UTI (Ullage Temperature Interface) is a detector used to measure the ullage, temperature, and the oil-water interface onboard tankers. On this page, we examine the UTI functions, principles of working and the importance of its annual calibration.
The UTI detector is a portable liquid level gauge that is commonly used in the shipping industry to measure the amount of hydrocarbons and chemicals in a ship’s tank. This device includes a sensor probe, measurement tape, display unit, and winding drum. Its primary purpose is to determine the temperature and oil-water interface on tankers by attaching the sensor probe to the measurement tape, which can vary in length from 15m to 40m. Manufacturers offer a temperature range between -40°C and 110°C. All UTI meters have earth grounding capabilities for safety purposes.
Note: It is very important that the Ullage Temperature Interface system is grounded to the tank before the probe is introduced into the tank and remains grounded until after complete withdrawal from the tank.
In the following paragraphs, we will introduce how the ullage, temperature and oil-water interface are detected onboard:
The ullage detector of the UTI integrates two elements (1) electronic circuits and (2) two piezoceramic plates. When the sensor head reaches the oil or petroleum, an ultrasonic sound is emitted. The receiver processes and sends this sound to the instrument unit that emits a continuous beep sound.
The sensing component of the UTI detector is a Platinum Resistance Temperature Detector (RTD). This element is situated in the temperature electrode that is filled with a heat transfer compound paste to hasten the latency. After digitizing the RTD element signal, the micro-controller in the sensor probe corrects and compensates for any errors. The RTD element’s attributes are saved in the sensor memory and are exclusively for that sensor, so a new calibration is not required when replacing the sensor. The micro-controller sends the data to the Display Unit that can be read by the technician.
The operating principle for oil-water interface level detection of the UTI detector involves measuring conductivity between an active electrode and a grounded electrode. When the liquid measured is conductive (e.g., water), the ullage sensor detects its existence. Afterwards, the conductivity electrodes and their related electronic circuits modify the coded signal generating an intermittent beep sound.
UTI meters can be either open or closed types, with the latter having a gas-tight body to prevent hazardous gases from escaping the measurement tank.
The Portable Closed Flexi-Dip measuring tapes are battery-operated electronic units that are totally gas-tight. When installed in a vapour-control valve mounted on a storage (cargo) tank, it forms a tightly sealed system that prevents toxic vapors from escaping and creates a closed gauging system for that tank. This tight environment reduces the diffusion risk of any (inert) gas. The tape is marked in metric or English units and is anti-static coated (as is the sensor). In addition, the tape is color marked to make tape direction and motion easily seen and to ensure full rewind position. A coiled grounding cable with a large alligator clip is standard. This closed system is recognized by many worldwide regulatory bodies as equivalent to a fixed gauging system as long as the tape remains in the valve from the beginning until the end of loading or discharging of the (cargo) tank.
Restricted and Open Gauging Tapes provide a convenient and accurate means for measuring ullage, product temperature and the oil-water interface. The units are configured to operate in the trimode, bimode, interface or temperature mode. Each instrument is designed to maximize ease of use. A single penetration of each tank can provide comprehensive data about internal tank conditions. When the electronic probe senses hydrocarbon, a steady tone is heard; when sensing water, it emits an intermittent tone. Temperature is shown on an LED display in the hub of the instrument.
To ensure the UTI detector’s accurate measurements and function, it should be calibrated once a year by a specialized maker service company. Mr. Marine Instruments & Controls repairs and calibrates all types of UTI detectors and has a large stock of spare parts in our warehouses.
As specialized partners for MMC and Honeywell, we also have a stock of new and refurbished UTI systems available for fast delivery. Please feel free to contact us for more information about Ullage Temperature Interface.
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