Vial Seal Sizing FAQs: Sizes, Dimensions, Opening Force and Packing

Question 1

Which seal designs come in which sizes at Autofits?

Accepted Answer

The FlipTop Optima flip-off seal is made in 13, 20, 28, 32 and 34 mm, in bridge, button and flower designs. The FlipTop Pull Ring is made in 20 and 32 mm, the FlipTop Tear-Down in 13, 20 and 32 mm, and all-aluminium tear-off seals in 13, 20 and 32 mm, with an all-aluminium tear-down seal at 20 mm. For threaded bottles, aluminium pilfer-proof (ROPP) caps are made in 22, 25, 28, 35 and 38 mm.

Question 2

How do I tell whether my vial takes a 13 mm or a 20 mm seal?

Accepted Answer

Measure the outside diameter of the crown, the flange at the top of the vial neck, or read it from the vial drawing. A crown of about 13 mm takes a 13 mm stopper and seal, and a crown of about 20 mm takes 20 mm components. The seal has to pass over the stopper flange and the crown: the inner diameter of the Autofits 13 mm Optima is at least 13.36 mm, and of the 20 mm Optima at least 20.22 mm. Confirm the vial's neck finish against its drawing before ordering.

Question 3

Does the seal size change with the vial's fill volume or dose?

Accepted Answer

No. The seal size follows the neck finish, and neck finishes are shared across vials of different capacities, so two vials holding different volumes, or different doses of the same drug, can take the same seal. Equally, two vials of the same volume from different makers can have different necks. A question such as which cap suits a 1000 mg vial is answered by measuring that vial's crown, not by the dose.

Question 4

Why is the stopper wider than the opening of the vial neck?

Accepted Answer

That is by design. The stopper's plug sits inside the bore of the neck, while its flange is wider and rests on the flat top of the crown. When the seal is crimped, its aluminium skirt rolls under the crown and holds the flange compressed against that surface, which is what makes the closure tight. A stopper that is tilted, lifted or missing before capping is rejected rather than crimped.

Question 5

When are 28 mm, 32 mm and 34 mm seals used?

Accepted Answer

These sizes close vials and bottles with wider necks than the common 13 and 20 mm finishes, typically larger-volume presentations. At Autofits, 28 and 34 mm are made as FlipTop Optima flip-off seals, and 32 mm is made as Optima, Pull Ring, Tear-Down and tear-off. As with the smaller sizes, the choice is made by measuring the container's crown and matching the stopper, not by volume.

Question 6

Is there a 30 mm vial seal?

Accepted Answer

Not in the Autofits range. The flip-off range steps from 28 mm to 32 mm and then 34 mm. If a specification or tender asks for a 30 mm seal, measure the crown or check the vial drawing against the 28, 32 and 34 mm sizes before placing an order.

Question 7

What are the dimensions of a 13 mm flip-off seal?

Accepted Answer

On the FlipTop Optima 13 mm drawing, the inner diameter of the aluminium seal is 13.36 mm minimum, the outer diameter of the disc is 14.99 mm maximum, the disc height is 2.90 to 3.30 mm, the inner aluminium height is 6.15 to 6.40 mm, and the total seal height is 7.62 to 8.38 mm. Aluminium thickness is 0.16 to 0.20 mm, with six tapered bridges.

Question 8

What are the dimensions of a 20 mm flip-off seal?

Accepted Answer

On the FlipTop Optima 20 mm drawing, the inner diameter of the aluminium seal is 20.22 mm minimum, the outer disc diameter is 23.14 mm maximum, the disc height is 3.20 to 3.60 mm, the inner aluminium height is 7.37 to 7.62 mm, and the total seal height is 9.02 to 9.91 mm. Aluminium thickness is 0.16 to 0.20 mm, with six tapered bridges.

Question 9

What are the dimensions of 28, 32 and 34 mm flip-off seals?

Accepted Answer

The 28 mm Optima has an inner aluminium diameter of 27.60 to 28.20 mm, a disc diameter of 30.10 to 31.10 mm, an inner aluminium height of 8.70 to 9.30 mm and a total height of 11.06 to 12.06 mm. The 32 mm has an inner diameter of 32.10 to 32.90 mm, a disc of 35.50 to 36.50 mm and a total height of 14.30 to 15.50 mm. The 34 mm has an inner diameter of 33.60 to 34.00 mm, a disc of 35.50 to 36.50 mm and a total height of 15.00 to 16.00 mm.

Question 10

How thick is the aluminium in a vial seal?

Accepted Answer

It depends on the size. On the FlipTop Optima drawings the aluminium is 0.16 to 0.20 mm thick at 13 and 20 mm, 0.17 to 0.23 mm at 28 mm, 0.21 to 0.25 mm at 32 mm and 0.20 to 0.25 mm at 34 mm. The 20 mm Pull Ring and the 13 mm flip-top Tear-Down are drawn at 0.18 to 0.22 mm, and the 32 mm Pull Ring and 32 mm Tear-Down at 0.20 to 0.26 mm.

Question 11

How many bridges does a flip-off seal have?

Accepted Answer

The bridges are the narrow links in the seal top that break when the flip-off disc is lifted. The 13 and 20 mm FlipTop Optima seals have six tapered bridges, the 28 mm has eight, the 32 mm has twelve tapered bridges and the 34 mm has eight tapered bridges. All-aluminium tear-off seals at 13 and 20 mm have two bridges. The number of bridges is one of the things that sets the opening force.

Question 12

Do tear-off and pull-ring seals share the flip-off dimensions?

Accepted Answer

No, each design has its own drawing. The 20 mm all-aluminium tear-off seal has an inner diameter of 20.00 to 20.60 mm, a perforation diameter of 9.70 to 10.50 mm and a total height of 7.40 to 8.00 mm. The 20 mm FlipTop Pull Ring has an inner diameter of 20.00 to 20.60 mm, a disc of 22.00 to 23.00 mm and a total height of 9.00 to 10.00 mm. Because heights differ, capping settings are checked when a line changes from one design to another.

Question 13

What is the maximum opening force for a 13 mm flip-off seal?

Accepted Answer

Autofits specifies a maximum opening force of 30 N for its 13 mm flip-off seals. If your own specification quotes a limit taken from ISO 8362-6, the standard for aluminium-plastic caps, compare that figure with the current edition of the standard and with the value on the Autofits drawing before approval, so both documents state the same requirement.

Question 14

What opening forces apply at 20, 28 and 32 mm?

Accepted Answer

The maximum opening force is 35 N for the 20 mm and 28 mm flip-off seals and 65 N for the 32 mm seal. A value for the 34 mm seal is not published and is confirmed on enquiry. These are maximums: a seal that opens with less force passes, and a seal that needs more than the stated force fails.

Question 15

Why does a 32 mm seal need more force to open?

Accepted Answer

Opening force varies with the number of bridges and the size of the disc. The 32 mm FlipTop Optima carries twelve tapered bridges against six at 13 and 20 mm, and a disc of 35.50 to 36.50 mm, so more material has to break when it is flipped. That is why its maximum is 65 N while the 13 mm seal's is 30 N.

Question 16

Is there a published weight per piece for a 20 mm flip-off seal?

Accepted Answer

Weight per piece is not part of the published Autofits specification, so it is confirmed on the drawing for the exact design rather than quoted as a general figure. It is set by the aluminium thickness and height, the disc diameter and height, and the top design, which is why a bridge, button and flower seal of the same size can differ. For line planning, the box quantities below are the reliable figures.

Question 17

How many seals come in a box of each size?

Accepted Answer

Standard packing is 15,000 seals per box at 13 mm (three bags of 5,000), 6,000 per box at 20 mm, 3,000 at 28 mm (two bags of 1,500) and 1,400 at 32 mm (two bags of 700). The shipper box measures 420 × 270 × 320 mm. Tyvek bagging is available, and a standard quantity for 34 mm is confirmed on enquiry.

Question 18

Why do some 13 mm seals crimp better than others?

Accepted Answer

Crimp quality depends on the fit between the seal, the stopper flange and the crown, and on capper settings. The skirt has to be long enough to reach under the crown but not so long that it folds. The 13 mm Optima's total height is 7.62 to 8.38 mm and the 13 mm flip-top Tear-Down's is 6.80 to 8.30 mm, so a seal is checked against the actual stopper flange thickness and crown, and the capper is set in a trial.

Question 19

Which bottle volumes does each ROPP cap size typically suit?

Accepted Answer

Autofits makes aluminium roll-on pilfer-proof caps in 22, 25, 28, 35 and 38 mm. Typically, 22 mm closes small bottles of about 10 to 60 ml, 25 mm about 30 to 125 ml, 28 mm about 100 to 500 ml, 35 mm wider necks of about 150 to 500 ml, and 38 mm wide-mouth bottles of about 200 ml to 1 litre. These ranges are typical, and the bottle drawing decides.

Question 20

How is an ROPP cap size matched to a bottle?

Accepted Answer

The cap's nominal size matches the diameter of the bottle's pilfer-proof neck finish. Because the cap is supplied unthreaded and rolled onto the neck during capping, the thread pitch, the bead that holds the pilfer band and the neck height all have to suit the cap's shell height, so the match is confirmed against the bottle drawing and a capping trial rather than the nominal size alone.