Types of Storage Tanks

Every facility involved in the production of petroleum and related products reamers some type of storage. Technical Data used in the field explained in petroleum courses in Rawalpindi. This chapter discusses the types of storage commonly used and also provides general guidelines to aid selection of the proper type of storage for a particular application. References to various codes. standards. and recommended practices supplement the material provided in this chapter. Manufacturers also should be consulted for specific design information on a particular type of storage.

During the early day\ of oil production, the method of storing was almost exclusively white-pine wooden tanks. which were followed by cypress tanks. and then redwood tanks. However. because of the constant and steep rise in the cost of redwood lumber and the diminution of skilled erectors required, the installation of new wooden tanks is nearly nonexistent. The bolted-steel tank was developed next and virtually replaced the wooden tank. Some more details of petroleum courses in rawalpindi are as under.

Bolted tanks are designed and furnished as segmental elcmcntc assembled on location to provide complete vertical, cylindrical. aboveground. closed- and open-top steel storage tanks. Standard API bolted tanks are available in nominal capacities of 100 to 10,000 bbl, and are designed for approximately atmospheric internal pressures. Bolted tanks offer the advantage of being easily transported to desired locations and erected by hand. To meet changing requirements for capacity of storage, bolted tanks can be easily dismantled and re-erected at new locations.

If a tank develops a hole from corrosion or becomes damaged. a single sheet or more may be replaced. A complete tank bottom may bc replaced in the field without dismantling the tank. Also. a section may be removed from the tank. a new connection installed in the sheet. and the section replaced without danger. This is not true of any other type of steel construction. No special  (cranes. etc.) is required for the correction of bolted tanks. These tanks are erect& by no specialized crews using hand tools and usually an impact wrench. Bolted tanks are available with painted. galvanized. And special coatings. including factory-baked coatings. Painting on both sides of the sheets during fabrication gives the inside of the tank some corrosion protection. Galvanizing the sheets and all tank parts by the “hot-dip” process or applying a factory-baked coating affords high corrosion protection. The component parts of a typical bolted tank are shown in Fig. 1 I. I and partial API specifications. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join oil field after petroleum courses in Islamabad.

Electric Generating Systems

Where utility-furnished power is not available, generators may be used to provide electrical power required for operation of the pumping units. Technical Data used in the field explained in petroleum courses in Rawalpindi. This system allows the operator the benefits of electrification. When selecting equipment for the generating system, consider which type of motor will most efficiently use generator power. The ultrahigh-slip motors, which use fewer kilovolt amps (kVA) than conventional horsepower rated motors, are very popular. Distribution equipment for the generator system would be the same as for utility power if it were furnished. Some more details of petroleum courses in rawalpindi are as under.

Generated voltage depends on the size of the electrified field. The following considerations determine the most desirable generated voltage.  Where the system consists of a small number of wells (one to five) with short distances from generator to well site. the generator voltage may be the same as the  motor rated voltage. Where the field consists of many (5 to 50) wells, the distribution voltage should be higher than the motor rated voltage to minimize voltage drop. At each motor, a step down transformer would be used. This system would be considered a moderately sized system with a generator having a distribution of 2.300 or 4,160 V. 3. In an exceptionally large field (50+ wells), the generator voltage would be stepped up to 7,200 or 13.800 V for distribution. At each wellsite, a transformer would be installed to drop the distribution voltage to motor rated voltage. The generated voltage could be 2,300 or 4.160 V. The higher voltage allows smaller conductors to carry  the loads and lessen line drop voltage within acceptable limits.

The procedure used in selecting primary and secondary equipment should be the same as that used by the utility companies. Protective devices and grounding procedures outlined in this chapter apply to either system. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join oil field after petroleum courses in Islamabad.

Multiple Horsepower Rated Motors

When a new well is completed, sizing is based on basic information provided by the depth of the pump and fluid, size of pump, stroke length, speed of pumping unit, and specific gravity of the fluid. Technical Data used in the field explained in petroleum courses in Rawalpindi.  There are many variables in calculations that are not always considered and may affect the required motor size. Sometimes, overlooked variables influencing loading on the motor are: actual fluid level, viscosity of fluid, deviation of hole, friction in the pump, friction in the stuffing box, excessive friction coming from the pumping unit, and quality of electric power available. Because of the many variables involved, it is sometimes difficult to size a motor accurately for new installation on the first attempt. Sometimes multiple-rated motors are considered as pumping unit drivers. Some more details of petroleum courses in rawalpindi are as under.

Multiple horsepower rated motors usually have three different modes available. Table 10.4 lists typical sizes available.

An ultrahigh-slip motor is also a multiple-rated motor, usually being quadruple rated. The stator winding of this motor has been designed for multiple connections. The ultrahigh-slip capability is a result of special design characteristics incorporated in its rotor,  is two graphs that show a comparison of ultrahigh-slip motors to the horsepower rated motors. The first illustration shows the horsepower rated motors with only one torque mode available. The second shows an ultrahigh-slip motor with four-mode capability. For maximum benefits, the ultrahigh-slip motor should be used in the lowest-torque mode possible without exceeding its thermal limit. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join oil field after petroleum courses in Islamabad.

Diesel and Oil Engines

Some slow-speed, single-cylinder engines burn diesel or fuel oil by high-pressure injections into the cylinder. The compression is much greater than gas engines. Technical Data used in the field explained in petroleum courses in Rawalpindi.  Heat, developed by compressing the air in the cylinder, ignites the fuel sprayed into the cylinder. These engines are divided into two types: full diesels, which are cold-starting, and semidiesels, which require heating to start.

The cold-starting diesel has a compression ratio of 14:1, resulting in a pressure of approximately 500 psi. The semidiesel has approximately 250 psi compression, which requires a hot tube heated by a torch or electric glow plug to produce enough heat to ignite the charge. Once these engines are started, enough heat is produced in the cylinder to cause ignition of the fuel as it is injected into the cylinder. Some more details of petroleum courses in rawalpindi are as under.

High-speed, multicylinder diesel engines have been improved until they are now adaptable for oilwell pumping. These are not used commonly where gas is readily available. Diesel engines fill a need where other fuels are not readily available.

Five factors should be considered when determining which engine to purchase: fuel availability, equipment life and cost, engine safety controls, horsepower, and installation.

 Natural gas is the logical choice. Taken from the wellhead casing annulus, it is called “wet gas” and is used most frequently. Where there is insufficient gas available at the wellhead, gas maybe piped to the engine from the field separator. In either case, the gas must be scrubbed to remove oil and water. This is done in a double compartment volume tank where gas pressure also is reduced by a regulator. Gas from the separator will have most of the moisture and oil removed and is considered a better fuel.

Sour gas is a natural gas that contains excessive sulfur or CO2 and is not considered a good fuel. Two percent sulfur is considered excessive. Where sour gas must be used, suitable treaters are required to improve the quality of the fuel. Sour gas causes severe etching and wear of engine parts as well as quick contamination of the lubricating oil in the four-cycle engines. Two-cycle engines fare slightly better because of their construction. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join petroleum courses in Islamabad.

Four-Stroke Cycle

An engine designed for four-stroke cycle or Otto cycle is called a “four-cycle engine.” The four-stroke cycle includes intake, compression, power, and exhaust. Intake and exhaust valves are mounted in the cylinder head or the block and are actuated by cams and push rods. Technical Data used in the field explained in petroleum courses in Rawalpindi. The crankcase is connected directly to the cylinder, and contamination of the lubricating oil occurs sooner than it does in crosshead-type two-cycle engines.

The four-cycle engine is built in slow- and high-speed versions. Slow-speed engines usually have their cylinders  mounted horizontally, whereas high-speed engine cylinders are mounted vertically.

These engines use trunk pistons fastened to the crankshaft by connecting rods. Intake and exhaust valves are mounted in the cylinder head and actuated by cams and push rods. Some more details of petroleum courses in rawalpindi are as under. Some more details of petroleum courses in rawalpindi are as under.

A slow-speed, four-cycle engine usually is built with a single horizontal cylinder. A large unenclosed flywheel is provided to store energy and deliver at a fairly constant speed to the pumping unit.

High-speed, four-cycle engines are multicylinder and can operate at speeds up to approximately 2,000 rev/min. Normally, four- and six-cylinder engines are not operated at more than 1,400 rev/min to maximize engine life.

A typical four-cycle, high-speed engine used as a prime mover on a beam-type pumping unit is shown in This type of engine can operate on natural gas, LP gases, or gasoline. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join oil field after petroleum courses in Islamabad.