Petroleum Pumps’ Current and Vibration Signatures Analysis Using Wavelet Coherence Technique

Vibration analysis is widely used for rotating machinery diagnostics; however measuring vibration of operational oil well pumps is not possible. The pump’s driver’s current signatures may provide condition-related information without the need for an access to the pump itself. This paper investigates the degree of relationship between the pump’s driver’s current signatures and its induced vibration. This relationship between the driver’s current signatures (DCS) and its vibration signatures (DVS) is studied by calculating magnitude-squared coherence and phase coherence parameters at a certain frequency band using continuous wavelet transform (CWT). The CWT coherence-based technique allows better analysis of temporal evolution of the frequency content of dynamic signals and areas in the time-frequency plane where the two signals exhibit common power or consistent phase behaviour indicating a relationship between the signals. This novel approach is validated by experimental data acquired from 3？kW petroleum pump’s driver. Both vibration and current signatures were acquired under different speed and load conditions. The outcomes of this research suggest the use of DCS analysis as reliable and inexpensive condition monitoring tool, which could be implemented for oil pumps, real-time monitoring associated with condition-based maintenance (CBM) program. 1. Introduction Pumps and their associated systems are essential in oil and gas facilities for the efficient transportation of fluids. Common pumps found in these facilities include centrifugal, reciprocating, diaphragm, and rotary pumps [1]. The condition monitoring of pumps and their associated systems is an established application of CBM and is an existing area of research [2]. Rohlfing [3] provides three examples in the oil and gas industry where pump’s CBM has been effectively implemented. Azadeh et al. in [4] have developed a diagnostic mechanism for pump failures in which pump operating problems fall into two categories: (1) hydraulic problems that suggest the pump may fail to deliver liquid, deliver insufficient capacity, develop insufficient pressure, or lose its prime at starting and (2) mechanical problems that are characterised by the consumption of excessive power or development of mechanical difficulties at the seal chambers or bearings; in either case vibration, noise, or breakage may occur. Fatigue is a common cause of pump failure [5, 6]. Vibration monitoring is particularly suited to pumps due to the number of integrated rotating parts, which may show additional movement when faults develop