InstroTek
3
System Overview
The CoreLok uses a 1.25 hp vacuum pump in conjunction with control
electronics and a vacuum tight chamber to seal samples. The system is
completely integrated and operates on 120 or 220-volt (optional) power. The
sample is placed inside a specially designed plastic polymer bag, inserted in the
chamber and the door is closed. A switch recognizes the door closure and
activates the vacuum pump. The vacuum pump operates until the vacuum
gauge indicates 99% of full vacuum. An integrated pressure gauge monitors the
vacuum level and displays the vacuum within the chamber. The pump is
capable of producing 29.7 inches (754 mm) of Hg vacuum. At this point the
chamber and the bag are close to absolute vacuum. An automatic sealing
strip heat-seals the bag at the open end and air is allowed to enter the
chamber in a controlled manner. Since the bag is sealed and is under vacuum,
the increased pressure in the chamber forces the plastic bag around the
sample creating a tightly vacuum-sealed sample. Once the chamber reaches
atmospheric pressure, the chamber door automatically opens. The sample can
be removed and tested. The bag density is known and accounted for in the
calculation of the bulk specific gravity.
Critical Measurement Parameters
The following three aspects are important and should be recognized when using
the CoreLok system:
1.
Vacuum pressure
2.
Testing time after sealing
3.
Sample temperature prior to sealing
1.
Vacuum Pressure.
The pump should be able to create a vacuum of 29.7 in.
(754 mm) Hg inside the chamber. The residual volume after sealing the
sample should be less than 2% by volume of the specimen, the limit required
by the current ASTM D1188 for sealing asphalt specimens. The calculation
based on an asphalt sample 5” in height and 6” in diameter with a volume of
141.4 in
3
and 1% residual volume yields a pressure of 0.3 in. Hg using Boyle’s
