The following verification check points of DFT should 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 2
Note: Arrows of diagram indicate critical areas and should
be understood to mean indication for both sides.
.4 three gauge readings for each set of primary
support members and two 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 should be taken to verify
coating thickness for any area considered necessary by the coating
inspector.