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10E-1 The Lease Pumper's Handbook Chapter 10 The Tank Battery Section E CRUDE OIL LINE SYSTEMS AND EQUIPMENT

Figure 1. The crude oil lines in this diagram of a tank battery are labeled with an O. E-1. Lines from the Separator. Crude oil lines from the separator should lead directly to the stock tank. A diverter manifold is assembled in the line to provide line openings for connections to lead to and from specialized vessels, such as a heater/treater or a gun barrel. The crude oil then continues on toward the stock tank. The specialized vessel can then be utilized or bypassed according to need. When water and paraffin are also produced with medium- to low-gravity oil, the second vessel in the system will probably be a heater/treater. E-2. Lines from the Separator to the Heater/Treater. For fire safety the heater/treater is located a minimum of 100 feet from the nearest hatch that contains gas. Although the

10E-2 outside air supporting the flame in the heater/treater must travel through a flame arrester (for fire safety), this distance is always maintained. The lines to and from a conventional style heater/treater (Figure 2) are obvious. The highest side line on the right is the inlet. The second line down as seen from this angle is the oil outlet, and the water comes out the lower left opening. The gas comes off the top. On the vessel in the background of the photograph, the right line is the inlet, the second line to the left is the oil outlet, the third line is the gas line, and the fourth (the one on the left) is the water disposal line. serves a different purpose. Even a casual examination of the line and the connections that make up that line will allow the lease pumper to easily identify the purpose of each line. However, during installation of the vessel, it may be necessary to remove a round manway plate and examine the inside using a spark-proof flashlight to verify the purpose of each outlet. The manufacturer will also be able to provide this information. When the crude oil enters the vertical heater/treater, it travels down to contact a spreader baffle in the lower section of the vessel. A plate welded in the vessel just below the inlet channels the incoming oil down a tube, allowing the water to drop to the bottom of the vessel and out. The oil migrates up through the water section, contacts the heated tube, and moves upward through the wash section. There, the baffle plates remove most of the remaining water. Water continues to drop out of the oil until the time that it enters the sales line. The horizontal heater/treater, which uses electricity to separate water and oil, dramatically increases the efficiency of the operation. This type of heater/treater is described in Chapter 13, Testing, Treating, and Selling Crude Oil. E-3. Lines from the Heater/Treater to the Gun Barrel. If a gun barrel is the next vessel in the system, the oil outlet line from the heater/treater drops to ground level and travels to the gun barrel. The line enters the gun barrel down through a central flume or through an external boot arrangement (Figure 3). In this system, the crude oil inlet line comes in from the back side, travels up through the 2-inch line, and enters the gas boot from the left side. The flash separator (the large container on top) allows the gas to

Figure 2. The lines on these heater/treaters are color-coded to identify the fluids they contain. For the lease pumper, understanding the use of each line does not create any problem, even if the lines are buried because each one

10E-3 break out of the liquid and travel upward and into the low-pressure gas system. The line system from the separator should always provide a means of producing directly to the stock tanks without going through the heater/treater or the gun barrel. E-4. Lines from the Gun Barrel to the Stock Tanks. The oil outlet line from the upper side of the gun barrel to the stock tank is normally installed directly to the top of the stock tanks. This line may come off the gun barrel at a 45o angle, so the distance is usually only a few feet away to the first stock tank. Figure 4 illustrates how the line is installed to allow the oil to flow by gravity feed to the stock tank. A shutoff valve is normally installed just above the stock tank as shown. The line must be of sufficient size to avoid restrictions and to accommodate production.

Figure 3. The gun barrel crude oil inlet boot (center). The oil then travels down through the inlet boot, enters the vessel at about the 12-inch level, and travels across the spreader. The spreader is a long horizontal pipe crossing the bottom of the gun barrel with many small holes in it to distribute crude oil all the way across the vessel. The oil comes out of the holes and works its way up through the water in droplet form. Free water remains in the lower part of the gun barrel and travels through the water leg to the disposal system. As shown in Figure 3, additional support is often provided to the boot by braces, such as the V-shaped brace attached to the top edge of the tank to stabilize the boot. A second stabilizer is welded to the boot down-comer and the side of the tank for additional support.

Figure 4. The oil line from the gun barrel (left) to the stock tank. Note that the handle of the valve is perpendicular to the flow of the line, meaning that the valve is closed. E-5. The Equalizer Line from Stock Tank to Stock Tank. The equalizer line is a line located near the top edge of the tank at an angle of 45o to the side and approximately 10 inches down.

10E-4 This line connects the two stock tanks. This equalizer line allows the lease pumper to top out a tank (fill it almost full) during any time of the day or during the hours that the lease pumper is off so that the tank is full of oil when the lines are switched. This saves the pumper much time, and the tank is always full when the oil is sold. There are two ways of installing an equalizer line. Figures 5 and 6 show both systems. In the system in Figure 5, the oil must go to the next tank, while in the system shown in Figure 6, the oil can go to any selected tank. Most walkways, however, fit snugly to the tank so that the second approach is not always available. The pipe would occupy part of the walkway space, and this would be a safety hazard. When the crude oil is sold through a pipeline, several valves will have to be closed, a seal inserted, and the valve handle locked in a closed position. There are two common styles of seals. One is a flat strap that locks together, and the second is a wire and lead seal. The gauger will probably seal both the drain line and the oil inlet. The seal on the sales line will then have to be broken to remove the valve handle. These seals will have the name of the pipeline company and a serial number stamped on them in raised letters for identification. After the oil has been sold, the valve is closed and a new seal is put in place to make sure that this valve remains closed when oil is not being purchased. All seal numbers are accounted for, and occasionally the company will require that the used seals accompany the sales ticket when it is turned in to the office.

Figure 5. An equalizer system in which equalizing can be done only to the next tank.

Figure 6. An equalizer system in which any of several tanks can be selected for filling next.


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