Post on 06-Feb-2018
transcript
Structural Bolting Assemblies according to EN 14399
EN 14399-1…10 High Strength Structural Bolting assemblies for preloading.
• UNI EN 14399-1:2005 General Requirements
• UNI EN 14399-2:2005 Suitability test for Preloading
• UNI EN 14399-3:2005 System HR. Hexagon bolt and nut assemblies
• UNI EN 14399-4:2005 System HV. Hexagon bolt and nut assemblies
• UNI EN 14399-5:2005 Plain washers
• UNI EN 14399-6:2005 Plain chamfered washers
• UNI EN 14399-7:2008 System HR. Countersunk head bolt and nut assemblies
• UNI EN 14399-8:2008 System HV. Hexagon fit bolt and nut assemblies
• UNI EN 14399-9:2008 System HR or HV. Direct tension indicators for bolt and nut assemblies
• UNI EN 14399-10:2009 System HRC. Bolt and nut assemblies with calibrated preload
Structural Bolting according to EN 14399
There are three approved technical solutions for High-Strength Structural Bolting in
Europe, as outlined below
HR ASSEMBLIES HV ASSEMBLIES HRC ASSEMBLIES
GENERAL REQUIREMENTS EN14399-1
SUITABILITY TEST FOR PRELOADING EN14399-2 , additional tests on request
BOLT AND NUT EN14399-3 EN14399-7 EN14399-4 EN14399-8 EN14399-10
BOLT MARKING HR HR HV HVP HRC
NUT MARKING HR HR HV HV HR or HRD
PROPERTY CLASS 8.8/8 -
10.9/10
8.8/8 -
10.9/10
10.9/10 10.9/10 HR or HRD
WASHER(S) EN 14399-5 or EN14399-6
WASHER MARKING H
DIRECT TENSION INDICATOR WASHER LEANED AGAINST THE
NUT AND/OR THE BOLT
EN14399-9
AT USER’S
DISCRETION
DTI MARKING H8 or H10 H10
MARKING OF THE WASHER LEANED AGAINST THE NUT
HN MARKING OF THE WASHER LEANED AGAINST THE BOLT HB NA HB
HOT DIP GALVANIZING AND BLACK OXIDE ARE THE MOST COMMON COATINGS
HR System
• diameters from M12 to M36
• Wrench according to Large ISO series
(except M20 and M12)
• Oversized under head radius
connections
• Partial thread ISO 888
(l variable thread with l=shank)
• nut height as style 1 ISO (~ 0,8d ÷ 0,85d )
• nut proof load larger than ISO 898-2
• 2 heat treated washers (300÷370 HV),
chamfered under head washer
HV System
•diameters from M12 to M36
• Wrench according to Large ISO
series (except M20 and M12)
Oversized under head radius
connections
• Short Partial Thread
(lg. Threaded part depending on
diameter)
•nut height ~ 0,75d ÷ 0,8 d (DIN 6915)
• nut proof load according to ISO 898-2
• 2 heat treated washers (300÷370 HV),
chamfered under head washer
HRC System
•diameters from M12 to M36
• Wrench according to Large ISO
series (except M20 and M12)
• Oversized under head radius
connections
•Partial thread ISO 888
(l variable thread with l=shank)
nut height as style 1 ISO (~ 0,8d ÷ 0,85d )
•2 heat treated washers (300÷370 HV),
chamfered under head washer
• spline end sheared off when preload is
achieved
Depending on the system chosen, the parts can be supplied according to the three classes K0,
K1 e K2 , to which correspond different functional features and tightening methods
K0, K1 and K2 affect the supply terms of the assemblies
SYSTEM
HR HV HRC
K -CLASS
K0 X X X
K1 X X
K2 X X X
Variable
factors
EN14399/3 HR SYSTEM
Hexagon Head
EN14399/4 HV SYSTEM
Hexagon Head
EN14399/10 HRC
SYSTEM (K2-class)
Hexagon/ Round head
K1 K2 K1 K2 K2
Thread
Long thread:
lengths can be
adapted using a
limited number of
codes
Long thread:
lengths can be
adapted using a
limited number of
codes
Short thread: use of
various dimensions
Interchangeability is
limited
Short thread: use of
various dimensions
Interchangeability is
limited
Long thread: lengths can be
adapted using a limited
number of codes
Tightening
methods
The combined
method (torque +
angle ) involves
several tightening
steps and many
workers
The torque method
standardizes the
tightening process
but involves a high
number of workers
The combined method
(torque + angle)
involves several
tightening steps and
many workers
The torque method
standardizes the
tightening process but
involves a high number
of workers
Use of a Shear wrench, The
procedure is simple and
functional (no technical
skills required, erection
time reduced )
Number of
workers
VERY HIGH
HIGH
VERY HIGH
HIGH
LOW
Coatings
Black Oxide/ HDG
According to
specifications
Black Oxide /HDG
According to
specifications
Black oxide /HDG
According to
specifications
Black oxide/HDG
According to
specifications
Black oxide/HDG
According to specifications
Inspections Difficult , according
to 1090-2
Difficult , according
to 1090-2
Difficult , according to
1090-2
Difficult , according to
1090-2
Easy, thanks to the spline
end breaking
Torque method Combined method Direct Tension
Indicator method
TCB method (HRC)
General
Before commencement of preloading the connected components shall be fitted together.
Each bolt assembly shall be brought at least to snug-tight condition with special care being given to avoid
over-tightening. The tightening process shall be carried out from bolt to bolt of the group starting from the most rigid
part of the connection and moving progressively towards the least rigid part. To achieve a uniform snug tight
condition, more than one cycle of tightening may be necessary.
Tooling
The bolts shall be
tightened using a torque
wrench offering a
suitable operating
range. Impact wrenches
may be used for the first
step of tightening only.
Torque wrenches used
in all steps shall be
capable of +/-4%
accuracy and checked
weekly.
For torque wrenches
used in the first step of
the combined
installation method an
accuracy of +/-10% is
required with annual
testing.
Bolts fitted to snug-tight
using a normal size
spanner.
Bolts tightened using
appropriate tooling to
achieve compression of
the DTI.
Shear wrenches do not
require calibration.
Firs tightening step
For the first step the wrench shall be set to a torque
value to achieve about 0.75Mr,i with Mr,i=Mr,i or
Mr,test. The first step shall be completed for all bolts
in one connection prior to commencement of the
second step.
The first step of
tightening to reach a
uniform snug-tight
condition of the fastener
assembly shall be when
initial deformation of the
DTI protrusions begins.
The first tightening step
is achieved using the
shear wrench. When the
outer socket stops
turning and the gearing
backtracks, it allows the
tool to be taken off the
bolt.
Torque method Combined method Direct Tension
Indicator method TCB method (HRC)
Second tightening
step
For the second step, a
torque wrench shall be
set to a torque value of
1.1Mr,i with Mr,i=Mr,2 or
Mr,test.
The torque reference
values Mr,i to be used for
a nominal minimum
preloading force Fp,C are
determined for each type
of bolt and nut
combination used by one
of the following options:
1. Values based on
k-class declared
by the fastener
manufacturer.
2. Values
determined by
Annex H of EN
1090-2 (test to
determine torque
values for
preloaded bolts
under site
conditions)
The second tightening
step involves a specified
part turn to be applied to
the bolt assembly.
The position of the nut
relative to the bolt
thread shall be marked
after the first step using
a marking crayon or
paint so that the final
rotation of the nut
relative to the bolt
thread can be easily
determined.
The additional rotation
during the second step
shall be in accordance
with values given in
table 21 of EN
1090-2:2008.
The second step of
tightening bolts shall be
as EN 14399-9 and
annex J of EN 1090-2;
Indicators are usually
applied under the bolt
head and the bolt is
usually tightened by
rotation of the nut.
A feeler gauge (as
specified in table J.1 of
EN 1090-2) shall be
used to determine
whether the DTI has
compressed in
accordance with the
requirements.
No more than 10% of
the indicators in a
connection bolt group
shall exhibit full
compression of the
indicator.
The second tightening
step is achieved when
the spline end of the
bolt shears off.
Inspection tooling Torque wrenches used for inspections shall be
calibrated and have +/- 4% accuracy.
Feeler gauge used as a
“no-go” inspection tool
NA
Torque method
Combined method
Direct Tension
Indicator method
TCB method (HRC)
Inspection of bolts
during and after
tightening.
General
All connections with preloaded fasteners shall be visually checked after they are initially bolted up and before
commencement of preloading
The number of bolts inspected at random depends on the Execution Class specified
EXC1 to EXC4. If the inspection leads to rejection, all of the bolting assemblies in the
group shall be checked.
The inspection shall be
carried out on 100% of the
bolting assemblies by
visual inspection.
Overall number of bolts to be checked in a class EXC2 structure - 5% for the second
step
EXC3 and EXC4 -10%
for the second step
EXC3 and EXC4 -5% for
the first step and -10%
for the second step
EXC3 and EXC4 -10%
for the second step.
Inspection shall be carried out using a sequential sampling plan according to annex
M of EN 1090-2. If the result of the inspection to sequential type A is negative, the
inspection may be enlarged to sequential type B.
If fasteners are not applied in accordance with the defined methods, the removal
and re-installation of the whole bolt group shall be witnessed.
Torque method
Combined method
Direct Tension
Indicator method
TCB method (HRC)
Inspection at second
step
Specific
The inspection of a bolt
assembly shall be
carried out by the
application of a torque to
the nut using a
calibrated torque
wrench.
The objective is to check
that the torque value
necessary to initiate
rotation is at least equal to
the torque value 1.1Mr,i
with Mr,i=Mr,2 or Mr,test.
After the second step the
marks shall be inspected
with the following
requirements:
1. If the rotation
angle is less than
15° below
specified value,
the angle shall be
corrected.
2. If the rotation is
more than 30°
over specified
angle or the bolt
has failed, the
assembly shall be
replaced.
After the final tightening,
assemblies selected for
inspection shall be checked
to establish that the final
indicator settings are in
accordance with the
requirements specified in
EN 14399-9 and Annex J of
EN 1090-2
Fully tightened assemblies
are identified as those with
the spline sheared off..
Notes
Inspection shall be
carried out between 12
and 72 hours after the
final completion of
tightening of the bolts
concerned