Screw Caps
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description
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Transcript of Screw Caps
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Screw Caps
There are many slight variations of vial thread although they are all commonly referred to as a
finish or GPI (Glass Packaging Institute) internal manufacturing standard. These are commonly
described as 8-425, 13-425 or 24-400. It is critical to marry correctly the container finish to the
correct cap size.
Closures are designated by their inside diameter in millimeters followed by a CMA (Closures
Manufacturers Association) designation number. For example 8-425 closure identifies the cap
as having an 8mm inside diameter and will fit a 425 finish container.
The 9mm short thread cap does not have a standardized description and needs careful
marrying to specific vials.
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Table of suggested Torque values for Screw Caps
As a basic guide application torque in inch-pounds should be about half the closures diameter
in millimeters
Application Torque
Cap Size (mm) Inch-Pounds
8 04-06
9 04-07
10 05-08
13 06-09
15 07-10
20 08-12
24 12-18
28 14-21
33 16-25
Copyright Fundamentals of Packaging Technology by Walter Soroka
Screw caps do not fit or sample leaking is occurring
o Closure materials must be compatible with the sample within the container.
o Be careful not to over tighten any cap by exerting greater torque than is necessary for a
compatible thread alignment.
o Check that the septa are correctly seated down inside the cap.
o Check the vial finish against the cap internal diameter
Septa are pushing down through the cap
o A press-fit or non-bonded septa into any cap where the septa is not correctly seated can
cause septa push-through
o Check autosampler injection speed and ensure compatibility to recommended septa.
o Blunt needle instruments will perform better with bonded septa or slit septa
o There could be thread incompatibility between cap and vial leaving poor top seal
change to alternative cap
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ILT patented Bonded InterSeal System totally eliminates
septa push-through
o True bond at the molecular level of plastic and rubber
o Prevents septa fall out or push-through
o Significant bond strength
o Withstands multiple injections
o Withstands multiple sterilizations and or cleaning
o Broad chemical resistance
o Wide pH range
o Cost effective
o Low bleed
o Excellent resealability
