1532 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 56, NO. 5, OCTOBER 2007 Design and Implementation of a New Nonradioactive-Based Machine for Detecting Oil–Water Interfaces in Oil Tanks Ahmed M. Al-Naamany, Mahmoud Meribout, Member, IEEE, and Khamis Al Busaidi Abstract—In the oil industry, many applications require the measurement of more than one liquid level interface, often in challenging environments. In this paper, a new ultrasonic-based technique has been developed to determine oil, emulsion, and water levels in oil tanks. It consists of a compact and program- mable ultrasound-based multilayer level measurement device for which a feed-forward neural network is implemented. The ad- vantages of this method over current methods include contactless distance measurement, higher accuracy, lower cost, simpler setup, and not using ionizing radiation. The other advantage of this technique over light-based methods is its insensitivity to a dusty and smoky environment and independence of the object material and surface. Preliminary experiments have been conducted on the device. In this paper, the design and operating parameters of the device are discussed, and evidence of satisfactory performance is given. Index Terms—Emulsion level detection, hardware design, multilayer level measurement (MLLM), neural network, oil tank, ultrasonic device. I. I NTRODUCTION O IL PRODUCING institutions in many parts of the world are still faced with the problem of producing water and gas, together with oil from oil fields. Separating these three components from each other requires settling them in large tanks for a short period of time generating oil at the top, oil/water mixture in the middle, and water at the bottom. Water will then be pumped out from the tank. However, in order not to pump out oil with water, the level of the mixed liquid (water–oil) needs to be monitored continuously, particularly during the pumping process. In [1], an extensive literature review on currently available level measurement methods have been investigated. The authors claimed that most of the devices have been designed to detect only the top level of the liquid in the tank. These measurement sensors include RF capaci- tance, conductance, nuclear, radar, differential pressure, optical switches, and ultrasonic. A microwave-based sensor is among the few devices that have been recently designed for the ex- traction of the levels of the emulsion layers in the tank [2]–[4]. Manuscript received April 30, 2006; revised January 15, 2007. This work was supported by the Petroleum Development Oman Corporation. A. M. Al-Naamany and M. Meribout are with the Electrical and Computer Engineering Department, College of Engineering, SQU University, Muscat 123, Oman (e-mail: meribout@squ.edu.com). K. Al Busaidi is with the Petroleum Development Oman Corporation, Muscat 123, Oman. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2007.895665 However, the system is expensive. Additionally, the high en- ergy of the microwaves makes the technique inappropriate for combustible liquids. In this paper, a new ultrasonic-based hardware device for multilayer level measurement (MLLM) is presented. This so- lution makes use of the fact that the ultrasonic properties of an emulsion or suspension vary significantly with a varying disperse phase volume fraction. The actual results are very encouraging and demonstrate that the device can easily mea- sure, with very good accuracy, the emulsion in a single vessel. Furthermore, since its electronics is placed outside the tank, the device can work in hazardous, clean, or sterile environments and cope with surface foam or bottom sludge. Hence, the approach can be extended to allow the measurement of other fluid types as well. The system was designed in such way that it can work autonomously during long periods in remote areas where environmental conditions (i.e., temperature) may vary within wide ranges. II. MULTILEVEL DETECTION SENSOR HARDWARE ARCHITECTURE A. Concept The basic idea of our device is that the amount of ultrasound waves received and its speed depends upon the density of the liquid: Since the acoustic impedance of the water and oil (1.55 and 1.072 MRayls for water and Kerosene, where 1 MRayls =(kg/(sxm 2 ) × 10 6 [5]) are not similar, different responses for both liquids can be expected. Hence, by measur- ing the signal response at different vertical positions in the tank, the two levels of the interface (i.e., lower and higher levels) can be measured. Fig. 1 shows the layout of the tank, which has a capacity of 0.25 m 3 . An ultrasonic emitter and receiver are mounted inside two vertical stands, respectively. A thin layer of silicon is inserted between the active surface of both sensors and the interior wall of the vertical stands in order for ultrasound waves not to be back-scattered. Both sensors move up and down at the same horizontal level providing acoustic characterization. One advantage of this design is that the results are independent from the geometrical and chemical properties of the walls of the tank. Fig. 2 is a photograph of the tank. Fig. 3 shows the overview hardware architecture of the MLLM device. It is composed of an ultrasonic emitter-receiver pair placed inside the two vertical stands and transmitting at a programmable frequency. 0018-9456/$25.00 © 2007 IEEE