engine is run, the rings will tend to rotate around the piston and not remain in the position as fitted. Many rings will then stick in one spot at random and remain there for the life of the engine. For this reason, ring position during build cannot be considered to be important although most engine builders would feel uncomfortable assembling an engine with the gaps aligned.

When fitting new rings to a used engine, special "ridge dodger" rings are sometimes used for the top compression ring, to improve compression and oil consumption without reboring the cylinder. These have a small step of iron removed from the top section to avoid making contact with any wear ridge at the top of the cylinder, which could break a conventional ring. These are not widely recommended, however, as they are usually not required and may give inferior oil consumption. A more acceptable method is to remove the wear ridge with a "ridge reamer" tool

before lightly honing the bore to accept new rings. In fact if the "ridge " is measured it will generally be apparent it is not really a ridge but a relatively local hollow caused by the top ring near the ring reversal point. The upper edge of this hollow will take the form of a "ramp" about 2mm long from the point of maximum wear to the point of zero wear. In this case there is not actually any ridge to hit, so light honing may be all that is required.

Hose couplingFrom Wikipedia, the free encyclopedia

A hose coupling is a connector on the end of a hose to connect (or couple) it with another hose or with a tap or a hose appliance, such as an irrigation sprinkler. It is usually made of steel, brass, stainless steel, aluminium or plastic.

Types

Air King

The "Air King" Universal Air Hose Coupling (see Dixon Valve) is malleable iron or brass "quarter turn" "sexless coupling" usually found on pneumatic tools like jackhammers. The fitting is considered "universal" because a common two lug head is used on all sizes ranging from 1/4" through 1".

Cam and groove

A Cam and groove is a quick connect fluid transfer hose coupling that consists of a male "adapter" and female "coupler". The "adapter" has a groove on the outside that is engaged by the "cam arms" on the outside of the "coupler" to effect a seal against the gasket inside the "coupler". They are most commonly found in petroleum or chemical[ambiguous] applications. [1]

Ground joint

A "Boss" Ground Joint Coupling valve hose coupling is primarily used for compressed air or steam. It consists of a stem, wing nut and spud. It seals as a soft copper seat located in the spud is drawn against the stem by tightening the wing nut.

Hoselink

Hoselink is a bayonet type connector utilizing an 0 Ring compression to provide a watertight connection for home and commercial garden hoses.

Hozelock

Hozelock is a push-fit connector used for garden hoses.

Storz

Storz connection on a standpipe.

A Storz coupling is a "quarter turn coupling", or "sexless coupling", commonly used to connect to fire hydrants, easy to connect, no particular male or female end, lugs are on inside of coupling. The standard coupling on fire hoses in Germany.

Guillemin symmetrical clutch

The Guillemin symmetrical clutch is widely used in France and in Belgium by firefighters to couple fire hoses. It is also commonly known under the name of DSP connector.

It can be fastened by hand, but it is also possible to use a tricoise wrench. It is also "quarter turn" and "sexless" (symmetrical).

Each end has a ring with two protuberances outside; when the ring turns, the protuberances lock to the hook of the other hose.

Barcelona

Spanish fire hose coupling.

It is the coupling used by the Spanish firefighters. It is a "sexless" coupling with 3 engaging lugs.

Nakajima

A "quarter turn" or "sexless" coupling used on fire hoses in Japan.

Gost

A "sexless" coupling used on fire hoses in Russia.

Machino

A quick connect and disconnect coupling used on fire hoses in Japan.

NST

Side view of a 1.5 inch to 2.5 inch adapter.

National Standard Thread (NST), also known as National Hose thread (NH). The most common type of fire hose coupling used in the USA. The male and female straight (non-tapered) threads screw together and the connection is sealed with a gasket.

Expansion Ring

A Expansion Ring Fire Hose Coupling (see Red Head) is commonly used on lay flay fire hose, it has the advantage of providing no flow restriction, as the expansion ring is expanded to match the inner diameter of the hose. They are installed with special machinery using a drawbar expander. In the USA it is most commonly supplied with NST (NH) threads.

Holedall

Mulconroy

Mulconroy/Holedall Swaged Hose Coupling (see Dixon Valve) is commonly found on larger diameter hoses used in higher pressure applications or where the hose is exposed to higher end pull (i.e., Oil Suction & Discharge (OS&D) hose). They are installed with special hydraulic ram machinery and special dies.

IX

Holedall IX Internally Expanded (Internally Swaged) Hose Coupling (see Dixon Valve) Used in higher pressure applications, or where the hose is exposed to higher end pull, or where a full flow is required. They are installed with special hydraulic pull bar machinery using special pull plugs.

Scovill/Rostra

Holedall (Scovill/Rostra) Internally Expanded Hose Coupling (see Dixon Valve) Used primarily on fuel oil hose applications, where a full flow is required. They are installed with special hydraulic pull bar machinery using special pull plugs.

Radial shaft sealFrom Wikipedia, the free encyclopedia

Radial shaft seals are used to seal rotary elements, such as a shaft or rotating bore. Common examples include strut seals, hydraulic pumps seals, axle seals, power steering seals, and valve stem seals. Early radial shaft seals utilized rawhide as the sealing element, and many elastomeric seal companies today once were tanneries. The advent of modern elastomers replaced rawhide, industry also added a garter spring which helps the sealing lip compensate for lip wear and elastomer material changes.

The seal construction will consist of a sprung main sealing lip which has a point contact with the shaft. The point contact is formed by two angles, with the air side angle usually less than the oil side angle. Depending on the seal type these two angles are varied to create a pressure distribution at the seal contact point which has a steeper slope on the oil side of the seal. The shallower the slope on the oil side of the seal the wetter the seal will run. The spring is positioned such that axially the centerline of the spring is biased to the air side of the lip contact point.

In order to exclude contaminants numerous types of dust lips or exclusionary lips may be used. Common elastomers are: FKM, ACM, NBR, HNBR, AEM. In order to resist wear the compounds' durometer (hardness) is typically 70 to 85 Shore A.

A different seal design for similar applications is a rotating face seal.

Standards

Standards and other documents relating to radial shaft seals

ISO 6194-1:1982 Rotary shaft lip type seals - Nominal dimensions and tolerances ISO 6194-2:1991 Rotary shaft lip type seals - Vocabulary

ISO 6194-3:1988 Rotary shaft lip type seals - Storage, handling and installation

ISO 6194-4:1988 Rotary shaft lip type seals - Performance test procedures

ISO 6194-5:1990 Rotary shaft lip type seals - Identification of visual imperfections

SAE J946-1989 Application Guide to Radial Lip Seals

RMA OS-4, 1984 Application Guide for Radial Lip Type Shaft Seals

RMA OS-7, 1982 Storage and Handling Guide for Radial Lip Type Shaft Seals

RMA OS-8, 1977 Visual Variations Guide for Rotating Shaft Seals

DIN 3760 Radial-Wellendichtringe (Radial shaft seals)

DIN 3761 Radial-Wellendichtringe fur Kraftfahrzeuge (Motor Vehicles Radial shaft seals), Parts 1-15. This standard covers all aspects including vocabulary, material requirements and test methods.

GOST 8752-79. CIS standard for rotary shaft seals.

Dry gas sealFrom Wikipedia, the free encyclopedia

Dry gas seals are non-contacting, dry-running mechanical face seals consist of a mating (rotating) ring and a primary (stationary) ring. When operating, grooves in the rotating ring generate a fluid-dynamic force causing the stationary ring to separate and create a gap between the two rings. Dry gas seals are mechanical seals but use other chemicals and functions so that they do not contaminate a process. These seals are typically used in a harsh working environment such as oil exploration, extraction and refining, petrochemical industries, gas transmission and chemical processing.

The dry gas seal has spiral grooves, with provides for lifting and maintaining separation of seal faces during operation. Grooves on one side of the seal face direct gas inward toward a non-grooved portion of the face. The gas that is flowing across the face generates a pressure that maintains a minute gap between the faces, optimizing fluid film stiffness and providing the highest possible degree of protection against face contact. The seal's film stiffness compensates for varying operations by adjusting gap and pressure to maintain stability.

Design and use

Grooves on the seal direct gas inward toward the non-grooved portion. The action of the gas flowing across the seal generates pressure that keeps a minute gap, therefore optimizing fluid film stiffness and providing protection against face contact.[1][2]

The use of these seals in centrifugal compressors has increased significantly in the last two decades because they eliminate contamination and do not use lubricating oil. Non-contacting dry gas seals are often used on compressors for pipelines, off-shore applications, oil refineries, petrochemical and gas processing plants.[3] Dry Gas Seal configurations: there are many dry gas seal configurations base on their application. 1- Single gas seal 2- Tandem gas seal 3- Tandem gas seal with intermediate labyrinth 4- Double opposed gas seal

Also the dry gas seal can be unidirectional or bidirectional.

History

John Crane Inc. issued the first patent for dry gas seals in 1968 with field applications beginning in 1975. When the technology was introduced, it was aimed at correcting the problems with dry gas film environments by eliminating friction. Soon, the technology became a common replacement for other lubricated seals. The patented spiral-groove technology of the dry gas seal allows for easy lifting and separation of seal faces during operation. There are three common types of lubrication for these seals: full liquid film, which contains oil and requires light-duty conditions; partial liquid/gas film, which requires a 50 percent balance of liquid to preserve the seal; and dry gas film, which has an absence of liquid that creates hot localized areas that may lead to cracking or damage to the seal. Seal failure results from a flooded compressor with oil or liquid, foreign contaminants and alignment problems.[4][5]

SealantFrom Wikipedia, the free encyclopedia

A sealant is a viscous material that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire, smoke or liquid from one location through a barrier into another. Typically, sealants are used to close small openings that are difficult to shut with other materials, such as concrete, drywall, etc. Desirable properties of sealants include insolubility, corrosion resistance, and adhesion. Uses of sealants vary widely and sealants are used in many industries, for example, construction, automotive and aerospace industries.

The main difference between adhesives and sealants is that sealants typically have lower strength and higher elongation than do adhesives. Since the main objective of a sealant is to seal assemblies and joints, sealants need to have sufficient adhesion to the substrates and resistance to environmental conditions to remain bonded over the required life of the assembly. When sealants are used between substrates having different thermal coefficients of expansion or differing elongation under stress, they need to have adequate flexibility and elongation. Sealants generally contain inert filler material and are usually formulated with an elastomer to give the required flexibility and elongation. They usually have a paste consistency to allow filling of gaps between substrates. Low shrinkage after application is often required. Many adhesive technologies can be formulated into sealants.

Sealants fall between higher-strength adhesives at one end and extremely low-strength putties and caulks at the other. Putties and caulks serve only one function – i.e., to take up space and fill voids. Sealants, on the other hand, despite not having great strength, do convey a number of properties. They seal the substrate at the glue line; they are particularly effective in keeping moisture in or out of the components in which they are used. They provide thermal and acoustical insulation and may serve as fire barriers; sometimes they contain electrical properties. They may also be used for smoothing or filleting. In short, sealants are often called upon to perform several of these functions at once.

No matter what the application, a sealant has three basic functions.

1. It fills a gap between two or more substrates.

2. It forms a barrier through the physical properties of the sealant itself and by adhesion to the substrate.

3. It maintains sealing properties for the expected lifetime, service conditions and environments.

The sealant performs these functions by way of correct formulation to achieve specific application and performance properties. Unlike adhesives, however, there are not many functional alternatives to the sealing process. Soldering or welding can perhaps be used as a sealant in certain instances, depending on the substrates and the relative movement that the substrates will see in service. However, the simplicity and reliability offered by organic elastomers usually make them the clear choice for performing these functions.

Silicone is an example of a sealant.

Types of sealants Acrylic sealants Asphalt sealants

Pipe thread sealants

Acoustic sealants

Adhesive sealants

Aerospace sealants

Aircraft sealants

Aquarium sealant

Butyl rubber sealants

Car sealant

Casting sealants

Cement sealants

Concrete sealants

Construction sealants

Dental sealants

Elastic sealants

Electronic sealants

Engine sealant

Environmentally friendly sealants

Epoxy sealants

Extruded sealants

Firestop sealants

Floor sealant

Foam sealants

Gasket sealants

Self-leveling silicone firestop system used around pipe through-penetration in a two-hour fire-resistance rated concrete floor assembly.

O-ringFrom Wikipedia, the free encyclopedia

This article is about is about the mechanical seal. For other uses, see Oring.

Typical O-ring and application

An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.

The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons.

O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable, and have simple mounting requirements. They can seal tens of megapascals (thousands of psi) pressure.

History

The US patent claim for the O-ring was filed in 1937 by a then 72-year-old Danish-born machinist, Niels Christensen.[1] He came to the USA in 1891 and soon after that patented an air brake system for streetcars (trams). Despite his legal efforts, his intellectual property rights were passed from company to company until they ended up at Westinghouse.[2] During World War II, the US government commandeered the O-ring patent as a critical war-related item and gave the right to manufacture to other organizations. Christensen got a lump sum payment of US$75,000 for his efforts. Litigation resulted in a $100,000 payment to his heirs in 1971, 19 years after his death.[3]

Theory and design

O-ring mounting for an ultra-high vacuum application. Pressure distribution within the cross-section of the O-ring. The red lines are hard surfaces, which apply high pressure. The fluid in the seams has lower pressure. The soft O-ring bridges the pressure over the seams.

O-rings are one of the simplest, yet most engineered, precise, and useful seal designs ever developed. They are one of the most common and important elements of machine design. O-rings are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and the cross section diameter (thickness). In the US the most common standard inch sizes are per SAE AS568B specification (i.e. AS568-214). ISO 3601-1:2008 contains the most commonly used standard sizes, both inch and metric, worldwide. The UK also has standards sizes known as BS sizes, typically ranging from BS001 to BS932. Several other size specifications also exist.

Typical applications

Successful O-ring joint design requires a rigid mechanical mounting that applies a predictable deformation to the O-ring. This introduces a calculated mechanical stress at the O-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed the

contact stress of the O-ring, leaking cannot occur. Fortunately, the pressure of the contained fluid transfers through the essentially incompressible o-ring material, and the contact stress rises with increasing pressure. For this reason, an o-ring can easily seal high pressure as long as it does not fail mechanically. The most common failure is extrusion through the mating parts.

The seal is designed to have a point contact between the O-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the O-ring body. The flexible nature of O-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline. Surface finish is also especially important in dynamic applications. A surface finish that is too rough will abrade the surface of the o-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film.

Vacuum applications

In vacuum applications, the permeability of the material makes point contacts quite useless. Instead, higher mounting forces are used and the ring fills the whole groove. Also, round back-up rings are used to save the ring from excessive deformation [4][5][6] Because the ring feels the ambient pressure and the partial pressure of gases only at the seal, their gradients will be steep near the seal and shallow in the bulk (opposite to the gradient of the contact stress [7] See: Vacuum_flange#KF.2FQF. High-vacuum systems below 10−9 Torr use copper or nickel O-rings. Also, vacuum systems that have to be immersed in liquid nitrogen use indium O-rings, because rubber becomes hard and brittle at low temperatures.

High temperature applications

In some high-temperature applications, O-rings may need to be mounted in a tangentially compressed state, to compensate for the Gow-Joule effect.

Material

Some small O-rings

O-ring selection is based on chemical compatibility, application temperature, sealing pressure, lubrication requirements, quality, quantity and cost.

Synthetic rubbers - Thermosets:

Butadiene rubber (BR) Butyl rubber (IIR)

Chlorosulfonated polyethylene (CSM)

Epichiorohydrin rubber (ECH, ECO)

Ethylene propylene diene monomer (EPDM)

Ethylene propylene rubber (EPR)

Fluoroelastomer (FKM)

Nitrile rubber (NBR)

Perfluoroelastomer (FFKM)

Polyacrylate rubber (ACM)

Polychloroprene (CR)

Polyisoprene (IR)

Polysulfide rubber (PSR)

Sanifluor

Silicone rubber (SiR)

Styrene butadiene rubber (SBR)

Thermoplastics:

Thermoplastic elastomer (TPE) styrenics Thermoplastic polyolefin (TPO) LDPE, HDPE, LLDPE, ULDPE

Thermoplastic polyurethane (TPU) polyether, polyester

Thermoplastic etheresterelastomers (TEEEs) copolyesters

Thermoplastic polyamide (PEBA) Polyamides

Melt Processible Rubber (MPR)

Thermoplastic Vulcanizate (TPV)

Other seals

There are variations in cross-section design other than circular. These include the O-ring with an x-shaped profile, commonly called the X-ring, Q-ring, or by the trademarked name Quad Ring. When squeezed upon installation, they seal with 4 contact surfaces—2 small contact surfaces on the top and bottom. This contrasts with the standard O-ring's comparatively larger single contact surfaces top and bottom. X-rings are most commonly used in reciprocating applications, where they provide reduced running and breakout friction and reduced risk of spiraling when compared to O-rings.

There are also rings with a square profile, commonly called square-cuts, lathe cuts, or Square rings. When O-rings were selling at a premium because of the novelty, lack of efficient manufacturing processes and high labor content, Square rings were introduced as an economical substitution for O-rings. The Square ring is typically manufactured by molding an elastomer sleeve which is then lathe-cut. This style of seal is sometimes less expensive to manufacture with certain materials and molding technologies (compression molding, transfer molding, injection molding), especially in low volumes. The physical sealing performance of Square rings in static applications is superior to that of O-rings, however in dynamic applications it is inferior to that of O-rings. Square rings are usually only used in dynamic applications as energizers in cap seal assemblies. Square rings can also be more difficult to install than O-rings.

Similar devices with a non-round cross-sections are called seals or packings. See also washer (mechanical).[8]

Failure modes

O-ring materials may be subjected to high or low temperatures, chemical attack, vibration, abrasion, and movement. Materials are selected according to the situation.

There are O-ring materials which can tolerate temperatures as low as -200 C or as high as 250+ C. At the low end, nearly all engineering materials become rigid and fail to seal; at the high end, the materials often burn or decompose. Chemical attacks can degrade the material, start brittle cracks or cause it to swell. For example, NBR seals can crack when exposed to ozone gas at very low concentrations, unless protected. Other failures can be caused by using the wrong size of ring for a specific recess, which may cause extrusion of the rubber.

Challenger disasterMain article: Space Shuttle Challenger disaster

The failure of an O-ring seal was determined to be the cause of the Space Shuttle Challenger disaster on January 28, 1986. A contributing factor was cold weather prior to the launch. This was famously demonstrated on television by Caltech physics professor Richard Feynman, when he placed a small O-ring into ice-cold water, and subsequently showed its loss of pliability before an investigative committee.

O-rings are now examined under high-power video microscopes for defects

The material of the failed O-ring was FKM which was specified by the shuttle motor contractor, Morton-Thiokol. FKM is not a good material for cold temperature applications. When an O-ring is cooled below its Tg (glass transition temperature), it loses its elasticity and becomes brittle. More importantly, when an O-ring is cooled near, but not beyond, its Tg, the cold O-ring, once compressed, will take longer than normal to return to its original shape. O-rings (and all other seals) work by creating positive pressure against a surface thereby preventing leaks. On the night before the launch, exceedingly low air temperatures were recorded. On account of this, NASA technicians performed an inspection. The ambient temperature was within launch parameters, and the launch sequence was allowed to proceed. However, the temperature of the rubber O-rings remained significantly lower than that of the surrounding air. During his investigation of the launch footage, Dr. Feynman observed a small out-gassing event from the Solid Rocket Booster (SRB) at the joint between two segments in the moments immediately preceding the explosion. This was blamed on a failed O-ring seal. The escaping high temperature gas impinged upon the external tank, and the entire vehicle was destroyed as a result.

The rubber industry has gone through its share of transformation after the accident. Many O-rings now come with batch and cure date coding, as in the medicine industry, to precisely track and control distribution. For aerospace and military/defense applications, O-rings are usually individually packaged and labeled with the material, cure date, and batch information. O-rings can, if needed, be recalled off the shelf.[9] Furthermore, O-rings and other seals are routinely batch-tested for quality control by the manufacturers, and often undergo Q/A several more times by the distributor and ultimate end users.

As for the SRBs themselves, NASA and Morton-Thiokol redesigned them with a new joint design, which now incorporated three O-rings instead of two, with the joints themselves having onboard heaters which can be turned on when temperatures drop below 50 °F (10 °C). No O-ring issues have occurred since Challenger, and they did not play a role in the Space Shuttle Columbia disaster of 2003.

Future

An O-ring is one of the most simple, yet highly critical, precision mechanical components ever developed. But, there are new advances that may take some of the burden of critical sealing away from the exclusive domain of O-rings. There are cottage industries of elastomer consultants assisting in designing O-ring-less pressure vessels. Nano-technology-rubber is one such new

frontier. Presently, these advancements are increasing the importance of O-rings. Since O-rings encompass the areas of chemistry and material science, any advancement in nano-rubber will affect the O-ring industry.

Already, there are elastomers filled with nano-carbon and nano-PTFE and molded into O-rings used in high-performance applications. For example, carbon nanotubes are used in electrostatic dissipative applications and nano-PTFE is used in ultra pure semiconductor applications. The use of nano-PTFE in fluoroelastomers and perfluoroelastomers such as Viton improves abrasion resistance, lowers friction, lowers permeation, and can act as clean filler.

Using conductive carbon black or other fillers can exhibit the useful properties of conductive rubber, namely preventing electrical arcing, static sparks, and the overall build-up of charge within rubber that may cause it to behave like a capacitor (electrostatic dissipative). By dissipating these charges, these materials, which include doped carbon-black and rubber with metal filling additives, reduce the risk of ignition, which can be useful for fuel lines.

Standards

ISO 3601 Fluid power systems -- O-rings ISO 3601-1:2008 Inside diameters, cross-sections, tolerances and designation codes ISO 3601-2:2008 Housing dimensions for general applications

ISO 3601-4:2008 Anti-extrusion rings (back-up rings)

Jenis Bearing

There are many types of bearings, each used for different purposes. Ada banyak jenis bantalan, masing-masing digunakan untuk tujuan yang berbeda. These include ball bearings, roller bearings, ball thrust bearings, roller thrust bearings and tapered roller thrust bearings. Ini termasuk bantalan bola, bantalan rol, bantalan bola dorong, dorong bantalan rol dan bantalan rol tapered dorong. 1. Ball Bearings

Ball bearings , as shown below, are probably the most common type of bearing. bantalan Ball, seperti yang ditunjukkan di bawah ini, mungkin merupakan jenis yang paling umum bantalan. They are found in everything from inline skates to hard drives . Mereka ditemukan dalam segala hal dari skate inline untuk hard drive . These bearings can handle both radial and thrust loads, and are usually found in applications where the load is relatively small. Bantalan ini dapat menangani keduanya radial dan beban dorong, dan biasanya ditemukan pada aplikasi di mana beban adalah relatif kecil.

Photo courtesy The Timken Company Foto milik Perusahaan Timken

Cutaway view of a ball bearing Cutaway melihat sebuah bantalan bola

In a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to the inner race. Dalam bantalan bola, beban yang ditransmisikan dari ras luar untuk bola, dan dari bola ke inner race. Since the ball is a sphere , it only contacts the inner and outer race at a very small point, which helps it spin very smoothly. Karena bola adalah bola, hanya kontak dan luar inner race pada titik yang sangat kecil, yang membantu berputar sangat lancar. But it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining the bearing. Tetapi juga berarti bahwa tidak ada sangat banyak bidang kontak beban yang memegang, jadi jika membawa kelebihan beban, bola dapat merusak atau squish, merusak bantalan.

Our Products main function is to minimize any friction caused by any relative movement of two or more objects, in order to reach the maximum efficiency of energy usage, we aim to minimize the "converted to heat" energy. Produk utama kami fungsi adalah untuk meminimalkan gesekan yang disebabkan oleh gerakan relatif dari dua atau lebih objek, untuk mencapai efisiensi maksimum penggunaan energi, kami bertujuan untuk meminimalkan "diubah menjadi panas" energi. A great variety of types and designs are known, the manifolds of the bearings is justified by their various purpose of application, each type of bearing has a certain characteristic technical properties, rolling bearings have the following advantages compared with the plain bearings: Berbagai besar jenis dan desain yang diketahui, manifold dari bantalan dibenarkan oleh berbagai tujuan mereka aplikasi, masing-masing jenis bantalan memiliki karakteristik sifat teknis tertentu, bantalan rolling memiliki beberapa keuntungan dibandingkan dengan bantalan biasa:

Low starting moment. Rendah mulai saat. Low friction at all speeds. Rendah gesekan pada semua kecepatan.

Low energy consumption. Rendah konsumsi energi.

High reliability. Kehandalan tinggi.

Small width. Kecil lebar.

Low consumption of lubricant. Konsumsi yang rendah pelumas.

Long relubrication intervals. Long relubrication interval.

Easy to mount and dismount. Mudah untuk me-mount dan turun.

Standardized dimensions. Standar dimensi.

2. Roller Bearings Roller bearings like the one illustrated below are used in applications like conveyer belt rollers, where they must hold heavy radial loads. Bantalan rol seperti yang digambarkan di bawah ini digunakan dalam aplikasi seperti rol ban berjalan, di mana mereka harus menahan beban radial berat. In these bearings, the roller is a cylinder , so the contact between the inner and outer race is not a point but a line. Dalam bantalan, rol adalah, silinder sehingga kontak antara dan luar inner race bukan merupakan titik tetapi garis. This spreads the load out over a larger area, allowing the bearing to handle much greater loads than a ball bearing. Ini menyebar beban di atas area yang lebih luas, memungkinkan bantalan untuk menangani beban jauh lebih besar daripada bantalan bola. However, this type of bearing is not designed to handle much thrust loading. Namun, jenis bantalan tidak dirancang untuk menangani beban dorong banyak.

A variation of this type of bearing, called a needle bearing , uses cylinders with a very small diameter. Sebuah variasi dari jenis bantalan, disebut bantalan jarum, menggunakan silinder dengan diameter sangat kecil. This allows the bearing to fit into tight places. Hal ini memungkinkan bantalan untuk masuk ke dalam tempat-tempat yang ketat.

Photo courtesy The Timken Company Foto milik Perusahaan Timken

Cutaway view of a roller bearing Cutaway melihat sebuah bantalan rol

3. Ball Thrust Bearing Ball thrust bearings like the one shown below are mostly used for low-speed applications and cannot handle much radial load. Dorong bantalan bola seperti yang ditunjukkan di bawah ini sebagian besar digunakan untuk aplikasi kecepatan rendah dan tidak dapat menangani beban

radial banyak. Barstools and Lazy Susan turntables use this type of bearing. Barstools dan Lazy Susan turntable menggunakan jenis bantalan.

Photo courtesy The Timken Company Foto milik Perusahaan Timken Ball thrust bearing

Bantalan dorong bola 4. Roller Thrust Bearing

Roller thrust bearings like the one illustrated below can support large thrust loads. Roller dorong bantalan seperti yang digambarkan di bawah ini dapat mendukung beban dorong besar. They are often found in gearsets like car transmissions between gears , and between the housing and the rotating shafts. Mereka sering ditemukan di gearsets seperti transmisi mobil antara roda gigi , dan antara perumahan dan poros berputar. The helical gears used in most transmissions have angled teeth -- this causes a thrust load that must be supported by a bearing. The gigi heliks transmisi yang digunakan dalam sebagian besar memiliki sudut gigi - ini menyebabkan beban dorong yang harus didukung oleh dikenakan.

Photo courtesy The Timken Company Foto milik Perusahaan Timken Roller thrust bearing

Roller bantalan dorong 5. Tapered Roller Bearings

Tapered roller bearings can support large radial and large thrust loads. bantalan gulung tapered dapat mendukung dorong beban radial besar dan besar.

Photo courtesy The Timken Company Foto milik Perusahaan Timken

Cutaway view of (left) a spherical roller thrust bearing and (right) a radial tapered roller bearing Cutaway

pandangan (kiri) roller dorong bola bantalan dan (kanan) tapered roller bantalan radial

Tapered roller bearings are used in car hubs, where they are usually mounted in pairs facing opposite directions so that they can handle thrust in both directions. Bantalan gulung tapered hub digunakan dalam mobil, di mana mereka biasanya dipasang di pasang menghadap arah yang berlawanan sehingga mereka bisa menangani dorong di kedua arah.

Enam Cara Bikin Awet Laher Article Date: Source: Motor Plus Online

Bearing mampu tahan lama dan tidak cepat terkikis syaratnya tergantung perlakukan. Berikut contoh penyebab kerusakan laher baik baru atau sudah lama.

Pemasangan Salah

Pemasangan salah penyebab cepat rusak. Pukulan yang tidak seirama pada cincin luar dan dalam, clearance yang dimiliki laher tidak lagi rata. Sehingga bola-bola yang mestinya bergelinding ideal, jadi rusak lantaran gesekan nggak seirama.

Kurang Pelumas

Pelumas diperlukan untuk meredam panas dan gesekan. “Pastikan yang berkualitas. Khusus laher di dalam mesin, kudu lebih teliti lagi saat mengganti oli. Sebab geram pada oli bekas memperpendek usia laher,” wanti Athanasius Ketut Hargunanto mekanik Aneka Motorsports di

Jl. WR. Supratman, Denpasar, Bali.

Beban Awal Berlebih

Hati-hati kala membeli laher baru. Pastikan ukuran yang tertera di cincin laher. “Sebab bila salah, terjadi beban awal berlebih sangat mungkin lantaran ketika pasang dipaksakan,” tutur Nyoman Tri Mantara, Product Development & Marketing PT SKF Indonesia.

Jalan Berlubang

Trek yang dilalui berlubang beban yang diterima roda dan berpusat di laher. Makanya untuk meminimalkan laher rusak, caranya cuma hati-hati memilih jalur yang tepat. Kalau tidak sempat, ganti laher baru lebih awal guna menghindari dudukan laher yang cepat oblak.

Geram, Kotoran atau Air

Khusus laher yang di luar mesin. Biar tidak cepat dihingapi debu, geram dan air, pastikan laher yang dipakai tertutup pelat besi atau karet. Laher yang dilindungi sil jangan lupa dipasang dan hindari debu atau air.

Beban Berlebih

Kalau beban putar berlebihan, ditambah bobot yang harus ditopang tidak sesuai kekuatan laher, wajar bila bantalan gelinding cepat rusak. “Makanya disarankan pilih ukuran laher sesuai kebutuhan,” jelas Erwin Susanto, mekanik Wins Motor di Jl. Bendungan Jago Raya, Kemayoran, Jakarta Pusat.