BS EN 3908 2017 pdf free download.Aerospace series — Nipples, lubricating, axial type, in corrosion resisting steel, passivated
This European Standard specifies the required characteristics and the tests for lubricating nipples of the axial type, in corrosion resisting steel, passivated. Annex A (normative) states the clearance space requirements for the coupling and uncoupling of the lubricating gun and the maximum permissible diameter of the lubricating gun barrel, together with installation thread requirements.
Lubricating nipples according to this European Standard are intended for use in aerospace assemblies, where regular lubrication of moving parts is required.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 2424, Aerospace series — Marking of aerospace products
EN 2516, Aerospace series — Passivation of corrosion resisting steels and decontamination of nickel base alloys
EN 9100, Quality Management Systems — Requirements for Aviation, Space and Defense Organizations
ISO 68 (all parts), ISO general purpose screw threads — Basic profile
IS0 413, Aircraft — Heads of lubricating nipples
ISO 965-2, ISO general purpose metric screw threads — Tolerances — Part 2: Limits of sizes for general purpose external and internal screw threads — Medium quality
ISO 2859-1, Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
STANAG 1135:2008, Interchangeability of fuels, lubricants and associated products used by the armed forces of the North Atlantic Treaty Nations 1 )
3 Required characteristics
3.1 Configuration – Dimensions – Masses
The envelope dimensions for the nipple head are shown in Figure 1, detail “Z” and are in accordance with ISO 413. The tip design of the nipple (face with the sealing ball) is left at the manufacturer’s option provided the profile remains within the envelope dimensions shown in figure 1 and the requirements of Clause 7 are met.
The dimensions apply after surface treatment.
A check valve (composed of a spring and ball) shall be located at the surface of the nipple to prevent the ingress of foreign matter into the nipple tip. Other internal design shall be at the manufacturer’s discretion provided the nipples meet the requirements specified in Clause 7.
3.2 Surface roughness
R a = 6,3 μm unless otherwise specified. The values apply prior to surface treatment.
The surface roughness of the thread will be as achieved by normal methods of manufacture.
3.3 Materials
Austenitic chromium-nickel steel; ultimate strength min. 550 MPa. See also 7.6.2.
The nipple head surface shall be case hardened to a depth of 0,08 mm to 0,13 mm to give a minimum hardness value of HV 533 (52 HRC). The nipple body shall withstand a tightening torque of 9 Nm without strain.
Material and surface treatment for the internal parts of the nipple shall be at the manufacturer’s option.
3.4 Surface treatment
EN 2516, process appropriate to the material
5 Marking
EN 2424, style F for products (see Figure 1) and style G for each packing
6 Technical specification
The lubricating nipples shall meet the requirements of this European Standard. For quality assurance requirements, see EN 9100.
7 Requirements and test methods
Acceptance tests shall be carried out for each inspection lot. Samples shall be selected from the inspection lots in accordance with the requirements of ISO 2859-1. For non-destructive tests “General inspection level” II and an AQL of 1,0 for sample size (n) shall be used (see Table 1). For destructive tests “Special level” S4 and an AQL of 1,5 for sample size (n) shall be used (see Table 2).
NOTE The requirements for “continuation of inspection”, “switching procedures” and “discontinuation of inspection” shall be in accordance with 9.2, 9.3 and 9.4 of ISO 2859-1.BS EN 3908 pdf download.