Emulsions and Electrostatic Treater Principles

Emulsions and Electrostatic Treater Principles - At some point in the life of every oil well an unacceptable amount of water will be produced with the

At some point in the life of every oil well an unacceptable amount of water will be produced with the oil. Water usually seeps into the formation as oil and gas are produced from the reservoir. Generally, the older the well the more water produced. As well fluids move through the formation, artificial lift equipment, etc., oil and water are mixed. Production separators are used to separate the mixed fluids. Two-phase separators separate natural gas from the liquids. Three-phase separators separate natural gas and the liquids, e.g., oil from free water.

Well fluids which do not easily separate, referred to as emulsions, must be treated before they will separate into the various components. Electrostatic treaters are used to treat or break emulsions. Treating emulsions is an expensive process. To ensure treating is done at the lowest cost, prop-erly sized equipment must be installed, maintained and monitored. Complete records should be kept for each lease, e.g., chemical usage, fuel gas, etc.

Emulsions
Some water produced with oil readily separates from the oil and is referred to as free water. On the other hand, some water produced is mixed in such a way with the oil that treating is necessary to separate them. Such a combination of oil and water is called an emulsion.
In an emulsion one of the liquids is spread out, or dispersed, throughout the other in the form of small dropiets. In oil field emulsions, water is usually dispersed in oil and is referred to as a water-in-oil emulsion. When the opposite happens, an oil-in-water emulsion is formed. Emulsions may be tight (difficult to break) or loose (easy to break) depending on the type and amount of emulsifying agent present.

Emulsifying Agents

An emulsifying agent is a substance that promotes the formation and stability of an emulsion. This is accomplished by the emulsifying agent collecting on the surface of water droplets and forming a tough film which keeps the droplets from joining. Emulsifying agents commonly found in oil field emulsions include asphalt, resins, paraffins, and oil soluble organic acids. Different emulsifying agents occur naturally in different reservoirs.

In order to break an emulsion, the film must be neutralized or destroyed by using treatment methods. Treating is usually done in the field using various types of equipment (free-water knockouts, separators, heater treaters, electrostatic treaters, etc.) and by adding chemicals to the emulsion immediately after it is produced.

Emulsion Stability

A stable emulsion is one which will not break down or separate without some form of treating. The stability of an emulsion is dependent on several factors :

Emulsifying agent. The effect depends on the type of agent and conditions under which the emulsion is produced. The formation of a stable emulsion would be very difficult without an emulsifying agent.

Viscosity of oil. Oil with a high viscosity (resistance to flow) tends to keep water droplets in suspension creating a more stable emulsion.

A.P.I. gravity of oil. Oil with a low A.P.I. gravity tends to keep water dropiets in suspension creating a more stable emulsion.

Water percentage. Generally, a smaller percentage of water in an emulsion means greater stability.

Agitation. Increased agitation means greater dispersement of water and greater stability.

Droplet size. Emulsions containing small water droplets are more stable because small droplets are lighter and will not settle out as easily.

Age of emulsion. The longer an emulsion remains untreated, the harder it is to break.

Treating Emulsions

Water produced from reservoirs may vary from a small fraction of one percent to 99 percent. Pipeline companies do not pay for water; therefore, most or the water must be removed before it can be delivered to the pipeline. In most cases this requires treating an emulsion. An emulsion should be tested frequently. No two emulsions are alike. Even the emulsion from a single weli changes over time thereby requiring changes in the treatment process. The treating process must be monitored carefully since revenue is affected by the gravity of oil. Natural gas also generates considerable revenue for our company and must be monitored closely to ensure maximum yield and minimal waste. Treating emulsions may include one or more of the following procedures: allowing settling time, applying heat, injecting chemicals, using electricity, or operating mechanical devices.

Settling Time

The time needed to completely separate an emulsion is called settling time. The settling rate of a water-in-oil emulsion is affected by viscosity, size of water droplets, and gravity. If the oil has a high viscosity (thick), then the water droplets cannot move without considerable resistance and wilt not settle out easily. Settling rate is also affected by the size of the water droplets. Smaller droplets are lighter and take longer to separate through settling.

If the difference in A.P.I. gravity between water and oil (the gravity differential) is small, separa-tion is slow. However, water weighs more than oil and will eventually settle to the bottom of a vessel. Some emulsions can be adequately treated with settling alone. Others need additional treatment procedures which are designed to speed up the settling process.

Applying Heat

The ideal way to treat oil is without heat; however, treatment frequently requires heat to speed up separation. Heat by itself will not break an emulsion, but it aids in several ways: (1) Heat causes water droplets to move faster and strike each other with greater frequency and force. When the droplets collide, the film of emulsifying agent ruptures, and larger, heavier droplets form. They then yield to gravity differential and settle out; (2) Heat lowers the viscosity of oil and allows the water droplets to settle out more easily; and (3) Heat speeds up chemical action. Chemicals make the fiim of emulsifying agent around water droplets rigid. When heat is applied, the water droplets expand and break the film. The droplets can then merge into larger ones and settle out.
Heat must be applied only as needed because too much heat will waste energy (fuel) and cause greater wear on the equipment. Also, excessive heat can cook off the lighter ends of crude oil which will change the oil's gravity and result in lost revenue.

Adding Chemicals

Emulsion breaking chemicals are injected into the well stream ahead of the electrostatic treater. They react with the film around water droplets, destroying or neutralizing the film, thereby al-lowing the droplets to coalesce (combine) and separate from the oil. There must be sufficient agitation to allow the chemical to come into contact with each water droplet. The amount and type of chemical required directly affects how well the emulsion breaks and the time needed for settling. Also, the warmer the emulsion, the less chemical is needed.

Chemicals must be applied only as needed because too much chemical is wasteful and could cause an oil-in-water emulsion to form. This would allow oil to leave the vessel through the water outlets, resulting in lost revenue\and environmental pollution.

Using Electricity

Electricity, usually used in conjunction with heat and chemicals, will separate oil and water. The vessel used to do this is called an electrostatic treater and will be discussed in sections two and three of this module.

Using Mechanical Devices

Devices such as gun barrels and free-water knockouts are used in the treatment of emulsions. A gun barrel is basically a settling tank used to separate oil and water in the field. After emulsified oil has been heated and treated with chemicals, it is pumped to the gun barrel where water and oil separate by gravity setting. Gun barrels are largely being replaced by heater treaters or electrostatic treaters but are still common, especially in older fields.

A free-water knockout is a gravity-type separator used to remove excessive water from the produced fluid ahead of the treating unit. Sometimes a filter or excelsior, called hay, is used to catch particles of oil that may be entrained in the free water as it passes through the filter. The free water is drained off and only emulsion passes on to the treating unit. This device prevents over-loading of the treating vessel and saves fuel.

Electrostatic Treater Design

An electrostatic treater is a pressure vessel which combines all the equipment necessary to treat an emulsion. Sometimes it is referred to as a chem-electric or electrochemical treater. its overall goal is jobreak the emulsion and allow water to settle so that clean oil can be obtained. The specific combination of treating methods in a given unit will vary depending on the type of treatment and the unit's position within the treating system. Electrostatic treaters can be direct-fired or use an external medium for a heat source.

Electrostatic Treater

The electrostatic treater, like other emulsion treaters, uses both heat and chemicals to break an emulsion. However, the electrostatic treater also uses an electrical charge to help coalesce water droplets so they will settle out. The electrostatic treater for any given lease is designed to handle the well fluids of that lease. Any number of modifications in the basic design can be made. For example, both the size of internal sections and the amount of heat required may vary.

Selection of the right treater with emphasis on the right combination of functions depends on factors such as climate, amount and type of well fluids to be handled, and the characteristics of the emulsion being treated. Treating should be done at the least possible least cost, possible addition of heat, and the least possible loss of oil gravity. Electrostatic treaters receive the emulsion which has already been chemically treated. The emulsion enters the top, and then flows horizontally through various treating sections. Each step brings the emulsion closer to the desired result of complete separation of oil, gas and water.

External Components

The external or outside components of an electrostatic treater are those that are readily ap-parent. Located all around the treater, they serve varying purposes as the treating process is taking place internally.

Fire Boxes. The fire boxes contain gas burners which provide a heat source for the treater. Most electrostatic treaters will have two or three fire boxes.

Stacks. The stacks are metal cylinders from which exhaust gases are vented after flowing through the firetubes.

Thermometer. The thermometer indicates the temperature at which the emulsion is being treated.

Thermowell. The thermowell provides a location for the thermostat temperature probe which allows a thermostat to maintain the desired treating temperature in the vessel.

Inlet Line. Produced fluids (emulsions) enter the treater through the inlet line.

Gas Equalizer. This pipe allows gas pressure to be equalized between internal sections of the treater.

Gas Outlet. Gas leaves the treater and enters the gas outlet line through the gas outlet. Some treaters have a gas dome which is designed to remove any liquid particles entrained in the gas stream prior to leaving the vessel.

Gas Back-Pressure Valve (not shown). This valve, located on the gas outlet line, maintains sufficient pressure in the vessel to dump liquids.

Safety Device. The safety device may be a relief valve, rupture disc or both. They are designed to open or burst if too much pressure builds up in the treater.

Make-up Gas Line (not shown). Some treaters may have a make-up gas line with a regulator to maintain proper operating pressure of the unit.

Free Water Outlet. Free water, which has settled out of the emulsion, leaves the unit through this outlet located on the bottom of the treater.

Free Water Level Controller. This device maintains the free water level in the treater.

Free Water Dump Valve. This valve is located on the free water outlet line. It allows free water to leave the vessel.

Oil Outlet. Oil leaves the treater and enters the oil outlet line through the oil outlet.

Oil Dump Valve. This valve is located on the oil outlet line. The oil dump valve allows clean oil to leave the treater and is controlled by a level controller.

Treated Water Outlet. Treated water, which has settled out of the oil, leaves the unit through this outlet located on the bottom of the treater.

Treated Water Dump Valve. This valve is located on the treated water outlet line. It allows treated water to leave the vessel.

Treated Water Level Controller. This device maintains the treated water level in the treater.

Drains. On the bottom of the treater are drains to empty the vessel for repairs or to remove accumulated solids, e.g., sand, clay, etc.

Transformer. The transformer steps up incoming voltage to create the high-voltage electrostatic field in the treater.

Sight Glasses. These devices enable a pumper to see the water/oil interface levels in the treater. They help him to determine abnormal fluid levels (upset condition).

Gas/Air Supply Lines. These lines provide gas or compressed air to the level controllers so they can work properly. Gas/air supply lines usually contain a regulator, drip trap, and filter to help supply clean, dry gas or compressed air to the level controllers.

Internal Sections

The internal sections are arranged in the following order from fire boxes to opposite end of the treater: inlet section, surge section, and treating section.

Inlet Section. The inlet section, which is the first section to receive emulsion, serves two purposes. Entrained gas separates and leaves through the gas outlet thus preventing agitation of the emulsion later. Also, free water which has separated upon entry to the treater and after being heated by the firetubes, falls to the bottom where it is drained from the unit.

Baffle. The baffle separates the gas separation area from the heating area of the inlet section. It helps to divert incoming emulsion to the bottom of the treater.

U-Shaped Hood or Downcomer. This device covers the firetubes in the gas separation area. It diverts incoming emulsion to the bottom of the treater.

Water Wash. In this area of the inlet section, the emulsion gives up free water. Water washing is the process where large water droplets coalesce with small water droplets and settle out.

Flow Spreader. The flow spreader disperses emulsion along the length of the firetubes to ensure maximum use of the heating area by using the total surface area of the firetubes.

Firetubes. The firetubes supply heat to the emulsion causing oil viscosity to be lowered so water droplets can settle out.

Weir. This is a dam-like device over which emulsion from the inlet section flows into the surge section.

Surge Section. The surge section is the middle section which serves to keep the treating section "fluid-packed," that is, liquid completely filling the treating section with no gas on top.

Clean Oil Distribution Pipe. This pipe connects the clean oil collection header with the oil outlet located near the bottom of the surge section. Some units do not have an internal distribution pipe and oil is removed from the top of the treater.

Treating Section. Final treating and settling of the emulsion takes place in this section.

Flow Spreader. The flow spreader receives emulsion from the surge section and disperses it along the length of the treating section to ensure uniform distribution over the electrical grids.

Electrical Grids. There are two electrical grids made of steel rods. The lower grid is electrically charged while the upper grid is grounded. Grids are suspended from the vessel shell with insulated hanger rods.

Clean Oil Collection Header. This header runs horizontally across the top of the treating section and is used to skim off clean oil for removal from the vessel.

Monitoring and Safety Devices.
In order to operate properly and safely, every electrostatic treater is equipped with safety devices and monitoring features.

Fiame Arrestors. Flame arrestors fit on the front of fire boxes. They have a series of aluminum vanes placed very closely together so heat generated in fire boxes is dispersed in the air before it can cause a fire outside the vessel. Flame arrestors should be used on any fired emulsion treater.

Fuel Gas Scrubber. The fuel gas scrubber prevents entrained liquids from "going to the burners with the fuel gas. If the scrubber fills with liquid, a float rises and shuts off a valve which stops gas from flowing to the burners, preventing the possibility of a fire. The scrubber has a drain valve that the pumper should open each day to drain off liquids collected in it.

Safety Relief Valve. A safety relief valve is a pressure-relieving device designed to open at a pre-set pressure to relieve excessive pressure within a vessel or line. It may also be called a pop valve.

Rupture Disc. A rupture disc is a fail-safe pressure relief device made of metal that is designed to burst at a pre-set pressure. The pre-set pressure is usually at or below the maximum safe working pressure of the treater.

Sight Glasses. Sight glasses or gauge glasses are not safety devices themselves, but they have safety features built in. They are the best way for the pumper to see if the treater is doing its job. If the sight glass is broken, a safety feature of the sight glass valve will cause a steel ball to seat and shut off the flow. However, if the sight glass valve is not wide open, the ball will not seat.

Low Level Controller. The low level controller is a safety device installed on an electrostatic treater to ensure that the firetubes are always covered with liquid. It is designed to shutdown the burners if liquid level falls below the desired level. Shutting down the burners keeps the firetubes from overheating, which results in tube failure and a safety hazard.

Indicator Light. The indicator light, located on the transformer, remains on as long as the electrical grids are functioning properly or unless power has been lost to the treater.

Voltmeter. The voltmeter measures the voltage of incoming electricity to the treater. It should read 220 or 440 volts during normal operation depending on the electrical power source.

Circuit Breaker. A circuit breaker, located between the power source and the transformer, protects the transformer from power surges.

Ammeter. Some electrostatic treaters have an ammeter to measure the strength of electric current across the grids.

Electrostatic Treater Operation

Electrostatic treaters are used for three-phase separation: separating oil, water and gas. Chemicals are usually injected into the emulsion upstream from the treater. Therefore, the treating process has already begun by the time the emulsion reaches the treater.Emulsion enters the inlet section at the top of the unit and falls to the bottom of the vessel. It then travels upward across the firetubes and spills over a weir into the surge section. From the surge section, emulsion flows through a spreader into the treating section where final separation of water and oil takes place.

Inlet Section.

Emulsion enters the treater, splashes over the U-shaped hood or downcomer and flows down-ward to the bottom of the vessel. Free gas is released as emulsion strikes the hood or down-comer and rises to the top of the inlet section. Most free water in the emulsion quickly settles out and the remaining lighter liquids move upward through the water, which serves as a heated wash.

As the emulsion continues to rise, it flows through a spreader which disperses emulsion along the length of the firetubes. This action ensures maximum use of the firetubes for heating emulsion.

Several things happen as emulsion moves upward across the firetubes. The firetubes heat the emulsion which aids in separation of oil and water. Heated emulsion rises and spills over a weir out of the inlet section. Water, which has separated from the emulsion, settles to the bottom of the inlet section for removal. Gas, which has separated from the emulsion, rises to the top of the inlet section. A gas equalizer pipe allows the gas from both sides of the baffle to be equalized, gathered, and removed from the vessel through the gas outlet.

Some treaters have a heat exchanger installed on the inlet line. If used, incoming emulsion is preheated by the heat of outgoing oil. Therefore, the firetubes need to provide less heat. The settling time for incoming oil is decreased, and the outgoing oil is cooled to a desirable storage temperature which minimizes vaporization and maintains a higher oil gravity.

Surge Section.

A major purpose of the surge section is to keep the treating section "fluid-packed." Fluid- packed is when a vessel or section of a vessel is completely full of liquid with no gas on top. No clean oil leaves the treating section unless an equal amount of fluid enters the surge section. This is controlled by a float in the surge section which is mechanically linked to the oil dump valve.

Treating Section.

Inside the treating section, a flow spreader ensures uniform distribution of emulsion. It is in this section that final treating and settling takes place. From the spreader emulsion rises upward toward the high-voltage, alternating-current, electrical grids. The lower grid is charged with 15,000- 20,000 volts of electricity while the upper grid is grounded. Electrostatic treating begins below the lower grid and is completed between the upper and lower grids where water droplets coalesce and settle out.

As heated emulsion rises through the electrostatic field, water droplets are given an electrical charge, which causes them to become elongated and polarized. When a water droplet becomes polarized, it acquires a positive ( + ) charge on one end and a negative (-) charge on the other end. Alternating current on the lower electrical grid GRIDS causes it to reverse polarity (change from positive to negative) 120 times per second or 60 cycles per second. This causes the water droplets to move around rapidly and collide with each other with enough force to break the thin film surrounding each droplet.

The water droplets coalesce into larger droplets and settle to the bottom of the treating section for removal. Oil, which has separated from the water, rises to the top of the treating section. A clean oil col-lection header skims off the clean oil for removal from the treater.

Electrical System.

The electrical system consists of a step-up transformer and two electrical grids (electrodes). Step-up transformers increase the incoming voltage to a higher level, e.g., most electrostatic treaters are supplied by 440 volts which is then stepped-up to 15,000-20,000 volts to produce the electrostatic field around the grids.

The two grids are suspended one above the other in the treating section. The upper grid is grounded to the vessel shell and is adjustable so that the electrostatic field can be regulated to meet varying coalescing requirements. The lower grid is not grounded and receives the electrical output from the transformer. Both grids are suspended from the top of the vessel shell by insulated hanger rods. All components of the electrical system are designed for high voltage service.

The transformer is the heart of the electrical system. Most electrostatic treaters have a reac-tance type transformer which has a reactor to protect the transformer from power surges and high voltage dispersion. These transformers are oil-immersed and meet all reasonable electrical safety requirements. A circuit breaker, located between the power source and the transformer, protects the transformer from electrical power failures. A fused disconnect at the power source is recommended for maximum safety.

Fluid Levels.

Oil level in the treating section is maintained by the oil dump valve, which is operated by a float in the surge section. When emulsion rises above a pre-set level in the surge section, the float rises with the emulsion and causes the dump valve to open, which allows oil to leave the vessel. When the emulsion returns to the pre-set level, the dump valve closes and allows oil to accumulate in the treating section.

Free water and treated water levels in the treater are maintained by water dump valves. As with the oil dump valve, water dump valves open to remove water when the interfaces rise above pre-set levels and close when the interfaces return to pre-set levels.

Both water dump valves operate by means of Interface level controllers which use gas or compressed air to open and close the dump valves. This is achieved by the level controller diverting gas or compressed air to the diaphragm of the dump valve. Gas or compressed air pressure offsets the spring tension holding the diaphragm in the closed position. This action lifts the diaphragm and allows water to flow through the dump valve. When the interface returns to its pre-set level, the level controller vents the gas or compressed air and allows the diaphragm to seat, closing the dump valve.

Some electrostatic treaters are designed to allow water in the inlet section to join water in the treating seciion before being removed from the treater. This arrangement utilizes one dump valve and level controller to maintain water ievels in the treater. Mechanically operated oil dump valves and gas-operated water dump valves have been discussed in this manual. Other types of oil and water dump valves may be used on electrostatic treaters.

Operating Temperature.

Operating temperature is important and will vary from lease to lease. The lowest possible temperature to adequately treat the emulsion should be used. In warmer climates, heating may be necessary only in colder months.

When heating is required, lower temperatures can be used in electrostatic treaters than in conventional heater treaters. Treating temperatures normally range between 85°F and 135°F. Temperature of emulsion in the inlet section should be somewhere around 140°F so the tem-perature of fluid in the treating section around the grids never falls below 70°F. If fluid temper-ature gets below this level, the grids will not have the proper treating effect on the emulsion. The relation of chemicals to temperature is an important factor to be considered. Usually less chemical is required to treat a warm emulsion. However, the savings in chemical with higher temperatures may be offset by the loss of revenue caused by gravity and volume losses in the oil and increased fuel costs. Temperature controls or thermostats are an important part of any emulsion treater. If they fail to function properly, the burners could remain off or on all the time.

If they remain off, the emulsion may cool so that it does not completely break up. If the burners remain on, the treater may overheat and be damaged, the lighter ends of the oil may be cooked off changing gravity, and oil volume will be decreased resulting in lost revenue.

Firetubes should be inspected at periodic intervals. Since most emulsions being treated contain a certain amount of sludge and solids, the firetubes should be checked for corrosion, rust and accumulation of scale.

The burner flame should aim straight down the center of the firetube. If it hits the firetube directly, a hot spot will form and premature firetube failure will occur. The burner should come on and burn steadily for a long period of time rather than blasting on and off. A yellow flame with just enough air to keep from forming soot is best.

Operating Pressure.

Electrostatic treaters operate under working pressures of 5 to 50 psi. The maximum working pressure for a treater can be found on the manufacturer's information plate attached to the treater. The type of valves and controls used varies depending on the treater construction. Oil, water, and gas discharge lines must be equipped with controls. Since electrostatic treaters operate under pressure, they should be equipped with pressure relief devices that have enough capacity to protect the treater if pressure increases.

Gas leaving at the top of the treater is controlled by a gas back-pressure valve which controls the pressure in the treater. The inlet and surge sections are held at a slightly higher pressure than the treating section. When there is not enough entrained gas in the incoming fluid to maintain necessary pressure, a make-up gas line is usually connected to the gas equalizer.

There are several reasons why a higher pressure is maintained in the first two sections.

The differential pressure assures a positive flow of fluid from the surge section to the treating section.
The treating section must be fluid-packed.
There must be enough differential pressure to move the clean oil to storage tanks.

Pressure of the natural gas used to fire the electrostatic treater must be regulated. Any pressure

over the range of the thermostat will keep the thermostat from closing and overheating of the

treater will result.

Troubleshooting.

Emulsion in the Lease Tank. Emulsion in the lease tank is an indication that the proper chemical-heat combination is not being applied. Both the chemical injector and treater should be checked for any necessary corrections. If neither is malfunctioning, it may be that the characteristics of the emulsion have changed and a different chemical is required.

Free Water in the Lease Tank. If the water outlet lines are plugged or the water dump valves do not open, water has nowhere to go except out the oil outlet into the lease tank. If the valves are operating properly, it may be that the treater simply cannot handle the amount of free water produced, and a free- water knockout unit should be installed upstream of the treater.

Oil in the Water Disposal System. This can happen if the oil outlet is plugged, the oil dump valve is stuck closed, or the water dump valves are stuck open. Sometimes when the oil outlet on a treater is below the oil inlet on the lease tank and the back-pressure valve fails to hold a positive pressure on the treater, oil will go through the water outlets into the water disposal system.

SAFE LIGHTING PROCEDURE

Recommended steps for safely lighting a gas-fired electrostatic treater.

STEPS

Close pilot valve, gas burner valve, and main gas supply valve.
Be sure all gas is vented from firetube and flame arrestor is in place.
Be sure firetube is covered with fluid.
Stand to one side while inserting burning torch. This protects the operator from ignition of residual vapors.
Adjust torch position to ignite pilot. y6. Open main supply valve.
Slowly open pilot valve.
Open burner valve after pilot is lighted and torch removed.
Adjust gas and air mixture to obtain proper flame.
Set fuel pressure as low as possible to maintain proper temperature.

MAINTENANCE CHECKS

For smooth operation, the following maintenance checks should be performed as indicated :

STEPS :

Daily

Check indicator light on transformer. It should always be on and bright.
Check the voltmeter. It should read 220 or 440 volts depending on electrical power source.
Check free and treated water levels using sight glasses. Adjust levels if necessary.
Check gas back-pressure valve for correct vessel pressure. Adjust pressure if necessary.^
Check the oil dump valve linkage.
Check the water dump valves for condensation or accumulation of liquids in the gas/air supply lines by opening the bleed valves provided.
Drain the drip traps that supply gas/air to the water dump valves.
Check treater temperature to make sure fires aren't out and the thermostat is operating in the right range. Adjust temperature if necessary.
Drain the fuel gas scrubber.
Check chemical pump and chemical surge tank.

Weekly

Open the bottom drains on the treater briefly. This will prevent build-up of sediment and help prevent drain clogging.
Sight glass valves should be checked to prevent clogging. Sight glasses should be cleaned if needed.
Take inlet and outlet samples to check BS&W content.

Monthly

Check the burners and pilots for good performance. Clean if necessary.
Check the burners to make sure they remain centered in the firetubes.
Check the flame arrestors to make sure they are not clogged. Clean if necessary.

Yearly

Inspect and clean entire vessel. Use proper safety procedures for confined space entry.
Inspect the firetubes, remove from vessel and check for heat stress and cracks.
Inspect the fuel gas scrubber float to make sure it works.
Inspect dump valves. Clean and repair if necessary.

WATER LEVEL CHECKS

Water levels are pre-set. When the water level changes, these checks can be done to restore it to the pre-set condition :

PROBLEM : Low Water Level
POSSIBLE CAUSE : Emulsion build-up at the interface. Increased weight of emulsion on the water will cause the level to drop.

PROBLEM : No Water Level
POSSIBLE CAUSE : Low gas pressure. Back-pressure valve may be leaking or set too low. Safety relief valves may be leaking.
An oil valve stuck in the closed position. This would force all liquid out the water dumps or the gas outlet.
Circulating pump rate is too high. More volume than the treater can handle.
Leaking water dump valves. This would cause loss of the fluid seal and low gas pressure.

PROBLEM : High Water Level
POSSIBLE CAUSE : Plugged water dump lines. Usually caused by scale build up.

There are many problems that can occur with electrostatic treaters. If you observe unusual conditions, check with your field foreman.

GLOSSARY

Alternating Current : (A.C.) Electrical current which reverses flow at regular intervals, usually 120 reversals per second or 60 cycles per second.
A.P.I. Gravity : Specific gravity as defined by the American Petroleum Institute.
BS&W : Basic sediment and water.
Coalesce : Combining water droplets into larger droplets so they will settle out of oil.
Direct Current : (D.C.) Electrical current which flows continuously in one direction.
Emulsifying Agent : The substance which determines the stability of an emulsion; it forms a film around the suspended droplets.
Emulsion : Mixture of liquids which can only be separated by a treating process.
Emulsion Stability : Measured by the degree of difficulty in breaking the emulsion; affected by several factors.
Fluid-Packed : Condition when a vessel or section of a vessel is completely full of liquid with no gas on top.
Free Water : Water which readily separates from other fluids.
Interface : The point at which the oil and water meet.
Loose Emulsion : An emulsion which is easy to break.
Polarized : When a substance acquires a positive ( + ) charge on one end and a negative (-) charge on the other end.
Settling Time : Time it takes for water to separate from oil.
Sight Glass : Device located on the outside of a vessel used for monitoring liquid levels.
Three-Phase Separation : Separating gas, oil, and water.
Tight Emulsion : An emulsion which is difficult to break.
Treated Water : : Water which separates from other fluids only after treating with heat, chemicals, etc.
Two-Phase Separation : Separating natural gas from liquids.
Viscosity : Thickness of oil; resistance to flow.
Weir : A dam-like device which controls liquid level and flow through the electrostatic treater.

[accordion]

1. Emulsions and Electrostatic Treater Principles

2. Electrostatic Emulsion Treatment Video

3. Emulsions and Oil Treating Equipment by Maurice

4. API 12L-2008 Speci fication for Vertical and Horizontal Emulsion Treaters

5. ASME BPVC 2023 Code Cases Boilers and Pressure Vessels

6. PLP P-7-2003 , Crude Oil Emulsion Treating-3rd Ed-Brown

7. PLP P-8-2003 , Hydrate Inhibition-3rd Ed-Rosen

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