Send one data sheet to three fabricators and three quotations come back. The lowest can be a third of the highest for what looks like the same 3,000 L glass-lined reactor with a jacket and a mechanical seal. That spread is not two suppliers being honest and one being greedy. It is three different vessels wearing one specification. We are KAVORTE, 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, and this is how we compare quotations so the number you accept is the vessel you actually wanted.
1. Identical specifications almost never stay identical
A typical enquiry sheet carries volume, material, design pressure, design temperature and perhaps an agitator speed. That is enough to price a vessel and nowhere near enough to build one to a known standard.
Start with volume. A nominal figure such as 3,000 L is a label, not a measurement. Actual working volume, heat-transfer area and weight vary with design pressure, jacket type, sealing arrangement and any non-standard requirement, and they are confirmed against the final technical drawing rather than the enquiry sheet. A supplier who trims the shell to hit the nominal number is quoting less steel.
Then heat-transfer area in m². Two glass-lined vessels of the same nominal volume can be built with different jacket areas. An exothermic step that holds comfortably in one will run away in the other, and the difference is not visible on the price list.
For glass-lined vessels, four figures separate a real quotation from a placeholder: lining thickness in mm, high-voltage test in kV, thermal shock limits of cold shock ≤ 110 °C and heat shock ≤ 120 °C, and a media statement. Glass lining is not suitable for hydrofluoric acid or fluoride-bearing media, for phosphoric acid ≥ 30 % above 180 °C, or for strong alkali above pH 12 at 100 °C. A quotation that does not say this has not checked your process.
2. Where the money actually goes
A handful of decisions accounts for most of a threefold spread. Ask each supplier to state all of them in writing.
- Shell material and plate thickness. Carbon steel, 304 or 316L, titanium, duplex stainless, Hastelloy and clad plate sit in very different price bands. Plate thickness follows design pressure in MPa, and a thinner plate with a small corrosion allowance saves material that you will pay for later.
- The glass lining itself. Lining thickness in mm and the number of firing coats drive both cost and service life. The kV figure on the high-voltage works test is where thin spots and pinholes show up before the vessel ships.
- Heat-transfer arrangement. Jacket, inner coil, immersion tube or half-pipe coil. A half-pipe coil takes higher jacket pressure and delivers more heat transfer per m² of shell, and it costs more welding. Decide from the duty, not from the quotation.
- Agitator and drive. Paddle, anchor or frame, disc turbine, hydrofoil, impeller or dispersion disc, plus motor kW, speed in r/min and the gearbox behind it. On many vessels this line costs more than the shell, and it is the line most often left vague.
- Sealing. Packed seal, mechanical seal or sterile-grade mechanical seal. A packed gland costs less and is permitted to weep slightly, which is acceptable for a solvent at ambient temperature and unacceptable for a toxic or sterile duty.
- Finish, testing and documentation. GMP mirror polish with no dead corners, material certificates, pressure test records, third-party inspection, spare parts list and English documentation. Each one is a real line item.
3. Read the commercial terms before the price
Ex-works, FOB and CIF are not the same number. Sea freight and inland haulage for a 3,000 L vessel with a drive and a gearbox is not a rounding error, and it belongs in the comparison before you rank anyone.
Then compare validity, currency, payment terms and warranty length, and check whether spare gaskets, seal cartridges and wearing parts are inside the price or sold separately afterwards.
Calibration helps. A 3,000 L glass-lined reactor with a jacket and a mechanical seal is a normal purchase, and it lands somewhere between $8,000 and $14,000 depending on how it is built. A quotation far below that band is not a discount. It is a description of a different vessel.
4. Build a comparison grid and make it the only document you rank
Put every quotation into the same rows, in the same units, and send the grid back to any supplier whose answer reads "standard".
- Nominal and actual volume in L, confirmed against the drawing
- Heat-transfer area in m² and jacket type
- Shell material and plate thickness in mm
- Lining thickness in mm, number of coats, high-voltage test in kV, thermal shock limits in °C
- Written media compatibility statement
- Agitator type, motor kW, speed in r/min, gearbox make
- Seal type and gasket material
- Internal finish and surface condition
- Tests and certificates included, and who pays for third-party inspection
- Spare parts, documentation language, Incoterms, port of loading, warranty, price validity
Then request the technical drawing with the quotation. Two drawings side by side settle in ten minutes what a price list will hide for a month.
If a supplier will not fill in a row, that row is where the saving is hiding.
5. When the cheaper vessel is the right one
Price is not the enemy. A 1,000 L stainless steel vessel mixing a non-corrosive solvent at ambient temperature on day shift does not need mirror polish or a sterile-grade mechanical seal. A 304 shell with a hygienic finish and a packed gland is enough, and paying more for that duty is overspending rather than insurance.
The reverse also holds. A glass-lined vessel specified for a process with a cold shock above 110 °C is the wrong vessel at any price, and no saving on the lining recovers a contaminated batch and a stripped bottom head.
6. What to do next
- Rewrite the enquiry with the missing parameters: actual volume, heat area in m², plate thickness in mm, lining thickness in mm, test voltage in kV, agitator kW and r/min, seal type, finish and required certificates.
- Ask every supplier to quote the same Incoterm and to list spare parts as a separate line, so you can add them back yourself.
- Require the technical drawing with the quotation, and compare drawings rather than totals.
- Normalise freight, spares and validity before you look at the headline number.
- Keep the grid after the order is placed. When a seal fails in year two, the same rows tell you what you actually bought.