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API MPMS 7.3 2011 pdf free download

API MPMS 7.3 2011 pdf free download.Manual of Petroleum Measurement Standards Chapter 7.3 Temperature Determination—Fixed Automatic Tank Temperature Systems.
4 Precautions 4.1 General Safety considerations shall be included in all equipment specifications, installation and operation. Refer to API 500, API 551 [3] , NFPA 70 [9] , and API 2003 [4] 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 [1] . 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) [9] . 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. 4.2 Equipment Precautions The following general precautions affect the accuracy and performance of all types of ATT systems. These precautions should be observed where they are applicable. All ATTs should be capable of withstanding the pressure, temperature, and other environmental conditions likely to be encountered in the designated service. When an ATT is installed in a corrosive service, any parts exposed to the liquid or vapor should be of durable, corrosion-resistant construction to avoid both product contamination and ATT corrosion. All ATTs should be sealed to withstand the vapor pressure of liquid in the tank. ATTs mounted on marine vessels with an inert gas system (IGS) should be designed to withstand the operating pressure of the IGS.
The operational range limits, as well as the ambient impact on the measurement accuracy of all equipment as part of a temperature measurement system shall be clearly stated and provided by the equipment manufacturer. The design and installation of ATTs may be subject to the approval of the national measurement organization and/or classification societies, who may have issued a general type approval for the design of the ATT for the particular service for which it is to be employed. Type or pattern approval is normally issued after an ATT has been subjected to a specific series of tests and is subject to the ATT being installed in an approved manner. Security—ATT systems should provide security to prevent unauthorized adjustment. ATT systems used in fiscal/ custody transfer application should provide facilities to allow sealing for calibration adjustment. 5 Equipment and Design Requirements 5.1 Equipment and Apparatus 5.1.1 Temperature Sensors ATTs generally use one of the following types of temperature sensors: — resistance temperature detector (RTD); — thermocouple. These devices are usually housed in metal probes that normally mount into thermowells (spot ATTs) or protection tubes (multi-spot or variable length ATTs). For spot ATTs, the probes are generally tip-sensitive. Thus, the probes shall be securely seated in the bottom of the thermowell for optimum heat transfer. Spring-loaded or adjustable-length probes are recommended. The wiring to the probe is critical because of the low signal levels of the devices. These devices should be installed as recommended by the manufacturer for best accuracy. These sensors require linearization that is typically accomplished within the associated transmitter. Each type of sensor requires its own unique circuit. The selected sensor shall meet the requirements given in Table 4.
5.1.1.1 Resistance Temperature Detectors The resistance temperature detector (RTD) is typically made of platinum although other metals such as copper may be used, which is encapsulated in protective material to guarantee long term stability. The sensing element itself should be packaged in an enclosure suitable for the application and installation (typically this is made out of stainless steel). A suitable electronic circuit can be used to measure the transducer resistance by means of a small current (to prevent self heating) and convert the value into a corresponding temperature. For platinum RTD temperature sensors, standards such as IEC 60751 [8] and ASTM E1137 [7] are available which specify accuracy and performance requirements. These standards cover requirements for various types of testing and define different classes or grades corresponding to different tolerance requirements, as well as mathematical expressions characterizing the temperature-resistance relationship. Sensors produced according to these standards result in the use of either classified or characterized 1 sensors with a stable and well defined relationship between operating temperature and expected tolerances.

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