BS ISO 5597:2018 pdf download – Hydraulic fluid power — Cylinders — Dimensions and tolerances of housings for single-acting piston and rod seals in reciprocating applications
5.2 Axial length The short axial length, L, as given in Tables 3 and 5, shall be adopted only after consultation with the manufacturer. Consultation with the manufacturer is recommended when making the appropriate selection from the available choices.
NOTE This document includes a choice of axial length for every nominal piston and rod diameter, the exception being cylinders conforming to ISO 6020-2 in which case only one length is provided (see Clause 1 and Tables 4 and 6). 5.3 Radial depth The larger radial depth (cross-section) of the seal housing, S, shall be chosen where higher stresses or wider tolerances are involved. Consultation with the manufacturer is recommended when making the appropriate selection from the available choices.
NOTE This document includes an alternative seal housing radial depth (cross-section) for most piston and rod diameters, the exception being at the upper and lower extremities of the diameter range as well as cylinder seal housings conforming to ISO 6020-2, in which case only one radial depth is provided. 6 Dimensions and tolerances NOTE See ISO 3320. 6.1 Piston seal housing dimensions
6.1.1 Illustrated examples of piston seal housing dimensions are given in Figures 1 and 2.
6.1.2 Piston seal housing dimensions (except in the case of cylinders conforming to ISO 6020-2) shall be selected from Table 3.
6.1.3 Piston seal housing dimensions for use with cylinders conforming to ISO 6020-2 shall be selected from Table 4.
6.2 Rod seal housing dimensions 6.2.1 Illustrated examples of rod seal housing dimensions are given in Figures 3 and 4.
6.2.2 Rod seal housing dimensions (except in the case of cylinders conforming to ISO 6020-2) shall be selected from Table 5.
6.2.3 Rod seal housing dimensions for use with cylinders conforming to ISO 6020-2 shall be selected from Table 6.
6.3 Radial seal space tolerances 6.3.1 Reference shall be made to Table 7 for radial seal space tolerances.
6.3.2 References shall be made to NOTES 1 and 2 of Table 7 for the formulae for calculating tolerances on d (see Figures 1 and 2) and D (see Figures 3 and 4).
NOTE 1 The equations and values shown in Table 7, when used in conjunction with ISO 286-2 limits of D H9 and d 3 f8 (for the piston case) or d f8 and d 5 H9 (for the rod case), in most cases result in tolerances within the span of d h10 and D H10, respectively.
NOTE 2 If alternative limits to those given in NOTE 1 are selected for D and d 3 (for the piston case) or d and d 5 (for the rod case), then the use of the formulae will maintain the necessary radial seal space limits, i.e. any relaxation of tolerance on one housing diameter will be compensated by a tighter tolerance on the other diameter.
6.4 Housing length A tolerance of +0 25 , mm shall be used on the length of the housing. 0 7 Extrusion gap The extrusion gap is determined by the diameter (d 4 or d 3 ) of the adjacent metal components behind the seal. It is recommended that details concerning d 3 (see Figures 1 and 2) and d 4 (see Figures 3 and 4) be subject to consultations between the housing designer and seal manufacturer.
NOTE 1 Maximum value for the extrusion gap is achieved when the piston or piston rod is in contact with one side of the cylinder or bearing, respectively.
NOTE 2 The extrusion gap for piston seals is further widened by the expansion of the cylinder due to internal pressure.
8 Surface roughness 8.1 General The surface roughness of the seal housing and any mating part has a significant impact on the life and sealing performance of the seal. Where surface roughness measurements are taken, it is recommended that instruments complying with ISO 3274, including an electric wave filter, be used.
8.2 Sliding and static sealing surfaces
8.2.1 Unless otherwise agreed the roughness values shall be in accordance with Table 1.
8.2.2 Unless otherwise agreed, the material ratio Rmr of housing surfaces that are in mating contact with the seal should be between 50 % and 80 % at a profile section level (Rδc) of 25 % of Rz, from a reference level, C0, of 5 % Rmr (in accordance with ISO 4287:1997, 4.5.4).
8.2.3 For some seal designs, a minimum surface roughness of 0,1 μm Ra may be required for the sliding sealing surface as the surface otherwise may be too smooth to provide adequate lubrication for the seal.
8.2.4 Exceptional service conditions may necessitate the selection of other grades of surface roughness, in which case they should be subject to agreement between manufacturer and user.
8.2.5 All surfaces against which a seal operates should be free from chatter marks and scores along the operating axis of the seal.