WHY REPLACE FITTED BOLTS WITH EXPANSION BOLTS?

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Coupling bolt connections of gears and shafts, as used in wind turbines, turbines of hydroelectric power plants, gas turbines or in drive technology in general, pose a major challenge for technicians and engineers already in the planning phase. Conventional fitted bolts are traditionally used in order to transmit the greatest possible transverse forces through positive locking. This contradicts the interpretation of the connection, which assumes a clearance-free form-fit.

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To achieve a clearance-free form-fit, time-consuming and costly additional measures are often required, such as freezing in order to press-fit bolts. Even with careful preparation, it often turns out during assembly that the fitted bolts and bores do not match because the required manufacturing tolerances cannot be achieved. The bores then have to be laboriously reworked on-site. Despite all efforts to achieve a perfect form-fit, clearance reappears in the connection during pre-tensioning, as the fitted bolts contract radially due to transverse contraction. Typically, this is not apparent to the user and leads to micro-movements in the joint under high loads. Even minimal shifting causes the fitted bolts to tilt in the bore. As a result, the coupling flanges are subjected to extreme localized stresses, which can lead to plastic deformations. These increase the clearance in the connection which leads to greater movements in the joint and further increases the clearance - a vicious cycle.

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In worst case, a complete failure of the connection occurs, which can cause significant damage to machines and equipment. Disassembly of the connection is complicated due to the tilting of the fitted bolts. If the fitted bolts are removed by force, the bores in the coupling flanges may be damaged, so that reworking is necessary. As a result, this leads to the problem that the original fitted bolts no longer match with the bore dimensions and have to be re-produced.

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HEICO-TEC® Expansion Bolts are the perfect product solution for connecting large and rotating couplings - precise, reliable, and quickly assembled!

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• Optimal alignment of components

• Adapts perfectly to the bores due to radial expansion

• No expensive and time-consuming reboring of holes or new fitted bolts

• Easy to handle – even for non-specialist users

• Quick assembly

• Reusable

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HEICO-TEC® Expansion Bolts are customized to your specific application and precisely tailored to your requirements. Whether you prefer the compact series of HEICO-TEC® Tension Nuts due to limiting constraints, or you wish to optimize the product lifespan of the bolt by using an elastically resilient HEICO-TEC® Reaction Nut, or want to protect your connections against self-loosening, the variety of options is nearly unlimited.

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We are also please to assist you with all questions related to corrosion protection, ensuring that your expansion bolts remain durable and reliable despite adverse environmental and weather influences. In this way, you ensure that your components stay safe and ready for long-term use. In cooperation with you, we will design the perfect solution for your application!

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Click here to watch the video which shows the application of our through-bore expansion bolt in a marine propulsion system.