Mech Seal Presentation

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TRAINING PROGRAMON

MECHANICAL SEAL

Andrew Maxwell

Mechanical Engineer Madina Group WLL

Doha, Qatar June 2010


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What is a Seal?A Seal is a device which prevents the passage,

leakage or flow of fluid

Why seal is Required? To isolate a high pressure system from surrounding

Transmission of Power requires an opening in thepressure body, necessitating a seal

Environmental factors extending from aesthetics of aclean shop to water pollution

Survivability of fluid handling equipment

Reduce Energy & Production loss


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Seal

Static Seal Dynamic Seal

Clearance Seal Contact Seal

Face Seal/Mechanical SealLabyrinthSeal Bushings CompressionSeal

Packed Gland

Lip Seal

Seal Classification


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Typical Centrifugal Pump

1. Suction 2. Impeller 3. Discharge 4. Stationary casing 5. Shaft

6. Mechanical Seal 7. Gland Plate 8. Bearings


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Gland packing

Lea

Flush port

Gland follower / plate

Gland packing


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Typical Stuffing Box with Gland

Packing

Compression

Packing

Fastener

Packing Pusher Impeller

Stuffing Box


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LEAKED FLUID

GLAND PACKING ARRANGEMENT


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Limitations of Packed Glands

Power consumption is High. The ratio ofpower consumption of Mechanical Seal to

compression packing is 1:8

Leakage is very high and unpredictable. Varies with

compression on the packing. The ratio of Leakage ofmechanical seal to compression packing is 1:600

No automatic wear compensation

Fretting on sleeve or shaft


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MECHANICAL SEAL IS A DEVICE THAT

PREVENTS / RESTRICTS UNDESIRABLE

LEAKAGE OF FLUID IN ROTATING

EQUIPMENT FROM HIGH CHAMBERPRESSURE TO LOWER ONE SIDE .


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PUMP WITH MECHANICAL SEAL.

MECHANICAL SEAL


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A Simple Mechanical Seal

Seal Holder

Collar

Grub ScrewSprings Drive Pin Seal Plate

O Ring

Seal Seat

Seal Face

O Ring

Hardwares:Seal Holder, Seal Plate

Seal Faces :Seat and FaceSecondary Seals :O Rings

Tertiary Seals :Gaskets

Gasket


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A Simple Mechanical Seal

P th f L k


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Paths of LeakageTertiary Seal

Secondary

Seal

Secondary

Seal

Primary Seal


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PRINCIPLE OF SEALING

BASIC SEAL WORKS ON THE PRINCIPLE OF :

THIN LIQUID FILM BETWEEN THE TWO SURFACES.

ONE SOFT FACE (ROTATING) AND ONE HARD FACE (STATIONARY)AGAINST EACH OTHER.

NO INTERRUPTION IN LIQUID FILM.

NO GAS PHASE TO PREVENT FACE CONTACT.

NO SOLID PARTICLES TO DAMAGE SEAL FACE.

Cl ifi ti f M h i l S l


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Classification of Mechanical Seal

1. By Mounting Inside Mounted Outside Mounted

2. By Hydraulic

Balance

Unbalance Seal Balance Seal

3. By Loading

Mechanism

a. Pusher Type Single Spring Seal Multiple Spring Sealb. Non Pusher Type Metal Bellow Seal Teflon Bellow Seal Rubber Bellow Seal

4. By Arrangement a. Single Sealb. Double Seal Tandem Seal Back to Back Seal Face to Facec. Catridge Seal


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1. Seal By Mounting


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Unbalance seal

Hydraulic Load plus Spring load Close Faces

Area A always Greater Than Area BFace stress is therefore high

High Temperature

High face wear


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A Single Unbalanced Seal


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Single Balanced Seal


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REVERSE BALANCE SEAL

A Si l C il S i P h S l


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A Single Coil Spring Pusher Seal


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PUSHER SEAL

Multiple Spring Seal


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Pusher versus Bellows seal


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Cartridge Seals

Most seals used on modern plants are cartridgeseals.

These come pre-set as a complete package.

All you have to do is fit them to the shaft, and

fasten the plate to the pump and REMOVE thegrub screws holding the rotating section to the

stationary section.

Any maintenance on these is normally done by

the manufacturer.


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Failure Modes For most seals if any of the conditions required for

operation are absent, even for a short time, failure willresult.

Common causes are dry running, this is when theliquid film between the faces is interrupted.

The faces will become very hot, thermal crazing willoccur, which will lead to fracture of the faces.


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Test your knowledge


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Any Questions?

Mech Seal Presentation

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