lock bolts and the low maintenance mainline frog · pdf filelock bolts and the low maintenance...

LOCK BOLTS AND THE LOW

MAINTENANCE MAINLINE FROG

AREMA 2007

CONFERENCE AND EXPOSITION

Chicago, Illinois September 9-12, 2007

Michael Roney Canadian Pacific Railway

Suite 500 Gulf Canada Square

401-9th Avenue SW

Calgary Alberta T2P 4Z4

403-319-7800 fax 403-205-9009

Luigi Pisano Canadian Pacific Railway

Suite 500 Gulf Canada Square

401-9th Avenue SW

Calgary Alberta T2P 4Z4

403-218-7770 fax 403-205-9009

Rocco DiRago Alcoa Fastening Systems

6150 Kennedy Road, Unit #10

Mississauga Ontario Canada

L5T 3J4

905 564-4825 fax 905-564-1963

Larry Mercer Alcoa Fastening Systems

P.O. Box 8117

Waco, TX, USA 76714

phone 254.751.5273 fax 254.751.5587

ABSTRACT

In April of 2005, Canadian Pacific Railway adopted lock bolts as the standard for

use in all mainline frogs. This followed seven years of experience with their use

in various special installations of frogs and diamond crossings. Lock bolts were

found to offer superior resistance to backing off under vibration, and have been

shown to require considerably lower maintenance when compared to

conventional threaded fasteners.

This paper explains how lock bolts produce consistent bolt tension as opposed to

the complex nut-thread-torque interaction that produces variation in clamp force.

This is related to comparative maintenance requirements recorded by

roadmasters and CPR field tests. Finally, this paper shares that swaging of lock

bolts to ensure the desired long term low maintenance regime that is demanded

of today's higher tonnage mainlines.

Key words: lock bolt, collar, swage

INTRODUCTION

Consistently obtaining the required preload (also called bolt tension, or clamp) in

high tensile bolts is a familiar and difficult problem. Many variables exist in field

applications which cause wide fluctuations in bolt tension, and the joint becomes

susceptible to slippage or fatigue failure. Various features and techniques

attempt to compensate for variation in bolt preload, but they cannot eliminate the

primary problem, which is using torque to induce bolt tension. Lock bolts avoid

this problem by being installed in direct tension. Preload is controlled by

component dimensions and hardness; torque is not a variable. Preload is

maintained by steel-to-steel press fit around the entire bolt thread, which allows

no relative movement from vibration, so lock bolts do not loosen.

Lock bolts have been used in the transportation industry for the last half century.

High, consistent clamp and fatigue strength make lock bolts ideal for structural

applications that are subject to high vibration and cyclical loading, such as rail

track. Basic physical and performance differences between lock bolts and

conventional bolts are presented, along with how this technology has been used

in rail track applications to extend service life. Best practices that have been

developed for rail track applications are also described.

LOCK BOLT COMPONENTS AND INSTALLATION TOOLING

Lock bolts are classified as an alternative fastener in the American Institute of

Steel Construction, Specification for Structural Joints Using ASTM A325 or A490

Bolts (1). Lock bolts are made from the same materials and are processed in the

same way as conventional bolts. Lock bolts have the same under-head bearing

areas as conventional bolts, but since they are installed by direct tension instead

of torque-induced tension, lock bolts may have a round head instead of a hex

head. Also, lock grooves (also called threads) can be either annular or helical.

Some lock bolts have a pintail section that breaks off and is discarded after

installation, while others do not have a pintail.

The nut counterpart of a lock bolt is the collar, although there are several

differences due to different functions. Both the nut and the collar are used to

develop bolt clamp and tensile strength, but the collar has no internal threads or

external hex wrenching surfaces. Instead, the collar is a tubular member that is

designed to lock into the bolt grooves as it is drawn into the swage cavity (similar

to a wire die) of an installation tool. Lock bolts and collars are shown in Figure 1.

An installation sequence is shown in Figure 2. For 1/2" through 1-3/8" diameter

lock bolts, the installation tool is powered by hydraulics. Low voltage electricity

from the installation tool is used to actuate hydraulic valves for pull (swage) and

return (eject) cycles. Installation tools are shown in Figure 3.

HOW LOCK BOLTS OBTAIN PRELOAD

Figure 4 compares clamp variation for a specified torque using different methods

of tightening (2, 3, 4). Methods based on torque are the least reliable, because

torque is an indirect creator of clamp, and only about 10% of the torsional energy

used in tightening a bolt goes into direct clamping force (5). Tension or

elongation based methods have more consistent clamp.

Figure 5 shows the relationship between tension and elongation which results

from tightening a bolt with torque and with direct tension. Both the ultimate

tensile strength and elongation for torque induced tension are about 15% lower

than for direct tension (6). These decreases occur because a torqued bolt is in

both tension and torsion during installation. Lock bolts keep their full strength

during installation because there is no torsional component.

Lock bolt preload occurs in three stages. First, before the collar swages onto the

bolt, considerable force is exerted on the application to pull out gap. During

swaging, the collar lengthens as it is reduced in diameter, so it stretches the bolt

and creates clamp. Finally, the collar dilates (similar to a nut) when the swage

anvil comes off, and preload drops a few percent. Minimum preload specification

for lock bolts is 70% of the minimum tensile specification for the corresponding

diameter of either A325 or A490 grade level.

HOW LOCK BOLTS MAINTAIN PRELOAD

The maximum recommended slope that is allowed for structural bolting is 1:20,

or about 3° (1). However, structural nuts and bolts are relatively hard and do not

conform to sloped surfaces, which allows embedment and/or slippage, and loss

of preload. Lock bolt collars are made from mild steel in order to flow into the

bolt grooves, and the base of the collar will also flow to fully seat against sloped

or contoured surfaces. Spot surfacing or special washers may not be necessary.

Figure 6 shows a collar that has fully seated on a 10° beveled surface, although

there is 1% to 2% loss of preload at installation per degree of slope.

Vibration is a dominant cause of bolt loosening in service. Deformed threads and

thread fillers attempt to overcome the inherent gap between nut and bolt threads,

but these are not reliable. Collars are designed to completely match the grooves

of lock bolts, including damaged threads, so there is no gap. Figure 7 compares

thread gap of conventional bolts and lock bolts. Because lock bolts have no gap

between bolt and collar contact points, there is no opportunity for any relative

movement or slippage.

If bolt tension is reduced, the influence of cyclical loading becomes greater, and

the bolt becomes susceptible to fatigue failure. In addition to maintaining bolt

tension better, lock bolts have modified threads which are shallower than coarse

threaded bolts, and have a larger root radius than fine threaded bolts. Lock bolts

therefore have a larger cross-sectional area plus less stress concentration, which

help to dissipate service loads better than conventional fine or coarse threaded

bolts.

LOCK BOLT USAGE AT CANADIAN PACIFIC RAIL

In April of 2005, Canadian Pacific Rail (CPR) adopted the use of lock bolts on all

mainline frog joints from 115LB, 132LB and 136LB rail frog configurations #9, 10,

11, 12,13,15,16 and 20. This decision was made after vigorous testing over a

seven year period across the CPR network. Lock bolts were found to offer

superior resistance to the fastener backing off under vibration and have shown to

require considerable lower maintenance requirement when compared to

conventional threaded fasteners.

(7) CPR operates over 24,000km (15,000 miles) of railway between Vancouver

on the west coast of Canada and New York on the east coast of the USA. In

western Canada, coal is transported over 1207km (750 miles) on a route

consisting of sharp curves and steep grades in unit trains with payloads of

13,250 metric tons (14,500 tons), powered by three 4400HP AC traction

locomotives. The route carries approximately 78 million gross tons (86MGT) per

year of mixed freight, grain, double stacked inter-modal container cars as well as

coal.

The route is predominately single track, running bi-directional traffic. With 46% of

the routing traversing curves sharper than 3492m radius (1/2 degree), 129km (80

miles) of curves less than 312m radius ( greater than 6 degree), and a maximum

curvature of 160m radius (11 degrees). Temperatures in the Thompson River

valley range from +43C (110F) to -34C (-30F). The rail in curves of 218m radius

(8 degrees) and sharper is predominately 68kg/m (136lb/yd) 350-390BHN head

hardened rail. Ties in curves are 274cm (9 ft.) long hardwood ties on 41cm (16

inch) rolled eccentric plates.

INITIAL CPR APPLICATIONS

For the past two years CPR has ordered all frogs with lock bolts. This decision

was made after extensive testing by CPR. The first tests were at the following

locations. A #13 136lb frog with lock bolts was installed at Sicamous, British

Columbia, on Canada’s west coast, at mile 44.4 in 1997 (Figure 8) with over 70

million gross tons at the time of the picture, with no bolt maintenance, tightening,

removal or replacement. In Pritchard, BC, at mile 103.8, in track since April,

1997, with an excess of 70 million gross tons at the time of the picture (Figure 9).

After these results, CPR decided to expand testing to 100 main line frogs, with

lock bolts to be installed over several years. Fifty two of these joints were

tracked (Figure 12). An unpublished frog tracking report was prepared by

Moffatt Supply. The tracking took place from 1997 to 2003, and was updated in

2005. Fifty two RBM frog joints in the #13 configuration with 115 and 136lb/yd

saw individual tonnages as high as 120 million gross tons and a total tonnage

over all frogs of over 3 billion gross tons. Regular maintenance on all these frogs

was greatly reduced, with less welding and no bolt replacement or tightening.

RECENT CPR TRACK PERFORMANCE

Since April of 2005, over 600 frogs of various configurations from # 9 to #20 in

115lb to 136lb/yd have been installed in CPR track. All cases have proven to

reduce maintenance and increase longevity of frogs. Lock bolts in the 1-3/8 inch

diameter, in lengths from 7 inches of grip to 20 inches of grip, were proven to

increase service life of frogs as well as reduce maintenance during typical frog

life. To date, all new CPR frogs are ordered with lock bolts. These new frogs are

assembled with Lock Bolts at the Progress Rail frog shop in Winnipeg, Manitoba,

Canada.

In addition, several TMS crews are now equipped with installation tools (Figure

10) to install lock bolts in existing frogs. Conventional threaded fasteners in the

heel part of the frog are removed and replaced with lock bolts (Figure 11),

extending the life of existing frogs. In December, 2005, CPR installed lock bolts

in four # 9 136LB RBM frogs in the high coal haulage corridor of British

Columbia. This particular test, at the Page subdivision, has resulted in Canadian

Pacific Rail approving and endorsing the field use of lock bolts for replacement of

conventional threaded fasteners on heels of frogs. This procedure has resulted

in reduced bolt maintenance as well as extended frog life.

CONCLUSION

Lock bolts have many features that make them especially suitable for rail track

applications. High, consistent preload, seating on sloped surfaces, vibration and

fatigue resistant features combine to give lock bolts superior performance. Rail

track experience has shown that the use of lock bolts on frog joints will extend

the typical life of mainline frogs, while reducing maintenance during its service

life. In an environment of high tonnages, difficult terrain, extreme temperatures

and higher expectations on existing work crews, lock bolts offer a viable solution

to fastening rail joints for both new components as well as in field track repair.

BIOGRAPHICAL SKETCH

Larry Mercer has been a Product Engineer for Alcoa Fastening Systems in

Waco, TX, for the last ten years. He joined the organization in 1979 when it was

Huck Manufacturing Company, and has held the positions of Project Engineer

and Manager of Heat Treat and Plating. Larry holds a Bachelor of Science

degree in Metallurgical Engineering from the University of Oklahoma.

Rocco DiRago has been the Canadian Sales Manager for Alcoa Fastening

Systems in Mississauga Ontario Canada since 2005. He joined the organization

1988 as an account manager. Rocco has been instrumental in promoting the

use of lock bolts in track for the mining industry surface and underground track

as well as Toronto Transit (TTC) for all street car surface track as well as class 1

rail roads main line track. Rocco holds a Business Administration degree from

Dawson College in Montreal as well as a Bachelor of Commerce degree from

Concordia University also in Montreal.

Michael Roney is General Manager, Track Maintenance, at Canadian Pacific

Railway.

Luigi Pisano is Track Design for Canadian Pacific Railway.

REFERENCES

1. Research Council on Riveted and Bolted Structural Joints, "Structural Joints

Using ASTM A325 and A490 Bolts", Publication S 314, Sections 2(d) and

3(a), 1978, American Institute of Steel Construction, New York.

2. Rodkey, E., "Making Fastened Joints Reliable…Ways to Keep 'em Tight",

Assembly Engineering, March, 1977, pp. 24-27.

3. Irving, R., "Who Knows How Tight Is Tight?", Iron Age, October, 1968,

pp.85-92.

4. Munse, W., "An Evaluation of Huck Bolts for Use in Steel Structures",

University of Illinois, a report to Huck Manufacturing Company, February,

1960.

5. Brenner, H., "Standard Threaded Fasteners", Standard Handbook of

Fastening and Joining, 3rd Edition, McGraw Hill, 1997, ISBN 0-07-048589-

5, Section 1-18.

6. Kulak, G., Fisher, J., Struik, J., "Bolts", Guide to Design Criteria for Bolted

and Riveted Joints, 2nd Edition, Wiley, 1987, ISBN 0-471-83791-1, pp. 39-

41.

7. Canadian Pacific Railway 100% Effective Friction Management Strategy

Peter Sroba PEng Principal Engineer National Research Council Canada

Kevin Oldknow PhD Field Application Engineer Kelsan Technologies Corp.

Russ Dashko PEng Manager Track Standards Canadian Pacific Railway

Michael Roney PEng General Manager Track Maintenance Canadian

Pacific Railway.

Figure 1

Figure 2

COLLAR PINTAIL

LOCK BOLT WITH PINTAIL

PINTAIL-LESS LOCK BOLT

A B C D

Figure 3

Figure 4

PRELOAD VARIATION BY TYPE AND METHODTYPE METHOD VARIATION Torque Impact Wrench ± 45% Torque Feel ± 35% Torque Torque Wrench ± 30% Tension Turn of Nut ± 15% Tension Load Indicating Washer ± 10% Tension Elongation Measurement ± 5% Tension Swaged Lock Bolt ± 5%

A

B

Figure 5

Figure 6

Figure 7

Std. Bolt

Nut

Gap Contact length

B

No Gap

Lock Bolt

Collar

A

CAPTIONS FOR FIGURES

1. Typical lock bolts and collars.

2. Lock bolt installation sequence. (A) Lock bolt is placed in hole, and collar is

placed onto lock bolt. (B) Installation tool engages and pulls on lock bolt.

(C) Tool swages collar onto lock bolt grooves. (D) Pintail breaks off of lock

bolt and tool pushes off of collar.

3. Hydraulic installation tools for 1-3/8" lock bolts. (A) Lock bolt with pintail.

(B) Pintail-less lock bolt.

4. Bolt tightening methods based on tension have less variation than methods

based on torque.

5. Bolt tension and elongation based on method of tightening. Torque-induced

tension has lower tensile strength and elongation than tensile-induced

tension during the tightening process.

6. Flanged collar that has fully seated on a 10° bevel after swaging.

7. Thread gap comparison. (A) No gap exists between the swaged collar and

crest, pressure and relief side of the lock bolt thread. (B) Nut thread

contacts bolt thread along the pressure side of the thread. Gap at the crest,

root and along the thread relief side allows for relative movement and

loosening from vibration.

Figure 8

#13 #13 SicamousSicamous BC mile 44.4 1997.BC mile 44.4 1997.

Over 70 million gross tons at time of picture.

Figure 9

Pritchard BC mile 103.8 in track April 97Pritchard BC mile 103.8 in track April 97

These were first test frogs for CP with C50L product frogs exceeded expected life and fasteners required no maintenance during life of frog.

Figure 10

Figure 11

Figure 12

Tracking Report-Canadian Pacific Railway Lock Bolted Frogs

Prepared by: Moffatt Supply at request of CP Rail October 2005

Manitoba Canada

Gord Lowen Brandon Manitoba mile 2.5 Brandon West Broadview Sub

Installed August 14,2001 #13-136LB Tonnage 72 million ytd.

Gord Lowen Brandon Manitoba Brandon East

Installed Feb. 1,2002 #13-136LB Tonnage 70 million ytd

Gord Lowen Brandon Manitoba Mile 57 Hargrave Sub

Installed December 10,2002 #13-115LB Tonnage 38 million ytd

Gord Lowen Brandon Manitoba Mile 118.4 Whitewood Sub

Installed December 18,2002 #13-115lb Tonnage 38 million ytd

Gord Lowen Brandon Manitoba Mile 31.7 East Oak Lake

Installed October 2003 #13-115lb Tonnage 35 million a year

Gord Lowen Brandon Manitoba East Rotave

Installed October 2002 #13-115 tonnage 35 miilion per year

Gus Sezesny Carberry Manitoba Chater

Installed November 2002 #13-115lb Tonnage 30 million ytd

Gus Sezesny Brandon Manitoba Mile 94.1 Sydney

Installed October 2003 #13-136lb Tonnage 33 million

Ontario Canada

Doug Gilberton Kenora Ontario Dryden West

Installed June 2003 #13-136lb tonnage 40 million year

Doug Gilberton Kenora Ontario East River

Installed November 2003 #13-136lb Tonnage 40 million year

Doug Gilberton Ignace Ontario Summit Lake


Saskatchewan Canada

Albert Major Regina Sask. Mile 30.05 Wocseley East Storage


Albert Major Regina Sask. Mile 31.18 Wocseley West Storage

Installed November 12,2001 #13-115lb Tonnage 70 million ytd

Ken Leys Moose Jaw Sask. Madrid

Installed October 21 2001 #13-136lb Tonnage 135 million ytd

Tim DiMarco Swift Current Sask. SC Sub Caron West 2 installed here.

Installed December 2001 #13-136lb Tonnage 114 million ytd each.

Tim DiMarco Swift Current Sask. SC Sub Mortlach East

Installed December 2001 #13-115lb Tonnage 110 million ytd

Tim DiMarco Swift Current Sask. SC Sub Parkberg West


Tim DiMarco Swift Current Sask. SC Sub Secratan East


Tim DiMarco Swift Current Sask. SC Sub Chaplin West


Tim DiMarco Swift Current Sask. SC Morse East

Installed December 2001 #13-115lb Tonnage 110 million ytd.

Tim DiMarco Swift Current Sask. SC Sub Morse West


Tim DiMarco Swift Current Sask. SC Sub Rush Lake West


Tin DiMarco Swift Current Sask. SC Sub Waldeck West

Installed December 2001 #13-115Lb Tonnage 110 million ytd

Tim DiMarco Swift Current Sub Aikens


Tim DiMarco Swift Current SC Sub Enfold west

Installed September 2001 #13-115lb Tonnage 50 million per year

Gord Brudevold Maple Creek Sask. Mile 5.5 Java


Gord Brudevold Maple Creek Sask. Mile 15 Steward West

Installed November 2001 #13-115lb tonnage 120 million ytd.

Gord Brudevold Maple Creek Sask. Mile 13.3 Seward East


Gord Brudevold Maple Creek Sask. Mile 138.5 Antalope


British Columbia Canada

Roger Dubielewicz Invermere Fairmount South Siding

Installed June 2001 #13-115lb replaced due to broken wing rail October 2002

Bill Cowie Salmon Arm BC Mile 55.5 Canoe east Power Switch

#13-136lb

Bill Cowie Salmon Arm BC Mile 63.5 Salmon Arm West Power Switch

#13-136lb

Bill Cowie Salmon Arm BC Mile 70.5 Tappen North Crossover Switch

#13-136lb

Bill Cowie Salmon Arm BC Mile 88.2 Squalix West Power Switch

#13-136lb

Bill Cowie Salmon Arm BC Mile 93.6 Chase east Power Switch

#13-136lb

Bill Cowie Salmon Arm BC Mile 93.63 Chase East #1 Track

#13-136lb

Vic Parr Kamloops BC Mile 120.4 Northbend

Installed November 2001 #13-136lb Tonnage 85 million ytd.

Vic Parr Kamloops BC Mile 31.8 Walbachin East

Installed June 2002 #13-136lb Tonnage 125 million ytd

Vic Par Kamloops BC Mile 33.5 Walbachin West

Installed October 2004 #13-136lb Tonnage 100 million year

Dave Ryles Mission BC Mile 2.1 Cascade

Installed October 2001 #13-136lb

Stan Sadek Golden BC Glenogle

Installed December 2003 #13-136lb

Ed Palasy Revelstoke BC Mile 94.11 Flat Creek Mountain Sub

Installed August 1997 #13-136lb

Ed Palasy Revelstoke BC Mile 119.83NT Greely X over Mountain Sub

Installed August 15 2001 #13-136lb

Ed Palasy Revelstoke BC Mile 123.22ST White X Over Mountain Sub

Installed September 2003 #13-136lb

Ed Palasy Revelstoke BC Mile 123.26NT White X Over Mountain Sub

Installed April 9 2003 #13-136lb Tonnage 100 Million year

Ed Palasy Revelstoke BC Mile 14.68-3 Valley East Shuswap Sub

Installed December 5 2003 #13-136lb Tonnage 100 million per year

Ed Palasy Revelstoke BC Mile 22.45 Taft East Shuswap Sub

Installed December 15 2003 #13-136lb Tonnage 100 million per year

Ed Palasy Revelstoke Mile 44.00 Storage Track Shuswap sub

Installed November 21,2003 #13-136lb Tonnage 100 million per year.

Terry Rota Revelstoke BC

Installed November 2004 #13-136lb Tonnage 100 million per year

Stan Sadek Kamloops BC Mile 48.5 Ashcroft west Frog #248

Installed October 2003 #13-136LB Tonnage 100 million per year.g

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