Hydraulic Bolt Tensioner: How It Works

 For simpler and more accurate tightening of large-diameter stud and bolt assemblies, hydraulic bolt tensioners are mechanical fasteners that are utilized in place of normal bolts or hex nuts. Several bolt tensioners use manual or hydraulic techniques to apply torque. Devices that use hydraulics employ fluid force. Products that require manual power are turned using a hand tool such as a torque wrench. There are also hydraulic bolt tensioners that impart torque using different non-manual, non-hydraulic techniques. The greatest amount of rotating force that can be generated for all varieties of bolt tensioners is indicated by the torque rating. Thrust collar inner diameter and threaded diameter are additional crucial characteristics. To discover more about how hydraulic bolt tensioners operate, read the entire article.

How does it work? 

Large diameter bolts can be accurately and quickly tightened to high preloads using a hydraulic bolt tensioner. Like hydraulic torque wrenches, flogging spanners, or impact wrenches, it does not employ torque and does not call for the bolt or nut to be turned firmly.

More than 80% of the torque energy provided to the bolt or nut is used up by overcoming thread tension between the washer and nut, leaving less than 20% of the power to create applicable pressure in the bolt shank. Uneven stress in bolts that have been tightened to the same impact or torque wrench setting is caused by variations in this friction loss from bolt to bolt. An annular hydraulic jack that fits over the bolt and nut that has to be tightened is a hydraulic bolt tensioner. The jack applies pressure to the bolted joint while pulling on the bolt's end, which must be at least one diameter longer than necessary to accommodate the bolt tensioning tool.

A tension equivalent to the load produced by the hydraulic jack develops in the bolt's shank as a result of the jack's force being delivered directly to the end of the bolt. It is feasible to crank the nut with zero torque until it is tight while the jack is applying tension. When the hydraulic jack's load is relieved, a significant portion of the load is retained in the bolt's shank, depending on the diameter and length of the bolt.

Multiple bolts can be tightened concurrently to the precise and same preload using a group of bolt tensioning tools. To create a hydraulic ring main, flexible hoses with self-sealing quick connect couplings are utilized to join the bolt tensioning tools. Typically, a compressed air supply is used to pressurize the tensioning tools and ring main using an air-driven pump.


This is especially helpful for compressing gaskets in flanged connectors for pipelines or pressure vessels. A significantly better seal is produced by the gasket flowing into the surface imperfections of the flange due to the high load created by the numerous bolt tensioning tools being spread uniformly throughout the joint.


Why utilize hydraulic bolt tensioning?


  • It makes sure there are no leaks in the operations. Keeping the staff safe is more essential than saving money and time.


  • The necessary amount of compressive weight should be applied to the gasket or sealing surface in order to create a fastened assembly that is leak-free. Because tensioning is precise, quick, and safe, it is the best delivery method for this load.


  • It is accurate as bolt tensioning delivers the necessary dependability by applying accurate bolt loads to the joint.


  • Bolt tensioning, as opposed to bolt torquing, can reduce cross-talk and gasket compression and transmit simultaneous bolt load across the whole joint, which makes it quick. Additionally, tensioning significantly lowers the possibility of galling threaded fasteners, assisting in preventing delays and rework.


  • Tensioners are hands-free devices that reduce work-related accidents, make them safe.


Types of hydraulic bolt tensioning systems 


Bolt-tensioning systems come in two different categories. There are methods for simultaneously tensioning every bolt. Some people will tension half at once, then the other half right away.


The operation is sped up by tightening every bolt at once, however a damaged bolt may fail.


A damaged bolt won't immediately cause an issue when doing half and half because the other half is still in place. As a result, it is simpler to spot damaged bolts, swap them out, and get the right amount of stress.


Essentially the same principles apply to both varieties of hydraulic bolt-tensioner systems. They tighten the bolt by applying tension, slip over the stud, and remove the nut. The nut is tightened to the appropriate torque specifications after the desired tension level is attained.


Conclusion


Safety is crucial while using hydraulic tensioning. High pressure hydraulic fluid, which travels from the tensioner pump to the load cell and subsequently to the other tensioners, should be the main worry. The right safety steps, cleanliness and storage, should be ensured prior to use because a high-pressure fluid can cause serious harm. Any hoses or fittings should be replaced if it is worn out or broken.






Content Sources :- ABSGroup


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