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Tensioner Nuts & Bolts

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Tensioner Nuts & Bolts

  • Tensioner Nuts & Bolt is designed for direct replacement of Conventional Hex Nut & Bolt. No need of requirement of more space, just required to replace the hex nut. Normally in medium & heavy Industries, different bolted joints / connections are to be used which requires high Clamping Force. So, these require more effort in Tightening & Untightening.

Major two difficulties in Large size Bolt:

  • How to tighten the Bolt.
  • How to keep it tight.

Tightening a Bolt having an elastic stretch which keep the bolted assembly together. If the distance between Bolt head and nut is less, the elasticity will be insufficient. The better way to improve elasticity of a bolting system is by the use of our developed proven bolting system called Tensioner Nut Assembly.

  • Standard hex nuts used in such connections are tightened by the known tightening systems such as Ordinary hand, Torque wrench, Hydraulic or Pneumatic impact wrench, Thermal tightening & Sledge hammering methods.
  • These systems do not allow easily to tightening bolts of large diameter, to the stress level required for maintaining safe operations. However, when it comes to untightening, such as in maintenance, often creates problems and they cannot be dismantled by the way they have been tightened with, and the only solution is to torch cut, when corrosion distorted threads makes it impossible to unload the bolts.
  • NMTG Tensioner Nuts & Bolt is simplest, Inventive & cost-effective solution in Bolted joints. This joint can be tightened without requiring heavy tooling. Also higher sizes can be Installed or removed by Ordinary tooling with minimum workers. If Proper Installed, NMTG Tensioner Nuts & Bolt can provide more life as compared to Conventional Nut & Bolt. Also, If Application is Critical or Special then also NMTG can supply Customized model as per Application requirement.
  • Because of reducing friction on main thread as well as in bearing contact area, almost all theoretical preload can be achieved without fretting corrosion. Also main thread is Tensioned in pure Tension without any Torsion effect.
NMTG

Standard Tensioner Nuts Series

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NMTG

Compact Tensioner Nuts Series

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NMTG

Flexnuts (Reaction Nuts)
 

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NMTG

Tensioner Bolts
 

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NMTG

Protection Caps & Accessories

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NMTG

Hex Bolts & Studs
 

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Working Principle

  • In Tensioner Nut & Bolt, total clamping force is divided into no. of clamping screw. By tightening the clamping screws, a strong clamp force is generated. This clamping force is directed against a thrust washer and bolt having small friction diameter so it will help to create high clamping force with relatively little torque input.
  • The Clamp Force are transferred through nut body which is positioned on main threaded bolt or stud.
  • A Thrust washer is hardened so it is able to transfer the force while protecting the flange face.
  • The Clamp Force of many Clamping screws and the reaction force of the main bolt head create a Strong Clamping Force on the flange.
  • The Clamp Force from the Clamping Screw creates an equally strong Reaction Force in main Bolt.

Features & Advantages

Reliability
  • Tensioner nut bolt help to increase fatigue life of bolt joint.
High Preload
  • Tightening in Pure Tension allows on higher Preload on bolt versus other Tightening method.
Reusability
  • Preload can be transfer to everywhere under any condition with simple hand tools.
Easy Removal
  • Removal process is easy so that it will help to reduce down-time with compare to standard bolting system.
Less Requirement of Stuff
  • Because of only hand tightened tool required, it do not require multiple worker.
Reduction in Downtime
  • Tensioner bolt joint will never come loose in service. So it will help to reduce downtime.
No Thread Gailing
  • Even tightening in pure tension method eliminates thread galling that commonly occurs with direct torque method.
Elasticity
  • Added elasticity help to increase fatigue life of bolted joints.
Space Restriction
  • Tensioner bolt with multi clamping screws are easy to install in limited space.
Eliminate Vibration Loss
  • Achieved Preload is higher than Separating Force which will prevent bolt from vibration loss.
Accuracy
  • Even tightening will reduce the tendency of leakage or uneven loading of fasteners.
Higher Safety
  • There is only small hand tighten tool required for installation so safety is higher. So there will be no safety hazards from hydraulic pressure, heavy lifting, large tool, socket break etc.
Design Option
  • Requirement of space for tensioner bolt joint is less. So it will help to reduction in tooling size, reduction in handling size, material cost etc.
Customized Solution
  • Customized or Special Solution against any type of Environmental condition

Application

Mining:

  • Girth Gears
  • Pinion Gears
  • Split Gears
  • Gyratory Crusher
  • Hoist Motor
  • Bolted Segments

Gas Compression:

  • Crosshead Jamnuts
  • Piston end Nuts
  • Connecting Road Nuts
  • Compressor Cylinder
  • End Plates
  • Valve jack bolts

Wind Turbine

  • Gearbox to Generator Coupling
  • Rotor Blade to Gearbox Coupling
  • Front Main Bearing
  • Nacelle Yaw Bearing
  • Nacelle Frame
  • Tower Bolting
  • Foundation Bolting

Presses:

  • Press Column
  • Stamping Press
  • Cylinder Ram Bolting
  • Tie Roads
  • High Pressure Piping
  • Anchor Bolts
  • Die Cushions

Power Generation:

  • Boiler Feed pump head
  • Barrel Casing
  • Stop valve
  • Turbine Inlet Flange
  • Feed water heater
  • Servo Piston Nuts
  • Turbine Runner
  • Pelton Turbine nozzles
  • Turbine wheel to Shaft Bolting
  • Turbine Stop valve

Steel Mills:

  • Cranes
  • Hydraulic Cylinders
  • Pipe Mills
  • Universal joints
  • Tie rod Nuts
  • Coupling Bolts
  • Thrust Collars

Oil, Gas & Petrochemical:

  • Mud Pumps
  • Reactor Covers
  • Heat Exchanger Heads
  • Pipe Flanges
  • Turbine Control Valves
  • Couplings

Tensioner Nut VS Hex Nut Comparison

Tensioner Nut
VS.
Hex Nut

Tensioner Nut

vs.

Hex Nut

Just hand apparatus / Tools are required for any size tensioner nut.

 Tooling

Above 1” in or M24 Diameter, Hex nuts require expensive and potentially dangerous high energy tolling stuffs.

Necessity of space for tensioner bolt joint is less. So it will help to decrease in tooling size, decrease in handling size, reduction in material cost, etc.

 Design

Tooling necessities can cause issue with space limitation, awkward locations.

For same size of bolt, Higher Preload can be achieved in bolt due to pure Tension & added Elasticity will help to increase Fatigue life of bolted joints.

 Preloads

As size increases, the necessary torque increments by an intensity of three. In this way, it is difficult to achieve proper preload levels.

There is only small hand tighten tools required for installation so safety is higher. There will be no safety hazards from hydraulic pressure, heavy lifting, large tool, socket break.

 Safety

Accidental injury to fingers, hands, back, and face can happen when using basic / common bolting methods.

Utilizing air instruments and different workers can results in time and labour saving.

 Installation Times

Required set-up time for actual tightening for hex nut bolting techniques is higher which will result in longer Installation time compared to NMTG Tensioner Nut.

Removal process is easy so that it will help to reduce down-time with compare to standard bolting system.

 Removal Process

Above 1” in or M24 Diameter, Hex nut removal process is very tuff due to expensive and potentially dangerous high energy tolling required.

Even tightening in pure tension method eliminates thread galling that commonly occurs with direct torque method.

Thread Galling

During tightening process the thread slides. So in this manner galling and stud seizures are normal.

Tensioner bolt joint will never come loose in service. So it will help to reduce downtime.

Downtime

Removal process in Hex bolt is difficult because of jamming issue after long time. So downtime will be higher.

Advantages of Flex Nut

(Reactive Side Solutions)

Flexnuts for through hole applications

Flexnuts are used in combination with NMTG’s Tensioner Nuts and are designed to flex out at the bottom and flex in toward the top of the nut. This distributes the bolt load along many threads, adds elasticity, and prevents stress concentrations in the first few threads.

For through hole applications we have developed the flexnut, which is a reactive nut that is able to flex elastically. Putting a Flexnut gives the same advantages as the tensioner nut on the reactive side. Under load they flex at the bottom and at the top. This helps relieve stress concentrations and increases the fatigue life of the bolt. Since flexnuts are reactive nuts to be used opposite our tensioners, they are never torqued directly to achieve preload.

Advantages with NMTG Flexnuts

  • Under load they ensure an equal load distribution on the thread of the bolt/stud.
  • Adds elasticity in the joint.
  • Increases the fatigue life of the bolt/stud.
  • NMTG Flexnut meet all requirements of ISO 898-2. They therefore have the same strength as conventional hex nuts and can replace them 1:1.
  • Reusable: Flexnuts are entirely reusable. The bolted joint will not be damaged during tightening and loosening.
  • Compatible: Flexnuts meet all requirements of ISO 898-2. They can replace any conventional nut with the same strength class as long as they are only reactively loaded and are not used for active tensioning.
  • Durable: The more elastic a bolt is in relation to the clamped parts, the less stress it will be subjected to. Due to their flexing, Reaction Nuts reduce the load on the bolt and thus increase the durability of the bolted joint
  • Secure: Also the more elastic a bolted joint is, the less susceptible it is to untightening and self-loosening. The additional elasticity stored in the Flexnuts counteracts preload losses due to settling or creeping. This ensures that the bolted joint remains securely tightened.

The NMTG Flexnut offers decisive advantages over other products:

  • Hex Nuts

    • Conventional hex nuts are very rigid and have little elasticity.

  • Problem: In the thread the preload acts in tension, while an equally high compressive force is generated on the contact surface of the hex nut. As a result, the preload force is very strongly deflected in the first load-bearing threads and leads to an uneven load distribution. This is why bolts often break here.

    Advantage of the NMTG Flexnut: The NMTG Flexnut creates an almost even load distribution in the thread. The service life of the bolts is significantly increased!