A glass-lined reactor is not a commodity with a market price. Two quotations for “3,000 L glass-lined reactor, jacket, mechanical seal” can differ by three times, and neither supplier has to be lying. The difference lives in six decisions, and a buyer who asks about all six will get a price that means something.
1. Lining thickness and firing quality
The standard lining is 0.8–2.0 mm of vitreous enamel fired onto the steel wall. Within that range, thicker and more evenly fired linings survive thermal cycling and mechanical knocks far better. Ask for the specified thickness in writing, and ask for the 20 kV spark test record on your unit. A supplier who will not commit to either is telling you something.
2. The jacket type
A conventional jacket, a half-pipe coil and a dimple jacket are not interchangeable. Half-pipe and dimple jackets handle higher pressures and give better heat transfer per square metre, but they cost more and restrict how close together you can place vessels. Tell the supplier your heating medium, its temperature and its pressure, and make them justify the choice.
3. Sealing: packed gland or mechanical seal
Packed sealing is rated to about 0.1 MPa inside the vessel. A mechanical seal takes it to 0.4 MPa and, with a double-face design, up to 1.6 MPa. If your process runs under vacuum or contains a solvent you cannot release, the seal is not a place to save money — and a double-face seal needs a circulation and protection system, which is a separate line item most buyers forget.
4. Agitator type and drive
Six standard agitator forms exist, chosen by viscosity and by what you are trying to do — blend, disperse, suspend or transfer heat. A paddle and a disc turbine behave completely differently in the same vessel. Alongside the agitator sits the gear drive, and its selection is driven by torque rather than by price. This is the single most common place where a cheap quotation quietly becomes an unusable one.
5. Steel and testing standards
Ask which pressure vessel standard the design follows — GB/T, ASTM or ASME — and what testing is included: X-ray of the main seams, hydrostatic pressure test, dimensional inspection. Testing that is “available on request” is testing that will not be done.
6. What is actually in the price
Finally, separate the vessel from everything around it: agitator, seal, seal support system, nozzle orientation, packing, inland transport, sea freight, and whether the price includes the test reports. A line-by-line quotation is the only kind you can genuinely compare.
Rule of thumb: if two quotations differ by more than 40 % for the same nominal specification, one of them has changed a decision above. Find out which.