Hydraulic Nut PG9

Axial Bolt Tensioning using High-Pressure Hydraulic

Cost-reducing - Powerful - Reusable

Hydraulic Nuts do not require a thread projection as Bolt Tensioners do and, therefore, can be used in older constructions to replace conventional torque wrenched bolt connections. For large bolt connections in particular, this eases work and increases the safety of the tension force. Compared with Bolt Tensioners, Hydraulic Nuts enable quicker changing times for connections that need tightening and loosening on a regular basis. This speeds up checking load forces.

The distinguishing feature of the Hydraulic Nuts of product group 9 is that an axial force is produced by hydraulic pressure and is maintained for a reasonably long period of time.

HM Grundstellung — Basic setup
Screw the Hydraulic Nut (HM) on the bolt to be pretensioned, and down to the flanges' surface. A hydraulic high-pressure generator pumps the oil through a high-pressure hose into the space between cylinder and piston. The hydraulic pressure rises.

HM Zu spannende Schraube — Bolt to tension

HM Dehnung und Stauchung — Bolt elongation

Through the rising pressure and the resulting axial force, the bolt is elongated and the flange parts are compressed. The lock nut is lifted off the cylinder. When the preset pre-tensioning force is achieved, the pressure supply is stopped.

HM Beidrehen der Sicherungsmutter — Screwing the lock nut

The pre-tensioning force has been achieved and the lock nut is turned by hand down to the stop face of the cylinder. Thus, the pre-tensioning force is maintained within the screw joint and the hydraulic may be released. The Hydraulic Nut remains on the bolt connection.

Advantages

Capability to start simultaneous tensioning at multiple points

„Crossover-tightening“ of several bolts at several points is no longer necessary, since SCHAAF SSV and HM offer the possibility of tightening all the bolt connections simultaneously with exactly the same tensioning force. This also applies when increasing the tensioning force.

Start of tensioning independently of tensioning path

As opposed to thermal screw starting procedures, SCHAAF SSV and HM make it possible to eliminate different gaps between individual components. Each bolt can be tensioned with exactly the same force and not over the same distance!

Quickest test capability at any time

SCHAAF SSV and HM make it possible to apply a residual tensioning force by means of test force stress application in order to determine if any settling of the screw may occur, and if so, to eliminate it.

Universal application

With a compact unit and the ability to interchange the component parts relating to the size of the bolt, SCHAAF SSV can also be used for other thread sizes.

Saving of time

SSV and HM will dramatically save time required for tensioning applications. This effect increases for higher tensioning forces, larger bolt thread diameters and also the installation of several SCHAAF SSV or HM. Time savings up to 99% are possible! It is no longer necessary to apply large torque by hand. There is a number of handling features available, designed to make work easier with SCHAAF Bolt Tensioners and Hydraulic Nuts, especially when it comes to large dimensions.

Features HM PG9

hydraulic pre-tensioning force application for short bolt threads
light construction type

More Hydraulic Nuts

A HM of product group 9 is characterised by the fact that an axial force is generated and can be maintained by pressurisation.

A HM of product group 10 is characterised by the fact that the pre-tensioning force transmitted by an annular piston is maintained by means of a mechanical counter-holder without leaving the HM permanently pressurised.

A HM of product group 11 is characterised by the fact that the pre-tensioning force transmitted by a stepped piston is maintained by means of a nut part separate from the pressure cylinder, without leaving the HM permanently pressurised.

A HM of product group 12 is characterised by the fact that the pre-tensioning force transmitted by a stepped piston is maintained by means of a mechanical counter-holder without leaving the HM permanently pressurised.

A HM of product group 13 is characterised by the fact that several HM are integrated as a compound in or on a ring or similar and thus several bolt threads can be clamped simultaneously.

Versions

In addition to a number of standardized Bolt Tensioners and Hydraulic Nuts, SCHAAF has already delivered thousands of customized axial Bolt Tensioners. The Design on Demand CAD system allows to realize customer solutions very quickly. Based on axial pre-tensioning technics, a number of patented, specialized solutions have been developed during the last years. Bolt Tensioners, Hydraulic Nuts and ExpaTen, as well as the A-Loc and EcoRolls, both developed especially for rolling mills, all represent a 100% system solution with SCHAAF’s accessories such as high-pressure hoses and high-pressure generators.

Areas of Application

The application areas for Bolt Tensioners and Hydraulic Nuts are unlimited. The great amount of user solutions have resulted in a great number of various designs. For this reason it is not always possible to classify all Bolt Tensioners and Hydraulic Nuts into a specific product group. For example, the tensioning force can be transmitted by a thread or a bayonet. Please contact us for your special application.

Quality Assurance

All Bolt Tensioning Tools and Hydraulic Nuts are checked for material quality, dimensional accuracy, proper operation, and pressure resistance. They are subject to quality assurance measures during order execution and delivered with detailed documentation.

Services

SSV and HM are, of course, delivered packaged, ready for installation and operation. SCHAAF SSV and HM are user-friendly, reliable and are manufactured in accordance with the highest level of technical know-how. Our highly-motivated staff will be pleased to train your personnel, in situ or at our works, in the general handling of high-pressure equipment.