Spacer sleeves: more grip length for reliable preload

A spacer sleeve is a tubular section that sits on the shank of a reduced-shank bolt between the nut and the component. It artificially extends the grip length of the joint: the bolt becomes longer without the components having to be thicker. Because a long bolt stretches further under the same force, the joint stores more elastic energy. Settling of the gasket, creep at high temperature or differing thermal expansion of bolt and casing then take away only a small part of the preload. Spacer sleeves are standardised in DIN 2510-6 as part of the system of reduced-shank bolted joints.

Where spacer sleeves are used

High-pressure plants in the chemical industry, flanged joints on steam turbines and steam lines, reactor covers and autoclaves, large compressors and hydraulic presses; wherever leak-tightness is required under changing temperatures over long service lives. The spacer sleeve is often part of a bolting assembly consisting of a reduced-shank bolt or stud, spacer sleeve and nut made of the same material, so that all parts expand equally.

What production requires

Spacer sleeves are turned parts with plane-parallel end faces and a defined wall thickness, often with an internal contour, collar or wrench flats; the end faces must be perpendicular to the axis so that the nut does not bear on one side only. The materials match the bolt: quenched and tempered steels, creep-resistant steels such as 21CrMoV5-7 or austenitic stainless steels. RS Randack turns spacer sleeves up to 300 mm in diameter and supplies them together with the reduced-shank bolts, tested and documented in one certificate, with ultrasonic testing of the raw material and third-party inspection on request.

What you should specify

Drawing, material, length, inside and outside diameters with tolerances, surface finish of the end faces, associated bolt and nut, certificate type.