What is a Refinery?

Inside a maze of silver towers and pipes is a fascinating factory that changes hydrocarbon
molecules to make gasoline.

A refinery is a factory. Just as a paper mill turns lumber into legal pads or a
glass works turns silica into stemware, a refinery takes a raw material--crude oil--
and transforms it into gasoline and hundreds of other useful products.
A typical large refinery costs billions of dollars to build and millions more to
maintain and upgrade. It runs around the clock 365 days a year, employs
between 1,000 and 2,000 people and occupies as much land as several
hundred football fields. It's so big and sprawling, in fact, that workers ride
bicycles from one station to another.

Gasoline's lowly status rose quickly after 1892, when Charles Duryea built the
first U.S. gas-powered automobile. From then on, the light stuff from crude oil
became the right stuff.
Today, some refineries can turn more than half of every 42-gallon barrel of
crude oil into gasoline. That's a remarkable technological improvement from 70
years ago, when only 11 gallons of gasoline could be produced. How does this
transformation take place? Essentially, refining breaks crude oil down into its
various components, which then are selectively reconfigured into new products.
This process takes place inside a maze of hardware that one observer has
likened to "a metal spaghetti factory." Employees regulate refinery operations
from within highly automated control rooms. Because so much activity happens
out of sight, refineries are surprisingly quiet places. The only sound most visitors
hear is the constant, low hum of heavy equipment.

The complexity of this equipment varies from one refinery to the next. In
general, the more sophisticated a refinery, the better its ability to upgrade crude
oil into high-value products. Whether simple or complex, however, all refineries
perform three basic steps: separation, conversion and treatment.

Separation:  heavy on the bottom, light on the  top

Modern separation--which is not terribly different from the "cooking" methods used at the        Pico Canyon stills--involves piping oil through hot furnaces. The resulting liquids and vapors are discharged into distillation towers, the tall, narrow columns that give refineries their distinctive skylines. Inside the towers, the liquids and vapors separate into components or fractions

according to weight and boiling point. The lightest fractions, including gasoline and liquid

petroleum gas (LPG), vaporize and rise to the top of the tower, where they condense back to

liquids. Medium weight liquids, including kerosene and diesel oil distillates, stay in the

middle. Heavier liquids, called gas oils, separate lower down, while the heaviest fractions with the highest boiling points settle at the bottom. These tarlike fractions, called residuum, are literally the "bottom of the barrel."

The fractions now are ready for piping to the next station or plant within the refinery. Some components require relatively little additional processing to become asphalt base or jet fuel. However, most molecules that are destined to become high-value products require much more processing.

Conversion:  cracking and rearranging molecules to add value

            This is where refining's fanciest footwork takes place--where fractions from the distillation towers are transformed into streams (intermediate components) that eventually become finished products. This also is where a refinery makes money, because only through conversion can most low-value fractions become gasoline.

       The most widely used conversion method is called cracking because it uses heat and pressure to "crack" heavy hydrocarbon molecules into lighter ones. A cracking unit consists of one or more tall, thick-walled, bullet-shaped reactors and a network of furnaces, heat ex-changers and other vessels.

           Fluid catalytic cracking, or "cat cracking," is the basic gasoline-making process. Using intense heat (about 1,000 degrees Fahrenheit), low pressure and a powdered catalyst (a substance that accelerates chemical reactions), the cat cracker can convert most relatively heavy fractions into smaller gasoline molecules.

            Hydrocracking applies the same principles but uses a different catalyst, slightly lower temperatures, much greater pressure and hydrogen to obtain chemical reactions. Although not all refineries employ hydrocracking, some of industry leader in using this technology to cost-effectively convert medium- to heavyweight gas oils into high-value streams. The company's patented
hydrocracking process, which takes place in the Isocracker unit, produces mostly gasoline and jet fuel.Some refineries also have cokers, which use heat and moderate pressure to turn residuum into lighter products and a hard, coal like substance that is used as an industrial fuel. Cokers are among the more peculiar-looking refinery structures. They resemble a series of giant drums with metal derricks on top. Cracking and coking are not the only forms of conversion. Other refinery
processes, instead of splitting molecules, rearrange them to add value. Alkylation, for example, makes gasoline components by combining some of the gaseous byproducts of cracking. The process, which essentially is cracking in reverse, takes place in a series of large, horizontal vessels and tall, skinny towers that loom above other refinery structures. Reforming uses heat, moderate pressure and catalysts to turn naphtha, a light, relatively low-value fraction, into high-octane gasoline components. Chevron's patented reforming process is called Rheniforming for the rheniumplatinum catalyst used.

CONVEYORS

                                                CONVEYORS

Conveyors are used to transport the bulk or grain solid material from one place to another. The transportation of material can be carried out by different methods depending upon the type of material to be transported and the position of the discharge point with reference to loading point.

 Types of Conveyors:

A.   Belt conveyors

B.   Screw conveyors

C.   Pneumatic conveyors

D.   Hydraulic conveyors

E.    Roller conveyors

F.    Chain conveyors

G.   Bucket conveyor

H.   Vibratory conveyors

A.   Belt conveyor: The belt conveyors are capable of carrying a greater diversity of bulk solid products from fine grain to bulk material at higher rates and over longer distances.

Principle of operation: A belt conveyor is simply an endless strap of flexible material stretched between two drums and supported at intervals on idler rollers. When the drum rotated by the driving motor, the belt will move with roller due to frictional resistance, there by the material placed on the belt will be transported from one place to other.

Majority of belt conveyors are equipped with flat belts. Troughing the belt or fitting sidewalls will increase the carrying capacity. Fitting the transverse slats or texturing the surface of the belt will help to operate the belt conveyor for steep inclined application. The end of the conveyor where transported material is loaded is termed as ‘tail end’ or ‘feed end’ and the other end, from which the load is discharged, is called as ‘head end’.

 

Parts of the belt conveyor:

-         Drums driving and non-driving.

-         Belt

-         Idlers

-         Belt tensioners

Belts: Belts may be flat or fitted with a pattern of cleats or flights molded into its surface to reduce the tendency for the conveyed material to slip. The belts may be constructed with vertical sidewalls, which may be supported by transverse slats to operate much steeper incline than the normally accepted. Two methods are employed i.e. vulcanized splice and mechanical fasteners at the ends of the belt to make the belt endless. The expensive vulcanized splice gives a much stronger and longer lasting joint. The cheaper mechanical fasteners tend to restrict the working conditions of the belt.

Idlers: The carrying capacity of the flat belt is increased by modifying the cross sectional profile of belt so that it forms a trough. This is achieved by troughing idler, which consists two to five rollers.

Drive arrangements: The drive may be at either end of the conveyor, but prefers to drive the head end drum since the smallest amount of belt being subjected to the maximum tension. The effectiveness of the conveyor drive is dependent upon the difference in tension between the ‘tight side’ and the ‘slack side’ of the belt, the friction between the belt and the drive drum and the angle of wrap or arc of contact of the belt to drum. The power that can be transmitted from the driving drum to the belt is limited by the point at which the belt begins to slip. In order to increase the power either coefficient of friction to be increased by applying a rubber lagging to the surface of the drum or to increase the angle of wrap by ‘snubbing’ the drum or by providing a multiple drive.

Belt slip: In the belt drive there will inevitably be a certain amount of belt ‘creep’ resulting from the varying tension in the belt as it passes around the drum. The term ‘creep’ refers to the relative movement between the belt and the surface of the drum that happens as the stretch in the belt decreases with the reduction in tension. The arc of the drum surface over which creep occurs will tend to increase as the tight side tension increases, for example as a result of increasing the load on the belt, and if the ‘angle of creep’ approaches the ‘angle of wrap’ the belt will be on the point of slipping. For this reason that a certain inherent tension should be maintained, even in the slack side of the belt.

Belt tensioning: The needed tension can be provided in a number of ways by suitable arrangement like pulling back the tail drum or idler pulley and also by providing ‘drop-weight’ or ‘gravity take-up’ device. Hydraulically or electrically powered automatic take-ups are also available which relay on a load-sensitive device to move the tensioning pulley in response to change in operating conditions of the belt.

Belt cleaners: When transporting bulk materials that have the tendency to stick to the surface of the belt, the belt conveyors will be equipped with some kind of cleaning technique at the head end to minimize the build-up of material on snub pulleys and return idlers. Theses cleaning methods are such as rotary brushes or scrapper blades of steel or rubber, which may be spring loaded or counterweighted to bear against the surface of the belt.

B.   Screw conveyors: It consists of helicoid (helical flights rolled from flat steel bar) flight, mounted on a pipe on or shaft and turning in a trough. Screw conveyors are preferably used to transport and to dose powder, fine grain or fibrous materials.

Parts of screw conveyor:

-         Shaft

-         Drive

-         Trough

-         Helical flights

-         Hanger

Classification of screw conveyors by its line of transport:

a.     Horizontal screw conveyor.

b.     Angular screw conveyor.

c.      Vertical screw conveyor.

Principle of operation: The intake end of conveyor is fed with a continuous supply of particulate material. The rotating screw in the trough or pipe will lift the material by a wedging action.  The screw will be rotated by drive and supported on bearings. The screws are constructed in different fashion for special applications.

Preventive Maintenance points:

1.     Grease or oil filling of the gears or geared motor as recommended by the manufacturer.

2.     Re-lubrication of bearings as per the requirement.

3.     The packing adjustment at the shaft passages of the screw conveyor.

4.     The chain drives cleaning with petroleum or p-3 solution and then applying grease or oil as per the recommendation of the supplier.

5.     Cleaning the screw conveyor depending upon the material in certain intervals, if found necessary.

C.   Pneumatic conveying system: Is transportation of dry bulk particulate or granular materials through a pipeline by a stream of gas. Normally air is used for conveying and occasionally nitrogen is used in situations where there is a fire or explosion risk.

Basic parts of pneumatic conveyor system:

-         Blower or compressor

-         Feeding device

-         Gas/solids disengaging device (Filters)

-         Pipe line

Principle of operation:

The pneumatic conveyor system consists of a source of compressed air, a means of feeding the product into the pipeline, and a receiving hopper fitted with a means of separating the conveyed product from the conveying air. The blower or compressor supplies the compressed air to the conveying system. This compressed will travel towards the less pressure side (positive pressure system). The solid material is fed into the air stream by means of feeder device like a rotary valve or screw feeder or venturi feeder etc. There by the solid particles are conveyed to another location by the travelling air. The product is separated from the conveying air by means of filter at the destination.

Classification of pneumatic conveyors:

a.     Based on method of carrying:

1.     Dilute- phase: In the case of dilute phase flow, the bulk solid is conveyed in suspension with the particles more or less uniformly distributed over the cross section of the pipe. To keep the particles in suspension in the pipe line it is necessary to ensure that the conveying velocity does not fall below a certain minimum value which for the majority of bulk solids, is about 13 – 15 m/s.

2.     Dense-phase: When the conveying velocity is less than that required to keep the bulk solid in suspension and particles begin to settle to the bottom of the pipe, the flow is said to be in a dense-phase mode.

b.      Based on  pressure:

1.      Low pressure conveying systems

i.       Positive-pressure systems.

ii.     Negative – pressure (Vacuum) system: In vacuum conveyor system bulk solid is picked up at inlet end of the conveying line and transported by  the flowing gas to the discharge end. The basic difference is the air mover is at the discharge end of the pipeline. The other differences are the components required to feed the bulk solid into the conveying line and to separate it from the gas at the discharge point. Since the conveying gas finally has to pass through the fan or blower, it is important to ensure that the solid material is adequately separated from the gas. Thus a high-efficiency gas/solid disengaging device is an essential requirement. Since the solid material does not have to be fed against an adverse pressure, the feeding mechanism is simple.

2.     High pressure systems: The conveying method will be in dense – phase. The blow tank provides the means for feeding the bulk solids to be transported into the pipeline. In this system product is delivered to the pipeline in batches as the blow tank is filled and emptied. The blow tank is essentially a pressure vessel, which is gravity fed with product from the top and then, after closing the feed valve, and with the valve on the conveying line closed, is pressurized. With the compressor still operating, the outlet valve is opened and conveying starts.

c.      Based on velocity:

1.     Low velocity conveying

2.     High velocity conveying

D.  Hydraulic conveying: Hydraulic conveying of solids involves the conveyance of solid particles in suspension in a moving liquid.

E.  Roller conveyors: These conveyors are used in our plant to transport bags. Rollers are available in a wide variety of constructions with tube end either bored or formed to take the bearing insert. The roller conveyors are powered with a pressure belt in contact with the lower surface of the rolls or the most expensive of the powered roller units are those in which each roll is equipped with V-belt or chain drives. The rotating roller will result to move the bulk solids like palletizer etc which is placed on the roller. There by transported bulk solids from one place to another place by the roller conveyor.

F.  Chain conveyor: These conveyors are used in our plant to transport palletizers. These devices for handling containers are available in either roller chain designs or other type. Chain conveyors are used only on loads which are too heavy for economical handling by belt or roller units, or which have odd shapes and not suitable for roller units. The end less chain will be made to travel between the sprockets which results to move the palletizers placed on the chain.

G.  Bucket elevators: These elevators are used to transport the granular material vertically. The essential components of the device are

i.                   An endless belt or chain as a traction element to which are attached a series of carrying vessels or buckets

ii.            A single or double casing, which serves to enclose or partially enclose the moving buckets.

iii.           A head at the upper end of the elevator which includes a belt pulley or chain wheel to turn the traction element and a suitable discharge chute.

i.              

ii.            A boot at the lower end which again includes a belt pulley or chain wheel, a tensioning device, and a means of feeding the material to be conveyed so as to ensure optimum filling.

H.  Vibratory conveyors: Vibratory conveyors are commonly used to carry a wide variety of particulate and granular materials. The vibratory conveyor consists of a trough, which is supported on or suspended by springs or hinged links and caused to oscillate at high frequency and small amplitude by an appropriate drive mechanism. The fundamental action of the vibrating trough on the bulk material carried in it is to throw the particles upward and forward so that they advance along the trough in a series of short hops.

What is interlock?

Interlock is logic developed for machine parameters / Process

 parameters,

• To annunciate alarm to alert operator

• To take corrective action automatically for defined   parameters

• To ensure that healthy compressor and process condition   are available to start the machine

• To safeguard  the Compressor by tripping automatically   if critical  parameters exceed danger limit & prevent   severe damage  

What is a Network?

What is a Network?

A network consists of two or more computers that are linked in order to share resources (such as printers and CD-ROMs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

The three basic types of networks include:

·                     Local Area Network (LAN)

·                     Metropolitan Area Network (MAN)

·                     Wide Area Network (WAN)

Local Area Network

A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. Rarely are LAN computers more than a mile apart.

In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network. Computers connected to the file server are called workstations. The workstations can be less powerful than the file server, and they may have additional software on their hard drives. On most LANs, cables are used to connect the network interface cards in each computer. See the Topology, Cabling, and Hardware sections of this tutorial for more information on the configuration of a LAN.

Metropolitan Area Network

A Metropolitan Area Network (MAN) covers larger geographic areas, such as cities or school districts. By interconnecting smaller networks within a large geographic area, information is easily disseminated throughout the network. Local libraries and government agencies often use a MAN to connect to citizens and private industries.

One example of a MAN is the MIND Network located in Pasco County, Florida. It connects all of Pasco's media centers to a centralized mainframe at the district office by using dedicated phone lines, coaxial cabling, and wireless communications providers.

Wide Area Network

Wide Area Networks (WANs) connect larger geographic areas, such as Florida, the United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of network.

Using a WAN, schools in Florida can communicate with places like Tokyo in a matter of minutes, without paying enormous phone bills. A WAN is complicated. It uses multiplexers to connect local and metropolitan networks to global communications networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN or a MAN.

LNG process block diagram and key Process

Block diagram of  LNG process:

Key Process Units

SInlet Facilities (onshore):

             Reception and separation of offshore feed wet gas into gas, condensate, and water. 

SAcid Gas Removal (AGR):

             Remove acid gas (H2S and CO2) by amine system                     ( Ucarsol ).

SSulphur Recovery Unit (SRU) / Acid Gas Injection (AGI): 

              Recover H2S and Mercaptans (RSH) into pure liquid Sulphur (Claus process), or inject the acid gas into onshore acid gas injection wells.

SGas Treating (Dehydration & SELEXOL):  

                 Remove mainly water, Mercaptans (RSH) and Sulphur compounds from saturated gas

SMercury Removal: 

                 Remove mercury (Hg) form the dry gas

. 

SNGL Recovery:

                 Recover NGL (mainly C2+ or C3+).

SFractionation:

               Recover Ethane (C2), Propane (C3), Butane 

(C4), also iso-Pentane (i-C5) and plant condensate (n-C5+)

SRefrigeration: 

              Use Propane and Mixed Refrigerant (MR) for   gas      pre-cooling and liquefaction.  

SLiquefaction: 

              Liquefy the dry sweet gas by Main Cryogenic Heat Exchanger (using C3-MR).

Qatar Petroleum jobs

What is purge level system ?

This method is also known as bubbles method of level measurement. A pipe is installed vertically with its open end at the zero level. The other end of the pipe is connected to a regulated air supply and to a pressure gauge or to ^P transmitter. To make a level measurement the air supply is adjusted so that pressure is slightly higher than the pressure due to the height of the liquid. This is accomplished by regulating the air pressure until bubbles can be seen slowly leaving the open end of the pipe. The gauge then measures the air pressure needed to over come the pressure of the liquid.

/\ P  = H  X  D

USE : On for corrosive liquids where the transmitter cannot be directly connected to process eg... Acids, Some organic liquids.

How is D.P. transmitter applied to an open tank ?

On an open tank level measurement the L.P. side is vented to atmosphere. Whatever pressure acts is on the H.P. side which is a measure of level.

Three way manifold valve operation:

Three way manifold valve operation:

• The following photograph shows a three-valve manifold bolted to a Honeywell model ST3000 differential pressure transmitter. 
• A bleed valve fitting may be seen inserted into the upper port on the nearest diaphragm capsule flange.
• In normal operation, the two block valves are left open to allow process fluid pressure to reach the transmitter. 
• The equalizing valve is left tightly shut so no fluid can pass between the “high” and “low” pressure sides.                
• To isolate the transmitter from the process for maintenance, one must close the block valves and open the equalizing valve. 
• The best sequence to follow is to first close the high-pressure block valve, then open the equalizing valve, then close the low-pressure block valve.
• This sequence ensures the transmitter cannot be exposed to a high differential pressure during the isolation procedure, and that the trapped fluid pressure inside the transmitter will be as low as possible prior to “venting” to atmosphere. 
• Finally, the “bleed” valve is opened at the very last step to relieve pent-up fluid pressure within the manifold and transmitter chambers.

Instrument calibration

Instrument calibration

Calibration and ranging are two tasks associated with establishing an accurate correspondence between any instrument’s input signal and its output signal. 

To calibrate an instrument means to check and adjust its response so the output accurately corresponds to its input throughout a specified range.

In order to do this, one must expose the instrument to an actual input stimulus of precisely known quantity.

For a pressure gauge, indicator, or transmitter, this would mean subjecting the pressure instrument to known fluid pressures and comparing the instrument response against those known pressure quantities.

One cannot perform a true calibration without comparing an instrument’s response to known, physical influence or impact.

To range an instrument means to set the lower and upper range values (LRV & URV), so it responds with the desired sensitivity to changes in input.

For example, a pressure transmitter set to a range of 0 to 200 PSI (0 PSI = 4 mA output ; 200 PSI = 20 mA output) could be re-ranged to respond on a scale of 0 to 150 PSI (0 PSI = 4 mA ; 150 PSI = 20 mA).

In analog instruments, re-ranging could only be accomplished by re-calibration, since the same adjustments were used to achieve both purpose (i.e. Flow measurement).

In digital instruments, calibration and ranging are typically separate adjustments (i.e. it is possible to re-range a digital transmitter without having to perform a complete re-calibration), so it is important to understand the difference, As smart Transmitters using HART or FOUNDATION FIELDBUS protocols.

What is LNG?

 •LNG is natural gas cooled to -161o Centigrade, the temperature at which its main 

  component, methane, liquefies.

•Its volume is reduced to around one six-hundredth of its volume  as a gas

•It is stored and transported at atmospheric pressure as a boiling liquid

•It is an odorless, colorless liquid .

P&ID valve symbols

P&ID valve symbols

What is pressure?

Pressure: It is defined as Force per unit Area. P = F/A

Units      : bar, Pascal, kg / cm², lb / in².

PRESSURE CONVERSIONS

PRESSURE CONVERSIONS :

1psi =	27.74 " H2O
1 Kg/cm2 =	14.223 psi
1 Bar =	14.504 psi
1 Kpa =	0.145 psi
1 Kg/cm2 =	10.000mm of H20
1 Bar =	1.0197 Kg/cm2
1 Kg/cm2 =	0.98 Bar
1 Torr =	1 mm of Hg.