API MPMS 7.1-2017 pdf download.Manual of Petroleum Measurement Standards, Chapter 7.1 Temperature Determination— Liquid-in-Glass Thermometers.
3.3 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. 3.3.1 liquid-in-glass thermometer (LIGT) A glass thermometer containing mercury or a low-hazard liquid that indicates the temperature being measured. 3.3.2 low-hazard liquid A liquid that is biodegradable, non-hazardous and considered non-toxic in quantities specified for the thermometer specification. 3.3.3 mercury-in-glass thermometer (MIGT) A glass thermometer containing mercury that indicates the temperature being measured. 3.3.4 partial-immersion thermometer A liquid-in-glass thermometer designed to indicate temperatures correctly when the bulb and a specified part of the stem are exposed to the medium being measured. 3.3.5 total-immersion thermometer A liquid-in-glass thermometer designed to indicate temperatures correctly when just that portion of the thermometer containing the liquid is exposed to the medium being measured. 4 General Precautions 4.1 Safety Safety shall be considered for the specification, installation and operation of all equipment. Refer to API RP 500 and NFPA 70 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, Safety of Life at Sea, API MPMS Chapter 3, and API RP 2003. Care must be taken with all liquid-in-glass thermometers to prevent breakage, which will result in a safety hazard. If the liquid in the thermometer is mercury, additional care must be taken.
6 Equipment and Design Requirements 6.1 Liquid-in-Glass Thermometers 6.1.1 General Information Due to the identified hazards associated with mercury-in-glass thermometers (MIGTs), its use is being phased out. API, in collaboration with the U.S. Environmental Protection Agency, conducted a comparison study of MIGTs to other liquid-in-glass and digital thermometers in order to provide a comparison of the accuracies of each type of device. The testing indicated that alternative liquid-in-glass thermometers meeting the requirements in ASTM E2251 can be substituted for MIGTs. Annex A provides additional details of the testing that was conducted. 220.127.116.11 Thermometer Specifications Glass thermometers include total-immersion thermometers and partial-immersion thermometers (see Figure 1 and refer to ASTM E344). These thermometers should conform to the specifications in ASTM E1 or E2251 for thermometers, or to the National Institute of Standards and Technology (NIST) specifications. Calibration does not have to be done by a national metrology institute (NMI) (e.g. NIST in the United States), but the certified instruments used for the calibration shall be traceable to a NMI. ASTM thermometers are designed to be either total immersion (thermometer immersed in the medium to be measured to the top of the thermometer liquid column) or partial immersion (thermometer in the medium to be measured to a specific depth marked on the thermometer). Tank thermometers used in conjunction with a cup-case assembly are total-immersion thermometers that are completely immersed into the tank but only a portion of the thermometer is immersed in the cup when read. Testing has shown that the accuracy of the reading is not affected when read quickly after being raised out of the tank.
Operating thermometers that are used in static or dynamic measurement shall be compared on a regular basis (see Section 8) to a temperature standard. The recommended allowable tolerances between the operating thermometer and the NMI traceable thermometer are shown in Table 1, and are provided as a reference for limits considered acceptable for static and dynamic temperature determinations in custody transfer measurement of petroleum and petroleum products. 18.104.22.168 Permanent Glass Thermometers Securely mount permanently installed glass thermometers in a thermowell and protect from breakage by the use of a housing. They shall have the same high resolution scale graduation interval and tolerance as glass test thermometers. These thermometers shall be calibrated and checked using test thermometers as described in Section 8. 22.214.171.124 Tank Thermometers Tank thermometers shall be of the total immersion type and shall be made in accordance with the specifications in ASTM E1 or E2251. Each thermometer shall be the liquid-in-glass type with nitrogen or another suitable inert gas filling the space above the liquid column, and with graduation marks permanently etched on its glass stem. Angle- stem thermometers may use a separate graduated scale, as discussed in 6.2.3. The thermometers listed in Table 2 shall be used.