Sealing Washer 21x28x1,5mm

Washer 42033 is a copper sealing washer to DIN 7603A with dimensions 21×28×1.5mm – internal diameter 21mm, external diameter 28mm, thickness 1.5mm. It seals threaded connections through face compression of the soft copper between the threaded component surface and its seat – copper deforms plastically when tightened and fills microscopic surface irregularities, forming a permanent barrier against the working fluid. Used at valve plugs, fittings and hydraulic connections in the Kranzle pressure washer pump.

Application

The washer is seated under the head or flange of a threaded component, between its face surface and the seat in the valve block or pump housing. When the threaded component is tightened, the copper washer compresses and permanently deforms, sealing the space between two metal surfaces. Unlike an O-ring or rubber gasket, a copper washer is a single-use seal – once compressed it retains its deformed shape and does not return to its original thickness of 1.5mm.

Replaced at every disassembly of the connection it was seated under, or when a leak appears at a face connection despite the threaded component being correctly tightened.

Symptoms – when to replace

• Water or oil leak at a face connection despite the plug or fitting being correctly tightened – the washer is permanently flattened and will not seal on reassembly.
• Washer visibly deformed, thinned or cracked on removal – not suitable for reuse.
• Corrosion or pitting on the washer surface – particularly with prolonged contact with aggressive cleaning agents or water at extreme pH.
• Washer thin and flat after removal – the material has exhausted its capacity for plastic deformation sealing.

How to select the right part

Three dimensions must match simultaneously: internal diameter 21mm, external diameter 28mm and thickness 1.5mm. The internal diameter of 21mm matches the threaded component the washer seats under – too small will not pass over the thread; too large will not seal the face surface. Thickness 1.5mm defines the material available for deformation – a washer that is too thin may not provide sufficient compression at the nominal tightening torque.

Standard DIN 7603A, variant A = copper. When ordering a replacement, confirm the material – the same DIN 7603 standard also covers aluminium washers (variant C) with identical geometric dimensions. Copper is softer and seals better at lower tightening torque than aluminium.

Compatibility

Copper sealing washer DIN 7603A for threaded connections in Kranzle pressure washer pumps. Dimensions 21×28×1.5mm. Verify the exact compatibility range – which fittings and plugs it seals – by reference number 42033 and the dimensions of the threaded component in the specific connection.

[faq]

Can a DIN 7603A copper washer be reused after disassembly, or must it be replaced every time?|A copper washer is standardly replaced at every disassembly – once compressed it is permanently deformed and will not seal again at the same tightening torque. Reconditioning by annealing (heating to red heat and slow cooling) is possible, which restores copper softness and plastic deformation capacity. In service conditions annealing is feasible, but fitting a new washer is more reliable and cheaper – the cost of one washer is incomparably lower than the risk of a leak when reusing the old one.

How does a DIN 7603A copper washer differ from an O-ring, and when is each used?|An O-ring seals through elastic rubber compression in a groove – it works under motion and is reusable. A copper washer seals through plastic metal deformation between two flat surfaces – it works exclusively statically and is a single-use component. An O-ring requires a precisely machined groove with strictly defined geometry. A copper washer requires only flat face surfaces on the threaded component and its seat. In threaded connections without an O-ring groove, a copper washer is the standard face sealing solution.

Can washer 21×28×1.5mm be replaced with a standard steel washer of the same dimensions?|No – steel is too hard to deform plastically at the normal tightening torque of a fitting or plug. A steel washer will not seal the microscopic surface irregularities of the face surfaces and leakage at the connection will be inevitable. Copper is specifically used in DIN 7603A washers precisely for its softness – it deforms at a tightening torque typical for hydraulic fittings without requiring excessive force.

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