“TECHNICAL PAMPHLET ON CLASS K (6 X 9”) CTRB ......IRCAMTECH/MP2/Class ‘K’...

Government of India

Ministry of Railway

“TECHNICAL PAMPHLET ON CLASS K (6 1/2" X 9”)

CTRB FITTED ON 25t AXLE LOAD LWLH BOGIE OF FREIGHT STOCK”

For Official Use Only

IRCAMTECH/GWL/MP2/2020-21/1.0

May-2020

D.D Nagar, Maharajpur, Gwalior-474005(India)

QUALITY POLICY

“To develop safe, modern and cost

effective Railway Technology

complying with Statutory and

Regulatory requirements, through

excellence in Research, Designs

and Standards and Continual

improvements in Quality

Management System to cater to

growing demand of passenger and

freight traffic on the railways”.

CONTENTS

Description Page No

Cover page i Quality Policy II

Contents III 1.0 Introduction 1-9

1.1 General Description 1

1.2 Background 1

1.3 Technical features 2-5

1.4 Pictorial View of AP-2 Class ‘K’ bearing and its advantages

1.5 Constructional & Dimensional Comparison between Class ‘E’ & Class ‘K’

5

6-9

2.0 Class ‘K’ Approved manufactures 10-13

a. Timken : AAR Approval Number- 27 10

b. BRENCO: Approval Number- 28 11

c. SKF: Approval Number- 30 12-13

3.0 Important Technical Parameters of Class ‘K’ CTRB 14-15

3.1 Operation parameters for which class ‘K’ is designed

15

ANNEXURE I 16-19

ANNEXURE II 20-21

ANNEXURE III 22-24 References 25

Disclaimer 25

Reference Letter (Railway Board) IV-V

IRCAMTECH/MP2/Class ‘K’ Bearing/Pamphlet/May 2020/1.0 Page 1

1.0. Introduction:

1.1 General Description

Cartridge Tapered Roller Bearings Class “E” (6”x11”) to RDSO STR No. AB/RB-39-2002

(Rev. 3 with Amendment No.3) are being used on freight stock of IR. These wagons are

designed for 20.3/22.9t axle load and are in service on IR for about three decades. Even

though “E” Class CTRB is designed up to 25t axle load, it may not be suitable for 25t

operation in Indian conditions.

Studies reveal that L10 life of “E” Class bearing operating at 25t axle load will reduce by

52%. The major difference in maintenance and operation practices of American Railroad is

extensive use of way side Hot Box Detector and Acoustic Bearing Detector which provide

advance warning on the health condition of Axle bearing and Bogie suspension. Whereas on

IR, condition of Axle bearings and Bogie suspension is assessed by manual visual rolling in

examination which is not so accurate and reliable as Hot Box Detectors and Acoustic Bearing

Detectors.

In AAR, whenever wheels are re-profiled/changed the bearing must be removed from service

which is not so in IR where the bearings are inspected and reconditioned during every POH.

A policy decision has therefore been taken to adopt “K” Class CTRB on new design of 25t

axle load wagons to achieve high reliability between two successive POH.

1.2 Background

When the axle bends whilst rotating in heavy haul operations due to high wagon and dynamic

loads, small movements between the tight fitted cones and axle journal cause fretting wear on

the cone bores and journal outer diameter. This results in what is known as cone bore growth,

which damages the bearing seat and renders cones unfit for further service. It also causes loss

of internal clearance which leads to further damage of bearing components and eventually

causes a hot box set out. The greater the bending arm moment the higher will be the chance

of occurrence of such kind of abnormalities due to very high bearing loads. This axle

deflection is shown in Figure 1.0.

Due to axle flexure as discussed in the above paragraph, fretting wear also occurs between

the back face of the cone and the seal wear ring, as well as the seal wear ring and journal.

Fig: 1.0 Axle Deflection under load


The AAR has specified a limit of 0.127 mm depth in the cone back face for the cone to be

acceptable for further service. Cones with fretting wear greater than this can be salvaged by

machining the cone back face to a maximum of 0.254 rmn depth. Figure 1.1 illustrates

typical cone back face fretting wear. The AAR has specified a limit of 0.0508 mm depth for

seal wear ring grooves in axle journals. If the groove is deeper than this the axle must be

repaired by returning the journal diameter to its original size using expensive plating

methods. Figure 1.2 shows the area damaged by seal wear ring grooving.

Class E (6” X 11”) was introduced as a replacement for the widely used friction journal

bearings. This self-contained, pre-lubricated bearing package quickly became the design of

choice for the industry. Over time, rail operations evolved. The industry was challenged to

improve efficiency and productivity and to lower costs. To achieve this, freight-car weights

increased, and trains were operated at higher running speeds. Heavier loads caused more

wear and tear on equipment, including fretting wear. These factors raised concerns about

bearing reliability. To meet these growing challenges of increased loads, speeds and longer

wheel life, Class K (61/2” x 9”) is finally accepted as remedy for freight car in Indian

Railway.

Class K (61/2” x 9”) design provides for reduced journal axle flexure and less fretting wear.

Its compact design incorporates fewer components and hence less maintenance problem. The

Class K (61/2” x 9”) bearing also offers improved safety and reliability and runs at lower

operating temperatures and lower torque.

1.3 Technical Features

RDSO‟s STR No. AB/RB-41-2016 for Class „K‟ (61/

2” X 9”) Cartridge Tapered Roller Bearings

for freight stocks fitted with Light Weight Low Height (LWLH) bogies (Narrow Jaw) for 25t axle

load application.

Dominating Features which make Class K (61/2” x 9”) CTRB better than Class E

(6” X11”):

1) Fretting Index Value: It is the measurement of failure occurring due to fretting

wear. Lesser the value of Fretting Index, lower will be its chances of failure due to

fretting wear.

Fretting Index Class K 0.30

Fretting Index Class E 1.0

Fig: 1.1 Cone back face fretting

wear

Fig: 1.2 Groove caused by seal wear ring


The development of the class-K bearing had taught the rail industry the

importance of looking at the “fretting index” of an application. This calculated

measurement provides a strong indication of thepotential for a bearing to

experience cone back-face wear. It is based on formulas for bending and shear

and uses application inputs that include bearing load, journal diameter, and the

length (width) of the inboard section of the bearing. The complete formula is

shown in Figure 1.3.

Based on this formula, the fretting index for the class-K & class E can be

determined. This was achieved in the Brenco class-K bearing by shortening the

backing ring, the wear ring/seal area, and the center spacer area of the bearing.

2) L10 Life: It is defined as the number of hours in service that 90% of bearings will

survive.

L10 Life Class K 16 Lac Km

L10 Life Class E 10 Lac Km

3) Use of special type Low-Torque Seals1: Seals have following add on features-

a. It provides best protection against water and other contaminants entering the

bearing cavity..

b. It works with significantly lower torque, which results in lower fuel operating

costs.

Seals1: Brief description about seal is available at ANNEXURE I

Fig: 1.3 Groove caused by seal wear

ring


4) It is coupled with less flexure due to increased axle guard diameter, the Timken

design provides shortest distance between the cone face and the dust guard. This

design reduces the amount of movement and the resultant wear.

5) Fitted backing ring design reduces the potential for water ingress and resulting

fretting corrosion in the axle fillet area.

6) Use of Polyamide cage2: This refined cage is made of reinforced polymer and has

demonstrated excellent performance. The main user benefits are reduced friction,

roller slip, wear and operating temperature and improved safety. Even under

emergency running conditions, the unit operates without blocking.

7) Compact design: This principle offers decreased journal-length (Figure: 1.9)

opportunities and consequently lower axle bending, which allows higher loads.

The decreased distance between the rows of rollers improves internal load sharing.

The shorter axle journal design provides a longer and stiffer guard. This reduces

the stress at crucial axle fillet area.

8) By removing seal wear ring (in Timken Design), axle grooving and resulting

scrapping of seal wear ring or expensive repairs are eliminated. (See the expanded

view of Class K CTRB)

9) Use of Polymer spacer: Fretting corrosion between the backing ring and the cone

side face is caused by journal bending during operation. This corrosion not only

causes foreign particles to enter the bearing but also increases axial bearing

clearance, resulting in reduced performance and reliability. The development

target was to avoid fretting corrosion by changing the steel-to-steel contact

between the backing ring and the cone side face to steel-to-polymer contact. A

spacer of reinforced polymer material is clamped onto the bearing components.

Cage2: Brief description about cage is available at ANNEXURE II

Journal size of class K (61/

2” X 9”)

Journal size of class E (6” X11”)

Fig: 1.9 Comparison between Journal-length


10) Premium Rail Grease3: premium rail grease is specifically formulated for use in

railroad car wheel journals. It lasts longer and provides better protection against

water etching compared to conventional freight journal greases. Fortified with a

high-performance corrosion inhibitor for increased bearing protection, it can

withstand the toughest conditions including humid environments. It provides

excellent mechanical shear stability, water resistance and oxidation stability for

reliable performance. This lubricant meets AAR specification M-942-98.

1.4 Pictorial view of AP-2 Class ‘K’ bearing and its advantages

Grease3

: Brief description about grease is available at ANNEXURE III

Fig: 1.20 Pictorial View of Class ‘K’ Bearing & its adevantages


1.5 Constructional and Dimensional comparison between Class E (6” x 11”) & Class K (61/2” X 9”) CTRB

o Exploded View of Class ‘E’ and Class ‘K’ bearing

Fig: 1.21 Class E ( 6” X 11” )

Fig: 1.22 Class E ( 6 1

/2” X 9” )


Class ‘E’ Bearing comes under TIMKEN APTM

bearing with AAR

approval nos. 1 & 1A

Class ‘K’ Bearing comes under TIMKEN APTM

bearing with

AAR approval nos. 27

Fig: 1.23 Bearing Nomenclatures


o Designation Structure of bearing (FAG)

Class ‘E’ Class ‘K’

Features Bearing

Class

Class ‘K’ Class ‘E’

Journal-

size

Less Compare to Class „E‟ More Compare to Class „K‟

Bore-size More Compare to Class „E‟ Less Compare to Class „K‟

Roller

density

High Compare to Class „E‟ Low Compare to Class „E‟

Seal wear

ring

Not available/Integrated part

of inner ring(cone)

Available


NAME OF THE FIRM

AAR

Approval No.

(as on April -2011)

Diameters are averages AMOUNT OF GREASE

gram(oz.) ROLLERASSEMBLY OUTER RING/CUP BACKING

RING

MAX. BORE mm

(inch)

OUT OF ROUND

mm (inch)

MINIMUM O.D. mm

(inch)

MAXIMUM C. BORE

mm (inch)

MINIIMUM C. BORE

mm (inch)

OUT OF ROUND

mm (inch)

MAXIMUM C. BORE

mm (inch)

EACH ROLLER

ASSEMBLY

AROUND SPECER

TOTAL

QUANTITY ± 30gm

TIMKEN 1A 144.488 (5.6885)

0.076 (0.003)

220.345 (8.675)

209.677 (8.255)

209.423 (8.245)

0.127 (0.005)

178.511 (7.028)

115 (4)

170 (6)

400 (14)

BRENCO/ NBC

5A 144.488 (5.6885)

0.076 (0.003)

220.345 (8.675)

209.677 (8.255)

209.423 (8.245)

0.127 (0.005)

178.511 (7.028)

115 (4)

170 (6)

400 (14)

FAG 32 144.488 (5.6885)

0.076 (0.003)

220.345 (8.675)

209.677 (8.255)

209.423 (8.245)

0.127 (0.005)

178.511 (7.028)

115 (4)

170 (6)

400 (14)

SKF 23 144.488 (5.6885)

0.076 (0.003)

220.345 (8.675)

209.677 (8.255)

209.423 (8.245)

0.127 (0.005)

178.562 (7.030)

115 (4)

170 (6)

400 (14)

ALL DIAMETERS ARE THE AVERAGE OF 3 MEASURRMENTS, 60

0 APART

Make/ Bearing

Class ‘K’

(6 ½”X 9”)

Diameters are averages AMOUNT OF GREASE

gram

(oz.)

ROLLERASSEMBLY OUTER RING/CUP

BACKING

RING

MAX. BORE

mm

(inch)

OUT OF

ROUND

mm

(inch)

MINIMUM

O.D.mm

(inch)

MAXIMUM

C. BOREmm

(inch)

MINIIMUM

C. BOREmm

(inch)

OUT OF

ROUND

mm (inch)

MAXIMUM

C. BOREmm

(inch)

EACH

ROLLER

ASSEMBLY

AROUND

SPACER

TOTAL

QUANTITY

BRENCO

(AAR-28& 31) 157.175

(6.1880)

0.076

(0.003)

249.555

(9.825)

238.252

(9.380)

237.998

(9.370)

0.127

(0.005)

191.211

(7.528)

170

(6)

15

(1/2)

355

(12½)

TIMKEN

( AAR-27)

157.175

(6.1880)

0.076

(0.003)

249.555

(9.825)

238.252

(9.380)

237.998

(9.370)

0.127

(0.005)

191.211

(7.528)

57

(2)

170

(6)

284

(12)

Class E (6” x 11”) CTRB

Class K (61/2” x 9”) CTRB


2.0. Class ‘K’ Approved Manufacturers (AAR Approved)

a. Timken : AAR Approval Number- 27

Class & Size Roller

Assembly

Outer

Ring

Spacer HDL

Seals

Fitted

Backing

Ring

End Cap Locking

Plates

Cap

Screw

K(61/2 X 9) NP877824** NP335917 NP115833 K153401 K153494 K154496 K84324 K84351

Dimensions are average Amount of grease in Once

Classes and Size Roller Assembly Outer Ring Fitted

Backing

Ring

Each

Roller

Assembly

Around

Spacer

Total

Quantity

Max.

Bore

Out of

roundness

Min.

OD

Max.

C

Bore

Min

C Bore

Out of

roundness

Max. C

Bore

K(61/2 X 9) 6.1880 0.003 9.8250 9.380 9.370 0.005 7.258 2 6 10

Conversion

Factor

1 Ounce

=28.3495

1 Inch

= 25.4 mm


b. BRENCO: Approval Number- 28

Dimensions are average Amount of grease in Once

Classes and Size Roller Assembly

(Cone)

Outer Ring

(Cup)

Fitted

Backing

Ring

Each

Roller

Assembly

Around

Spacer

Total

Quantity

+/- 1

Max.

Bore

Out of

roundness

Min.

OD

Max.

C

Bore

Min

C Bore

Out of

roundness

Max. C

Bore

K(61/2 X 9) 6.1880 0.003 9.8250 9.380 9.370 0.005 7.258 5

1/2 1 12

Conversion

Factor

1 Ounce

=28.3495

1 Inch

= 25.4 mm


c. SKF: Approval Number- 30

Conversion

Factor

1 Ounce

=28.3495

1 Inch

= 25.4 mm


SKF


3.0. Important Technical Parameters of Class ‘K’ CTRB

The roller bearings is suitable for

axle journal to RDSO‟s drawing

number WD-15020-S-02 Alt. nil or

latest (journal of this axle is

identical to AAR Class „K‟ axle

journal of M-101 of MSRP Section

G).

Axle end Cap screws (ø 1 1/8” - 7

UNC-2A, 2 1/2” threads length to

Spec. no. IS: 1367-Part 3 Class

P8.8)

Side frame Key (item No. 2) & Key

bolt, Nut, Spg. Washer and ᶲ 4

Split pin (item no 4) to RDSO

Drawing No. WD-13012-S-04 Alt. 4

or latest

Narrow Jaw Adapter to RDSO

Drawing No. WD- 15020-S-03 Alt.

2 or latest

Tightening torque of end cap

screws mentioned above in inch

sizes is 570 N-m

Fig: 1.24 Exploded view of Class ‘K’ Bearing


3.1. Operational parameters for which bearing class ‘K’ is

designed

Operational Parameters Value

Track Gauge (mm) 1676

Maximum /Normal Axle Load 25

Weight of one wheel-set(Kg)

(840 mm Dia. Wheel-Set)

1200(Appr.)

Maximum/ Normal speed of

wagon (Kmph)

130/100

Average run of wagon(Km/day) 500(Appr.)

Weight of wagon(tonnes)

Empty Condition

Loaded Condition(max.)

20(Appr.)

100

Type of brake system Air Brake(Graduated release )

Type of wheel braking Trade Braking (One brake block

„K‟ type per wheel)

Maximum braking force per

wagon in loaded condition(Kg)

18955

Wheel Trade Diameter (mm) New

Condemning

840

780

Atmospheric Temparature

Range(°C)

Maximum

Minimum

50

-10

Loaded to Empty ratio of wagon

operation

80:20


ANNEXURE I

Low Torque Bearing Seals

I. Timken HDL(Hydrodynamic Labyrinth) Seal (AAR-27 Class K bearing)

HDL™

Seals

This close-clearance designed seal never touches the mating surface. Its benefits include

lower torque, lower temperatures and better fuel efficiency with fewer set outs, higher

service speeds and lower operating costs than other lip-type seals.

Applications

Railroad journal roller bearing application

Design Attributes

Low torque

Low temperatures

Better fuel efficiency

Details

Timken‟s Hydrodynamic Labyrinth (HDL) seal is one of the key components in the

industry-leading packaged rail bearing design. This seal marries the best lip-type and

labyrinth (close-clearance) sealing technology.

Compared to conventional lip-type seals, the HDL design:

Reduces seal torque and operating temperatures

Extends grease life and fatigue life

Improves lube film

Enhances overall bearing life and performance

Bearings with HDL seals run cooler and keep more grease in the bearing, which keeps

dirt, debris and water out.

Fig: 1.4 HDL Seal


II. SKF LL (Labyrinth Lip) Seal

New integrated low torque seal

The new compact design principle makes additional spacers or seal wear rings

unnecessary. The sealing function is integrated into the bearing unit between the outer

ring and the inner ring. This feature helps save space and, as a result, minimises axle

bending in many applications. The design is based on a low-friction rubber seal

principle; the main features are a combination of labyrinth, lip and flinger elements.

Improved protection against contamination extends service life.

Fig: 1.5 LL Seals design for

compact TBU

Fig: 1.6 Inch size compact TBU

for Class K for Freight car

Fig: 1.4 Comparison among seals designed by TIMKEN


Friction torque is reduced by 75% compared with a garter seal arrangement. As a

consequence, the operating temperature is reduced by 20°C, which contributes to longer

grease life and energy savings. Results from the SKF seal test, which evaluates water

and dust contamination, confirmed that the design was effective in excluding

contamination. Long-term endurance tests have been conducted under very severe

operating conditions. The new integrated seal has also passed all AAR approval tests.

For new freight cars with increased cargo, the inch size compact TBU class K is used.

This SKF design is fitted with LL seals (Figure: 1.5) and a polymer clip ring and is

approved by AAR.

III. BRENCO® Tru-Guard® Seal

Over the years, in addition to increasing bearing life and reliability, Brenco product

engineers have developed new sealing technologies that lower bearing operating

torques and temperatures. These seals have been benefiting customers in the form of

reduced set-outs and fuel savings.

In fact, The Ausbrid bearing came standard with a BRENCO® ST-212™ seal, our first

low-torque seal without a garter spring. More recently, a new sealing technology has

been developed that reduces seal torque to essentially zero while improving moisture

exclusion. The new seal (Figure: 1.7), dubbed the BRENCO® Tru-Guard®, has been

successfully running in the Russian market in metric bearings since 2010. This seal

utilizes the successful labyrinth “insert” and “rotor” from the BRENCO® Efficiency

Plus™ seal, and replaces the “dust guard” with a “slinger” / shield that forms a

labyrinth with the seal case.

Fig: 1.7 BRENCO® Tru-Guard®

Seal


The result, shown in Figure 1.8, is a seal that retains grease and excludes contaminants

without moulded rubber lips and the friction they generate. Friction is only produced by

the shearing of a small quantity of grease located between the walls of the labyrinth.

The first field testing of a Tru-Guard seal took place on the JSC Railway Research

Institute (VNIIZhT) test loop in Shcherbinka, Russia. The bearings were run under load

at various speeds. During periodic stops for bearing inspection, the bearings were found

to be cool enough to make full prolonged hand contact. In addition to running in the

Russian market, a class-K version of the Tru-Guard has been conditionally approved

by the AAR and is running in North American service.

Figure shown bellow depicts a chart of data collected over a 1.5 day period during a

seal life test. With above ambient cup temperatures of about 15°F [8°C] and unloaded

bearing torques averaging 10 to 11 lb.×in., the test result were similar to those of

bearings without seals. As a performance benefit, the Tru-Guard seal has been made

standard on both the Ausbrid Plus and MEGA-TONNE bearings.

Fig: 1.8 BRENCO True –Guard Seal Performance


ANNEXURE II

Cage for Bearing

Historically cages used for railway axle boxes have been -

Machined brass cages in a two-piece design with rivets or one-piece cages for

cylindrical roller bearings; and pressed steel cages for taper roller bearings and units

such as tapered bearing units, TBU. Today both bearing types are offered with a

polymer cage.

In general engineering applications, a polymer material is chosen for two important

reasons. The first is its specific properties such as low weight and wear, high toughness

and elasticity with an additional damping effect. The second is the moulding process,

which allows the production of complex shapes that cannot be produced efficiently by

traditional machining methods

Polymer Cage

Significantly improved performance can be achieved through the use of polymer cages

for roller bearings in railway journal bearing applications.

Today, all new German rolling stock, ICE high-speed trains, locomotives, passenger

coaches and multiple units as well as freight cars have polymer cages as standard. Also,

other main European railway companies use the same bearing design with excellent

results. Detailed information about this can be found in Evolution 4/1998.

Four main customer benefits can be identified:

The polymer material is resilient, unlike soft, malleable steel that can cause pitting,

spalling and fretting within the bearing.

The channelled roller pocket design reduces roller slip and improves the distribution

of grease throughout the bearing.

Polymer has a lower friction coefficient than steel, and these results in lower bearing

operating temperatures and frictional moment values, lower wear and less fatigue of

components and lubricant.

The polymer is a self-lubricating material that enables the bearing add on feature of

lubrication. This helps prevent bearing seizure, burn-offs and derailments.

Increased safety and performance is also an important consideration. One question

sometimes asked by railway companies is “How much time do we have to detect a hot

running bearing?” This is strongly influenced by the cage type and design. To evaluate

this, a lubrication shut-off test can measure the time between the loss of lubrication and

bearing failure. A steel cage can operate for a short period without lubrication, after

which the bearing temperature increases considerably to reach the hot running condition

that causes the bearing to seize.


The polymer cage can operate under the same conditions for much longer without any

lubrication. After this period, the temperature increases, the cage bars melt and coat the

rolling elements. This serves as an additional emergency lubricant. Even under such

severe conditions (essentially without a cage), the bearing runs for several hours as a

full complement bearing without seizing. In those cases where infrared methods are

used to detect hot boxes, bearings with a polymer cage allow much more time for

railway operators to react.

The graph illustrates the lubrication starvation comparison test between a steel-cage

bearing and polymer-cage bearing, conducted at the SKF Railway Test Center. Both

bearings were placed on a test rig where the lubrication was removed after the initial

run-in period. The steel-cage bearing temperature rose dramatically; bearing seizure and

failure occurred at 70 km (44 miles). The polymer-cage bearing temperature rose to a

sustained level and continued operating effectively for 500 km (311 miles), at which

point the test was concluded.

The SKF polymer cage is standard for all kinds of railway journal bearing applications

such as high-speed trains, locomotives, coaches, freight cars and mass-transit vehicles

made from a special polymer material, the new Universal Polymer Cage (UPC) design

universally replaces the conventional steel cages within a tapered bearing unit.

The railway operators or wheel-set maintenance companies no longer need to acquire

new bearings to take advantage of this polymer cage technology, and the benefits of the

SKF Universal Polymer Cage are not just limited to safety. This cage also helps to

extend the service life, performance and reliability of the bearing. Positive field-test

results in North American rail services led to the conditional approval from the AAR

for SKF to retrofit and upgrade existing bearing units, manufactured by all major

bearing suppliers to the North American market, with the SKF UPC.

Temperature vs Distance for Steel Cage & Polymer Cage Roller Slip vs Speed for Steel Cage & Polymer Cage

http://evolution.skf.com/wp-content/uploads/2011/12/The-universal-6.png


ANNEXURE III

Lubricants used for rail bearings (Grease):

Selecting grease can be a delicate process. SKF has developed several tools in order to

facilitate the selection of the most suitable lubricant. The wide range of tools available

includes those from easy-to-use application driven tables to advanced software allowing

for grease selection based upon detailed working conditions. The basic bearing grease

selection chart provides you with quick suggestions on the most commonly used

greases in typical applications.

**For more about grease specification see AAR M-942-2012/2020 or RDSO STR No.

AB/RB-41-2016


Grease

Lubricating grease is a mixture of a lubricating base fluid, a thickening agent, and

additives. The thickening agent is a material that, in combination with the base fluid,

produces the solid to semi fluid structure. The primary type of thickeners typically used

in grease is metallic soaps. These soaps include, among others, lithium, aluminium,

clay, polyurea, sodium, and calcium. The base oil that performs the actual lubrication

can be mineral oil, synthetic oil, or biobased oil. The thickener gives grease its

characteristic consistency and is sometimes thought of as a “sponge” that holds the oil

in place. The majority of greases on the market are composed of mineral oil blended

with a soap thickener although the use of synthetic greases and bio based greases are

growing. Additives enhance performance and protect the grease and lubricated surfaces.

Grease is classified by penetration number and by the type of soap thickener. The

consistency, or rigidity, of a grease is a measure of its resistance to deformation by an

applied force and is, in most cases, the most important characteristic of a grease. A

grease that is too stiff may not feed into areas requiring lubrication, while a grease that

is too fluid may leak out. Grease consistency depends on the type and amount of

thickener used and the viscosity of its base oil. In the United States, penetration

classifications have been established by National Lubricating Grease Institute (NLGI)

and range from 000 to 6. A penetration number indicates how easily a grease can be fed

to lubricated surfaces or its pumpability, and also how well it remains in place. The

number 000 is a semi fluid and the number 6 is a solid. Grease penetration numbers of

0, 1, and 2 are the most common for hydraulic gate drives and gate pivot points.

Dropping point is an indicator of the heat resistance of grease. At or above the

dropping point, grease will act as a fluid. As grease temperature rises, penetration

increases until the grease liquefies and the desired consistency is lost. Dropping point is

the temperature at which a grease becomes fluid enough to drip and indicates the upper

temperature limit at which a grease retains its structure. It is not the maximum

temperature at which grease may be used. Some greases have the ability to regain their

original structure after cooling down from the dropping point. Operating condition of

the grease be at least 56°C or 100°F below the dropping point.

Oxidation stability is the ability of a grease to resist a chemical union with oxygen.

The reaction of grease with oxygen produces insoluble gum, sludge, and lacquer-like

deposits that cause sluggish operation, increased wear, and reduction of clearances.

Prolonged high-temperature exposure accelerates oxidation in greases.

Pumpability is the ability of a grease to be pumped or pushed through a system at very

low temperatures. More practically, pumpability is the ease with which pressurized

grease can flow through lines, nozzles, and fittings of grease dispensing systems. An

example of this is grease lines for miter gate pintle bearings and radial gate trunnion

bearings. In northern climates, it is important that grease reach the bearing surfaces of

the pintles. Feedability is its ability to be drawn (sucked) into a pump. Fibrous greases

tend to have good feedability but poor pumpability. Buttery-textured greases tend to

have good pumpability but poor feedability.


Water resistance is the ability of grease to withstand the effects of water with no

change in its ability to lubricate. Soap/water lather may suspend the oil in the grease,

forming an emulsion that can wash away or, to a lesser extent, reduce lubricity by

diluting and changing grease consistency and texture.

Consistency of Grease depends on the type and amount of thickener used and the

viscosity of its base oil. Grease‟s consistency is its resistance to deformation by an

applied force. The measure of consistency is called penetration. Penetration depends on

whether the consistency has been altered by handling or working. ASTM D 217 and D

1403 methods measure penetration of un-worked and worked greases.

To measure penetration, a cone of given weight is allowed to sink into a grease for five

seconds at a standard temperature of 25°C (77°F).The depth, in tenths of a millimeter,

to which the cone sinks into the grease is the penetration. A penetration of 100 would

represent a solid grease while a penetration of 450 would be semi-fluid. The NLGI has

established consistency numbers or grade numbers, ranging from 000 to 6,

corresponding to specified ranges of penetration numbers.

Composition of Grease

“Grease” is basically oil that contains a thickening agent to increase its viscosity. The

thickening agent may be a soap or it can be a solid with a high surface area. Fatty-acid

soaps of lithium, calcium, sodium, aluminum, and barium are commonly used in

concentrations of 8%–25%. Finely divided clays such as bentonite and hectorite are

used as high-surface solids, usually after coating with a quaternary ammonium

compound for improved compatibility with the oil.

The clays were used more commonly in early greases and the soap-thickened greases

are more common today. Compared to the other thickeners, PTFE has the lowest COF

and is suitable for use up to 300°C but is typically considered for use only with up to

moderate loads. PTFE is used as a “fortifier” in combination with one of the other

thickeners or is used alone, especially for greases that are for high temperature use or

applications involving long life expectations


References:

1. Schedule of Technical Requirements No. AB/RB-41-2016 for Class „K‟ (6 1/2” X

9”) Cartridge Tapered Roller Bearings for freight stocks fitted with light weight low

height (LWLH) bogies (narrow jaw) for 25t axle load application- Jan-2018, RDSO,

Lucknow. 2. Installing and Maintaining Timken

AP™ and AP-2™ Bearings, Maintenance

instructions via website

3. Williams, S.R. "The Timken Company railroad bearing low-resistance seal

development program", The Winter Annual Meeting of the American Society of

Mechanical Engineers. VoL 3, 1989, pp 39-44.

4. Williams, S.R., "Seal technology to enhance railroad journal roller bearing

performance", International Wheel-set Congress, Sydney, 27 September - I October,

1992.

5. Association of American. Railroads, Roller Bearing Manual, Manual of Standards and

Recommended Practices, 1994, Section H - Part II, Washington, D.C.

6. Williams, S.R., "Evolution of journal roller bearings for heavy-haul freight car

service", International Heavy Haul Association Conference on Freight Car Bogies,.

Montreal, 9 -12 June 1996.

7. Williams, S.R., "Bearing design and maintenance to maximise operating reliability",

Sixth International Heavy Haul Railway Conference, Cape Town, 6 - 10 April 1997.

8. Fetty, M., Evolutionary and Revolutionary Changes of the Journal Roller Bearing

for Today's Heavy Haul Railroad Markets, Proceedings of 7th International Heavy

Haul Association Conference, Brisbane, June 2001, June, Brisbane Old Australia.

9. Ker, P., Fortes cue takes another step in plan to boost Pilbara railway loads, The

Sydney Morning Herald, October 24, 2011, Sidney, AUD.

10. Mark Fretty, AUSBRID PLUS® AND MEGA-TONNE™ – New Bearings for

increased reliability and capacity in iron-ore operations, IHHA 2015 Conference, 21-

24 June 2015, Perth, Australia.

DISCLAIMER

THE INFORMATION GIVEN IN THIS PAMPHLET DOES NOT SUPERSEDE

ANY EXISTING PROVISIONS LAID DOWN IN RDSO AND RLY. BOARD’S

INSTRUCTIONS. THIS DOCUMENT IS NOT STATUTORY AND

INSTRUCTIONS GIVEN IN IT ARE FOR THE PURPOSE OF GUIDANCE

ONLY. IF AT ANY POINT CONTRADICTION IS OBSERVED, RLY.

BOARD/RDSO’S GUIDELINES OR ZONAL RLY.’S INSTRUCTIONS MAY BE

FOLLOWED.

The information given in this pamphlet is only for guidance. If you have any suggestion

or comment, please write to:

Email ID- [email protected], FAX – 0751 2 470841.

Director (Mechanical), CAMTECH, Maharajpur, Gwalior (M.P.) – 474 005

mailto:[email protected]

“TECHNICAL PAMPHLET ON CLASS K (6 X 9”) CTRB ......IRCAMTECH/MP2/Class ‘K’...

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