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A Brief Presentation on Storage Tanks _ What is Piping

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A Brief Presentation on Storage Tanks _ What is Piping
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  14/11/2557A Brief Presentation on Storage Tanks | What is Pipinghttp://www.whatispiping.com/brief-presentation-storage-tanks1/11  A Storage Tank is a static equipment which is used to store products (liquids) in atmospheric pressureconditions. Storage Tanks can be split in to two typesSite-built Tanks Smaller Tank s (transported to site fully assembled) In general site built tanks are designed as verticalc ylinders however smaller tanks may be either vertical/horizontal cylinders or rectangular/square inshape.Large Storage Tanks are constructed on site, onprepared foundations as they are too large to transport.To reduce site work and the amount of equipment required, the component parts of the tank are normally pre-fabricated or pre-formed prior to delivery.  Application: Refinery and PetrochemicalFertilizerOil and GasChemical Type of Storage Tank (Fig. 1): What is Piping  An attempt to explain process piping engineering basics in detail to help all the process piping engineeringprofessionals around the world. HOMEABOUT USPIPING STRESS  PIPING SUPPORTSPIPING DESIGN  FORUMPRIVACY POLICYCONTACT USMISC.  12th November 2014    want2learn   Detail Design    0 Comments A Brief Presentation on Storage Tanks 7  0 271  14/11/2557A Brief Presentation on Storage Tanks | What is Pipinghttp://www.whatispiping.com/brief-presentation-storage-tanks2/11 Storage Tanks can be defined in to three typesCone Roof Storage Tank: A Cone Roof Storage Tank has vertical sides and is equipped with a fixed cone-shapedroof that is welded to the sides of the tank.Open Top Floating Roof Storage Tank: An Open Top Floating Roof Storage Tank is similar to the cone roof tank in construction but with the exception that it has no fixed roof. A pontoon type roof floats directly on theflammable liquid surface.Internal Floating Roof/Covered Floating Roof Storage: An Internal Floating Roof/Covered Floating Roof Storage(see “red” dome) Tank is a combination of both the cone roof or dome and the open top floating roof tank. The tank has a cone roof but with the addition of an internal floating roof or pan that floats directly on the fuel surface. Fig. 1: Cone Roof and floating Roof Storage Tank  Location of Storage Tanks: Storage Tanks are mostly located inside a Tank Farm area inside a bunded area (Fig. 2).Bunded area is necessary around storage tank when the potential environmental and economic risk of tank spillageis great. Its function is to contain spillage so that subsequent damage to adjacent tanks and surrounding areas can be minimised. Fig. 2: Tank location inside Bund Area Component of Storage Tanks: Typically a Tank consists of three components (Fig. 3).  14/11/2557A Brief Presentation on Storage Tanks | What is Pipinghttp://www.whatispiping.com/brief-presentation-storage-tanks3/11 Shell: A cylindrical portion which is resting on the bottom plate and covered by the roof.Bottom Plate: A welded flat bottom plate which is placed beneath the cylindrical shell.Roof: The fixed roof tank is mostly provided with a conical top roof .Larger diameter conical roof tanks are supported by roof structures or columns and the open top tank is mostly provided with a floating roof. Fig. 3: Components of a Storage Tank  Construction of Tank Shell: Tank shell is constructed by butt welding steel plates of specified length and width at there edges in order to form acylindrical shell. Construction of Tank Bottom: The bottom of a tank is constructed from flat plates. Plates are arranged with rectangular plates in the centre andsketch plates (cut to suit radius) around the perimeter. Construction of Tank Roof: The top of a tank is constructed from flat plates. Plates are arranged with rectangular plates in the centre and sketchplates (cut to suit radius) around the perimeter. Type of Roof Support Structures: Fixed Conical or Dome roof tanks are provided with internal rafters or trusses (Fig. 4).Some larger diameter Conical or Dome roof tanks are also provided with column supports. Fig. 4: Various types of roof Supports International Design Codes for Site Built Storage Tanks: The main design codes for vertical cylindrical tanks are:  14/11/2557A Brief Presentation on Storage Tanks | What is Pipinghttp://www.whatispiping.com/brief-presentation-storage-tanks4/11 BS EN 14015:2004 “Vertical Steel Welded Storage Tanks with Butt-Welded Shells for the Petroleum Industry” API 650 “Welded Steel Tanks for Oil Storage”DEP 34.51.01.31-Gen and DEP 64.51.01.31-Gen Design Aspects of Tank: The design aspects of the tank can be divided in to the following:Design standards: The tank can be designed by using different International standards as API 650 and BS EN14015.Plate Size: Although the physical size of the shell plates is a function of the height and diameter of the tank, theactual size is also dependent upon material availability, fabricators facilities and handling/logistic issues. A large plate is the more difficult to form and to handle, however a large plate requires less welding during tank erection. The plate size must therefore be considered on a case by case basis to achieve the most economicaldesign. For example, for a 10m high tank, the most practical and economical plate width would be 2.5m so as toachieve four shell courses. Plates 3.33m wide are large and nonstandard.Loading Conditions:– External / Internal: External loads on a tank may result from adjoining piping or structures. These loads may bedue to for example their static weight or as a result of thermal growth. Due to the useof relatively thin and thereforeflexible steel plates, tanks have a poor ability to resist external loads and therefore measures should be taken tominimize all external loads. Methods to analyze external pipe loads can be found in API 650.– Wind / Earthquake: Wind and earthquake loads depend greatly on the environmental conditions of the proposedsite. Guidance on how to analyze wind and earthquake loads can be found in the appropriate design codes howeverparticular attention should also be given to the risk of wind and earthquakes during tank erection where the fullstability of the tank is not yet available and temporary facilities have to be deployed.– Pressure / Vacuum: Although the maximum external design pressure of tanks is very low (6mbar), it should be noted that tanks are inherently very poor at resisting partial vacuum’s. Care must be taken to ensure that vacuum breaker valves are correctly sized to prevent a partial vacuum forming during for example liquid draw off/draining.See below slide for an example photograph of a tank collapse due to vacuum.Foundations: Although a fabricated tank is relatively light for it’s physical size, due to the static head from theliquid contents the overall load onto the foundations can be considerable. The design of the foundations isespecially important where the ground conditions are soft or inconsistent which could result in the risk of sinking or uneven settlement which could cause failure of the tank. To prevent this problem occurring it isimportant that a soil survey of the proposed site is performed early in the project and the foundations designed tosuit. This analysis may be performed by a civil engineering contractor.On tanks where there is a potential for uplift caused by for example wind loading, the base of the tank should beanchored to the ground using foundation bolts. This is normally done by providing a concrete ring beam around theperimeter of the tank. On smaller tanks the entire foundation may be made from reinforced concrete however due tothe cost, a ring beam is more economical. Uplift can also result from internal pressure bowing the floor when empty and high pressure tanks should always be provided with foundation bolts. The area under the tank floor is typically compacted ground covered with a layer of bitumen coated sand which helps ‘bedding-in’ of the floor plates and as ameans of corrosion protection.Layout: Layout of tanks depends upon a number of parameters such as number of tanks, ground conditions,
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