Storage Tank

storage tank banner 1Storage tank, abbreviated as TK, is used to store volumes of fluids for storage or as part of a process.







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Storage Tank Glossry


Storage Tank Types

  • Vertical Tank (bolted and welded) (double wall and single wall)  -  Vertical storage tanks are most frequently used for bulk storage of water, fertilizer, agricultural and industrial chemicals.
    • Open Top Tank (atmospheric)  -  Normally for petroleum products but can contain cooling water and fire water.
    • Fixed Roof Tank (atmospheric, low pressure, high pressure)  -  Can either be self supported or rafter/trusses supported depending on the size of this non moving roof.  They have a solid top that is attached directly to the shell. Depending on age and design, these tanks may or may not be vapor and liquid tight.  These tanks meet the minimum requirements for storing most liquids and are the cheapest to construct.
      • Cone Roof Tank (supported and self supported)
      • Dome Roof Tank (supported and self supported)
      • Internal Floating Roof Tank (supported and self supported)
    • Floating Roof Tank  -  Roof sits directly on top of product.  These tanks are designed to reduce vapor emissions and volume inside of the tank. This is achieved with the roof floating on the surface of the liquid inside the vessel.  The roof raises and lowers with the liquid level, preventing a buildup of vapor inside.
      • External Floating Roof Tank  -  The roof floats directly on top of the product or on pontoons at the liquid level.  The tank is open to the atmosphere.
      • Internal Floating Roof Tank  -  This tank has two roofs.  The floating roof is the internal component, floating on the liquid.  Above it, there is a fixed roof at the top of the storage vessel.
  • Horizontal Tank (double wall and single wall)  -  A cylindrical steel tank with flat or dished end operating at atmospheric conditions or at pressure and provided with suitable support saddles intended for aboveground storage of non-corrosive, stable, flammable and combustible liquids.
    • Bullet Tank  -  This tank, also known as LPG or LNG storage containers are cylindrical vessels used to store and transport liquefied natural gas (LNG).
  • Spherical Tank  -  These tanks are a closed container designed to hold gas or liquid at a significantly different pressure with the external environment.


Storage Tank Standards

API Standards

  • API Std 620 - Standard for Design and Construction of Large, welded, Low-pressure Storage Tanks
  • API Std 650 - Standard for Welded Steel Tanks for Oil Storage
  • API RP 651 - Recommended Practice for Cathodic Protection of Aboveground Storage Tanks
  • API RP 652 - Recommended Practice for Cathodic Protection of Aboveground Storage Tanks
  • API Std 653 - Standard for Tank Inspection, Repair, Alteration, and Reconstruction
  • API Std 2000 - Standard for Venting Atmospheric and Low-pressure Storage Tanks: Nonrefrigerated and Refrigerated
  • API Std 2015 - Standard for Requirements for Safe Entry and Cleaning of Petroleum Storage Tanks

NACE Standards

  • NACE RP0193 - External Cathodic Protection of On-grade Metallic Storage Tank Bottoms
  • NACE SP0102 - In-Line Inspection of Pipelines
  • NACE SP0106 - Control of Internal Corrosion in Steel Pipelines and Piping Systems
  • NACE SP0169 - Control of External Corrosion on Underground or Submerged Metallic Piping Systems
  • NACE SP0188 - Discontinuity (Holiday) Testing of Protective Coating
  • NACE SP0193 - External Cathodic Protection of On-Grade Carbon Steel Storage Tank Bottoms
  • NACE SP0216 - Steel-Cased Pipeline Practices
  • NACE SP0205 - External Corrosion Control of Underground Storage Tank Systems by Cathodic Protection
  • NACE SP0285 - Corrosion Control of Underground Storage Tank Systems by Cathodic Protection
  • NACE SP0502 - Pipeline External Corrosion Direct Assessment Methodology
  • NACE SP0607 - Petroleum and Natural Gas Industries Cathodic Protection of Pipeline
  • NACE Publication 51317 - Performance Failure of API 650 Oil Storage Tank Bottom Plates Due to Soil Side Corrosion
  • NACE Publication 51318-11258 - Robotic Online Storage Tank Floor Inspection Case Study
  • NACE Publication 51318 - Linings of Aboveground Storage Tanks
  • NACE Publication 1E100 - Engineering Symbols Related to Cathodic Protection
  • NACE TR21447 - Consequences of Coating Failures as Related to Interaction with Cathodic Protection


Storage Tank Glossry


  • Absolute Pressure  -  A pressure at absolute zero can only exist in a total vacuum and any pressure above this is called absolute pressure.
  • Acid Gas (Sour Gas)  -  Any significant amount of hydrogen sulfide (H2S) and carbon dioxide (CO2) contains a natural gas that can cause corrosion.
  • Anchor Bolt  -
  • Anode  -
  • API Std 650 Tank Calculator  -  The API Std 650 standard published by the American Petroleum Institute (API) is designed to provide the petroleum industry with welded steel tanks for use in the storage of petroleum products and other liquid products commonly handled and stored by the various branches of the petroleum industry.
  • API Tank Size  - Based on 8.337 lbs/gallon and is based on stated capacity, not total volume.
  • Atmospheric Pressure  -  The pressure exerted upon the earth's surface by the air because of the gravitational attraction of the earth.


  • Baffle  -  Reduces disturbance and surges from the inlet fluids in horizontal or vertical.  The most used type is a perforated plate in the shape of a segmented circle.
  • Base Plate  -  A plate attached to the bottom of the support that sits on the foundation.
  • Barlow's Formula  -  The point just before or at when a pipe or tubing fails under pressure.
  • Blind Flange  -  A piping component for covering or closing the end of a pipe, valve, vessel or tank.


  • Catalyst  -  A material that aids or promotes a chemical reaction between other substances but does not react itself.
  • Cavitation  -  The creation and collapse of bubbles in a liquid.
  • Corrosion  -  The thinning of a pipe wall that is typically caused by a chemical reaction from a corroding fluid or agent and is limited almost exclusively to metal products.
  • Corrosion Allowance  -  The amount of material in a pipe or vessel that is available for corrosion without affecting the pressure containing integrity.
  • Corrosion Inhibitor  -  A substance that slows down the chemical reaction rate of corrosion on metal that is exposed to the environment.
  • Crude  -  A mixture of naturally occuring liquid hydrocarbons before refining.
  • Crude Oil  -  See crude


  • Data Plate  -  On all vessels. Gives the manufacturer, year manufactured, pressure, temperature, and any other indormation needed about the vessel.
  • Davit Arm  -
  • Design Pressure  -  The pressure the vessel is designed for.
  • Design Temperature  -  The temperature the vessel is designed for.
  • Distillate  -  Products of distillation formed by condensing vapors.


  • Enthalpy  -  Measures the sum of internal energy changes in heat under constant pressure of the system.


  • Flange  -  A bolted connection where two pieces of pipe, equipment, fittings or valves are connected together to form a piping system.
  • Flocculation  -  The process in which small pieces in a solution form clumps of fine particles which can rise or fall to the bottom of the tank.
  • Flush-type Cleanout  -


  • Gate Valve  -  One of the most frequently used valve in piping systems and is classified as either "rising-stem" or "nonrising-stem" valves.
  • Gas Boot Vapor  -
  • Gauge Hatch  -
  • Globe Valve  -  A type of valve used for regulating fluid flow, both on/off and throttling, it is a control valve.
  • Grounding Lug  -
  • Gusset Plate  -  A thick steel plate used to strengthen joints on new and retrofitted structures.


  • Head  -  The end closure of the vessel.
  • Heat  -  A form of energy that causes physical change in what is being heated.
  • Heat Transfer  -  The exertion of power that is created by heat, or the increase in temperature.
  • Heavy Crude  -  Crude oil with a high proportion of heavy hydrocarbons and metallic content.
  • Holiday  -  A discontinuity in painted or coated surfaces.


  • Inlet with Spreaded  -


  • Jacket Vessel  -  An external cavity around the vessel, controlling the temperature of the contents of the vessel through a cooling or heating fluid.



  • Latent Heat  -  The energy absorbed or released by a substance during a constant temperature or phase change from a solid to liquid, liquid to gas or vise versa.
  • Level Interface  -
  • Level Switch  - Provides a discrete input to the PLC.  The level switch is typically used as a method of control in tanks and vessels.
  • Light Crude  -  Crude oil with a light proportion of light hydrocarbons fractions and low metallic compounds.
  • Liquid  -  A specific volume and can hold any shape it is contained within.
  • Liquefied Natural Gas  -  Natural gas cooled to a liquid state.


  • Manway  -  An opening on a tank or vessel designed as an entryway for personal access and equipment.
  • Mass Flow Rate  -  The average velocity of a mass that passes by a point.
  • Maximum Operating Pressure  -  The maximum pressure permissible at the top of the vessel during normal operation.
  • Maximum Operating Pressure  -  The maximum temperature permissible that provides sufficient flexability during normal operation.


  • Nameplate  -  On all vessels. Gives the manufacturer, year manufactured, pressure, temperature, and any other indormation needed about the vessel.
  • Nozzle  -  An opening in a tank or vessel for a flanged connection.


  • Oil outlet  -
  • Overflow  -


  • Petroleum  -  See crude
  • PH  -  How acidic or alkakine water is.
  • Pressure  -  It is the force exerted perpendicular to the surface of an object and is expressed as force per unit area.
  • Pressure Loss  -  The difference in upstream and downstream pressure.
  • Pressure Safety Valve  -  Used to protect vessels and tanks from overpressure. It is designed to protect critical system components such as pressure vessels, tanks and flange ratings.
  • Programmable Logic Controller  -  The types of signals are analog output (AO), analog input (AI), discrete output (DO), and discrete Input (DI).



  • Raw Water  -  Untreated water.
  • Reinforcing Pad  -  A plate formed to the shape of the tank or vessel around a nozzle for extra strength. Also known as repad or weld pad.


  • Saddle  -  Used to support horizontal and vertical designs in locations to support the concentrated loads at on each end of the vessel.
  • Sample Box  -  A sample box is a series of pipe, valves and fittings located on a pressure vessel or tank that is used to manually determine the height of the liquid or where the interface between oil and water resides.
  • Sand Pan  -
  • Saturated Steam  -  The point (temperature and pressure) when steam is in contact with the liquid water (boiling) it came from.
  • Sensible Heat  -  The heat added to a substance which increases its temperature but not the phase is called sensible heat.
  • Shell  -  The cylinder portion of the vessel.
  • Shell Nozzle  -
  • Shell Platform  -
  • Slip-on Flange  -  Designed to slip over the outside of pipe, long-tangent elbows, reducers, and swages.
  • Sour Gas  -  See acid gas
  • Specific Gravity  -  The density or ratio of any substance to another substance.
  • Stack Gas  -  Anything that comes out of a burner stack in gaseous form.
  • Stress  -  The force per unit area of cross-section.
  • Stub End  -  Allows a flange to swivel in order to mate with another flanges bolt holes that may not align perfectly.
  • Sweet Crude  -  Crude oil with a sulfur content less than 0.5% by weight, no sulfur smell.


  • Tail Gas  -  The lightest hydrocarbon gas released from a refining process.
  • Tank Blanketing  -  The injection of gas into a storage tanks vapor space.  The purpose of the blanket is to maintain a layer of gas above the liquid to prevent the entrance of air into the tank.
  • Tank Coils  -  Placed in tanks and are designed to transfer heat from steam vapor or condensate to the tank.
  • Tank Foundation  -  The purpose of a tank foundation is to provide a level surface for the tank and to equally transmit the load of the tank and its contents to the soil.
  • Tank Vent  -  It relieves over pressure and under pressure scenarios caused by the process.
  • Temperature  -  The amount of heat or cold, but it is neither heat or cold.
  • Tension Strength  -  The capacity of a material to resist a force tending to stretch it.
  • Thermal Expansion  -  The increase in length, area or volume due to the increase (in some cased decrease) in temperature.
  • Thermowell  -  Used in temperature measurement and provide isolation from the temperature sensor and the process fluid.
  • Truck Connection  -



  • Vacuum Breaker  -  A vent on top of the vessel that allows air to be pulled into the tank.
  • Vacuum Tank  -  Uses high-pressure hoses to clean out liquids and sludges without any damage to the object being cleaned.
  • Vapor Recovery  -  A vapor recovery system is a series of components that work together to keep fugitive emissions from escaping into the surrounding environment.
  • Venting Roof Nozzle  -
  • Vessel Internals  -  Vessels have internals to help them effectively process the fluids go through it.
  • Viscosity  -  The measure of the internal friction/resistance to the flow of a liquid.
  • Vortex Breaker  -  When the flow exits a nozzle it will create a vortex.  A cross of plates on the discharge nozzle will prevent the discharge from swirling.


  • Water  -  Can exist in three of the four phases of matter: gas, liquid, or solid.
  • Water Outlet  -
  • Weep  -  A term applied to a minute leak.
  • Welding  -  The fabrication process that fuses like materials togeather by heating them to a suitable temperatures, this can be acomplished by brazing, soldering or welding.
  • Wet Gas  -  A gas containing a relatively high portion of hydrocarbons that are recoverable as liquids.
  • Wier Box  -



  • Yield Strength  -  The minimum stress that leads to permanent deformation of the material.



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