A Q-H PDF in a WeChat file named ISO9906-test.pdf is, more often than not, a catalogue plot from another diameter, another speed, or another factory. ISO 9906 is a test code with grades and tolerances. It is not a watermark you drop onto a brochure. This guide is how a buyer forces the curve to describe the impeller that will actually ship.
Five facts that must be on the sheet or it is not a test
- Impeller diameter as manufactured, in millimetres, not “max diameter” from the family nest.
- Speed of the test (r/min). 1450 and 2900 are different machines. Affinity-law scaling of a 2-pole plot onto a 4-pole motor is a quote trick, not a test.
- Liquid: clean cold water temperature. A curve run on 20 °C water is not your 80 °C mix or your 200 cP syrup.
- Standard and grade: ISO 9906 Grade 1B, 2B or 3B (or the GB/T 3216 equivalent you named). Grade 3B is the loose default on many Chinese commercial tests. If you paid for 2B, 3B is a failed hold point.
- Serial number of the tested pump, or an explicit statement that this is a typical curve of a geometrically similar unit — in which case it is selection data, not release data.
If any one of those five is missing, you are looking at marketing. KanBeng model pages show a flow/head envelope across trims. That rectangle is the opposite of a test: it is the cloud of possible cuts. Your order needs one cut.
How a recycled catalogue curve is built
Export sellers keep a library of family nests: six or seven impeller diameters on one axes set, a pretty BEP island, sometimes an NPSH inset. The quote engineer circles a duty with a red pen. That pen mark is not a measurement. Tells:
- File properties dated years before your PO, or a font that does not match the factory’s other documents.
- No shutoff head scatter, no power curve, or a power curve that never exceeds 0.9 × nameplate kW — someone drew the motor, not the pump.
- Duty sitting on the far right end of the largest impeller, where NPSHr is ugly and the factory would have offered a bigger hydraulic if this were real.
- Efficiency 78–82 % on a small end-suction that has no business there at that specific speed.
- The same PDF sent for ISW 50-160 and ISW 65-160 with only the header edited.
ISO 9906 grades, in buyer English
Grade 1B is tight (typically high-energy / guaranteed performance work). Grade 2B is a common industrial guarantee. Grade 3B is wider: more head and flow tolerance, easier to “pass” with a casual loop. GB/T 3216 tracks the same idea. If the contract says ISO 9906 and does not name a grade, the workshop will pick the grade they already stamp on every commercial pump. Write the grade. Write whether efficiency is guaranteed or indicated. Write the number of test points (shut-off, duty, plus one each side is a minimum; a single duty point is not a curve).
Power is where fake tests die
Demand shaft power or, if they only have a calibrated motor, input power plus a named motor efficiency. A “test” that shows flow and head but no kW is a tank with a valve. Compare absorbed power at duty to the motor nameplate. If absorbed power is 18.4 kW on an 18.5 kW motor with no service factor discussion, they are selling the nameplate, not the hydraulic. For 50 Hz versus 60 Hz, do not accept a 50 Hz curve with a verbal “it will be similar”. Either test at the nameplate speed or apply affinity laws in a signed calculation with the diameter held constant.
NPSHr is the second curve they hope you skip
NPSHr at BEP is useless if your duty is 120 % of BEP flow. Require an NPSHr curve, or at least NPSHr at the guaranteed duty and at 1.1 × duty flow. A single cell “NPSHr 3.2 m” copied from a catalogue is not a test point. If they cannot run NPSH on the loop, the document must say so, and your margin sits entirely on NPSHa you compute — which means the RFQ must include suction geometry, temperature and vapour pressure, not a hope.
Witness versus “we will email the curve”
Unwitnessed tests are still useful if the loop is calibrated (flow meter, gauges, torque or power analyser) and the serial is on the sheet. Witnessed tests are for the order that can kill a plant. Hold points: impeller diameter measured before the test (micrometer on the vane O.D., not a drawing), speed logged, duty valve set, photographs of the nameplate. If the factory offers to test “a sister pump” because yours is already painted, you are buying a sister, not yours.
What KanBeng will not do for you
The index will not generate an ISO 9906 sheet. If a model record lists GB/T 5657 / ISO 9906, that is a catalogue claim. Put the five facts, the grade, and serial binding in the RFQ. If the bidder cannot mark your duty on a curve that also shows diameter and speed, stop comparing prices.
Choose the curve for the job before comparing suppliers
A catalogue range helps you find a family; the next decision is which curve describes your installation. A building booster and a machine-tool coolant pump may both be centrifugal pumps, but they have different inlet conditions, installation dimensions and operating requirements.
Clean-water boosting and circulation
Compare the Shimge BL(T) inlet and stage requirements with the water-duty choices in the Dayuan profile. Ask for the exact hydraulic size, stages or impeller, inlet pressure and curve at the offered speed. A broad family envelope does not select a model.
Machine-tool tank cooling
The Fengchao QDYB2 and QDYB4 coolant families illustrate a different installation: a compact pump immersed in a tank. Request the separate curve for the chosen family, coolant composition, immersion length, minimum tank level and installation drawing.
If a variable-speed offer is the reason for the comparison, use the static-head and reduced-speed RFQ guide to separate system lift from friction. It explains what a bidder needs to show at normal and reduced demand, rather than applying a savings percentage to a catalogue maximum.
For the RFQ, put the required flow and total head in their own fields, name the candidate factory or series, and describe the suction arrangement and operating hours in Requirements. Ask for the selected curve, configuration and acceptance documents together. Send the duty and selection questions to the KanBeng desk.