agenda john crane mechanical...

Basic seal principles

Categories of mechanical seal

Pusher / bellows

Cartridge / Conventional

Wet Seals / Gas seals

Split / whole

Single / double Cross Reference Chart

Materials - Cross reference Chart

Sealant Systems

Basic principles

Regulating authorities Seal Selection Guides and gifts

John Crane Mechanical Seals AGENDA

Çandar Akışkan Teknolojileri- www.candar.com.tr

Sealing

Fundamentals

Part 1


Shaft

Process

Fluid Leakage

Environment Vessel

Wall

The Basic Sealing Problem: Preventing Leakage


Shaft

Process

Fluid

Leakage

Environment Vessel

Wall

Packing


Shaft

Process

Fluid

Leakage

Environment Vessel

Wall

The Concept of an End Face Mechanical Seal


Shaft Shaft

Movement

Required Features

Small axial clearance


Shaft

Movement

Required Features

Small axial clearance

Self adjusting


Mating

Ring

Primary Ring Secondary Sealing Element

A Flexible Seal

Hydrostatic loading

Secondary sealing elements

Replaceable parts


O-Ring

Shaft

Mating Ring

Primary Ring

Snap Ring

Anti-X Ring

O-Ring

Disk

Springs

Retainer

Set Screw

An Example of a Complete Seal


Simply put, a mechanical seal is:

1. A rotating face (primary ring)

2. A stationary seat, (mating ring)

3. A secondary sealing element

4. A mechanical loading device to press face

and seat together, and

5. Auxiliary components


Process Fluid Acts as Lubricant Between Faces

Gland Pump Housing

Process Fluid

Invisible Leakage:

Fluid Evaporates Upon Reaching Atmosphere

Primary Ring Mating Ring


Gland

Pump Housing

No Fluid Or Dry Running

Primary Ring Mating Ring

Without Lubrication, Faces Run Dry And Overheat


Heat Transfer

Conduction

Convection


Injection

Flushing

Removes Heat

Replenishes Cool Clean Lubricating Liquid


Primary Seal: Flush

Single Seal Flushing By - Pass from Discharge (API Plan 11)

By- pass Line from

Pump Discharge

to Seal Gland

Discharge

Flow

Suction


Design Features

Balance Ratio

Springs

Secondary Sealing Element Type


Balance ratio is used to control the face load.

Closing Force Opening Force

Design Features

Balance Ratio


Balance ratio is the ratio of the closing area

to the opening area.

A c

A o

Balance Ratio = Closing Area

Opening Area

Design Features

Balance Ratio


An Unbalanced Seal

A A c o F c

Design Features

Balance Ratio


A o A c

A Balanced Seal

Design Features

Balance Ratio


Design Features

Springs

Provide The Initial Closing Force

Are Very Important At Low Pressures

Are Not So Important At High Pressures


Design Features

Springs High Speed Seals Use Stationary Springs

(5000 ft/min Typical Break Point)


Design Features

Secondary Sealing Element Static

Dynamic


O-ring must

move axially

Design Features

Secondary Sealing Element Pusher Seal


Static O-ring

Design Features

Secondary Sealing Element Non-Pusher Seal


Teflon Bellows

Elastomeric Bellows

Half Convolution

Welded Metal Bellows

V Rings U Cup Wedge Encapsulated

O Ring

O Ring

Secondary Sealing Elements


Pusher Non-Pusher

O-ring secondary seal

must slide along shaft as

seal face wears

Bellows secondary seal

expands to accommodate

face wear. Bellows tail is

stationary against shaft

vs.

Pusher vs. Non-Pusher


-400°F

-200°F

0

400°F

600°F

200°F

Buna-N EPDM VitonTM

-54°C / -65°F

149°C /

300°F 121°C / 250°F

-240°C

-129°C

-18°C

204°C

316°C

93°C

AflasTM

204°C /

400°F

204°C / 400°F

-45°C / -50°F -29°C / -20°F

TeflonTM

287°C / 550°F

-212°C / -350°F

-29°C / -20°F

KalrezTM

287°C / 550°F

-40°C / -40°F

Secondary Sealing Elements Temperature Range


Arrangements

Single Inside Mounted

Outside Mounted Multiple

Pressurised

Non-Pressurised


Arrangements

Single Inside Mounted


Arrangements

Single Outside Mounted


Rotating Head and Rotating Seat

Use Rotating Head Assemblies up to: 3500 fpm for Single Spring Designs

5000 fpm for Multiple Spring Designs

Seal Head Seat { Rotating

Rotating Head

Seal Head Seat

Rotating {

Rotating Seat

Stationary

{ {

Stationary

Advantages Less Radial & Axial Space Requirements

Lower Cost

Advantages Higher Speed Capability

Tolerates Misalignment Better

Better Cooling

Arrangements


Classical “Tandem”

Process seal Backup seal

Process seal Barrier fluid seal

Classical “Double”

Multiple Seal Arrangements


Process

Buffer Atmosphere

Pre

ssu

re

Unpressurised

(Tandem)



Process Barrier

Atmosphere

Pre

ssu

re

PRESSURISE

D (double)



Types of Seal Failures

Installation

Operation or design of machinery

Seal specification


Failures of Seal Components

Seal Faces

Loss of Flexibility (hang up)

Secondary Sealing Elements

Material Compatibility


Leakage decomposes

or solidifies and locks

primary ring in place

Loss of Flexibility: Hang-up



Pusher / bellows



Split / whole

Single / double



Pusher Non-Pusher

O-ring secondary seal

must slide along the

retainer/carbon as the

seal face wears.

Bellows secondary seal

expands to accommodate

face wear.

vs.

SEAL CATEGORIES


SEAL CATEGORIES

O ring seals

Wedge seals

More material options

Higher Pressures

Easier to manufacture

Metal Bellows

Rubber Bellows

PTFE Bellows

No ‘hang up’

Better leakage rates

Better abrasive handling

More tolerant to

misalignments

PUSHER SEALS

(NON BELLOWS)

NON PUSHER SEALS

(BELLOWS)


O-ring

Metal Bellows

Rubber Bellows

Seal Selection by Type


Cartridge Seals / Component Seals

O-Ring Metal

Bellows

Elastomer

Bellows

SEAL CATEGORIES


Single O-Ring Type 5610


SEAL CATEGORIES

Easier to fit - reliable

Factory set - reliable

Less expensive

Adaptable

CONVENTIONAL

(COMPONENT)

CARTRIDGE SEALS


nitrogen injection 2 bar g / 30 psig above maximum seal chamber pressure

Shaft Rotation

ATMOSPHERE OUTBOARD

PROCESS SIDE

INBOARD

Clockwise Counter-Clockwise

Shaft Rotation

Type 2800


Inject nitrogen at 2 bar g / 30 psig above maximum seal chamber pressure

Clockwise Anti-Clockwise

ATMOSPHERE OUTBOARD

PROCESS SIDE

INBOARD

Type 2800E


SEAL CATEGORIES

Less expensive

More complicated support

systems

Can run at low speeds

V low power consumption

V long life

Can run at high speeds

Dry running

WET SEALS GAS SEALS


SEAL CATEGORIES

Can be replaced in stu Less expensive

More reliable

Easier to fit

Higher performance

WHOLE SEALS SPLIT SEALS


SEAL CATEGORIES

Less expensive

No support system Control over fluid film

Emissions containment

SINGLE SEALS DOUBLE SEALS


SEAL TYPE CROSS REFERENCE

U.S. TYPE

1 Rubber Bellows

1B HP Rubber Bellows

NA Rubber Bellows

8-1 O ring

8B1 H.P. O ring

9 PTFE WEDGE

9B H.P. WEDGE

20R PTFE BELLOWS

2800 GAS SEAL

T = Thin seal B = Balanced (HP) seal

R = Replaceable face 5600 is a global cartridge seal range

Types 1B; 2; 8-1; 8B1 do not use the same components in US and UK


SEAL TYPE CROSS REFERENCE

U.S. U.K. EUR TYPE

1 1A NA Rubber Bellows

1B 1B NA HP Rubber Bellows

NA 502 502 Rubber Bellows

8-1 8-1 58U O ring

8B1 8B1 58B H.P. O ring

9 109 59U PTFE WEDGE

9B 109B 59B H.P. WEDGE

20R 10R 10R PTFE BELLOWS

2800 2800E 2800E GAS SEAL

T = Thin seal B = Balanced (HP) seal

R = Replaceable face 5600 is a global cartridge seal range

Types 1B; 2; 8-1; 8B1 do not use the same components in US and UK


US/UK MATERIAL DESCRIPTION CODES

MATERIAL US

Viton X

Carbon F(28) F(3) F(50) F(51)F(55)

Ceramic O(10)

Silicon Carbide O(58)

Tungsten Carbide O(15)

Isolast X(14)

316 Stainless 1

Hastelloy H

Graphoil O(39)

NOTE The above are used only to describe the seal spec. The grades of material are only specified in the code.


US/UK MATERIAL DESCRIPTION CODES

MATERIAL US DIN UK

Viton X V A

Carbon F(28) F(3) F(50) F(51)F(55) B R

Ceramic O(10) V C

Silicon Carbide O(58) Q1 S

Tungsten Carbide O(15) U1 K

Isolast X(14) K X

316 Stainless 1 G 1

Hastelloy H M2 H

Graphoil O(39) G2 X

NOTE The above are used only to describe the seal spec. The grades of material are only specified in the code.


BASIC FUNCTIONS OF A SEALANT SYSTEM

To provide a fluid film when the pump can not, because

the liquid is:

Too hot

Too cold

Too viscous

Prone to solidify or crystallise

Abrasive

Close to boiling point

Contains dissolved gases

The liquid can not get to the seals

Dangerous liquid

Sensitive liquid



From an external source

Higher in pressure than the product at the seal

Contained, usually with another mechanical seal

The sealant as a fluid film must be:



A sealant system must be able to:

Store the sealant

Circulate the sealant

Pressurise the sealant

Cool or heat the sealant

Monitor the sealant



There are 2 type of sealant:

Tanks

Vessels


REGULATING AUTHORITIES

AUTHORITY INSPECTOR

DESIGN ASME VIII

APPLICATIONS API 610

API 682

HAZARDS EUROPE - CENELEC UK - BASEEFA

USA - NEC USA - UL


Process

Barrier

Atmosphere

Pre

ssu

re

Pressurized (Double)

Dual Seal Arrangement


Basic seal principles


Pusher / bellows



Split / whole

Single / double Cross Reference Chart

Materials - Cross reference Chart

Sealant Systems

Basic principles

Regulating authorities Seal Selection Guides and gifts



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