What is a hydraulic nut and what is it used for?
It is a permanent fastening element that axially tensions the stud with hydraulic pressure up to the target pre-load and then mechanically locks that load in place. No torque is applied; pre-load is achieved directly and repeatably.
How is a hydraulic nut different from tightening a conventional nut with torque?
With torque tightening, friction uncertainty reduces pre-load consistency and can cause thread galling or losses from settling. A hydraulic nut applies no torsion and achieves consistent pre-load within a ±5–10% band independent of friction; friction/lubrication uncertainty is eliminated, and the same consistency is maintained across multi-nut applications.
How does the HHN series hydraulic nut work?
The nut is first threaded onto the stud and connected to the pump line. Following the principle P = F / A, a tensile force develops across the piston area and the stud elastically stretches. The locking ring/collar is then turned to mechanically lock the load in place; once the pressure is released, the pre-load is retained in the nut.
How is elastic elongation (ΔL) calculated?
It is calculated with the basic relationship ΔL = (F × L) / (A × E), where F is the tensile force, A is the effective piston area, and E is the modulus of elasticity, with ΔL representing the elastic elongation.
What is the working pressure and load capacity of the HHN series?
The series operates at working pressures up to 1,500 bar. The models in the model table, from HHN-M33 to HHN-M180, cover a load range of 27.0–797.6 tons (270–7,950 kN).
What bolt/stud sizes do you manufacture hydraulic nuts for?
The standard model table covers the M33–M180 bolt range. Other sizes in the M24–M32 and M181–M200 range are manufactured to order upon request.
How do I select the right HHN model?
When you share your stud size, target pre-load and operating environment details, we provide a calculated model recommendation. The model table lists code, bolt size, hydraulic area, load (kN/tons), outer diameter and height values for comparison.
Is the hydraulic nut installed permanently, and how long does installation/removal take?
Yes, it is a permanent fastening element; it is not used like a tool and then removed — it stays in place on the part and can be re-adjusted during periodic maintenance. Installation and removal are completed within minutes using the pump, even in confined spaces.
Which industries and applications is the HHN series used in?
It is used in pressure vessel and flange connections in petrochemical plants, refineries and power plants; in press fits and large bearing housings for turbines and compressors; in steel and paper industry equipment in the shipbuilding and mining sectors; and in defense industry applications requiring high safety.
Do you provide maintenance/repair service and spare parts support for your hydraulic nut products?
Yes. We carry out maintenance and repair of the products we manufacture at our own facility — once you send us your faulty unit, we manage the repair process after inspection. We also manufacture original spare parts on request for the models we produce; we don't maintain a separate spare parts catalog, but you can contact us directly for the part you need.
What is the difference between a hydraulic nut and a hydraulic bolt tensioner?
Both create preload by pulling the stud axially. A bolt tensioner (HRT) is an installation tool: it is removed after tensioning and the nut is locked in the conventional way. A hydraulic nut (HHN) stays in place as part of the joint and holds the load with its own locking ring. Hydraulic nuts are preferred for joints that are opened often or are hard to reach; bolt tensioners are preferred for large numbers of standard joints.
Which pump and hoses does a hydraulic nut work with?
The HHN series is designed for 1500 bar working pressure. It is used with a 1500 bar hydraulic pump, a 1500 bar high-pressure hose and a pressure gauge. Use the system selector to put together a complete set.
Is it the same as a bearing mounting hydraulic nut?
No. Bearing mounting (drive-up) nuts are used to drive a bearing onto a tapered shaft. The HHN series is made to preload bolts and studs and hold that load permanently.
Do you supply customers outside Türkiye?
Yes. We manufacture in Ankara, Türkiye, and supply industrial customers abroad directly. Quotations are prepared in English.
What is the delivery time?
Delivery time depends on the model, size and quantity, and whether the size is a catalogue or a custom design. We confirm it in writing with each quotation.
