The Brief

Repeat and check the results from a previous settlement survey.

What We Proposed

Sending a qualified EEMUA and API inspector to check and verify results.

What We Delivered

A settlement survey was carried out by a local surveying team which revealed the tank was only 2mm from being out of limits. We were asked to go to site and repeat the survey from the same locations to compare results.

Our calculations revealed the following results:

  • Maximum allowable settlement (S) = 263.33mm
  • Maximum recorded = 215.00mm
  • Maximum difference between consecutive points allowable = 119.77mm
  • Maximum recorded (location G-H) = 101.00mm

It was noted by our EEMUA 159 and API 653 qualified inspector that the survey which was carried out at the marked locations on the concrete foundations were not distributed evenly around the tank circumference. The arc length should have been 11.977mm based on the circumference of the tank and number of required reference points. The following table shows the actual measured distances between arc locations:

A – B
B – C
C – D
D – E
E – F
F – G
G – H
H – A

11.90m
11.24m
14.65m
10.80m
8.55m
12.67m
15.40m
11.27m

As the maximum recorded difference between consecutive points was at location G – H, this arc length was actually 15.40m and not 11.97m as used in the calculations table, therefore, the result is better than that shown, i.e. 1% (the maximum differential settlement between any two points) of 11.977m is 119.77mm as compared to 1% of 15.40m, which is 154.00mm.