Hydraulic cylinder identification and what the markings mean

Hydraulic cylinder identification starts by separating the information on the unit. A model code, a part reference, a serial number and a dimension do not describe the same thing. The model identifies a configuration, the serial number distinguishes an individual unit, and dimensions describe its geometry. Reading the field labels is more useful than choosing the longest number on the plate.

Keep the field name with its value

If the plate includes Model, Part No or Serial No, retain each label. The machine parts catalogue may also have its own cylinder reference. That reference need not match the cylinder manufacturer’s model designation.

For a cylinder fitted to Caterpillar or Komatsu equipment, distinguish the machine record from the markings on the installed unit. A previous replacement can explain a difference. The discrepancy should trigger a documentation check rather than an attempt to make the numbers match by editing one of them.

Read a code using its own catalogue

Parker’s 2H and 3H family catalogue separates fields for ports, seals, rod configuration and stroke. In that catalogue, stroke is specified in inches. A number from that field should not silently become a millimetre dimension or a separate part number.

The example demonstrates a method: identify the product family, find its coding rules and interpret each field in context. It does not provide a universal decoder. A different manufacturer, or another family within the same brand, needs the relevant documentation.

Distinguish bore rod diameter and stroke

Rod diameter describes the projecting rod. Bore refers to the internal working diameter of the cylinder, while stroke describes working travel. Overall assembly length is a separate measurement. An unlabelled note saying “diameter” or “length” leaves the reader unsure which dimension was measured.

Two cylinders with the same stroke do not necessarily have matching mountings, ports, rods or seal specifications. One matching dimension is therefore not enough to accept a replacement. A correctly labelled drawing supports the full application check.

Preserve uncertainty when a plate is damaged

Retain an overall plate photograph and any available machine-catalogue reference. Mark unreadable characters as unknown. A service drawing can add labelled dimensions and units, but an invented model code creates false certainty for everyone who later uses the record.

Belra Impex handles hydraulic cylinder and related component enquiries. Ordering a specific cylinder requires its catalogue part number. Include it in your enquiry and attach a photo of the identification plate if available. Maintenance and purchasing businesses in South Africa or West Africa can also contact Belra to discuss a supply partnership for recurring requirements.

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