Size the chamber from your largest bag laid flat with the open end across the sealing bar, plus roughly 20 mm clearance each side. An oversized chamber does not run faster: the pump must evacuate the empty volume too, so every cycle costs time you never recover.
Measure the bag, not the product
A frequent specification error is sizing from the product. A 300 mm primal goes into a 400 mm bag, and that bag has to lie flat inside the chamber with its open edge on the seal bar. The bag dimension is what the chamber must accept.
- Lay the filled bag flat as it will sit in the chamber.
- Measure length and width in that state, not standing.
- Add clearance so the operator is not fighting the lid.
- Check the seal bar covers the full open edge in one pass.
Why an oversized chamber costs you on every cycle
Evacuation time is a function of pump capacity against chamber volume. Doubling chamber volume with the same pump roughly doubles pull-down time. Buying two sizes up for future flexibility means paying that penalty on every pack you make in the meantime.
Checks that get skipped
| Check | What goes wrong if you skip it |
|---|---|
| Seal bar length vs bag width | Bag needs two passes; weak overlap point |
| Chamber depth vs bag thickness | Lid closes on product; seal contaminated |
| Number of seal bars | Double-bag work needs two bars |
| Chamber material | Wet and acidic product needs stainless throughout |
When to specify an insert instead of a bigger chamber
Products with liquid, or products of very different heights, are usually better handled with an inclined platen or filler plate than with a larger chamber. The insert cuts the volume the pump has to move and holds product at the right angle for the seal.
Chamber dimensions are published on each series page in the vacuum packaging range.
Figures in this article are drawn from the 137 machine series SilverSeal currently supplies, not from generic industry averages. Specifications vary by model — check the individual series page before specifying.
Frequently asked questions
What clearance should I leave around the bag?
Around 20 mm each side is a practical margin. Less and operators slow down positioning; much more and you evacuate dead volume.
Does a deeper chamber help with bulky product?
Only until the lid still closes without touching the product. Beyond that, depth is dead volume that lengthens every cycle.
Can I run two small bags per cycle?
Yes, if both open edges sit on the seal bar. It is a legitimate way to raise output without a larger machine.
