Ask for Evidence, Not Assurance

An OEM fan manufacturer in China can look identical to a trading company on a website. The difference appears when you ask for specific quality records tied to your order. Below are the checks worth requesting during a fan factory audit and before you release a purchase order, together with the evidence each one should produce.

1. Fan Factory Audit: Follow the Production Route

Audit the process, not the meeting room. A walk-through should cover the melt furnace, the casting area, the heat treatment equipment, the machining shop, the balancing machine and the performance test bench. If a stage is missing, ask where it is subcontracted.

  • Melt furnace and charge records: is alloy identity confirmed before pouring?
  • Casting: are impellers cast in-house or bought from an outside foundry?
  • Heat treatment: is there an annealing furnace for stress relief and a T6 line for aluminium parts?
  • Balancing: is the balancing machine owned or rented? An in-house machine keeps rotor balancing inside the factory's own control loop.
  • Testing: does the test bench follow AMCA 210-07 or ISO 5801, and who calibrates the instruments?

SINDFAN owns its melt furnace, annealing furnace and balancing machine in Tianjin, so these stages can be inspected in a single visit.

2. Impeller Quality Control: Material and Casting

Impeller quality control starts before any machining. Ask for the alloy grade in writing and check it against the drawing. Aluminium impellers are commonly cast in LM6 or A356; both respond to T6 heat treatment, which raises strength and stabilises the casting. SINDFAN casts LM6 and A356 in-house and applies T6 heat treatment.

For marine or corrosive-duty impellers, ask about internal defect inspection. Radiography to ASTM E155 is a recognised method for detecting porosity and shrinkage in castings, and SINDFAN X-rays marine parts to this standard. Ask whether radiographic inspection applies to all castings or only designated parts, and request the film or digital images together with the report.

3. Balancing: Request the Report

Vibration complaints usually trace back to unbalance. Balance quality is specified by grade under ISO 1940; G4.0 is a practical target for many fan rotors. Ask two questions: is balancing performed on the impeller alone or on the assembled rotor, and does every rotor receive a report? SINDFAN balances every rotor to ISO 1940 G4.0 with a report. That report should identify the rotor, the balance grade, the machine used and the residual unbalance.

4. Performance Testing

Airflow, pressure, shaft power and efficiency should be measured under a recognised method — AMCA 210-07 or ISO 5801. Confirm whether the test runs on the actual impeller or a scaled model, where the test point sits relative to your duty point, and whether test data is issued per order.

5. Documentation and Delivery Terms

The document pack should match the physical shipment: material and heat treatment records, balancing reports, performance data and dimensional inspection results. Check when inspection happens relative to handover. As an example of the commercial framework, SINDFAN has supplied a USD 23,806.5 impeller order (PI Sin062, June 2026) on FCA Tianjin terms. Under FCA, the buyer takes over carriage and risk in Tianjin, so inspection and sign-off should be completed before that point.

Questions to Send Before Ordering

  • Which alloy is used, and is casting performed in-house?
  • Is T6 heat treatment applied, and how is it verified?
  • Is X-ray inspection used for marine parts, and to which standard?
  • What balance grade is specified, and is a report issued per rotor?
  • Which performance standard is followed, and at which test points?
  • Which documents ship with the goods?

Send your fan or impeller duty — airflow, pressure, temperature, medium and quantity — to SINDFAN on WhatsApp +852 9524 8434 or info@sind-tech.com, and we will confirm which of these checks apply to your order.