USING THE VACUUM GAUGE TO DETERMINE VACUUM
When requirements state a specified vacuum for a canned subsistence item, the
end-puncture gauge is normally used (see Figure 2-1). To obtain an accurate vacuum
reading, the following steps of procedure must be observed.
a. Prepare for Testing Vacuum.
(1) Assure that dented or defective cans are not used for testing vacuum.
For example, never select a swollen can.
(2) Measure vacuum at room temperature, which is normally between 70oF
(21oC) and 80oF (27oC).
b. Check the Gauge for Serviceability.
(1) Check for cracks and blockage. Assure that the air entrance is not
blocked with foreign material.
(2) Check the rubber gasket to ensure that it is capable of creating a seal.
Assure that the gasket is flexible, free of breaks, and has a smooth, clear contact
surface. A cracked or damaged rubber gasket will allow air leakage.
(3) Blow into the gauge. The needle should move to the right. The gauge
should read "0" when viewed as shown in Figure 2-1.
Prepare the Can for Puncture.
(1) Strike the manufacturer's end of the can on a flat surface in order to
compact the product.
(2) Place the can on a slanted surface to allow for optimal head-space. The
can should be positioned on the slanted surface in such a way that the optimal space is
in the area of the side seam and the manufacturer's end of the can.
d. Puncture the Can.
(1) Enter the can as close to the upper edge as possible (see Figure 2-3).
Puncture the can on the manufacturer's end as close to the edge of the can as possible,
in the area of the side seam, without entering the countersink.
(2) Push the point only far enough to pierce the metal. Pushing too far may
allow the gauge to penetrate the product. This will plug the gauge and prevent an
(3) Hold the gauge down to prevent a vacuum leak.