API MPMS 16.2:1994(R2012) pdf download.Manual of Petroleum Measurement Standards Chapter 16—Measurement of Hydrocarbon Fluids By Weight or Mass
1 Scope
This standard provides guidance on the installation, commissioning, maintenance, validation, and calibration of hydrostatic tank gauging systems for the direct measurement of static mass in petroleum storage tanks. This standard is applicable to hydrostatic tank gauging systems that use pressure sensors with one port open to the atmosphere. This standard is applicable to the use of hydrostatic tank gauging on vertical cylindrical atmospheric storage tanks with either fixed or floating roofs. This standard is not applicable to the use of hydrostatic tank gauging on pressurized tanks. Safety and material compatibility precautions should be taken when using HTG equipment. ManufacturerÕs recom- mendations on the use and installation of the equipment should be followed. Users should comply with all applicable codes and regulations, API standards, and the National Elec- tric Code.
2 Introduction
Hydrostatic tank gauging is a method for the determina- tion of total static mass of liquid petroleum and petroleum products in vertical cylindrical storage tanks. HTG uses high precision stable pressure sensors mounted at specific locations on the tank shell. Total static mass is derived from the measured pressures and the tank capacity table. Other variables, such as level, observed and standard volumes, and observed and reference densities, can be calculated from the product type and temperature using the established industry standards for inventory calculations. The term ÒmassÓ is used to indicate mass in vacuum (true mass). In the petroleum industry, it is not uncommon to use apparent mass (in air) for commercial transactions.
4 Definitions
For the purpose of this standard, the following definitions apply: 4.1 ambient air density: The density of air at the tank side on which the pressure sensors are mounted. 4.2 ambient air temperature: The representative temperature of the ambient air at the tank side on which the hydrostatic tank gauging (HTG) pressure sensors are mounted.4.3 critical zone height: The upper limit of the critical zone; the level at which one or more of the floating roof or floating cover legs first touch the tank bottom. 4.4 critical zone: The level range through which the floating roof or floating cover is partially supported by its legs. 4.5 floating roof mass: The manually entered value of the floating roof mass inclusive of any mass load on the roof. 4.6 free water level: The level of any water and sediment that exist as separate phases from the product and lie beneath the product. 4.7 gauge pressure sensor: A sensor that uses the ambient atmospheric air pressure as the pressure reference. 4.8 head mass: The total measured mass between the HTG bottom sensor and the top of the tank. 4.9 head space: The space inside the tank, above the bottom HTG sensor. Product and in-tank vapor are present in the head space. 4.10 heel space: The space inside the tank, below the bottom HTG sensor.
API MPMS 16.2:1994(R2012) pdf download
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