Pre-tensioning with ITH-Tension Nut
Perfect for hightemperature application
No need for new bolts
High repeatability
No friction

Bolt stretching by meansof differential threadTensioning of bolts with ITH-Tension Nut
Function of the ITH-Tension Nut

1. Assembling of theITH-Tension Nut on a boltwith the turning device

2. Assembling of thebolt-tensioning cylinder

General remarks
Bolts which are pre-tensioned by the ITH stretch method
require a thread projection of 0.8 to 1.0 x thread diameter above the nut for the hydraulic tool. As thisprojection does not normally exist, the bolts in place
have to be replaced by longer ones.
When the ITH-tension nuts are used, the existing nuts
are replaced by the tensioning nuts. The existing bolts
do not have to be replaced.
With the ITH-tension nuts, the bolt is stretched onlyin an axial direction. This means that the ITH-tension
nut is ideal for joints which are subjected to high temperatures because (in contrast to the torque process)the static friction does not have to be overcome when
the bolt is loosened.

3. Pulling of the bolt

4. Adjusting of the pressuresleeve with a pin

Function
The method by which the three-part patented ITHtension nut works is based on the principle of the differential thread. A special threaded sleeve (tensioningsleeve) which is screwed onto the bolt transmits theaxial pre-tensioning force from the bolt via the sleeveto the pressure disk and then to the flange. This causes
axial stretching of the bolt which means that noadditional torsion or other stresses can occur in thebolt. This causes purely axial stretching of the bolt. The
pressure sleeve is then turned into position by a device
on the bolt-tensioning cylinder or by a pin to the pressure disk.
The ITH tension nut consists of three parts:

When the torque process is used with bolt joints which
are subject to thermal stresses, a torque has to be applied which is between 2.5 and 4 times greater,
depending on the temperature in question to open
the bolt. This often causes such serious damage to thebolts or nuts that they have to be replaced, thereby
creating additional costs. In addition, the torque tool
is often damaged by the sudden release of energy
during loosening (Additional cost).

Tensioning sleeve
Pressure sleeve
Pressure disk

The ITH-Tension Nut offers you the following advantages:
high cost savings (no new bolts)
use of existing bolts
ideal for thermally stressed joints
easy assembly

no friction, simple bolt design
high reproducibility
mechanical components – no hydrauliccomponents (hydraulic nuts)

ITH Bolting Technology · www.ith.de · Phone +49 (0) 291 / 99 62 - 0

FE arrangement
The patented ITH-tension nut produces better distribution of stresses in the bolt. In contrast to conventionalnuts, the use of the patented ITH-tension nut considerably improves the fatigue strength of the bolt.
Through the special thread of the tensioning sleeve
and the geometric arrangement, a very even distribution of stresses is achieved in the components ofthe patented ITH-tension nuts.
All the patented ITH-tension nuts have been calculatedwith finite elements (FE).

bolttensioning sleeve
pressure sleeve
pressure disk

Even distribution of stresses on the bolt.

typeTN 30
TN 33
TN 36
TN 39
TN 42
TN 44TN 45
TN 48
TN 52
TN 56
TN 57
TN 63
TN 64
TN 72
TN 80
TN 90
TN 100TN 102Tension nut with hexagon head / bore

Tension nut with bolt-tensioning cylinder

Tension nuts for expansion bolts andinch-bolts max. 60 ksi

Bolt-tensioning cylinderorderno.

thread*

M 30
M 33 / 1,25''
M 36
M 39 / 1,5''
M 42
1,75''M 45
M 48
M 52 / 2,0''
M 56
2,25''
2,5''
M 64
M 72 x 6
M 80 x 6 / 3,0''M 90 x 6
M 100 x 6
4,0''

requiredmax.
tension casingø(mm)force(kN)290385450565
620
785
715
815
1.000
1.125
1.325
1.650
1.500
2.000
2.500
3.250
4.100
4.500

55
616772
7883
88
9697
104
107
119116
132
148
168
187
194

total
height(mm)

type

43
50
52
5960
70
65
6978
82
89
99
93
108
118
135
150
157

ES 30-290
ES 33-385
ES 36-450
ES 39-565
ES 42-620
ES 1,5''-785
ES 45-715
ES 48-815
ES 52-1000
ES 56-1125
ES 2,25''-1325
ES 2,5''-1650
ES 64-1500
ES 72-2000
ES 80-2500
ES 90-3250
ES 100-4100
ES 4,0''-4500

orderno.

thread

M 30
M 33 / 1,25''
M 36
M 39 / 1,5''
M 42
1,75''M 45
M 48
M 52 / 2,0''M 56 / 2,25''
2,25''
2,5''
M 64 / 2,5''
M 72 / 2,75''
M 80 / 3,0''M 90 / 3,5''
M 100
4,0''

Subject to technical change · *Other sizes and forces available on request · Status 2004

ITH Bolting Technology · www.ith.de · Phone +49 (0) 291 / 99 62 - 0outerø(mm)

totalheight(mm)Tension NutApplications

ITH-Tension Nut TN 140
Pre-tensioning of expansion bolts
M 140 x 6 in a confined space on arolling-mill stand.

ITH is a system supplier providing
a complete package consisting ofbolting tools and special bolts.
The leading position on the market
earned by ITH is reflected in thefollowing facts:

ITH-Tension Nut TN 36
Pre-tensioning of bolts on the foundationof a wind-power generator.

ITH-Tension Nut TN 72
Pre-tensioning of joint nuts M 72 x 6 in
the high-temperature zone (550°) of agas turbine.

Worldwide NetworkUSA

Head quarter- worldwide distribution network- international patents- expert advisory service by qualified
mechanical engineers (not salesmen) in all questions involving
bolts- experience in the bolting technology for more than 25 years- fast service

JapanChina

Main ITH facility
Service sales agent or ITH employee
Sales agent

INDUSTRIE-TECHNISCHEKONSTRUKTIONEN

HOHMANN
ITH-GmbH · Industrie-Technische Konstruktionen Hohmann
Auf’m Brinke 18 · D-59872 Meschede
Phone + 49 (0) 2 91 / 99 62 - 0 · Fax + 49 (0) 2 91 / 99 62 - 11
sales@ith.com · www.ith.com