A pre-shipment inspection is not a single document. It is a sequence of checks performed while the vessel is still at the works, before it is packed, before it is loaded, and while there is still time to correct something. We are an independent sourcing and engineering office in Zibo, Shandong. We source glass-lined, stainless steel and PTFE-lined reactors from 50 to 30,000 L. We do not own a factory. This is the 12-point checklist we walk through for a buyer who cannot be on site.
Use it as written. If an item cannot be verified, it is not a pass. A vessel can be 99 % correct and still fail at commissioning because a nozzle is 15 mm off or a mechanical seal was run dry.
1. Confirm the vessel against the signed drawing and service media
Start with paper. Match the model, nominal and actual volume, design pressure in MPa, design temperature in °C, operating temperature in °C, heat-transfer area in m², motor kW and speed in r/min to the approved drawing. Confirm vessel type: open with removable cover or closed with integral head. For glass-lined vessels, confirm the high-voltage test figure in kV and glass lining thickness in mm. Check thermal shock limits: cold shock ≤ 110 °C, heat shock ≤ 120 °C. Confirm the media list. Glass-lined vessels are not suitable for hydrofluoric acid, fluoride-bearing media, phosphoric acid ≥ 30 % above 180 °C, or strong alkali above pH 12 / 100 °C. If the service media falls outside the listed range, stop and resolve it before inspection continues.
2. Check the nameplate and traceability
The nameplate must be readable and permanently fixed. It should carry the model, serial number, design pressure, design temperature, volume and works identification. Cross-check the serial number against the material certificates and the inspection record. Do not accept a plate that was stamped after painting without a clear surface. A missing or mismatched serial number is a paperwork defect that becomes a spare-parts problem later.
3. Verify material certificates for the product-contact shell
For stainless steel vessels, confirm the shell material against the drawing: carbon steel, 304 / 316L, titanium, duplex stainless, Hastelloy or clad plate. Read the mill certificates for heat number, grade and chemical composition. For PTFE-lined vessels, confirm the shell material and the lining material: PFA, PTFE, ETFE (F40), ECTFE (F30) or FEP (F46). Check whether the lining is spray or rotational coating, as stated on the drawing. For glass-lined vessels, the steel substrate is not the wetted surface, but the lining thickness and high-voltage test record still matter.
4. Measure glass lining thickness at fixed points
Glass lining thickness is given in mm on the drawing. Measure it at the same points on every vessel: shell, head, nozzle necks, baffle welds and manway. Use a calibrated magnetic or eddy-current gauge suited to the lining. Record the lowest reading, not the average. If the drawing specifies a minimum, the lowest reading must meet it. Thin spots near welds and nozzle openings are where defects start. Photograph the gauge reading and the location.
5. Witness the high-voltage test on the glass lining
The high-voltage test, often called the spark test, applies voltage to a probe while the shell is earthed. A continuous lining does not conduct. A break that reaches the steel produces a spark and an alarm. Confirm the test voltage in kV against the drawing. Do not ask for a higher voltage than specified to be safe: too high can damage sound glass. Do not accept a lower voltage. Watch the probe path. The test should cover the full wetted surface, including nozzles, manway and baffles. Record any defect, its location, and the repair method.
6. Inspect PTFE lining continuity and thickness
For PTFE-lined vessels, check the lining material and colour against the drawing. Look for pinholes, blisters, scratches and incomplete coverage at flange faces, nozzle bores and weld seams. If the drawing calls for a spark test on the PTFE lining, witness it at the specified voltage. Otherwise use a thickness gauge and visual inspection. Confirm gaskets and fasteners: PTFE and rubber-encapsulated PTFE gaskets, with galvanised, stainless or fluoropolymer-lined bolts. PTFE-lined vertical and horizontal storage tanks are often supplied in black or white lining; confirm the colour if it matters to your process.
7. Check internal finish and cleanliness
For stainless steel vessels, confirm the internal finish against the drawing. GMP mirror polish and hygienic no-dead-corner construction are different from a standard industrial finish. Check for weld undercut, spatter, grinding marks and inaccessible crevices. For a sterile-grade mechanical seal, confirm the seal arrangement is the one specified. For glass-lined and PTFE-lined vessels, check that the lining is continuous and free of foreign matter. All vessels should be clean and dry before packing, with ports capped.
8. Inspect agitator, shaft, impeller and baffles
Confirm the agitator type against the drawing: paddle, anchor or frame, disc turbine, hydrofoil, impeller or dispersion disc. Check the shaft straightness, impeller diameter, pitch and keyway. Confirm baffle number, width and position. Inspect the shaft surface for scratches, especially on glass-lined and PTFE-lined agitators. Measure the bottom clearance between the agitator and the vessel head. Record the actual clearance. A correct agitator with the wrong clearance will not mix as designed.
9. Check the seal and drive train
Mechanical seals and packed seals have different inspection points. For a packed seal, confirm packing type, number of rings and lantern ring position. For a mechanical seal, confirm the seal type, face material and flush plan. Check the drive: motor nameplate kW and speed, gearbox ratio, coupling alignment and guard. Turn the shaft by hand before power is applied. It should turn without binding. If it does not, stop and investigate before the no-load run.
10. Witness the jacket and coil pressure test
The jacket and any inner coil, immersion tube or half-pipe coil must be pressure-tested. Confirm the test pressure and duration in the approved inspection plan. The test is normally hydrostatic, with the product side open or isolated as required. Watch the pressure gauge. A drop indicates a leak. Record the test pressure, duration, ambient temperature and result. This test is separate from the high-voltage test and does not replace it.
11. Verify nozzles, flanges and utility connections
Check every nozzle against the drawing: size, orientation, projection, flange standard, facing and gasket surface. Confirm the manway, sight glass, thermometer pocket, dip tube and cleaning connection. Check flange faces for scratches, rust and damage. On glass-lined and PTFE-lined vessels, inspect the lining at the nozzle bore and flange face. Confirm that all utility connections are labelled. A nozzle that is 10 mm out of position can force a pipe reroute on site.
12. Run the vessel with no load
The no-load trial run is the last functional check. With the vessel empty and safe, run the agitator at operating speed. Record motor current, vibration, noise and seal condition. Confirm rotation direction. Check for oil leaks from the gearbox and water leaks from the seal flush. Run for the duration stated in the purchase order. Do not run a mechanical seal dry. If the vessel has an automation package, test the instruments, control valves and interlocks. After the run, inspect the lining and internal surfaces again for any marks from the agitator or tools.
What to do before you release the vessel
Do not rely on a single inspection report. Ask for the records: material certificates, lining thickness readings, high-voltage test record, pressure test record and no-load run log. Cross-check serial numbers. Photograph each item. If you cannot attend, an independent sourcing office in Zibo can witness the checks as your representative. We are not the factory. We do not name the factory. We inspect, verify and ship, and we stay accountable after the invoice is paid.
The takeaway is simple. A pre-shipment inspection is not a formality. It is the last point where a glass-lined, stainless steel or PTFE-lined reactor can be corrected without a crane, a flight and a delay. Use the 12 items above, record what you see, and treat any unverified item as an open point.