It is important to achieve continuous, stable and efficient pumping well operation in actual
oilfield operation. Down-hole pumping well working conditions can be monitored in real-time and a
reasonable production scheme can be designed when computer diagnosis is used. However, it is difficult
to make a comprehensive analysis to supply efficient technical guidance for operation of the pumping
well with multiple faults of down-hole conditions, which cannot be effectively dealt with by the common
methods. To solve this problem, a method based on designated component analysis (DCA) is used in
this paper. Freeman chain code is used to represent the down-hole dynamometer card whose important
characteristics are extracted to construct a designated mode set. A control chart is used as a basis for
fault detection. The upper and lower control lines on the control chart are determined from standard
samples in normal working conditions. In an incompletely orthogonal mode, the designated mode set
could be divided into some subsets in which the modes are completely orthogonal. The observed data is
projected into each designated mode to realize fault detection according to the upper and lower control
lines. The examples show that the proposed method can effectively diagnose multiple faults of down-hole
conditions.