A cooking kettle looks like a simple purchase: a stainless pot with a stirrer on top. In practice it is the piece of equipment that decides whether your sauce line runs at the rated capacity or stalls every afternoon because product is scorching on the inner wall. We build these vessels in Shandong for food factories that export to Europe, Africa and Southeast Asia, and the questions buyers ask before an order tell us a lot about whether the project will go smoothly. This guide lists the parameters we recommend confirming before you send an RFQ, in the order that actually affects the outcome.
Kettle capacity is quoted as total volume, but the number that governs your throughput is the working volume, which is usually 75 to 80 percent of total. A 600 L kettle holds roughly 480 L of product per batch. If your recipe needs headspace for foaming, as milk and cream reductions do, plan on 70 percent. Buyers who size on total volume alone regularly end up with a vessel that cannot take the charge their recipe development assumed.
Convert to kilograms using the density of the actual product, not water. A chilli paste at 1.1 kg/L in a 600 L kettle gives 530 kg per batch, not 600 kg. Then check whether that batch size matches the downstream filling or packaging run. A kettle that produces 1.4 batches per filling shift wastes labour; one that produces 0.6 batches forces overtime.
There are four practical options and each has a real constraint:
If the site has steam, use it. If not, price the electrical upgrade before you compare kettle quotes, because the kettle is often the smaller number.
This is where most specification errors happen. Below roughly 3000 cP, an anchor or paddle agitator is sufficient and cheaper to run. Between 3000 and 20000 cP, a scraper agitator that sweeps the wall is needed to prevent burn-on. Above 20000 cP, or when the product contains solids that settle, a planetary stirrer is the right choice: it combines a slow revolution with a faster rotation at a non-integer ratio, so the blade lays down a new path on every pass and there is no dead zone in the centre of the pot.
Scraper clearance is the detail that determines whether the kettle still performs in year three. We set PTFE blades at 3 to 5 mm from the shell and shim them so they can be re-adjusted on site. A blade that has worn to 8 or 10 mm no longer scrapes, and the first symptom is a brown ring at the bottom of the pot that operators blame on the recipe.
A jacket rated at 0.3 MPa with a 6 mm inner shell and 2 mm outer jacket is the standard configuration for food work up to about 150 degrees C. If your process needs higher temperature for sterilisation or for a viscous mass that resists heat transfer, the shell and jacket thickness must increase together. Ask for the hydro test record: we test every unit at 0.45 MPa and keep the record in the crate with the wiring diagram. A supplier who cannot produce that record is a risk on a pressure vessel.
Bottom valves work for thin product. For pastes, jams and chunky stews, a tilting body empties the batch in minutes instead of relying on the product to flow. Hydraulic tilting costs more than manual worm-gear tilting but is the difference between a comfortable clean-down and an operator leaning into the pot with a hose. If you run more than three batches per shift, take the hydraulic option.
SUS304 covers most sauce, jam, soup and stew duty. Move to 316L when the recipe carries chloride load: brine-cured products, vinegar-heavy sauces, tomato concentrates held hot for long periods. The cost difference is modest relative to replacing a pitted shell. Also confirm that all wetted parts, including the discharge valve body and the agitator shaft, are the same grade, and that internal welds are ground and passivated.
PID temperature control on the steam or heating circuit, frequency inverter on the stirrer, and at least ten storable recipes. Insist that the setpoints, inverter parameters and steam valve trim are documented in English, otherwise every service visit becomes a remote diagnostic call. An IP54 panel is adequate for a wash-down area; IP65 if the panel sits in the splash zone.
Quotations often state a throughput in kg/h. Treat that number as an output at a specific recipe viscosity and a specific heating ramp, not as a constant. Ask what product and what inlet temperature the figure was measured at. If the answer is vague, the number is marketing rather than engineering.
If you send us your recipe, batch target, available utilities and the downstream filling rate, we will come back with a configuration and say plainly where a cheaper option would work. That is a shorter conversation than discovering the mismatch after installation.
A cooking kettle looks like a simple purchase: a stainless pot with a stirrer on top. In practice it is the piece of equipment that decides whether your sauce line runs at the rated capacity or stalls every afternoon because product is scorching on the inner wall. We build these vessels in Shandong for food factories that export to Europe, Africa and Southeast Asia, and the questions buyers ask before an order tell us a lot about whether the project will go smoothly. This guide lists the parameters we recommend confirming before you send an RFQ, in the order that actually affects the outcome.
Kettle capacity is quoted as total volume, but the number that governs your throughput is the working volume, which is usually 75 to 80 percent of total. A 600 L kettle holds roughly 480 L of product per batch. If your recipe needs headspace for foaming, as milk and cream reductions do, plan on 70 percent. Buyers who size on total volume alone regularly end up with a vessel that cannot take the charge their recipe development assumed.
Convert to kilograms using the density of the actual product, not water. A chilli paste at 1.1 kg/L in a 600 L kettle gives 530 kg per batch, not 600 kg. Then check whether that batch size matches the downstream filling or packaging run. A kettle that produces 1.4 batches per filling shift wastes labour; one that produces 0.6 batches forces overtime.
There are four practical options and each has a real constraint:
If the site has steam, use it. If not, price the electrical upgrade before you compare kettle quotes, because the kettle is often the smaller number.
This is where most specification errors happen. Below roughly 3000 cP, an anchor or paddle agitator is sufficient and cheaper to run. Between 3000 and 20000 cP, a scraper agitator that sweeps the wall is needed to prevent burn-on. Above 20000 cP, or when the product contains solids that settle, a planetary stirrer is the right choice: it combines a slow revolution with a faster rotation at a non-integer ratio, so the blade lays down a new path on every pass and there is no dead zone in the centre of the pot.
Scraper clearance is the detail that determines whether the kettle still performs in year three. We set PTFE blades at 3 to 5 mm from the shell and shim them so they can be re-adjusted on site. A blade that has worn to 8 or 10 mm no longer scrapes, and the first symptom is a brown ring at the bottom of the pot that operators blame on the recipe.
A jacket rated at 0.3 MPa with a 6 mm inner shell and 2 mm outer jacket is the standard configuration for food work up to about 150 degrees C. If your process needs higher temperature for sterilisation or for a viscous mass that resists heat transfer, the shell and jacket thickness must increase together. Ask for the hydro test record: we test every unit at 0.45 MPa and keep the record in the crate with the wiring diagram. A supplier who cannot produce that record is a risk on a pressure vessel.
Bottom valves work for thin product. For pastes, jams and chunky stews, a tilting body empties the batch in minutes instead of relying on the product to flow. Hydraulic tilting costs more than manual worm-gear tilting but is the difference between a comfortable clean-down and an operator leaning into the pot with a hose. If you run more than three batches per shift, take the hydraulic option.
SUS304 covers most sauce, jam, soup and stew duty. Move to 316L when the recipe carries chloride load: brine-cured products, vinegar-heavy sauces, tomato concentrates held hot for long periods. The cost difference is modest relative to replacing a pitted shell. Also confirm that all wetted parts, including the discharge valve body and the agitator shaft, are the same grade, and that internal welds are ground and passivated.
PID temperature control on the steam or heating circuit, frequency inverter on the stirrer, and at least ten storable recipes. Insist that the setpoints, inverter parameters and steam valve trim are documented in English, otherwise every service visit becomes a remote diagnostic call. An IP54 panel is adequate for a wash-down area; IP65 if the panel sits in the splash zone.
Quotations often state a throughput in kg/h. Treat that number as an output at a specific recipe viscosity and a specific heating ramp, not as a constant. Ask what product and what inlet temperature the figure was measured at. If the answer is vague, the number is marketing rather than engineering.
If you send us your recipe, batch target, available utilities and the downstream filling rate, we will come back with a configuration and say plainly where a cheaper option would work. That is a shorter conversation than discovering the mismatch after installation.
