An Australian innovation is making light work of some of the largest and most difficult bolt
tensioning applications encountered in high temperature areas of electricity generation, mining,
petrochemical and other processes.
In a recent application, Technofast Industries’ new EziTite® TR High Temperature Hydraulic
Nuts demonstrated their performance when they were used to assemble boiler feed pumps at
an electricity generating plant in South Korea.
This application involved the use of 12 large EziTite®
TR High Temperature Hydraulic Nuts
fitted to M110 X 4.0 studs.
The temperature resistant fasteners were used to replace the former method employing large
torque wrenches weighing more than 125kg.
The Technofast method resulted in an installation time of around thirty minutes using two
personnel, compared with eight hours and four personnel using the previous method.
Technofast’s Founder and Managing Director John Bucknell explained that time savings of this
order, and better, are possible using the EziTite®
fasteners instead of conventional methods
involving sledgehammers, stud heaters and multi-jackbolt tensioners.
“Large nuts of this diameter can require terrific torque forces to achieve the desired tensioning,
or require ‘jacknuts’ which have multiple forcing screws to bring the job within the power range
of hand tools.”
“Given the damage which can occur to the fastener components and joint faces, some
operators have opted to use these jacknut fasteners. However, large nuts such as those used
on the Boiler Feed Pump can easily have 24 of these forcing screws per nut, and they have to
be progressively and sequentially tightened to a specific torque at each step, or the individual
screws will be overstressed and fail. This can add days of downtime to a typical maintenance
operation.”
“Also, when jacknut fasteners need to removed, the forcing screws have to be backed off in a
strict sequence to avoid failure. If not, then excessive load will transfer to remaining screws
and cause failures. The jacknut assembly will then need to be cut off,” Mr Bucknell said.
EziTite® Hydraulic Nuts, by contrast, tension the bolt in one simple operation. They are rapidly
applied by being screwed by hand onto bolt studs, hydraulically actuated to stretch the bolt to
the precise tension required, then secured in place mechanically with an integral mechanical
lock ring.
The charging pressure is relieved, and the EziTite® Hydraulic Nuts remain in situ at the precise
target bolt load.
The reverse procedure permits equally rapid disassembly when it is eventually required. All
studs can be tensioned or de-tensioned simultaneously by manifolding them to a single
hydraulic source.
In addition to their simple and swift operation, the EziTite® Hydraulic Nuts used in the Korean
application overcame multiple issues experienced with the former method involving heavy
torque wrenches, including:
Horizontal stud position, which made handling difficult
Torque damage to studs, hex nuts and sump surfaces
Irregular torque readings that were difficult to relate to tensions applied (a result which
can be caused by common issues such as corrosion, thread damage and other factors
where multiple tensioning is involved).
EziTite® Hydraulic Nuts removed all these difficulties, as well as achieving precise bolt loads
over multiple studs through simultaneous tensioning achieved by hydraulically loading entire
groups of fasteners at once (as above).
Simultaneous tensioning gives an extremely accurate and even load onto the flange/joint,
enhancing its long-term security, safety and reliability.
Mr Bucknell said the customer was very impressed with the time and labour savings as well as
the safety improvements, and are now replacing all standard hex nuts on a further seven boiler
feed pumps with Technofast EziTite®
TR Hydraulic Nut technology.
Technofast technologies such as EziTite® Hydraulic Nuts and Bolts and the complementary
CamNut range are employed worldwide in applications including Australasia, Europe, Asia and
North America.
