Quick answer: open area is the share of the belt surface that is hole rather than plastic. It controls how fast water drains off the product, how much air reaches it in a cooling or freezing tunnel, and how well small items are supported. Higher is better for washdown and chilling, worse for small or soft products, and it always takes material out of the module. Across the Veybelt flush grid range the figures run from 7.7% up to 29.4%, so this is a choice with real spread in it.
What open area is, and what it is not
Open area is a percentage of the top surface, measured looking straight down at the belt. A flush grid belt at 25% is one quarter hole and three quarters plastic when viewed from above.
What the percentage does not tell you is the size of each hole, and that is the part that catches buyers out. A 12.7 mm pitch belt at 37.7% has many small openings. A 50.8 mm pitch belt at 29% has fewer, much larger ones. The percentage says the second belt is more solid. Anyone who has watched small caps fall through a coarse grid knows it behaves as the more open of the two. Judge drainage by the percentage and product support by the hole size.
Drainage
On a washing, blanching or draining section, water sitting on the belt surface is carry-over into the next process. Open area is the escape route. More hole means the water leaves under gravity across the whole belt length rather than pooling until the belt tips at the discharge.
It also matters for cleaning. A washdown crew spraying a flush grid belt needs the water to pass through and off, not run along the deck into the frame. This is the normal reason food plants specify a flush grid over a flat top in the first place, and it is why the flush grid variants exist in almost every series in the straight running modular belt range.
Airflow for cooling and freezing
In a cooling tunnel or a freezer the belt is between the fans and the product. Every square millimetre of solid plastic is a place where cold air does not reach the underside of the product, and the underside is usually the slow half of the job. Open area here buys you time, which on a fixed belt length means throughput.
It cuts both ways at low temperature. A very open belt in a blast freezer is also a belt with less material to resist the impact loading that plastic takes badly when cold, so the strength column is not a footnote in freezing applications. If the line runs cold, look at POM options and at the thicker, coarser pitch series rather than pushing the open area up on a thin belt, which is the argument set out in our note on material selection for a freezer line.
Product support: the limit on how open you can go
The rule that saves the most rework is simple. The smallest dimension of your product should sit comfortably across at least two ribs of the grid, and soft products need more support than that, because they deform into the openings and mark.
Things that go wrong with too much open area: small caps, nuts and hardware drop through; thin bags sag into the holes and pick up a grid pattern; raw dough and soft cheese press into the openings and stick; unstable containers rock on a coarse deck. If any of those describe your line, a lower open area or a fine pitch grid is the right answer, and a nub top or a flat top belt may be better still.
The strength side of the trade
Every opening is load bearing material that is not there. That is a real cost inside a given module design: the more you take out of the deck, the less section is left to carry belt pull.
The honest reading of the catalogue, though, is that published belt strength is set by the whole module design rather than by the grid pattern alone. Pitch, module thickness and material move the number far more than open area does. The 1100 series at 15.24 mm pitch gives only 7.7% open area and 12,300 N/m in PP. The 5997 at 57.15 mm pitch gives 23.8% open area and 47,500 N/m in PP. The coarser, thicker belt wins on both counts.
So use the range in the practical order. Pick the pitch family that carries your calculated belt pull over your conveyor length, then take the highest open area available inside that family, then check the hole size against your smallest product. Material choice is the last lever, and what PP, PE and POM each give you is set out separately: on the 986 series the same 22.8% open area is rated 18,056 N/m in PP and 30,851 N/m in POM.
Veybelt flush grid options with real numbers
| Series | Pitch | Open area | Belt strength | Thickness |
|---|---|---|---|---|
| 400 | 50.8 mm | 29.4% | 39,200 N/m (PP) | 15.9 mm |
| 926 | 12.7 mm | 37.7% | 9,500 N/m (PP) / 21,200 N/m (POM) | 8.9 mm |
| 900 | 27.2 mm | 31.7% | 17,500 N/m (PP) / 40,300 N/m (POM) | 9 mm |
| 936 | 38.1 mm | 25% | 33,000 N/m (PP) | 18 mm |
| 956 | 50.8 mm | 11.6% | 27,000 N/m (PP) | 16 mm |
| 966 | 25.4 mm | 25.3% | 26,800 N/m (POM) | 9.5 mm |
| 986 | 25.4 mm | 22.8% | 18,056 N/m (PP) / 30,851 N/m (POM) | 10 mm |
| 1100 | 15.24 mm | 7.7% | 12,300 N/m (PP) / 31,100 N/m (POM) | Not published |
| 5935 | 19.05 mm | 26.9% | 11,800 N/m (PP) / 20,700 N/m (POM) | 8.3 mm |
| 5997 | 57.15 mm | 23.8% | 47,500 N/m (PP) | 18.45 mm |
| OPB flush grid | 50.8 mm | 20% | 17,600 N/m (PP) | 16 mm |
| OPB reinforced | 50.8 mm | 14.5% | 17,600 N/m (PP) | 16 mm |
| OPB large open grid | 50.8 mm | 29% | 17,600 N/m (PP) | 16 mm |
The three OPB rows are the cleanest illustration in the range. Same pitch, same thickness, same rated strength, and open area from 14.5% to 29%. Inside one family the grid pattern is the variable you are actually choosing, and the reinforced version exists precisely because someone needed the deck back under heavier packs.
When to go open and when not to
| Situation | Position |
|---|---|
| Washdown line, product larger than a fist | Go high. Drainage and cleanability win, and support is not at risk. |
| Cooling or freezing tunnel | Go high, but check the belt strength and consider POM for cold impact. |
| Fruit and vegetable washing | High open area, coarse pitch. Water and debris both need to leave. |
| Small hardware, caps, closures | Go fine pitch or low open area. Hole size decides this, not percentage. |
| Soft or sticky product, dough, raw meat | Low open area, or a nub top surface to cut contact instead of adding holes. |
| Long, heavily loaded conveyor | Strength first. Choose the pitch family for the load, then the most open grid inside it. |
| Dry packaging line, no drainage need | Do not pay for open area. A flat top belt gives better support. |
If you are still deciding between families rather than between grid patterns, our guide on how to select a plastic modular belt covers the step before this one. Food contact applications can be supplied in food-grade material options compliant with FDA and EU regulations, so tell us if the belt touches unpacked product.
What to send with the enquiry
- What you are conveying, including the smallest dimension of the smallest item on the line.
- Belt width, conveyor length, and whether there are inclines.
- Load in kilograms per metre of belt, or product weight and how many are on the belt at once.
- Line speed and working temperature, including the coldest point if it runs through a freezer.
- Whether the line is washed down, and with what: water, caustic, or steam.
Send those five to us on the contact form or by WhatsApp and we will come back with two candidate series and a straight explanation of what each one gives up.
