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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Nomenclature & Symbols


Storage Tank Glossry


Storage Tank Types

Vertical tank (bolted and welded) (double wall and single wall)

  • Open top tank (atmospheric)  -  Normally for petroleum products but can contain cooling water and fire water.
  • Fixed roof tank (atmospheric, low pressure, high pressure)  -  Either be self supported or rafter/trusses supported depending on size.
    • 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.
    • External floating roof tank  -  Roof sits directly on top of product, open to atmosphere.
    • Internal floating roof  tank -  Roof sits directly on top of product, tank has a fixed roof.

Horizontal tank (double wall and single wall)

  • Bullet tank  -  Presurized liquid gas tank.

Spherical tank  -  Presurized liquid gas tank.


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  -
  • 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.
  • 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  -  A nozzle, abbreviated as NOZ, is a 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.


  • 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.
  • 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  -
  • 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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