SIST EN 2138:2001

SIST EN 2138:2001 is a Slovenian standard from SIST for aerospace-series flat washers in steel with cadmium plating. It specifies the characteristics of these washers for aerospace applications, with a maximum operating temperature of 235 °C. The washers are intended mainly for use under nuts, and use under bolt heads requires compatibility to be checked. It is identical to EN 2138:1999.

What does SIST EN 2138:2001 specify?

SIST EN 2138:2001 specifies the characteristics of flat steel washers, cadmium plated, for aerospace use. In practice, it is the product standard a designer, buyer, or inspector uses when selecting this washer type for a joint.

The scope ties the standard to a defined service limit and a defined application:

• Maximum operating temperature: 235 °C
• Primary use: underneath nuts
• Additional use: underneath bolt heads only after checking compatibility

That matters because the washer has to suit both the environment and the joint design. A washer that meets this standard is meant for aerospace assemblies, where material, coating, and installation position all need to match the intended service.

What are the key requirements of SIST EN 2138:2001?

SIST EN 2138:2001 focuses on a small set of practical conditions that define when the washer is suitable.

• Steel base material - The washer is specified as being in steel. For users, this means the part choice is not generic: the base metal is part of the specification and should match the assembly design and procurement description.
• Cadmium plating - The surface finish is cadmium plated. In practice, this is the specified protected form of the washer, so purchasers and incoming inspectors should check that the supplied parts match the plated version named in the standard.
• Aerospace application - The washer is intended for aerospace applications. That tells engineers and buyers to treat it as a controlled aerospace fastener item, not a general-purpose hardware washer.
• Maximum operating temperature of 235 °C - The standard sets a temperature limit for use. For design and maintenance, this means the washer should only be selected where the joint temperature stays within that limit.
• Primary installation under nuts - The standard says the washers are intended mainly for use underneath nuts. That is the normal use case and helps avoid misapplication during assembly planning.
• Use under bolt heads needs compatibility checked - If the washer is used under bolt heads, compatibility must be verified. In practice, this means the assembler or engineer should confirm the joint arrangement before approving that application.

Who uses SIST EN 2138:2001?

SIST EN 2138:2001 is used by aerospace design engineers, fastener specialists, buyers, quality teams, and suppliers of aircraft hardware. They use it to specify the right washer, verify what is acceptable on receipt, and decide whether a washer can be used in a particular joint.

It is also useful for anyone writing a purchase description, inspection plan, or assembly instruction for aerospace fasteners. The standard gives a common reference for the washer type, coating, temperature limit, and intended installation position.

What does the SIST EN 2138:2001 document contain?

SIST EN 2138:2001 contains the product specification for flat, steel, cadmium-plated washers for aerospace applications. The document defines the washer’s intended use and its service temperature limit, so it can be applied consistently in design and procurement.

The front matter identifies the national publication as identical to EN 2138:1999 and classifies it under washers and other locking elements. The technical content is centered on the washer characteristics and the note about where it is normally used in an assembly.