How to identify a compressor part when you don’t have the part number

To identify a compressor part without a part number, send a clear photo of the frame and cylinder nameplates (manufacturer, model and serial numbers), two or three photos of the part with a ruler for scale, any numbers stamped on it, and the operating conditions. With that, a supplier can usually match the part to the unit’s original build specification.

A worn valve, a cracked packing case, a rod that needs replacing, and the part number is nowhere to be found. It happens often on older units: manuals go missing, stamps wear off, and packages change hands between operators. The good news is that a part can usually be identified from information you already have on site.

Start with the nameplate

Every compressor frame and every cylinder carries a nameplate. Photograph each one straight on, in good light, so every character can be read. The details that matter most:

• Manufacturer and frame model (for example a JGK/4 or a DPC-360)
• Frame serial number, which ties the unit to its original build specification
• Cylinder class, bore and serial number for cylinder-related parts
• Rated speed and stroke

If a nameplate is painted over or damaged, a photo is still worth sending. Partial information narrows the search a lot.

Photograph the part itself

Take two or three photos of the part from different angles, with a tape measure or ruler in the frame for scale. Include:

• Any stamped or cast numbers, even partial ones
• The mating faces and bolt pattern
• Overall dimensions you can measure safely: outside diameter, thickness, bolt circle

Note the service conditions

Equivalent parts are selected for the duty as well as the dimensions. A short note helps:

• Gas composition, especially H₂S or CO₂ content (sour service changes material requirements)
• Suction and discharge pressure and temperature
• Whether the unit is lubricated or non-lube

What you can expect back

With the nameplate, photos and service conditions, a supplier can usually identify the part and quote it. A good quote states, line by line, whether each part is OEM genuine (sourced through an independent channel) or a qualified equivalent, with lead time and any documentation available, such as a certificate of conformance.

Use the quote form: attach up to three photos or PDFs, and leave the part-number field empty if you don’t have one. We reply within 5–10 business days. Read also why compressor valves fail and compressor packing and rider bands.

CHR is an independent supplier and is not an authorized dealer of the manufacturers named. Brand and model names are used only to identify equipment.

Frequently asked questions

Where is the nameplate on a reciprocating compressor?

The frame nameplate is usually on the crankcase or frame side. Each cylinder has its own nameplate, normally on the cylinder body. Packaged units may also have a packager’s nameplate on the skid with the package serial number.

Can a part be identified from a photo alone?

Sometimes, for common parts on popular models. A photo plus the frame and cylinder serial numbers is far more reliable, because the same frame model can be built with different cylinders and options.

What if the unit has been modified since it was built?

Mention it. Cylinders, valves and packing are often changed over a unit’s life, so the original build specification may not match what is installed. Measurements and photos of the installed part then matter most.

Do I need the part number to order an equivalent part?

No. Equivalent parts can be selected from dimensions, materials and service conditions. See OEM genuine vs qualified equivalent parts.