Seals

SEALS •

A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage containing pressure, or excluding contamination.

INDUCTION SEALING •

Induction sealing is a non-contact method of heating a metallic disk to seal the top of plastic and glass containers. This sealing process takes place after the container has been filled and capped. WORKING: • multilayer liner already inserted in the closure. 3 layers a).paper pulp(spot glued to the cap) b).wax c).polymer film laminated to the foil • after cap applied it passes through induction coli which emits varying electromagnetic field

Why induction sealing? •

Tamper evidence : The seal cannot be removed and reapplied without leaving visible evidence of entry. Seals applied by heat induction to plastic containers appear to offer a higher degree of tamper-resistance than those that depend on an adhesive to create the bond

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Leak prevention Retain Freshness

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Pilferage protection Pharmaceutical companies purchase liners that will purposely leave liner film/foil residue on bottles.

SEALANT 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 DESIRABLE PROPERTIES: •

1. Insolubility 2. corrosion resistance 3. Adhesion

VARIOUS TYPES • Acryl sealants • Polysulfide sealants • Polyurethane sealants • Silicone sealants • WTK sealants • Firestop

BODOK SEAL •

The Bodok seal is a specialised washer that ensures a gas-tight seal between the cylinder yoke or regulator of an anaesthetic machine or any medical device requiring a gas supply, and a gas cylinder.

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consists of a neoprene washer with a peripheral metal reinforcing ring which prevents splaying of the washer.

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The seal is incombustible and resistant to the high pressures imposed upon it by cylinder gases (a full cylinder has a pressure of approx 2000 psi / 140 bar).

BRIDGMAN SEAL •

seals a high pressure volume by the use of an unsupported area to create a higher pressure between two pistons.

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A viscous material such as copper or soap stone is used in the generated higher pressure area to seal the intended pressure area.

BUNG •

A bung is an apparatus used to seal a container, such as a bottle, tube or barrel.

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Partially inserted and displaces the inside volume

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Usually made of hardened rubber

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Plastic bungs are commonly used to stop the air leaking from the lower parts of an air-bed. This type of bung is commonly made in two parts; the plastic outer screw on cap and the inner rubber bung used to seal the hole.

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Examples: wine bottles and laboratory apparatus

COATING •

Coating is a covering that is applied to an object.

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The aim of applying coatings is to improve surface properties of a bulk material usually referred to as a substrate.

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One can improve amongst others appearance, adhesion, wetability, corrosion resistance, wear resistance, scratch resistance, etc

DIAPHRAGM SEAL •

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.

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

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Examples : Sanitary processes Pneumatic systems Pure process fluids

GASKET •

A gasket is a mechanical seal that fills the space between two objects, generally to prevent leakage between the two objects while under compression.

Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, fiberglass, or a plastic polymer

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Desirable that the gasket be made from a material that is to some degree compressible such that it tightly fills the space it is designed for, including any slight irregularities.

HERMETIC SEAL •

A hermetic seal is a seal which, for practical purposes, is considered airtight

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Used in electronic parts and food items to be air tight

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Can be made of meta or other material with metal lining. So that it is airtight after using.

LABYRINTH SEAL •

A labyrinth seal is a mechanical seal that fits around an axle to prevent the leakage of oil or other fluids.

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composed of many straight threads that press tightly inside another axle, or inside a hole, so that the fluid has to pass through a long and difficult path to escape

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Labyrinth seals on rotating shafts provide non-contact sealing action by controlling the passage of fluid through a variety of chambers by centrifugal motion, as well as by the formation of controlled fluid vortices. Turbines use labyrinth seals due to the lack of friction, which is necessary for high rotational speeds.

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LID •

A lid is part of a container, and serves as the cover or seal, usually one that completely closes the object.

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Lids have been found on pottery dating back as far as 3100 BC.

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Often a part of a living creature covering an opening is called a lid. The word has other usages for things that cover something.

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Also known as cap, closure, seal, closing element, closure element, sealing element

FACE SEAL •

A face seal is a seal in which the sealing surfaces are normal to the axis of the seal.

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Face seals are typically used in static application and are used to prevent leakage in the radial direction with respect to the axis of the seal.

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Face seals are often located in a groove or cavity on a flange.

Types of face seals • O-rings • E rings • C rings • Gaskets

O- RING • • • • •

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An o-ring is a loop of elastomer with a round (o-shaped) cross-section used as a mechanical seal or gasket. seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. joint may be static or have relative motion between the parts and the o-ring Joints with motion usually require lubrication of the o-ring to reduce wear O-rings are one of the most common seals used in machine design because they are inexpensive and easy to make, reliable, and have simple mounting requirements. tens of megapascals can be sealed.

PISTON RINGS •

A piston ring is an open-ended ring that fits into a groove on the outer diameter of a piston in a reciprocating engine

three main functions of piston rings in reciprocating engines are: • Sealing the combustion/expansion chamber. • Supporting heat transfer from the piston to the cylinder wall. • Regulating engine oil consumption.

COMPRESSION SEAL •

Is intended to seal some type of element (probe, wire, conductor, pipe, tube, fiber optic cable) when the element must pass through a pressure or environmental boundary purposes: • It restrains the element from moving as a result of a pressure delta. • It prohibits the leakage of gas/liquid media along the element • In some cases, it electrically isolates the element from the mounting device.

RECIPROCATING SEALS •

Dynamic seal used to seal pistons or rods that are in linear motion

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involve relative reciprocating motion along the shaft axis between the inner and outer elements. In reciprocating seal applications, the O-ring slides or rocks back and forth within its gland with the reciprocating motion.

ROTORY SEALS

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involve motion between a shaft and a housing. Typical rotary seals include motor shafts and wheels on a fixed axle.

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O-ring seals are NOT recommended for rotary applications under the following conditions: • Pressures exceeding 800 psi. • Temperatures lower than -40° C (-40° F) or higher than 107° C (225° F). • Surface speeds exceeding 600 feet per minute (fpm).

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When an elastomer is stretched and heated, it will contract.

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This is called the Gough-Joule effect. This is an important design consideration in a rotary application because if an O-ring is installed in a stretched condition, frictional heat will cause the O-ring to contract onto the shaft. This may cause the O-ring to seize the rotating shaft so that the dynamic interface becomes the O-ring O.D. and the groove I.D. The contraction will also cause more frictional heat, further exacerbating the situation and causing premature failure of the O-ring.

MECHANICAL SEALS •

Mechanical seals are engineered for most  pumps, mixer and agitator applications in maintenance.

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standard mechanical seals can suit most requirements-including temperatures to 500 degrees F and shaft speeds to 3600 RPM

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Seals can be ordered in balanced configurations to seal pressures above 200 psi, or used in a multiple for extremely high pressures or especially severe fluid services

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Special mechanical seals can be furnished to meet the most demanding of industrial applications considering pressure, temperature, speed or fluid.

Mechanical Seals failures seem to fall into four broad categories: •

The seal motion was restricted and the faces opened. 

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Heat caused the 0-rings to deteriorate.

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The seal materials were attacked by the fluid sealed.

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The seal was installed incorrectly.

Mechanical Seal materials attacked: When the correct materials are not selected,

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The 0-rings may swell locking up the mechanical seal,

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The mechanical seal faces may deteriorate rapidly, and

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The metal seal components may corrode.

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All can cause the mechanical seals to fail.

A good company specification for mechanical seals will include the following:

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 Mechanical Seal materials with the widest range of chemical compatibility Mechanical Seals that are easy to install

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Mechanical Seals with features that make seal repair easy and low cost

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Mechanical Seals that require the least amount of inventory and spare parts

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Mechanical Seals that operate over a wide range of temperature, pressure and speed, and

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Mechanical Seal designs that allow the easiest conversion of packed pumps to mechanical seals.