Transcript UBC Apprenticeship and Training Fund of North America

UBC International Training Fund
Presents
1
Computing Torque
The following material is intended to make you aware
of the currently acceptable and recognized methods of
performing the tasks described in this presentation.
However, every possible application of these methods
cannot be foreseen and the following material is not
designed to cover every potential application. Therefore,
you must always follow all current procedures and safety
regulations whenever you perform any of the tasks
discussed in this presentation.
HOW MUCH TORQUE IS RIGHT FOR A PARTICULAR BOLT?
In Your Work You Will Most Often Be Given Torque
Specifications In The Form Of A Torque Chart.
Behind The Numbers Are Factors Which Can Change
The Torque Values - Some Of The Major Ones Are:
•BOLT STRENGTH
•DESIRED TENSION
•BOLT DIAMETER
•LUBRICATION
•THREAD PITCH
•BOLT CONDITION
4
FACTORS AFFECTING TORQUE
BOLT DIAMETER
Everything Else Equal, A Big Bolt Will
Stand More Torque Than A Small One
Pre-load ( Remember, This Is What We Really Want)
Is Measured In Pounds Per Square Inch
Radius = ½ Diameter
B = 3.14
Area = B (r2)
1” bolt = .79 sq.in.
2” bolt = 3.14 sq.in.
5
FACTORS AFFECTING TORQUE
BOLT STRENGTH
A High Strength Bolt Will Stand More
Torque Than A Soft Bolt
S.A.E.
S.A.E.GRADE 5
S.A.E.GRADE 7
S.A.E.GRADE 8
_______________________________________________
YIELD_______________________________________________
90,000 P.S.I.
115,000 P.S.I.
130,000 P.S.I.
CLASS 5.8
CLASS 8.8
CLASS 10.9
METRIC
6
FACTORS AFFECTING TORQUE
DESIRED TENSION
Bolts Are Tightened To A Given Percent
Of Their Yield Based On The Engineered
Requirements Of The Job
50% Of Yield Means 50% Reserve Strength To Withstand Dynamic
Shock And Still Spring Back
7
FACTORS AFFECTING TORQUE
Remember The Example Of The Pipe Flange
Pre-load Per Bolt
@50%of Yield = 58,000 Lbs.
24 Bolts = 1,392,000 Total Lbs.
If The Pressure Trying To
Escape Is Less Than That
Then The Flange Will Seal
8
FACTORS AFFECTING TORQUE
LUBRICATION
A Lubricated Bolt Will Turn Easier
Than A Dry One
Friction (dry)
Friction (oil)
Friction (grease)
= 30% \
= 20%
= 10% /
3 TIMES THE TORQUE
(DRY VS. MOLY GREASE)
9
FACTORS AFFECTING TORQUE
THREAD PITCH
It Makes A Difference Whether The
Threads Are Coarse Or Fine
But Almost Every Bolt You Will See
Will Be Standard 8 Threads Per Inch
10
FACTORS AFFECTING TORQUE
BOLT CONDITION
New Turns Easier Than Old,
Smooth Turns Easier Than Rough
11
SAMPLE TORQUE CHART SHOWING FACTORS AFFECTING TORQUE
PRE-LOAD STRESS @ 50% OF MINIMUM YIELD STRENGTH
STUD DIA.
THREADS
PER INCH.
HVY.HEX
NUT SIZE
(TORQUE IN FT/LBS)
S.A.E. GRADE 5
S.A.E. GRADE 8
45,000 P.S.I. AT THIS TORQUE
60,000 P.S.I. AT THIS TORQUE
DRY
MCHN.OIL
MOLY-DS
DRY
MCHN.OIL
MOLY-DS
1"
8 UNC
1-5/8"
533
361
172
800
542
258
1-1/4"
"
2"
1023
693
330
1535
1040
495
1-1/2"
"
2-3/8"
1817
1231
586
2725
1846
879
1-3/4"
"
2-3/4"
2905
1968
937
4357
2952
1406
2"
"
3-1/8"
4334
2936
1398
6501
4404
2097
2-1/4"
"
3-1/2"
6169
4179
1990
9254
6269
2985
2-1/2"
"
3-7/8"
8457
5729
2728
12685
8593
4092
2-3/4"
"
4-1/4"
10180
6896
3284
15271
10345
4926
3"
"
4-5/8"
13522
9160
4362
20283
13740
6543
3-1/4"
"
5"
16787
11372
5415
25180
17057
8123
3-1/2"
"
5-3/8"
20953
14194
6759
31429
21291
10139
3-3/4"
"
5-3/4"
25761
17451
8310
38642
26177
12465
4"
"
6-1/8"
31248
21168
10080
46872
31752
15120
12
Let’s Try A Few Questions To Ensure
We Understand About Torque And Pre-load
(Quiz #2)
13
The End