VALERO MEMPHIS REFINERYTANK FARM OPERATING MANUAL
Revision Date: / TANK FARM Pumper No. 1/2/3 Section 1200 Mechanical Description / Annual Certification DateOriginal Date: Oct. 2001
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Section 1200: Mechanical Descriptions
Table of Contents
General Information:
Storage Tanks:
Cone Roof:
Floating Roof Tanks:
LPG / Pressurized Tanks:
Pumps:
Centrifugal Pump:
Positive Displacement Pump:
Peristaltic Pump:
Problems with Pumps:
Cavitation:
Other unusual noises to be alert to are:
For more information:
Valves:
General Information:
Gate Valve:
Globe Valve:
Ball Valve:
Butterfly Valve:
Diaphragm Valve:
Control Valve:
For more information:
Filters:
Clay Filter:
Sock Filters:
Heat Exchangers:
General Information:
For more information:
Miscellaneous Equipment:
General Information:
General information regarding equipment used in the Refinery was covered in Refinery Fundamentals classes. The books and videos covering this information are available for review in the Safety and TrainingCenter. This section provides more specific details on the functions, design, maintenance, and proper use of tanks, pumps, filters, and other equipment used in the Refinery tank farm. A full equipment list is included in the Appendix, Section 1500.
Storage Tanks:
Tanks for storage of petroleum products fall into two categories: those designed for storage atmospheric pressure and those designed for pressurized storage. Crude oil, kerosene, gasolines, and other liquid products use atmospheric storage tanks. Liquefied petroleum gases, butanes and propane, are stored in pressurized bullets.
Atmospheric storage tanks are either of the enclosed, cone roof design or floating roof design. In addition, some cone roof tanks, such as 47 Tk, are equipped with internal floating roofs. The floating roof design minimizes the escape of vapors into the atmosphere. External floating roof tanks can be fitted with domes to further reduce vapor emissions, as was done with 72 Tk and 60 Tk.
Cone Roof:
The cone roof tank design is the simplest and least expensive, but releases more vapors than other designs. Consequently, they are used for heavier hydrocarbon products such as fuel oils and kerosene.
Cone roof tanks are fitted with vents that allow the tank to breathe. Pressures within the tank that are substantially above or below atmospheric pressure can distort and damage the structure. Low pressure inside the tank can literally collapse the tank, due to the greater outside pressure.
Valero’s tanks are also equipped with flame arresters, which prevent outside ignition sources from igniting the tanks' contents.
Other auxiliaries on cone roof tanks include water draws, foam injection fixtures, thermal wells, and gauging devices. Tanks used for the storage of heavy oils such as No. 6 fuel oil or gas oil also contain steam coils, to keep the product fluid during the winter.
Floating Roof Tanks:
The floating roof design is used on gasoline storage tanks, as now required by law. This includes not only blended gasolines, but also raw gasolines used as blend stock. Older tanks now used for storage of lighter products have been retrofitted with internal floating roofs to prevent vapor emissions.
The floating roof tank design is a basic cylindrical shell with no roof. Near the top, running around the outer circumference of the tank, is a wind girder, a shelf-like structure that reinforces the tank shell and prevents collapse due to aerodynamic forces. The roof floats on the surface of the tank's contents, and is either of a double-deck or single-deck pontoon design. Most floating roofs in the Refinery tank farm are of the pontoon design. Around the outside edge of the roof is a flexible seal that prevents vapor loss. A drain in the middle of the roof prevents rainwater from accumulating, which could submerge or tilt the roof, damaging the tank and allowing the release of hydrocarbon vapors. Roof supports, or legs, support the weight of the roof when the product level is low.
LPG / Pressurized Tanks:
Most LPG storage tanks are of the horizontal, cylindrical, bullet design. They are constructed to store products that would normally vaporize at ambient temperatures and pressures. Typical pressures may range from atmospheric to about 150 psig.
Besides the usual temperature and gauging fixtures, LPG tanks are equipped with pressure relief valves that vent to the atmosphere in the event a tank is overfilled or over pressurized. The valves are set to release at 250 psig (350 for the P/P tanks).
Spheres are designed to hold pressurized liquefied petroleum gases in larger quantities than do the bullets. Like the bullets , the LPG spheres are fitted with temperature, gauging, and pressure relief fixtures.
Pumps:
Centrifugal Pump:
The differences in properties among different products used in the tank farm necessitate different types of pumps. The majority of pumps are of the single-stage centrifugal type. The centrifugal pump uses an impeller to impart a centrifugal mechanical force to move liquids through a pipeline. Centrifugal pumps are used with both light and heavy liquid petroleum products, as well as process and surface water.
Multi-stage centrifugal pumps differ from single-stage pumps in that they have multiple impellers. Examples of multi-stage pumps include the Jet A pipeline pumps.
In the tank farm, the Sundyne pump is used primarily for LPG applications. The Sundyne uses a vertically mounted motor and an internal gear assembly that increases impeller speeds.
Positive Displacement Pump:
The positive displacement pump operates differently than centrifugal pumps. Rather than using impellers, the pump uses pistons, gears, or other means of displacing liquids. Positive displacement pumps are often used for chemical and additive injection, where precise metering of the substance is necessary.
Peristaltic Pump:
Peristaltic pumps, also called hose pumps, use the principle of peristalsis to displace liquids in a flexible tube, using a rotary drive. The peristaltic pump is also useful for accurate metering of chemical additives.
Problems with Pumps:
Any time a pump is started, the pumper should perform a quick visual inspection. Make sure the pump is operating at normal pressure. Check the pump for leaks and ensure that the oil level is adequate. The pumper can correct leaks that can be sometimes remedied by tightening the packing. Leaks involving the pump casing should be reported to the Tank Farm Supervisor, Maintenance Supervisor and SAP Work Notification written.
Cavitation:
Check the pump for unusual sounds. A rattling noise in the pump is an indication of cavitation. Cavitation is the vaporization of product inside the pump casing. With vaporization comes a rapid expansion that places abnormally high mechanical force on internal components of the pump, which can lead to damage. Cavitation can result from having a pump suction valve closed or pinched down, or letting a tank go on air. When lining up a pump, always make sure the suction valve is fully open. Bleeding the air off of the pump can usually correct cavitation, by getting rid of vaporized product.
Other unusual noises to be alert to are:
A growling or buzzing sound coming from the pump can indicate worn bearings. Write a work order to have the bearings checked.
Broken internal components or foreign objects, such as welding rods or shards of sample bottles, may cause a rattling sound that is more pronounced than a cavitation noise. If you suspect damage, write a work order to have the pump checked by maintenance.
A screeching or grinding sound is usually caused by metal-to-metal contact. Check the pump oil level to make sure it is adequate; the noise may be a result of insufficient lubrication. If the oil level is OK, write a work order to have the pump examined.
For more information:
More detailed information on pumps can be found in the NUS Operations Process Training manuals, Pumps 1, Pumps 2, and Pumps 3, and their corresponding videos. This material is located at the Safety and TrainingCenter.
Valves:
General Information:
A valve is a mechanical device used to control or shut off flow of product through a pipeline. The valve is the single most important means of controlling product flow through pipelines, ensuring that product goes where it is supposed to, and equally important, ensuring that product doesn't go where it's not supposed to.
Valve types include gate valves, globe, ball, butterfly, and diaphragm valves. In addition to being manually operated, valves can be motor-driven, pneumatic, or solenoid actuated.
Check valves allow flow in only one direction, and are used to prevent the reversal of flow in pipelines. Relief or safety valves are set to open at a set pressure to prevent equipment failure or damage due to over pressurization.
Gate Valve:
The gate valve is the most common valve type in the tank farm. This is because the gate valve, when open, offers the least resistance to the product flowing through it. The gate valve is also the only suitable means of completely stopping flow through a pipeline. It does not offer a reliable means of throttling flow.
Globe Valve:
The globe valve is similar to a household water spigot. Its construction allows it to be useful in regulating the rate of flow, as the flow rate is related to the number of turns the hand wheel is opened.
Ball Valve:
Ball valves use a spherical internal part, through which a passage is bored, to control flow. This construction allows the valve to go from closed to fully open in a quarter of a turn.
Butterfly Valve:
The butterfly, or disc, valve uses a circular flapper to close off product flow. This type of valve offers quick control, but does not provide a tight shutoff.
Diaphragm Valve:
The diaphragm valve uses a flexible diaphragm to regulate or shut off flow. It is often used with corrosive substances like caustic soda, since the diaphragm seals the working parts of the valve off from the product that flows through the valve.
Control Valve:
Control valves use pneumatic pressure to actuate a valve plug to open, close, or regulate product flow. Control valves are usually remotely activated on a control loop and are tied in to temperatures, pressures, levels, or flow controls.
For more information:
If you need to know anything more about valves, you may examine the NUS Operations Process Training manuals, Valves 1 and Valves 2, and their corresponding videos. This material is located at the Safety and TrainingCenter.
The UOP TYRO manual also contains a section on valve construction.
Filters:
Products may contain particulate material that must be removed. This is accomplished through filtration. All products pumped to Bottom Loading are filtered. Jet A kerosene has stringent specifications for allowable particulates, and is filtered before going to storage and again before going to the truck dock. Product Filtration is accomplished using two different types of filtering media:
Clay Filter:
Filters on the kerosene rundown line are cylindrical, vertical vessels packed with clay. Kerosene enters at the top of the filter, passes through the filter medium, and then exits from the bottom. Particulates are trapped in the clay. As the filter collects particulate contamination, resistance to flow-through increases, and the clay must be replaced. Product flow is re-routed through a second spare filter so the first filter can be recharged with fresh clay.
Clay filters require an amount of back pressure in order to filter efficiently. The backpressure also helps prevent channeling, which is the displacement of the filter medium by the product flowing through it. As the product displaces the medium, it creates a path of least resistance to the filter outlet, reducing filter efficiency.
Sock Filters:
Filters on the bottom loading lines are kettle-shaped and packed with sock-like filter elements that can be changed out relatively quickly. This type of filter requires no additional back pressure, and traps particulates in the fibers of the socks as the product passes through. The socks must be replaced periodically due to the accumulation of particulates.
Heat Exchangers:
General Information:
Petroleum products may occasionally need to be heated or cooled, for example, to keep heavy products fluid in the winter, or to vaporize LPGs. A simple principle of physical science is that energy flows from areas of higher activity to areas of lower activity. For example, when an ice cube is placed in a glass of water, heat energy from the water transfers to the ice cube, causing it to melt. At the same time, the temperature of the water falls, cooling the water.
In a similar way, a heat exchanger raises product temperature by drawing heat from another source, such as steam, and transferring the heat energy to the product. The heat exchanger may also work in the opposite fashion, cooling hot product by transferring its heat to a cooler medium, such as water. In both cases the action is the same, the only difference being which liquids temperature is being adjusted.
The heat exchanger is constructed as a bundle of tubes encased in a shell. A material is pumped in to one side of the bundle, through the tubes, and out the other side of the bundle. Another material is pumped through the shell of the exchanger. Neither material actually comes in contact with the other; the heat exchange takes place through the walls of the tube bundle. As both materials pass through the exchanger, energy from the hotter material transfers to the cooler material. In this way, one material is heated, while the other is cooled.
The two heat exchangers found in the tank farm use steam to heat gas oil and LPG. The gas oil exchanger is used to keep the gas oil in a fluid state when it is necessary to use 68 tank for gas oil storage. Tank 68 has no steam coils or insulation, and any product stored in this tank can lose heat rapidly during the winter.
The LPG exchanger is a vaporizer, raising LPG temperature above its boiling point to keep pressure on the storage tank.
For more information:
If you want more information on heat exchangers, you may examine the NUS Operations Process Training manuals, Heat Exchangers 1 and Heat Exchangers 2, and their corresponding videos. This material is located at the Safety and TrainingCenter.
The UOP TYRO manual also contains a section on heat transfer equipment.
Miscellaneous Equipment:
From time to time, other pieces of equipment are required for tank farm operations. Such equipment may include stripping pumps, air compressors, and various devices for adding chemicals or additives to products. Description and use of this equipment varies, and details will be provided in supplemental training, as it is needed.
In addition, more information is available in the NUS Operations Process Training manual, Piping and Auxiliaries, located in the Safety and TrainingCenter. There is a video to accompany the book.
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Section 1200May 5, 2009