The Nord-Lock Group provides innovative bolting solutions such as superbolt tensioners and wedge-locking technology, essential for power generation applications facing challenges like heavy bolting tools and time-consuming procedures. Superbolt tensioners simplify installations, allowing for significant time and cost savings while enhancing safety by requiring only hand tools. The company aims to deliver effective, reliable, and safe bolting solutions across various industries, supported by decades of experience and rigorous quality standards.

1. Power Generation Applications
Bolting solutions for your critical joints

2. 2
The ultimate solution
for bolted joints
The Nord-Lock Group has been manufacturing safe and secure bolting
solutions since 1982. Our innovative solutions include wedge-locking
technology and Superbolt tensioners.
Bolting applications in the Power industry can be especially
challenging. You need a bolting solution that can be
installed and removed safely and quickly. One that will keep
your bolted joints tight through demanding operations
and improve your bottom line. That’s where Superbolt
tensioners come in.
On the following pages you will see several examples of
bolting problems solved with Superbolt tensioners from the
Nord-Lock Group. In addition to Superbolt products, we
offer wedge-locking solutions, expansion bolts, studs, and
more. We look forward to working with you on your critical
bolting applications.

3. 3
Bolts with a diameter greater than
1” cannot be effectively torqued to
capacity with hand tools. To achieve
high preload levels, some form of high energy equipment
is required. Slugging wrenches and crane wrenches are
dangerous and thermal tightening can be time consuming.
Hydraulic wrenching can be expensive, time consuming,
inaccurate and it often leads to thread galling problems.
Hydraulic tensioning also shares the same disadvantages
and is additionally difficult to retrofit when out in the field.
Superbolt tensioners are designed as
direct replacements for standard bolting.
They can be threaded onto a new or
existing bolt, stud, threaded rod or shaft. With Superbolt
tensioners, bolting is fast, safe, easy and accurate - only hand
tools are required.
Superbolt vs. Hydraulic Wrench: With a hydraulic wrench
one would need 18,925 lb•ft (22,500 Nm) of torque to stress
a 3” stud to 428,400 lbs (1,950 kN) using a hex nut. With a
3” MTX Superbolt tensioner, only 114 lb•ft (154 Nm) on each
of the jackbolts is needed to produce the same bolt load.
Challenge
How it works
The hardened washer is
installed first to protect the
joint surface. The Superbolt
tensioner is spun on hand
tight, for positioning. Easy
turn jackbolts “push” the
nut body up, tightening
the existing bolt or stud in
pure tension.
Torque vs. preload
comparison chart
Equivalent hex nut torque (Nm)
Superbolt jackbolt torque (Nm)
2” 3” 6”Thread
diameter
145,000
25,700
7,000
77 155 256
Solution

4. 4
Previously, a very large wrench in
conjunction with heating rods, was used.
This required 1 - 2 shifts (sometimes 3) with three workers
for installation or removal of the large diameter acorn nuts.
Occasionally, a nut would seize requiring destructive removal.
The old style acorn nuts were very heavy, requiring two workers
to handle. Manipulation of the heavy tool required three
workers: two to manipulate the tool and one to operate the
overhead crane. During a turbine outage, valuable crane time
is taken from the turbine work, or vice versa. Excessive bolting
time during an unscheduled pump repair can cost the utility
hundreds of thousands of dollars in lost generation for these
large units.
Superbolt tensioners are much lighter
than the original acorn nuts and can easily
be handled by one worker. 1/2” impacts are utilized for initial
tightening, and calibrated torque wrenches for final torquing
step. Two workers were utilized for the installation requiring
about 15 minutes to spin the tensioners into position and only 1
hour and 21 minutes to tighten! Superbolt tensioners not only
save time and money up front, but are also considered to be
an “insurance policy” against excessive bolting time during an
unscheduled pump repair.
The main problem with this application
was time for installation and removal.
Each installation required about 24 man-hours utilizing heating
rods and a 1-1/2” impact. Removal required about 24 to 40
man-hours.
The application shown utilized twelve
2-3/4” Superbolt tensioners and Flexnuts.
Installation of the studs, tensioners, and Flexnuts required only
3 man-hours. Only two workers were required for the job. Total
tightening time after the Flexnuts and tensioners were seated
was about 35 minutes. Eight jackbolts were tightened to 156
ft•lb (212 Nm) for a bolt stress of 45,000 psi (310 MPa).
Solution
Challenge
Challenge
Solution
Boiler feed pump (M130 studs)
Steam turbine inlet flange
Even gasket crush with two workers at 180° apart. Only small hand tools are needed for installation or removal of Superbolt
tensioners.
Two workers at 180° apart tighten the flange in a star pattern. Impacts are
used to tighten close to the target torque.
Hand torque wrenches are used for the final pass. Tightening completed in
35 minutes!

5. 5
Easy insertion of split sleeve and tapered stud shown.
Small 3/8” torque wrenches for low, 74 lb•ft (100
Nm) set screw torque. Original 3-1/8” diameter
bolts required tightening to 12,563 lb•ft (17,000
Nm) with a hydraulic wrench.
Expansion Bolt Components.
Turbine/generator coupling radial expansion bolts
High speed turbine couplings often
utilize fitted bolts which can be difficult
to install and remove. Often, hydraulic jacks are required to
remove the fitted bolts and sometimes they need to be drilled
out. Stud drilling can take as much as a full shift per stud.
This can increase the unit outage time if the turbine work falls
within the critical path of the outage.
Superbolt Expansion Bolts transmit a
large radial force to the coupling hole
but are inserted and removed with the ease of a loose fitting
through-bolt. Installation or removal of the full set of bolts can
be achieved in only a few hours with a small, 3/8” drive torque
wrench. Perfect alignment of the holes is achieved every time.
Challenge Solution
Comparison to hydraulic radial fit bolts: Hydraulic bolts are more complicated and much more expensive than the Superbolt system.
Hydraulic bolts require components such as a hydraulic pump, hydraulic tensioners, and various adapters. Additionally, the hydraulic
systems require expensive hydraulic alignment tools in order to insert the tight fitting solid sleeves. The Superbolt Split Sleeve Design
permits a much looser fit in the coupling bolt hole for easy installation and removal without an alignment tool. The Superbolt system
also requires fewer machining steps for preparation or modification of the couplings and spacers.
The awkward, vertical position of this
application made bolting difficult. The
handling of a heavy hydraulic wrench was labor intensive, back
straining and time consuming. Nut galling and stud seizure
also proved to be a problem, requiring stud drilling. Delays
and problems in this hot working environment is particularly
strenuous for the workers.
Superbolt tensioners installation required
only 1-1/2 hours. Actual tightening time
was less than 45 minutes.
Two workers 180° apart were utilized to achieve uniform gasket
crush during the procedure. Air impact wrenches were used for
the first, second, and third pass on the jackbolts. On the final
pass, calibrated torque wrenches were used.
Challenge
Solution
Boiler circulating water pump

6. 6
High pressure feedwater heater
This plant has four of these high pressure
heaters. The units were only in service
5 - 6 years when they were first disassembled. They experienced
substantial problems with thread galling upon removal and it took
nearly a week to drill out the seized bolts.
Superbolt bolt style tensioners were designed
with an external hex for easy installation and
removal. The installation torque was only 118 lb•ft (160 Nm) per
jackbolt to achieve an equivalent hex bolt torque of 12,000 lb•ft
(16,300 Nm). The tensioners eliminate galling of the main thread
since the main thread does not slide while loaded. Installation time
was cut dramatically to about 2 hours with two workers.
Challenge
Solution
Feedwater heater
Installation or removal of the standard nuts
was a headache! The upside down location
along with limited working room created a very difficult scenario
to manipulate the large hydraulic wrench. 10-12 hours with three
workers was required. Also, the heater had a history of leakage, even
after tightening to the required 17,000 lb•ft (23,000 Nm).
16 nut-style Superbolt tensioners 3-3/4” in
diameter were used. Superbolt JL-M lubricant
was utilized to keep the jackbolt torque to a low 91 lb•ft (123 Nm).
1/2” impacts on a reduced setting were first used. After three passes
around each tensioner with the impacts the jackbolts registered
75 - 85 lb•ft (100 - 115 Nm). Approximately 1-1/2 passes with a
calibrated torque wrench finished the job. Total tightening time was
approximately 1-1/2 hours. No leakage to date.
Challenge
Solution
Westinghouse steam turbine split casing
The inverted position of these nuts make it
difficult to obtain the required preload of
45,000 psi (310 MPa). Several nuts located further underneath the
ends of the unit, are awkward to reach. Before the studs can be
preloaded, initial clearances in the horizontal joint are taken up,
usually by hammer wrenching. Galling of thread surfaces and spot
faces promotes seizure of the nut on the stud.
The use of high temperature mechanical
tensioners from Superbolt made it possible
for two workmen to accurately stress the studs in only 3 hours. This
was accomplished by tightening the jackbolts in the tensioners with
a 3/8” hand-held torquewrench. The need for heavy tightening
equipment is eliminated. Preload is applied in pure tension thus
eliminating galling. Removal of the tensioners is just as easy. Once
preload is released, the studs are hand tight. Therefore, the studs will
not seize into the housing. Superbolt tensioners are reusable making
them a permanent and economical solution.
Challenge
Solution

7. 7
Steam turbine
Traditional methods of bolting, such as
stud heaters and hammer wrenching, are
inaccurate and often jeopardize employee safety. Previous to the
installation of Superbolt tensioners, this application was not only
time consuming to bolt, but dangerous.
Superbolt has taken great steps in increasing
the safety of employees while providing
fast and effective ways of bolting. Superbolt multi-jackbolt design
makes installation quick and safe, only requiring simple hand tools
to reach desired torque. The awkward, overhead position of these
studs proved to be ideal for the use of Superbolt products. Complete
tensioning time was only 6 hours. The estimated time savings this
turnaround is 2 days!
Challenge
Solution
Westinghouse M32 Steam Turbine, split case bolting. 45,000 psi (310 MPa)
bolt stress.
GE turbine stop valve
Feedwater heater
Past problems include steam leaks due to
insufficient stud stretching when torque values
were used to stretch the studs and galled threads resulting in repairs
and nut replacements. The large 4” diameter nuts were prone to
galling whether tightening with heating rods or with a hydraulic
wrench. Another disadvantage is that decarbonization of thread
surfaces can sometimes occur when the stud is heated and can
increase the chances of fatigue failure or stress corrosion cracking.
Three studs on this unit failed due to cracks in the threaded portion
of the stud in the valve body and were drilled out and replaced with
much effort and overtime.
All of the studs were replaced. Direct tensioning with Superbolt tensioners is expected to make future stud
replacements easier as the stud is never forced into the housing by torquing.
Installation - the total tightening time with two workers was 3 hours for both valves. This included time to stop and confirm stud
stretch with an extensiometer on all studs. The stud stretch was found to be very repeatable. Final jackbolt torque was 155 lb•ft
(210 Nm) to achieve a stud stretch in the target range of .019” - .024” (5 - 6 mm).
Removal - after 18 months of operation, removal was fast and easy, requiring only two hours. Tensioners were cleaned, relubed,
and re-installed with stretch results consistent to the initial installation.
Challenge
Solution
It was difficult to tighten the standard 1”
diameter hex nuts to the specified torque of
280 lb•ft (380 Nm) due to interference from the discharge head
studs and the pump shaft.
Special Superbolt tensioners were tightened to
17 lb•ft (23 Nm) with small 1/4” drive torque
wrenches. The result is easier pump setup and faster installation and
removal. This plant, along with its “sister” plant, has converted several
of these pumps with plans to convert them all.
Challenge
Solution

8. Nord-Lock Group
Tel: +46 (0)31 7192 300, Fax: +46 (0)40 240 851
Email: info@nord-lock.com
www.nord-lock.com
English•2014-08•70214EN
© Copyright 2014 Nord-Lock Group. NORD-LOCK and SUPERBOLT are
trademarks owned by different companies within the Nord-Lock Group.
All other logos, trademarks, registered trademarks or service marks used
herein are the property of the Nord-Lock Group. All rights reserved.
Joining parts together is one of the most critical steps when
delivering a product or system. The Nord-Lock Group is
focused on solving the toughest bolting challenges. We offer
a unique combination of bolting expertise and a wide product
range, including wedge-locking technology and Superbolt™
tensioners — all designed and developed in-house.
Nord-Lock holds decades of documented success in every
major industry, including oil and gas, energy, transportation
and mining. Our Production System includes rigorous internal
testing and full traceability, and our products hold several
certificates from independent institutes including AbP, ABS,
DIBt, DNV and TÜV.
The tools available through Nord-Lock Performance Services
add value throughout a project and ensure that your bolting
application pays back multiple times. We can also assist
you in the design phase with joint simulation and testing.
Additionally, we help you ensure successful operations over
time with our onsite support and remote product training.
Our mission is to safeguard human lives and customer
investments by securing the world’s most demanding
applications. The Nord-Lock Group looks forward to being
your partner in bolting solutions.
When safety really matters
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