PLCs, I/O modules and HMIs
Control-system spares are ordered by the full manufacturer order code, not the product family name: a Siemens 6ES7 number, an ABB 1SAP code, a Schneider TM or BMX reference, or an Omron model string. The code fixes the I/O count, signal type, supply voltage and hardware revision. For processors and communication modules, the firmware version also matters — a replacement CPU on a different firmware may need the project re-downloaded. Legacy ranges are progressively phased out by their manufacturers; when a module is no longer available new, the realistic options are remaining distribution stock or the manufacturer's successor model, and the quotation states clearly which one is offered and what changes at installation.
Sensors and transmitters
Discrete sensors — inductive and capacitive proximity switches, photoelectric sensors, limit switches — are defined by sensing range, housing (M12, M18, M30), output (PNP or NPN, NO or NC, IO-Link) and connector. Process transmitters for pressure, temperature, level and flow add the measuring range, process connection (G½, ½" NPT, flange), wetted materials, output (4–20 mA, HART, fieldbus) and, in classified areas, the ATEX or IECEx certificate. Two sensors with the same family name can differ in every one of these attributes, which is why the order code from the nameplate is the single most useful piece of information in an RFQ.
Relays, power supplies and hazardous-area interfaces
Interface relays, timers, terminal blocks and DIN-rail power supplies from makers such as Finder, Phoenix Contact, Weidmüller and Omron are specified by coil voltage, contact arrangement and the matching socket or base — the socket is a separate part number and is often forgotten. Signals crossing from a hazardous area into the control room pass through intrinsically safe barriers or isolators (for example Pepperl+Fuchs or R. STAHL). These must be certified to IEC 60079-11 and their entity parameters must match the field device, so replacements are quoted to the original order code or to a verified equivalent with the same certification.
Pneumatics and hydraulics
Pneumatic spares — solenoid valves (3/2, 5/2, 5/3), cylinders, filter-regulator-lubricator units, push-in fittings and tubing from makers such as Festo, SMC, Parker and Airtac — are matched on function, port size, coil voltage and connector. Hydraulic filter elements are matched on the manufacturer part number, which encodes the filtration rating in microns, the filter media, the collapse pressure and the seal material (NBR or FKM). Fitting a cheaper element with the wrong rating or seal shortens pump and valve life, so equivalents are only proposed with the cross-reference shown on the quotation.
What to include in an automation RFQ
| Item | Must include | Often missed |
|---|---|---|
| PLC / I/O module | Full order code, firmware version | Whether a successor model is acceptable |
| Proximity / photo sensor | Order code, output type (PNP/NPN), housing size | Connector type and cable length |
| Process transmitter | Range, process connection, wetted materials | Hazardous-area certificate, HART requirement |
| Relay / power supply | Coil or supply voltage, contact arrangement | Socket or base part number |
| Hydraulic filter element | Manufacturer part number, micron rating | Seal material (NBR / FKM) |
| Pneumatic valve | Function (5/2, 5/3), port size, coil voltage | Manual override and connector type |
Frequently asked questions
Can you supply a discontinued PLC module?
Send the full order code and firmware version. We check remaining distribution stock for the original part and the manufacturer's designated successor, and the quotation states which one is offered and whether any wiring, firmware or project changes are needed.
Do you quote equivalent brands?
Only when equivalents are acceptable to you — tick the option on the enquiry form or say so in your RFQ. Exact parts and proposed equivalents are listed separately on the quotation, with the cross-reference.
Can you supply instruments for hazardous areas?
Yes. Tell us the zone, gas group and temperature class required; Ex-rated instruments, barriers and junction boxes are quoted with the manufacturer's ATEX or IECEx certificate for the specific model.
What speeds up a quotation?
The manufacturer and full order code from the nameplate, quantity, delivery location and required date. A clear nameplate photo resolves most ambiguities in one step.