Conveyor Belt Selection for Food and Pet Food Lines: Types, Materials, and Duty

Most conveyor problems that show up in month six were decided in week one — usually in a five-minute conversation where somebody said "it's a belt conveyor, 6 metres, 400 wide" and everybody moved on. The machine that arrives does what was asked of it. It just was not asked much.

1. Start With the Product, Not the Machine

2. Belt Types and Where Each One Stops Working

3. Belt Material: The Decision Most Often Made by Default

4. Frame and Contact Surfaces: Two Separate Decisions

5. Food and Pet Food: Where the Duty Gets Serious

6. Selection Matrix by Product Type

7. Four Details That Decide Whether a Line Runs

8. What to Tell Your Supplier Before You Ask for a Quote

9. Frequently Asked Questions

A conveyor specification usually begins with geometry: length, width, height, and where it has to go. Those matter, but they are the last three questions, not the first three.

The first three are about what is riding on the belt. Physical form, moisture, fat, salt, temperature at loading, and how the product behaves when it is dropped rather than placed. A free-flowing dry pellet and a sticky meat emulsion of the same weight per hour are different machines wearing the same description, and a specification built only from geometry will happily produce the wrong one.

This is not a controversial idea. It is simply an expensive one when it is skipped.

Six conveyor forms cover most food and pet food duties. Each has a range where it is the obvious answer and a point where it quietly becomes the wrong one.

Two of these are worth a second look — not because they are unusual, but because the choice often gets made before the duty has been described.

Modular plastic belts solve a problem that flat belts cannot: they open. Cleaning solution reaches the underside, air passes through, and a curved section does not need a transfer. They are also the usual answer where a line is washed down in place. The trade-off is that the openings are a leak path for fine powders and a trap for anything that sets hard.

Screw conveyors are chosen for dust containment and they do that well. They are also the fastest way to turn fragile product into fines. Dry pet food kibble going up a screw is a different product coming out than going in, and the loss is invisible until someone weighs the output.

The frame gets argued about. The belt often does not — it gets ordered in whatever the last machine used. Belt polymer sets three limits that the frame alloy has nothing to do with.

Temperature. A belt rated to 80 °C will not survive a product arriving at 110 °C from a retort discharge, regardless of what the frame is made of. Continuous ratings and intermittent ratings are different numbers, and the difference is where failures live.

Chemistry. Fat, oil and cleaning agents attack different polymers differently. A belt that handles vegetable oil comfortably may swell or crack under a chlorine-based sanitiser at the same concentration. Cleaning regime and product chemistry have to be checked against the belt separately, because the frame material says nothing about either.

Release. Sticky product — marshmallow, dried fruit, high-fat emulsions, wet pet food — is a release problem before it is a transport problem. Surface texture and belt coating matter more here than belt strength, and a belt chosen for tensile load will simply carry the product around the return side.

Worth stating as a number rather than a description: "meat slurry" is not a specification. "Meat emulsion at 62 percent moisture, 1.2 percent sodium chloride, ambient to 45 °C" is, and it is the difference between a belt module that lasts three years and one that lasts eight months.

Material often gets specified machine by machine, when the duty varies inside a single machine — a dry infeed and a washdown discharge are not the same environment.

A conveyor frame, its legs and its guards rarely see product. What they see is the room: humidity, washdown, and whatever is in the air. Product-contact surfaces see something else entirely — the product, at its temperature, with its salt and fat content, plus whatever cleaning chemistry follows.

Those are two duties in one machine, and 304 covers the first one comfortably. The second one is where the duty decides: dry kibble is fine on 304, while wet, salted, heated product is where 316L stops being an upgrade and starts being the specification.

The parts that actually corrode are not the ones people worry about.

All four share one property: liquid collects and stays. A conveyor that drains outlasts a better alloy that holds water. That is a geometry outcome, not a purchasing one, and it is decided before anyone talks about grade.

Pet food is where a lot of general-purpose conveyor experience quietly stops applying, for three reasons that compound.

Salt. Wet pet food formulations commonly run 0.5–1.5 percent sodium chloride, and some meat-heavy recipes go higher. In the water phase that translates to several thousand ppm of chloride, which is exactly the band where 304 becomes marginal and 316L is comfortable.

Raw materials bring chloride with them. Fish meal, meat and bone meal, and poultry by-product meal all carry chloride into the plant before a single gram of salt is added. Fish meal in particular is one of the more aggressive materials a stainless tank or chute will meet, and in pet food it is a routine ingredient rather than an exception.

Wet lines run hot. Retorting at around 121 °C puts temperature, chloride and residual stress in the same place at the same time. That combination is the classic setup for stress corrosion cracking, which fails without the pitting or staining that usually gives warning first.

The dividing line is not the product category. It is moisture, salt and temperature together. Dry kibble lines run on 304 for years without complaint. Wet and canned lines are usually 316L from the first product-contact surface, and the changeover point is worth deciding deliberately rather than by default.

One detail that catches plants out: the highest chloride load on a dry line is often the CIP system, not the process equipment. A kibble line that is entirely 304 can still corrode its sanitising tank and return piping if the sanitiser is chlorine-based. The product never touches those parts. The cleaning solution does.

These four come up in almost every enquiry where the first machine did not work out, and none of them are material questions.

Belt surface against the actual product. A belt that carries dry pellets perfectly can release sticky product straight onto the return run. Surface texture and coating are selected against the product, not the load.

Incline angle derived from the product, not from a table. Published incline limits assume a generic dry bulk material. Fat-coated kibble, wet powders and sticky emulsions behave differently, and a belt that handles them at 20 degrees may slide at 15. The table has never met your product.

Peak throughput and whether the infeed is steady. A steady stream and a pulsed one at the same hourly average need very different belt loading. Where product arrives in surges from an upstream batch process, the belt has to clear the surge, not the average.

Drop height at every transfer. Every transfer point produces some breakage and the rate climbs steeply with drop height. Dry kibble is brittle, and two percent lost at each of four transfers is eight percent of your product on the floor instead of in the bag. This is geometry, decided at design time, and not adjustable once the steel is cut.

These four tend to settle the material question on their own.

The expensive problems in custom equipment are rarely component failures. They are specification gaps — a detail nobody mentioned at quotation stage, discovered after the machine is standing on the floor.

One of those rows sounds like a joke and is not. Custom equipment is built to the process, not to a shipping container, and a frame that will not clear the doorway is not a design problem, a material problem, or a supplier problem. It is a tape measure problem, discovered on delivery day with the truck still outside.

How do I choose between a flat belt and a modular plastic belt? Where the line is washed in place, needs to drain, or has to turn, modular plastic usually wins. Where the product is a fine powder or the load is heavy and steady, flat belt tends to. Cleaning method decides more of this than product weight does.

What belt width do I need? Width follows peak throughput and product depth on the belt, not the machine it is replacing. Sizing to the average rate is the most common reason a new belt backs up at the peak.

Can one conveyor handle both dry and wet product? Physically often yes, practically usually no. Wet product changes the cleaning regime, and the cleaning regime changes the belt polymer and the contact-surface material. Machines that do both tend to be built to the wet duty and cost accordingly.

How steep can the incline be? That depends on the product rather than the conveyor. Published limits assume generic dry bulk material; fat-coated, sticky or wet products need the angle derived from a test or from experience with that material.

How is a conveyor specified for a washdown area? Belt polymer, frame material, drainage geometry and motor enclosure rating are decided together. Standing water on a frame is a design issue rather than a material one, and it is the one that causes most complaints.

What information gives the most accurate quotation? Product description with moisture, fat and salt content; peak and average throughput; cleaning chemicals and frequency; available space including door dimensions; and infeed and discharge heights. The first four questions a supplier asks tell you a fair amount about what the quote will be based on.

About us. Shanghai Xisheng Taolan Intelligent Equipment Co., Ltd. builds custom conveyor systems for food and pet food producers. We are a research-and-manufacture operation, so the people who design a line are the people who build it, and material decisions get made zone by zone, because a dry section and a washdown section are not the same problem. If you are planning a new line, or replacing a section that never quite worked, the duty list above is where we start too — which is why we ask about salt content before we ask about length.