API MPMS 7:2001(R2012) pdf download.Manual of Petroleum Measurement Standards
5.1.2 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 pres- sure, 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 dura- ble, corrosion-resistant construction to avoid both prod- uct 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. ¥ CompatibilityÑTo avoid both product contamination and equipment corrosion, all parts of the ATT equip- ment in contact with the product should be compatible with the product. The ATT equipment should be designed to meet the operating conditions. Note 1: This protection may require mounting the ATT sen- sor(s) in a thermowell. Note 2: ATT sensors can be an integral part of the automatic tank gauging system (ATG) level sensor assembly (e.g., ßoat and tape, pole). Some designs (e.g., ßoat and tape) may need the level/temperature sensor assembly to be raised to a ÒstoreÓ position when it is not being used. Note that such ATTs cannot be used during tank washing on marine vessels.¥ All marine ATTs should be speciÞed and installed in accordance with the appropriate National and/or Inter- national (IMO, USCG, IEC, NEC, ISGOTT, ISO, etc.) marine electrical safety standards. ¥ ATTs should be certiÞed for use in the hazardous area classiÞcation appropriate to their installation. ¥ All external metal parts of ATTs mounted on tanks should be Þrmly connected to an electrical earth. This will be the shipÕs hull in the case of marine ATTs. ¥ All ATT equipment should be maintained in safe oper- ating condition and manufacturersÕ maintenance instructions should be complied with. Note: The design and installation of ATTs may be subject to the approval of the national measurement organization and/or classiÞcation 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 speciÞc series of tests and is subject to the ATT being installed in an approved manner. Type approval tests may include the follow- ing: visual inspection, performance, vibration, humidity, dry heat, inclination, ßuctuations in power supplies, insulation, resistance, electromagnetic compatibility, and high voltage. ¥ Tank LevelsÑTank levels should be measured at the same time the tank temperature is measured.
API MPMS 7:2001(R2012) pdf download
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