TechnicalReportNo.30
of tighteningmethodsfor
Comparison
high strengthbolts
W.S.Atklns& Partners,Consultingengineers
P.A.Management
ConsultantsLtd.(ProductResearchand Development
department)
Comparlson of tlghtentng methods for
htgh strenglth bolte
Introductlon
Customcr responsesuggestedthar many usersof high sfength bolting systemsbelieve that
thsre is a time-savingfactor in the use of Coronrt Load Indicaton.
Coopcr 6 Turnerdecided to establishwhether this had any validity and this repon sets down
the method and resultsof a seriesof controlledtestscarriedout with the co-operation of the
BritishSteelCorporationduringAugust,1970.
The time study was underlakenby P.A. ManagementConsultantsLtd., Product ResearchI
DevelopmentDepartment,and the testswere supervisedby W. S. Atkins & Partners,
Consulting Engineers.
Ernrnrrr
Threo basic systomsof bolting were compared: (1) The torque or calibratedwrench method;
(2) Thc Turn-ol-Nut method; (3) The CoronetLoad Indicatormethod'
Timings were made ol each step. A minimum time saving of 13% was shown by lhe Coronet
Load Indicator method comparedwith the other two systems.This saving was increasedto
3396with the omissionof initialspud wrenchtightening.
Procrrhrrc
A tcst pieco as shown in Fig. 1 was prepared,inro which could be inserted72 - l" dia. bolts
through if' dia. holes.The plate was divided into three egual areasof 24 holes and all three
Systsrfiswere usod during any one particularssquence.For each sequencethe separate
tightening,final tighteningand checking w€le completed tot all the
eiemenrsof p,reliminary
rystems before passingon to the next element.In order lo minimizs thc etfects ol operator
fetigue or familiarity,which might slow down or quicken tho tightening times' the positions
of each group wero cycled and tightening was always canied out starting from the same side
and procecding in rhe same order.
The tightening technique for each systemwas as lollows:
Wnnch method
I
Torqur or Celibrrtrd
( a ) All botts were insertedby hand and nuls snugged with a spud wrench'
( b ) The pnsumatic impaci wrench was calibratedby uss of a load cell to cut out when a bolt
tansion t 096higher lhan the minimum specifiedwas achiaved.
( c ) The bolts were tightened with the calibraredimpact wrench.
( d ) A normal torque wrench was calibraledin the load cell to indicate a totque 5% above that
necessaryto obtain the minimum tension.
( e ) The manual torque wrench was used for inspectiontesilng ol the tightened bolts.
medrod
2 Turn-of-ilut
(a) All bolts were insertedby hand and nuts snugged with a spud wrench'
the necdssarymark made on
iUl The nuts were checked for adequatepreliminarytightening and
tho nut and protruding thread with a chisel.
(c) Thr bolts were tightened to half turn of tho nut using the pneumatic impact wrsnch.
of tha nu1
iOi Thc ma*s were visually inspectedlo ensurothe required totation
t Corsret Lord Indicrtor mrdrod
(a) The Coronet Load Indicarorswaro placedunder the heads ol rht bolts snd the bolts
insertedby hand. Nuts were then snuggedwith a spud wrench'
gap using the pneumatic
(b) The bolts were tightened ro rhe requircdO-Ol5" averagoIndicator
impact wrench.
(c) Thc grp was checked.
Thc ttstt warc ropeatd five times and tho results aro ehown in eppcttdix 1. T;sstsI to 3 follor
pracisely the methods described ebove. In practice therc will bo occarions.where the plies
arc sufticisnrly welt drawn rogerherby fining-up bolts to make prclimin.Tytightsning with I
spud wrench unnacessaryin the torque control and Coronat Load Indicatot mathds; rcsts
4 and 5 were thcrelore canied out with thc spud wrcnch tightening eliminated from these
methods. An impact wrench was used for the Turn-of-Nut initial tightcning.
f,crultr
Averageresultsfor eachtest serieswete as follows:
Kev
T - torque(calibratedwrench)
'N- turn-of-nut
C : Coronet
Timeis in minutesper24 bolts
Tests1-3
T
N
C
6'52
6 70
HandplaceI handrighten 6 25
H a n d p l a c eo n l y
Spud tighten
F i n a lt i g h t e n
lnspecl
6.52
2-24
Total 25 10
18.78
N
C
1uu 339 Tu
,r,
*,
2.39
6 75
917
Tests4-5
T
5.32
1.22
1 34 9
8.11
5'14
1'69
3'99
l'65
16'28
25'26
15'78
10'50
It will be appreciatedthat the testing was carriedout in idoal shop conditions and these
figures may not be achievableon site, However,the comparisonof lhe rilsultswill in no way
b e a f f e c t e db y t h i s c o n s i d e r a t i o n
It will be seen that lhe Coronet Load lndicator method was the quickest of the three methods,
b o t h w i t h o r w i t h o u t i n i t i a ls p u d w r e n c h t i g h t e n i n g ,t h e c o m p a r i s o nb e i n g :
T i r n es a v e d b y C o r o n e t L o a d I n d i c a t o r :
Tests 1-3
compared with
13Yo
Turn-of-Nut
35%
Torque control
Appendir
1-
Individutl
Tests4-5
33%
58%
to3t rerultr
Kev
T - torque (calibrated wrench)
N - Turn-of-Nut
C - Coronet
PlaceBolts by Hand
IEST
NUMBER I
N
5.87
2
569
3
AVERAGE6 . 2 5
801
669
6.23
670
7.66
6.28
560
652
4
379
5
332
AVERAGE3 . 5 6
3.14
4.01
3.58
517
4.54
4.86
1
7.31
Spud Tighten
FinalTighten
25.2s
1
24 47
2
25.47
3
AVERAGE 2 5 ' 1 0
c
T
N
c
T
N
c
2.93
2.23
2.03
2.39
3.64
2'56
2.88
3.02
3.93
2.56
3.19
3.22
8 . r9
6.90
5.02
6.75
7.81
6.07
5'70
6'52
5 . 1 8 6 . 8 2 3.07 1 . 2 8
5.67 9'47 2'27 1 . 4 4
5 . t l 12.73 r . 3 9 .93
5.32 9 . 1 7 2.24 1 . 2 2
4.63
6.10
5'36
12'00 5.08 4.46
1 4 . 9 8 5.20 3.52
1 3 . 4 9 5 . 1 4 3.99
Total Time
T
Inspect
N
c
22'53
17.59
16.20
18'78
1 8 '05
05
1 5 95
.95
1 4 83
83
16'28
.
2 5 ' 1 8 14.44 1 059
4
25.13 1 7 ' t1 1 040
.
5
.
AVERAGE 25.26 1 5 ' 7 8 1 050
Timesare minutesper 24 bolts
T
N
9.39 r . 5 9
96
6.83 1 . 8 0 2.34
8 . r1 1 . 6 9 r . 6 5
urnaSure tLC
International
Headquarters
340 E. MapleAvenue
Suite305
Langhorne,
PA 19047
Fig. 1
Trrt Pimo
Telephone:
215-750-1
300
800-525-71
93
Facsimile:
215-750-6300
Website:www.turnasure.com
E-mail:info@turnasure.com
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