API MPMS 19.3E:1997(R2012) pdf download.Manual of Petroleum Measurement Standards Chapter 19.3—Evaporative Loss Measurement
3 Terminology
3.1 DEFINITIONS For the purpose of this standard, the following definitions apply. 3.1.1 data acquisition: The process of receiving signals from the sensors, determining the values corresponding to the signals, and recording the results. 3.1.2 deck: That part of a floating roof which provides buoyancy and structure, and which covers the majority of the liquid surface in a bulk liquid storage tank. The deck has an annular space around its perimeter to allow it to rise and descend (as the tank is flled and emptied) without binding against the tank shell. This annular space is closed by a fexi- ble device called a rim seal. The deck may also have penetra- tions, closed by deck fttings, which accommodate some functional or operational feature of the tank. 3.1.3 deck fitting: The device which substantially closes a penetration in the deck of a floating roof in a bulk liquid storage tank. Such penetrations are typically for the purpose of accommodating some functional or operational feature of the tank. 3.1.4 floating roof: A device that floats on the surface of the stored liquid in a bulk liquid storage tank. A foating roof substantially covers the liquid product surface, thereby reduc- ing its potential for exposure to evaporation. Floating roofs are comprised of a deck, a rim seal, and miscellaneous deck fttings. 3.1.5 indicator: An instrument that displays or records signals received from a sensor. The indicator is typically con- structed to express the signal in units that are useful to describe the observed value of measurement. For example, an electronic signal may be received by the indicator as volts, but then displayed as pounds. An indicator may be incorpo- rated into an electronic data acquisition system. An electronic data acquisition system typically has the capability to be pre- programmed to record data at prescribed intervals, to analyze the data that has been received, and to electronically store the results. 3.1.6 instrument: A device used in the measurement pro- cess to sense, transmit, or record observations. 3.1.7 internal floating roof: A floating roof that is not exposed to the ambient environmental conditions by virtue of being in a bulk liquid storage tank that has a fixed roof at the top of the tank shell. Internal floating roofs are thus distin- guished from extermal floating roofs, which are located in tanks that do not have a fixed roof to protect the floating roof from environmental exposure. Internal floating roofs are typically designed in accordance with Appendix H of API Standard 650. 3.1.8 loss factor: An expression used to describe the evaporative loss rate characteristics of a given floating-roof device. In order to obtain the total standing-storage evapora- tive loss rate for a bulk liquid storage tank equipped with a floating roof, the sum of the evaporative loss factors for each of the individual devices is modified by certain characteristics of both the climatic conditions and the stored liquid. The characteristics of the stored liquid are expressed as a vapor pressure function, the stock vapor molecular weight, and a product factor.