The following verification check points of DFT are to be
taken:
.1 one gauge reading per 5 m2 of flat
surface areas;
.2 one gauge reading at 2 to 3 m intervals and
as close as possible to tank boundaries, but not further than 15 mm
from edges of tank boundaries;
.3 longitudinal and transverse stiffener members:
One set of gauge readings as shown below, taken at 2 to 3 m
run and not less than two sets between primary support members;
Figure 3
NOTE: Arrows of diagram indicate critical areas and should
be understood to mean indication for both sides.
.4 3 gauge readings for each set of primary support
members and 2 gauge readings for each set of other members as indicated
by the arrows in the diagram;
.5 for primary support members (girders and transverses)
one set of gauge readings for 2 to 3 m run as shown in figure 3 above
but not less than three sets;
.6 around openings one gauge reading from each
side of the opening;
.7 five gauge readings per square metre (m2)
but not less than three gauge readings taken at complex areas (i.e.
large brackets of primary support members); and
.8 additional spot checks to be taken to verify
coating thickness for any area considered necessary by the coating
inspector.