Every pump quote starts with the same question: what exactly do you have? The fastest answer is bolted to the pump. A readable nameplate photo lets a supplier identify the unit, run the cross-reference, and price a replacement, often the same day. A quote request that says "big Goulds pump, maybe 20 years old" starts a round of back-and-forth that can add days.
Here's what each field on the plate means, and how to photograph it so it does the work for you.
Manufacturer and Model
The model number is the anchor. It identifies the product family, and with it the casing pattern, bearing frame, and parts list. Even for discontinued lines, the model number is what lets a supplier trace the design to a current equivalent, the starting point for any obsolete equipment search. Record it exactly, including suffixes and dash numbers; a single letter can distinguish two different bearing frames.
Size: What 3×4-13 Actually Means
Most centrifugal pump sizes follow the pattern discharge × suction × nominal impeller, in inches. A 3×4-13 pump has a 3-inch discharge, a 4-inch suction, and a casing that accepts impellers up to roughly 13 inches in diameter. This one field tells a supplier the flange sizes your piping expects and the hydraulic family the pump belongs to. Two manufacturers' 3×4-13 pumps built to the same standard are strong candidates for interchange, which is why size is one of the first fields we check against our centrifugal pump stock.
Impeller Diameter
The casing accepts a range of impeller sizes; your pump was shipped with one specific trim, and that trim sets the actual performance. A 13-inch casing with a 10.5-inch impeller behaves very differently from the same casing at full diameter. If the plate shows both a maximum and an actual diameter, record the actual. This is the field most often missing from quote requests, and it's the difference between "we can quote the pump" and "we can quote your operating point."
RPM
Speed places the pump on its curve family. Most industrial units run at nominal 1,750 or 3,500 RPM (4-pole and 2-pole motors on 60 Hz power). The same pump at the two speeds delivers radically different flow and head, so a replacement matched on model but not speed is not a match.
GPM and Head: The Rated Point
Flow (GPM) and head (feet) on the plate describe the duty point the pump was sold for. Two cautions: first, head is in feet of liquid, not PSI, the conversion depends on the fluid's specific gravity. Second, the plate shows the original rating, not necessarily what your system does today. If throttling valves, line changes, or process drift have moved the operating point, tell your supplier; matching a replacement to a stale rating repeats a twenty-year-old sizing decision.
Serial Number
The serial number is the pump's birth certificate. Many manufacturers can pull the original build record from it, impeller trim as shipped, materials, seal configuration, even the original purchase order, long after the model itself is discontinued. When a plate is partly illegible, a readable serial number alone can be enough to identify the unit.
Materials
Codes like CI (cast iron), DI (ductile iron), 316SS, or CD4MCu describe the wetted materials. This is a chemistry decision, not a preference: a replacement in a lesser material may bolt in perfectly and fail in months. If the plate lists a material code you don't recognize, photograph it anyway, decoding it is your supplier's job.
Photo Tips That Save a Day of Email
- Wipe the plate first. Thirty seconds with a rag recovers fields that a camera flash cannot.
- Shoot straight-on and fill the frame with the plate. Angled shots distort stamped characters.
- For stamped (not printed) plates, light from a low angle. Raking light throws shadows into the stamping and makes it legible.
- Take a second photo of the whole pump and motor from the side. Configuration questions, close-coupled or frame-mounted, coupling guard, baseplate, answer themselves in one wide shot.
- Photograph the motor nameplate too. Horsepower, frame size, voltage, and phase decide whether a replacement can reuse your motor and starter.
- If the plate is gone, shoot the casting numbers on the volute and any stamped numbers on the bearing frame.They often identify the family when nothing else can.
Frequently Asked Questions
What information do I need from a pump nameplate to get a quote? At minimum, a supplier needs the manufacturer, model number, size, impeller diameter, RPM, and materials of construction. A clear photo of the full nameplate typically captures all of this at once, along with the serial number if available.
What does a pump size like 3×4-13 mean? It follows the pattern discharge × suction × nominal impeller, in inches. A 3×4-13 pump has a 3-inch discharge, a 4-inch suction, and a casing sized to accept impellers up to roughly 13 inches in diameter.
Why does the serial number matter if I already have the model number? The serial number can unlock the pump's original build record, including the exact impeller trim, materials, and seal configuration as shipped. This is especially valuable for discontinued models or when the nameplate is partially illegible.
What if I can't read the nameplate at all? Look for casting numbers on the volute or stamped numbers on the bearing frame. These often identify the pump family even when the plate itself is missing or illegible.
Is the flow and head rating on the plate still accurate for my system today? Not necessarily. The plate shows the original rated point at the time of manufacture. If your system has changed over time, throttling valves, piping changes, or process drift, your actual operating point may differ from what's stamped on the plate. Let your supplier know if this is the case.
