Humboldt HM-2415 Soil Volume Change Meter (PVC) - Manual (Page 5)

F. Replace lucite container (#18) onto base, screwing it tightly to ensure
water seal.
G. Place loading disc (#17) on porous stone (#14) with the center indentation
at the top.
H. Place crosshead (#11) with proving ring (#2) on the supporting rods (#12).
(Be sure that the adjustable rod which extends down from the proving ring
dial does not strike the cover.) Add washers and nuts, then tighten firmly.
I. Set proving ring (#2) dial to zero by moving the band around the dial face.
Tighten the dial with the screw next to the top or the band. Push up on
proving ring dial to see that it appears to work properly.
J. By loosening nut (#14), turn adjustable rod exactly into the center of the
indentation on top of the loading disc (#17}. Be sure that the loading
disc is centered exactly over the stone. Firmly tighten lock nut (#14) on
adjustable rod. Be sure adjustable rod does not stick in loading disc.
K. Again loosen nut {#14) to turn adjustable rod until dial reads one division
past zero. Tighten lock nut (#14) firmly until adjustable rod has no play.
L. Record the time and the proving ring reading.
M. Add water to sample by squeezing from squirt bottle into the holes
located at the top of compaction ring (#15) until water level in lucite
container (#18) has covered the spacer ring (#16) and tops of the bolts.
(This procedure is used to reduce the amount of air entrapped in the ring
assembly and thus ensures that the sample has uniform access to water
over its entire top and bottom surfaces.)
N. Allow soil to expand until completely stabilized or for a maximum of 2
hours, then read proving ring dial.
Interpretation of Dial Reading
A. To obtain the approximate PVC category and plasticity index, take
the reading from the proving ring dial directly to the table in Figure 5.
Established on the basis of the swelling and shrinking behavior of the soil,
the following categories of PVC have been established:
PVC Rating Category
Less than 2 Noncritical
2 to 4 Marginal
4 to 6 Critical
Greater than 6 Very Critical