Petroleum Tankage and Terminal Design 8A

Petroleum Tankage and Terminal Design

Introduction Storage tank: container for holding liquids or compressed gasses. Tank farms: group of tanks for the commercial storage of oil and petroleum products. it is generally provided with a bund wall and contained pipe rack, drainage, fire-suppressant piping. bunds: designed to contain any spills from the tank or tank piping. Bunding is a legal requirement and a requirement for insurance companiesthe height of the bund walls is designed to assure the retention go any fuel spillage remain within the tank farm boundary. bund containment should exceed 110% of the storage capability in each bund * 180% of the volume of the largest tank) each tank is separated by bund walls to hold minor spillsWithout storage facilities, pipelines are limited in the markets they can serve and would be limited in the commodities they can haul.Pipelines are the only mode of transportation with no backhaul ( unidirectional) Buffers:synthetic crude oil that is semi refined. it is used as a buffer between the natural gas liquids and the refined products. this assures that NGL doesn't migrate into refined products and affect their vapor pressure and flash points. Typical volume is about 2000 to 3000 Product Storage depends on: what products are delivered how the products are delivered the rate of the products delivered the sequence of the products delivered Intermediate storage: crude charge: 1 to 2 days supply per crude grade + one identical tank unit rundown: 1 to 4 days production capacity + one identical tank per group Blending stock: 5 days storage at production rates + one identical tank per group Refined Product Storage: pipeline shipment: for each product, frequency rate, reliability Truck and rail: truck or tank car size, time for loading, loading capacity Marine Shipment: largest ship capacity and ship frequency, Number of ships at one time Basic tank Designs: fixed roof domed external floating roof variable vapor space external floating roof internal floating roof pressure Fundamental classification is based above whether they're above (AST) or below ground. (UST)storage tankes operate under very little to no pressure in the united states, they're cylindrical in shape and perpendicular to the ground with flat, slopping bottoms and a fixed or floating roof. Types of tanks: Atmospheric : Fixed roof, floating roof Pressurized: Variable vapor space, high pressure, low pressure Heated Tanks: high viscosity oil (bitumen, asphalt) Refrigerated Tanks: cryogenic, refrigerated the shape of the roof is an indicator of the type of a tank.the safe design of floating roof tank offers a considerable level of fire safety over other vertical tank designs ( thats why fire codes allow closer spacing between floating roof tanks) Fixed Roof Tanks: for hydrocarbon liquids with very high flash point at which the vapor pressure is of order 3.5 KPalosses from fixed roof tanks are caused by: changes in temperature changes in pressure changes in liquid level They are either: freely vented or equipped with a pressure vacuum vent this allows tanks to operate at a slight internal pressure or vacuum to prevent the release of vapors during small changes in P,T, & liquid level. It is the least expensive to construct and is considered the minimum acceptable equipment for strong organic liquidsroof designs: cone roofs: they have cylindrical shells in the lower part. most widely used for large quantities of fluid steel dome roofs: self supported or column supported. umbrella roofs: does not have to be supported by columns to the bottom of the tank geodesic dome-roof tanks: made of aluminum, advantages are that they have a higher corrosion resistance. they are more economical. they don't require supports and can be built to any required diameter Floating Roof Tanks External floating roof tanks internal roof tanks products stored there are those of a higher vapor pressure between 10Kpa and 77 Kpa those include light and medium crude, gasoline, reformat, naphtha and jet fuelsthey have a roof that floats on the surface of the liquid. it has the sufficient buoyancy to ensure that the roof will float under all expected conditions even if leaks develop in the roof. External floating roof: used to store large quantities of volatile petroleum products such as crude oil or gasolinethe float can be of the following designs: Pan type Pontoon type Double deck type Buoy roof type the floating roof consists of a deck, fittings, and rim seal system. the roof rises and falls with the liquid level in the tankthere is no ullage in the floating tank. this eliminates breathing losses Rim Seal System: attached to the deck perimeter and contacts the tank wall. this reduces the evaporative losses of the stored liquidAdvantages: environmental or economical reasons to limit product loss and reduce the emission of volatile compounds. it has a much smaller risk of internal tank explosion. Disadvantages: Rain water and snow can accumulate on the roof, the roof may eventually sink. the water is drained using a flexible hose that runs from a drain-sump on the roof, through the store liquid to a drain valve on the shell at the base of the tank. however; the hose often develops leaks and drains both water and product. Domed External Floating Roof Tanks: they have a heavier type of deck fixed roof at the top of the shell the function of the internal floating roof is to block the wind as well as keep rain and snow out of the tank and off the floating roof Internal floating roof tanks: has a permanent fixed roof and a floating roof inside.Types of internal floating roof tanks: fixed roof supported by vertical columns within the tank tanks with a self supporting fixed roof advantages: decreases the level of evaporation of stored product lower risk of fire has low height and storage capacity is increased offers protection from ambient climatic conditions no requirement for mounting of rood drain Pressurized Storage tank: used for storing hydrocarbon fluids and gases with high vapor pressures low pressure tanks: cylindrical spheroid Noted Spheroid High Pressure storage tanks bullets spheres they're equipped with a pressure/vacuum vent that is set to prevent venting loss from boiling and breathing loss from daily temperature or barometric pressure changes.