API MPMS 7.3 2011 pdf download.Manual of Petroleum Measurement Standards Chapter 7.3 Temperature Determination—Fixed Automatic Tank Temperature Systems.
220.127.116.11 multiple-spot ATT multiple-point ATT multi-point ATT A temperature instrument consisting of a number of individual spot temperature sensors (usually three or more) bundled together as a temperature element to measure the temperature at selected liquid levels in the tank. NOTE The display equipment for a multiple- spot averaging ATT should average the readings from the submerged temperature elements sensors to compute the average temperature of the liquid in the tank, and may also display the temperature profile in the tank. 18.104.22.168 variable-length ATT An averaging ATT consisting of several temperature sensors of varying length. All sensors extend upwards from a position close to the bottom of the tank. The ATT system selects the longest, completely submerged temperature sensor to determine the average temperature of the liquid in the tank. 22.214.171.124 averaging ATT An ATT which performs an averaging function, selects one or more temperature sensors submerged within the tank liquid, and determines a representative average temperature based on those sensor reading(s). An averaging ATT may be of the following types: — multiple-spot ATT: A component of the ATT system averages the reading of the submerged temperature sensors to compute the average temperature of the liquid in the tank. — variable-length ATT: The ATT system selects the longest, completely submerged temperature sensor to determine the average temperature of the liquid in the tank. 3.1.2 ATT system An automatic tank thermometer system includes one or more ATTs and device(s) used to display temperatures, perform calculations, and generate alarms as well as the means to transmit data between the ATT(s) and display device(s). 3.1.3 protecting tube A tube designed to enclose a temperature sensing device and protect it from the environment and process. NOTE A protecting tube is not designed for pressure-tight attachment to a vessel.
3.1.7 temperature sensor A temperature sensor is one part of a thermometer in which some physical change occurs with temperature and converts this change into a value on a scale, (e.g. the scale on a liquid-in-glass thermometer, a digital device that displays a unit of measure). 126.96.36.199 resistance temperature detector RTD A temperature measuring device that operates on the principle of a change in electrical resistance in wire as a function of temperature. 188.8.131.52 thermocouple A thermocouple is a junction between two different metals that produces a voltage related to a temperature difference. 3.1.8 temperature transmitter A device that converts the temperature measured by the sensor(s) to electrical or electronic signal, and transmits the signal to a remote or local display. 3.1.9 thermometer A device that measures temperature using any of a variety of different principles. A thermometer has two important components: a temperature sensor in which some physical change occurs that is dependent on temperature, and some means of indicating and/or transmitting this physical change as a value. 3.1.10 thermowell Pressure and liquid tight receptacle adapted to receive a temperature sensing element and provided with external threads, flanges or other means for pressure tight attachment to a vessel. A thermowell allows the temperature sensor to be removed and replaced without compromising the process.
4 Precautions 4.1 General Safety considerations shall be included in all equipment specifications, installation and operation. Refer to API 500, API 551  , NFPA 70  , and API 2003  for guidance. When loading liquids that can accumulate static charges, refer to the precautions described in the International Safety Guide for Oil Tankers and Terminals and in API MPMS, Chapter 3  . Safety and material compatibility precautions should be taken into consideration when using fixed ATT systems. The manufacturer’s recommendations on the use and installation of the equipment should be followed. Users of fixed ATT systems should comply with all applicable codes, regulations, API standards and NFPA 70, National Electric Code (NEC)  . All marine ATTs should be specified and installed in accordance with the appropriate National and/or International (IMO, USCG, IEC, NEC, ISGOTT, ISO, etc.) marine electrical safety standards. ATTs should be certified for use in the hazardous area classification appropriate to their installation.