API STD 2000 pdf free download
API STD 2000 pdf free download.Venting Atmospheric and Low-pressure Storage Tanks.
2.16 relief device Device used to relieve excess pressure and/or vacuum that has developed in a tank. 2.17 relieving pressure Pressure at the inlet of a relief device when the fluid is flowing at the required relieving capacity. 2.18 required flow capacity Flow through a relief device required to prevent excessive pressure or vacuum in a tank under the most severe operating or emergency conditions. 2.19 rollover Uncontrolled mass movement of stored liquid, correcting an unstable state of stratified liquids of different densities and resulting in a significant evolution of product vapor. 2.20 set pressure Gauge pressure at the relief device inlet at which the device is set to start opening under service conditions. 2.21 standard cubic feet per hour SCFH USC unit for volumetric flow rate of air or gas (same as free air or free gas) at a temperature of 15.6 °C (60 °F) and an absolute pressure of 101.3 kPa (14.7 psi), expressed in cubic feet per hour. 2.22 thermal inbreathing Movement of air or blanketing gas into a tank when vapors in the tank contract or condense as a result of weather changes (e.g. a decrease in atmospheric temperature). 2.23 thermal out-breathing movement of vapors out of a tank when vapors in the tank expand and/or liquid in the tank vaporizes as a result of weather changes (e.g. an increase in atmospheric temperature). 2.24 vapor pressure The pressure exerted when a liquid is in equilibrium with its own vapor. Vapor pressure is a function of the substance and temperature. 2.25 wetted area Surface area of a tank exposed to liquid on the interior and heat from a fire on the exterior. 3 Nonrefrigerated Aboveground Tanks 3.1 General Section 4 covers the causes of overpressure or vacuum; determination of venting requirements; means of venting; and selection and installation of venting devices.
3.2 Causes of Overpressure or Vacuum 3.2.1 General When determining the possible causes of overpressure or vacuum in a tank, consider the following: a) liquid movement into or out of the tank; b) weather changes (e.g. pressure and temperature changes); c) fire exposure; d) other circumstances resulting from equipment failures and operating errors. There can be additional circumstances that should be considered but are not included in this standard. 3.2.2 Liquid Movement into or out of a Tank Liquid can enter or leave a tank by pumping, by gravity flow, or by process pressure. Vacuum can result from the outflow of liquid from a tank. Overpressure can result from the inflow of liquid into a tank and from the vaporization or flashing of the feed liquid. The user is cautioned that a flashing feed stream can create an outbreathing load that is much greater than the volumetric inflow of liquid. See 3.3 for calculation methods. 3.2.3 Weather Changes Vacuum can result from the contraction or condensation of vapors caused by a decrease in atmospheric temperature or other weather changes, such as wind changes, precipitation, etc. Overpressure can result from the expansion and vaporization that is caused by an increase in atmospheric temperature or weather changes. See 3.3 for calculation methods. 3.2.4 Fire Exposure Overpressure can result from the expansion of the vapors and vaporization of the liquid that may occur when a tank absorbs heat from an external fire. See 3.3.3 for calculation methods. 3.2.5 Other Circumstances 3.2.5.1 General When the possible causes of overpressure or vacuum in a tank are being determined, other circumstances resulting from equipment failures and operating errors shall be considered and evaluated. Calculation methods for these other circumstances are not provided in this standard.
