BOILERA boiler is a device for generating steam, which consists of two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam. The steam or hot fluid is then recirculated out of the boiler for use in various processes in heating applications. OR A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.[1The boiler receives the feed water, which consists of varying proportion of recovered condensed water (return water) and fresh water, which has been purified in varying degrees (make up water)Fire-tube boilerA fire-tube boiler is a type of boiler in which hot gases from a fire pass through one or more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.The fire-tube boiler developed as the third of the four major historical types of boilers: low-pressure tank or "haystack" boilers, flued boilers with one or two large flues, fire-tube boilers with many small tubes, and high-pressure water-tube boilers. Their advantage over flued boilers with a single large flue is that the many small tubes offer far greater heating surface area for the same overall boiler volume. The general construction is as a tank of water penetrated by tubes that carry the hot flue gases from the fire. The tank is usually cylindrical for the most part being the strongest practical shape for a pressurized container and this cylindrical tank may be either horizontal or vertical.This type of boiler was used on virtually all steam locomotives in the horizontal "locomotive" form. This has a cylindrical barrel containing the fire tubes, but also has an extension at one end to house the "firebox". This firebox has an open base to provide a large grate area and often extends beyond the cylindrical barrel to form a rectangular or tapered enclosure. The horizontal fire-tube boiler is also typical of marine applications, using the Scotch boiler. Vertical boilers have also been built of the multiple fire-tube type, although these are comparatively rare: most vertical boilers were either flued, or with cross water-tubes.OperationIn the locomotive-type boiler, fuel is burnt in a firebox to produce hot combustion gases. The firebox is surrounded by a cooling jacket of water connected to the long, cylindrical boiler shell. The hot gases are directed along a series of fire tubes, or flues, that penetrate the boiler and heat the water thereby generating saturated ("wet") steam. The steam rises to the highest point of the boiler, the steam dome, where it is collected. The dome is the site of the regulator that controls the exit of steam from the boiler.In the locomotive boiler, the saturated steam is very often passed into a superheater, back through the larger flues at the top of the boiler, to dry the steam and heat it to superheated steam. The superheated steam is directed to the steam engine's cylinders or very rarely to a turbine to produce mechanical work. Exhaust gases are fed out through a chimney, and may be used to pre-heat the feed water to increase the efficiency of the boiler.Draught for firetube boilers, particularly in marine applications, is usually provided by a tall smokestack. In all steam locomotives since Stephenson'sRocket, additional draught is supplied by directing exhaust steam from the cylinders into the smokestack through a blastpipe, to provide a partial vacuum. Modern industrial boilers use fans to provide forced or induced draughting of the boiler.Another major advance in the Rocket was large numbers of small-diameter firetubes (a multi-tubular boiler) instead of a single large flue. This greatly increased the surface area for heat transfer, allowing steam to be produced at a much higher rate. Without this, steam locomotives could never have developed effectively as powerful prime moversFIRE TUBE VERSUS WATER TUBESo What is a Firetube Boiler?

The name firetube is very descriptive. The fire, or hot flue gases from the burner, is channeled through tubes that are surrounded by the fluid to be heated. The body of the boiler is the pressure vessel and contains the fluid. In most cases this fluid is water that will be circulated for heating purposes or converted to steam for process use.

Every set of tubes that the flue gas travels through, before it makes a turn, is considered a "pass". So a three-pass boiler will have three sets of tubes with the stack outlet located on the rear of the boiler. A 4-pass will have four sets and the stack outlet at the front.

Firetube Boilers are: Relatively inexpensive Easy to clean Compact in size Available in sizes from 600,000 btu/hr to 50,000,000 btu/hr Easy to replace tubes Well suited for space heating and industrial process applicationsDisadvantages of Firetube Boilers include: Not suitable for high pressure applications 250 psig and above Limitation for high capacity steam generationWhat is a Watertube?

A Watertube design is the exact opposite of a fire tube. Here the water flows through the tubes and are incased in a furnace in which the burner fires into. These tubes are connected to a steam drum and a mud drum. The water is heated and steam is produced in the upper drum. Large steam users are better suited for the Water tube design. The industrial watertube boiler typically produces steam or hot water primarily for industrial process applications, and is used less frequently for heating applications.

Watertube Boilers are: Available in sizes that are far greater than the firetube design. Up to several million pounds per hour of steam. Able to handle higher pressures up to 5,000 psig Recover faster than their firetube cousin Have the ability to reach very high temperaturesDisadvantages of the Watertube design include: High initial capital cost Cleaning is more difficult due to the design No commonality between tubes Physical size may be an issue

Safety considerationsBecause the fire-flume boiler itself is the pressure vessel, it requires a number of safety features to prevent mechanical failure. Boiler explosion, which is a type of BLEVE (Boiling Liquid Expanding Vapor Explosion), can be devastating. Safety valves release steam before a dangerous pressure can be built up Fusible plugs over the firebox melt at a temperature lower than that of the firebox plates, thereby warning the operators by the noisy escape of steam if the water level is too low to cool the firebox crown safely. Stays, or ties, physically link the firebox and boiler casing, preventing them from warping. Since any corrosion is hidden, the stays may have longitudinal holes, called tell-tales, drilled in them which leak before they become unsafe.The fire-tube type boiler that was used in the Stanley Steamer automobile had several hundred tubes which were weaker than the outer shell of the boiler, making an explosion virtually impossible as the tubes would fail and leak long before the boiler exploded. In nearly 100 years since the Stanleys were first produced, no Stanley boiler has ever exploded.

MaintenanceAn intensive schedule of maintenance is needed to keep a boiler in safe condition. A typical regime will involve regular external inspections (including the inside of the firebox), washouts (with an internal inspection), periodic detailed examination and a general overhaul.Daily inspectionThe tube plates, the fusible plug and the heads of the firebox stays should be checked for leaks. The correct operation of the boiler fittings, especially the water gauges and water feed mechanisms, should be confirmed. Steam pressure should be raised to the level at which the safety valves lift and compared with the indication of the pressure gauge.

WashoutCutaway of locomotive boiler. Note the narrow water spaces around the firebox and the "mudhole" for access to the crown sheet: these areas require special attention during washoutThe working life of a locomotive boiler is considerably extended if it is spared from a constant cycle of cooling and heating. Historically, a locomotive would be kept in steam continuously for a period of about eight to ten days, and then allowed to cool sufficiently for a hot-water boiler washout. The schedule for express engines was based on mileage.[4] Today's preserved locomotives are not usually kept continuously in steam and the recommended washout interval is now fifteen to thirty days, but anything up to 180 days is possible.[5]The process starts with a blowdown while some pressure remains in the boiler, then the draining away of all the boiler water through the mudholes at the base of the firebox and the removal of all the washout plugs. Scale is then jetted or scraped from the interior surfaces using a high pressure water jet and rods of soft metal, such as copper. Areas particularly susceptible to scale buildup, such as the firebox crown and narrow water spaces around the firebox, are given special attention. The inside of the boiler is inspected by sighting through the plug holes, with a particular check paid to the integrity of the firetubes, firebox crown and stays and absence of pitting or cracking of the boiler plates. The gauge glass cocks and tubes and fusible plug should be cleared of scale; if the core of the fusible plug shows signs of calcination the item should be replaced.On reassembly care should be taken that the threaded plugs are replaced in their original holes: the tapers can vary as a result of rethreading. The mudhole door gaskets, if of asbestos, should be renewed but those made of lead may be reused; special instructions are in force for the disposal of these harmful materials.[5] At large maintenance facilities the boiler would have been both washed and refilled with very hot water from an external supply to bring the locomotive back to service more quickly.Periodic examinationTypically an annual inspection, this would require the removal and check of external fittings, such as the injectors, safety valves and pressure gauge. High-pressure copper pipework can suffer from work hardening in use and become dangerously brittle: it may be necessary to treat these by annealing before refitting. A hydraulic pressure test on the boiler and pipework may also be called for.General overhaulIn the UK the specified maximum interval between full overhauls is ten years. To enable a full inspection the boiler is lifted from the locomotive frame and the lagging removed. All firetubes are removed for checking or replacement. All fittings are removed for overhaul. Before returning to use a qualified examiner will check the boilers fitness for service and issue a safety certificate valid for ten years.

Boiler fittings and accessories Safety valve: It is used to relieve pressure and prevent possible explosion of a boiler. Water level indicators: They show the operator the level of fluid in the boiler, also known as a sight glass, water gauge or water column is provided. Bottom blowdown valves: They provide a means for removing solid particulates that condense and lie on the bottom of a boiler. As the name implies, this valve is usually located directly on the bottom of the boiler, and is occasionally opened to use the pressure in the boiler to push these particulates out. Continuous blowdown valve: This allows a small quantity of water to escape continuously. Its purpose is to prevent the water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause water droplets to be carried over with the steam - a condition known as priming. Blowdown is also often used to monitor the chemistry of the boiler water. Flash Tank: High pressure blowdown enters this vessel where the steam can 'flash' safely and be used in a low-pressure system or be vented to atmosphere while the ambient pressure blowdown flows to drain. Automatic Blowdown/Continuous Heat Recovery System: This system allows the boiler to blowdown only when makeup water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash tank is generally needed as the blowdown discharged is close to the temperature of the makeup water. Hand holes: They are steel plates installed in openings in "header" to allow for inspections & installation of tubes and inspection of internal surfaces. Steam drum internals, A series of screen, scrubber & cans (cyclone separators). Low- water cutoff: It is a mechanical means (usually a float switch) that is used to turn off the burner or shut off fuel to the boiler to prevent it from running once the water goes below a certain point. If a boiler is "dry-fired" (burned without water in it) it can cause rupture or catastrophic failure. Surface blowdown line: It provides a means for removing foam or other lightweight non-condensible substances that tend to float on top of the water inside the boiler. Circulating pump: It is designed to circulate water back to the boiler after it has expelled some of its heat. Feedwater check valve or clack valve: A non-return stop valve in the feedwater line. This may be fitted to the side of the boiler, just below the water level, or to the top of the boiler. Top feed: A check valve (clack valve) in the feedwater line, mounted on top of the boiler. It is intended to reduce the nuisance of limescale. It does not prevent limescale formation but causes the limescale to be precipitated in a powdery form which is easily washed out of the boiler. Desuperheater tubes or bundles: A series of tubes or bundles of tubes in the water drum or the steam drum designed to cool superheated steam. Thus is to supply auxiliary equipment that does not need, or may be damaged by, dry steam. Chemical injection line: A connection to add chemicals for controlling feedwater pH.

A deaerator is a device that is widely used for the removal of air and other dissolved gases from the feedwater to steam-generating boilers. In particular, dissolved oxygen in boiler feedwaters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). Water also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005cm/L) or less.[1][2]There are two basic types of deaerators, the tray-type and the spray-type:[1][3][4][5][6]

Safety Boiler explosionHistorically, boilers were a source of many serious injuries and property destruction due to poorly understood engineering principles. Thin and brittle metal shells can rupture, while poorly welded or riveted seams could open up, leading to a violent eruption of the pressurized steam. Collapsed or dislodged boiler tubes could also spray scalding-hot steam and smoke out of the air intake and firing chute, injuring the firemen who loaded coal into the fire chamber. Extremely large boilers providing hundreds of horsepower to operate factories could demolish entire buildings.[3]A boiler that has a loss of feed water and is permitted to boil dry can be extremely dangerous. If feed water is then sent into the empty boiler, the small cascade of incoming water instantly boils on contact with the superheated metal shell and leads to a violent explosion that cannot be controlled even by safety steam valves. Draining of the boiler could also occur if a leak occurred in the steam supply lines that was larger than the make-up water supply could replace. The Hartford Loop was invented in 1919 by the Hartford Steam Boiler and Insurance Company as a method to help prevent this condition from occurring, and thereby reduce their insurance claims.

BOILER FEED WATERA boiler is a device for generating steam, which consists of two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam. The steam or hot fluid is then recirculated out of the boiler for use in various processes in heating applications.The boiler receives the feed water, which consists of varying proportion of recovered condensed water (return water) and fresh water, which has been purified in varying degrees (make up water). The make-up water is usually natural water either in its raw state, or treated by some process before use. Feed-water composition therefore depends on the quality of the make-up water and the amount of condensate returned to the boiler. The steam, which escapes from the boiler, frequently contains liquid droplets and gases. The water remaining in liquid form at the bottom of the boiler picks up all the foreign matter from the water that was converted to steam. The impurities must be blown down by the discharge of some of the water from the boiler to the drains. The permissible percentage of blown down at a plant is strictly limited by running costs and initial outlay. The tendency is to reduce this percentage to a very small figure.Proper treatment of boiler feed water is an important part of operating and maintaining a boiler system. As steam is produced, dissolved solids become concentrated and form deposits inside the boiler. This leads to poor heat transfer and reduces the efficiency of the boiler. Dissolved gasses such as oxygen and carbon dioxide will react with the metals in the boiler system and lead to boiler corrosion. In order to protect the boiler from these contaminants, they should be controlled or removed, trough external or internal treatment. For more information check the boiler water treatment Find extra information about the characteristics of boiler feed water.

RESULTING INGOT RID OF BYCOMMENTS

Soluble Gasses

Hydrogen Sulphide (H2S)Water smells like rotten eggs: Tastes bad, and is corrosive to most metals.Aeration, Filtration, and Chlorination.Found mainly in groundwater, and polluted streams.

Carbon Dioxide (CO2)Corrosive, forms carbonic acid in condensate.Deaeration, neutralization with alkalis.Filming, neutralizing amines used to prevent condensate line corrosion.

Oxygen (O2)Corrosion and pitting of boiler tubes.Deaeration & chemical treatment with (Sodium Sulphite or Hydrazine)Pitting of boiler tubes, and turbine blades, failure of steam lines, and fittings etc.

Suspended Solids

Sediment & TurbiditySludge and scale carryover.Clarification and filtration.Tolerance of approx. 5ppm max. for most applications, 10ppm for potable water.

Organic MatterCarryover, foaming, deposits can clog piping, and cause corrosion.Clarification; filtration, and chemical treatmentFound mostly in surface waters, caused by rotting vegetation, and farm run offs. Organics break down to form organic acids. Results in low of boiler feed-water pH, which then attacks boiler tubes. Includes diatoms, molds, bacterial slimes, iron/manganese bacteria. Suspended particles collect on the surface of the water in the boiler and render difficult the liberation of steam bubbles rising to that surface.. Foaming can also be attributed to waters containing carbonates in solution in which a light flocculent precipitate will be formed on the surface of the water. It is usually traced to an excess of sodium carbonate used in treatment for some other difficulty where animal or vegetable oil finds its way into the boiler.

Dissolved Colloidal Solids

Oil & GreaseFoaming, deposits in boilerCoagulation & filtrationEnters boiler with condensate

Hardness, Calcium (Ca), and Magnesium (Mg)Scale deposits in boiler, inhibits heat transfer, and thermal efficiency. In severe cases can lead to boiler tube burn thru, and failure.Softening, plus internal treatment in boiler.Forms are bicarbonates, sulphates, chlorides, and nitrates, in that order. Some calcium salts are reversibly soluble. Magnesium reacts with carbonates to form compounds of low solubility.

Sodium, alkalinity, NaOH, NaHCO3, Na2CO3Foaming, carbonates form carbonic acid in steam, causes condensate return line, and steam trap corrosion, can cause embrittlement.Deaeration of make-up water and condensate return. Ion exchange; deionization, acid treatment of make-up water.Sodium salts are found in most waters. They are very soluble, and cannot be removed by chemical precipitation.

Sulphates (SO4)Hard scale if calcium is presentDeionizationTolerance limits are about 100-300ppm as CaCO3

Chlorides, (Cl)Priming, i.e. uneven delivery of steam from the boiler (belching), carryover of water in steam lowering steam efficiency, can deposit as salts on superheaters and turbine blades. Foaming if present in large amounts.DeionizationPriming, or the passage of steam from a boiler in "belches", is caused by the concentration sodium carbonate, sodium sulphate, or sodium chloride in solution. Sodium sulphate is found in many waters in the USA, and in waters where calcium or magnesium is precipitated with soda ash.

Iron (Fe) and Manganese (Mn)Deposits in boiler, in large amounts can inhibit heat transfer.Aeration, filtration, ion exchange.Most common form is ferrous bicarbonate.

Silica (Si)Hard scale in boilers and cooling systems: turbine blade deposits.Deionization; lime soda process, hot-lime-zeolite treatment.Silica combines with many elements to produce silicates. Silicates form very tenacious deposits in boiler tubing. Very difficult to remove, often only by flourodic acids. Most critical consideration is volatile carryover to turbine components.

The principal difficulties caused by water in boiler are: Scaling; Foaming and priming; Corrosion.Feed-water purity is a matter both of quantity of impurities and nature of impurities: some impurities such as hardness, iron and silica are of more concern, for example, than sodium salts. The purity requirements for any feed-water depend on how much feed water is used as well as what the particular boiler design (pressure, heat transfer rate, etc.) can tolerate. Feed-water purity requirements therefore can vary widely. A low-pressure fire-tube boiler can usually tolerate high feed-water hardness with proper treatment while virtually all impurities must be removed from water used in some modern, high-pressure boilers.Only relatively wide ranges can be given as to maximum levels of alkalis, salt, silica, phosphates etc, in relation to working pressure. The actual maximum levels must be obtained fro the boiler manufacturer, who will base them on the characteristics of the boiler in question.Scaling in boilersBoiler scale is caused by impurities being precipitated out of the water directly on heat transfer surfaces or by suspended matter in water settling out on the metal and becoming hard and adherent. Evaporation in a boiler causes impurities to concentrate. This interferes with heat transfers and may cause hot spots. Leading to local overheating. Scaling mechanism is the exceeding of the solubility limits of mineral substances due to elevated temperature and solids concentration at the tube/water interface. The deposition of crystalline precipitates on the walls of the boiler interferes with heat transfer and may cause hot spots, leading to local overheating. The less heat they conduct, the more dangerous they are. Common feed water contaminants that can form boiler deposits include calcium, magnesium, iron, aluminum, and silica. Scale is formed by salts that have limited solubility but are not totally insoluble in boiler water. These salts reach the deposit site in a soluble form and precipitate. The values corresponding to their thermal conductivity are:Steel 15 kcal/m2.h per degree CCaSO4 1-2 kcal/m2.h per degree CCaCO3 0.5-1 kcal/m2.h per degree CSiO2 0.2-0.5 kcal/m2.h per degree C

Scaling is mainly due to the presence of calcium and magnesium salts (carbonates or sulphates), which are less soluble hot than cold, or to the presence of too high concentration of silica in relation to the alkalinity of the water in the boiler. A carbonate deposit is usually granular and sometimes of a very porous nature. The crystals of calcium carbonate are large but usually are matted together with finely divided particles of other materials so that the scale looks dense and uniform. Dropping it in a solution of acid can easily identify a carbonate deposit. Bubbles of carbon dioxide will effervesce from the scale. A sulphate deposit is much harder and more dense than a carbonate deposit because the crystals are smaller and cement together tighter. A Sulphate deposit is brittle, does not pulverize easily, and does not effervesce when dropped into acid. A high silica deposit is very hard, resembling porcelain. The crystal of silica are extremely small, forming a very dense and impervious scale. This scale is extremely brittle and very difficult to pulverize. It is not soluble in hydrochloric acid and is usually very light coloured.Iron deposits, due either to corrosion or iron contamination in the water, are very dark coloured. Iron deposits in boilers are most often magnetic. They are soluble in hot acid giving a dark brown coloured solution.

If unchecked, scaling causes progressive lowering of the boiler efficiency by heat retardation, acting as an insulator. Eventually, scale built-up will cause the tube to overheat and rupture. Boiler deposits can also cause plugging or partial obstruction of corrosive attack underneath the deposits may occur. In general, boiler deposits can cut operating efficiency, produce boiler damage, cause unscheduled boiler outages, and increase cleaning expense.The first anti-scaling preventative measure is to supply good quality demineralised water as makeup feed water. The purer the feed water is, the weaker the driving mechanism to form scale. Scale-forming minerals that do enter the boiler can be rendered harmless by internal chemical treatment. A long-established technique is to detach the hardness cations, magnesium and calcium, from the scale forming minerals and to replace them with sodium ions.

Presence of SilicaSilica can vaporize into the steam at operating pressures as low as 28 bars. Its solubility in steam increases with increased temperature; therefore, silica becomes more soluble as steam is superheated. The conditions under which vaporous silica carryover occurs have been thoroughly investigated and documented. Researchers have found that for any given set of boiler conditions using demineralized or evaporated quality make-up water, silica is distribute between the boiler water and the steam in a definite ratio. This ratio depends on two factors: boiler pressure and boiler water pH. The value of the ratio increases almost logarithmically with increasing pressure and decreases with increasing pH.If the silica enters the boiler water, the usual corrective action is to increase boiler blowdown, to decrease it to acceptable levels and then to correct the condition that caused the silica contamination.

For further information check our web page about silica scaling in boilers. Find information about the other main problems occurring in boilers: foaming and priming, corrosion. For a description of the characteristics of the perfect boiler water click here. Check also our web page about boiler water treatment, in particular through deaeration (deaerating heaters or membrane contractors).

6 Common Mistakes Made in Safety Valve Installation There are many safety equipments used for releasing or controlling over pressurization in chemical plant operation. One of the most common types is safety valve. Safety valve prevents equipment and piping from damage due to over pressure by releasing certain amount of fluid into the atmosphere.Safety valves are installed on pressure vessels or high pressure pipe line. They serve as protecting devices. However, because of improper installation, safety valves could do nothing to protect the equipment from over pressurization. So, it is very important to avoid common mistakes made during safety valve installation.Improper installation of safety valve could endanger plant equipments as well as safety of workers and people inside plant site. You have to know common types of those miss-installations. Here are six common mistakes made in safety valve installation.1. Safety valve is not mounted vertically.2. Block valves are installed at the upstream and or downstream of safety valve.3. The inlet pipe size is smaller than connection size of the safety valve.4. A cap or plug is installed at the vent line.5. The diameter of outlet pipe is smaller than the safety valve outlet.6. The discharge outlet is not located at safe distance that could harm workers safety and health. The vent discharge should also be considered to be far enough from ignition source if the discharging material is combustible or flammable.The above common improper practices of safety valve installation must be avoided. So, that safety valve as pressure releasing device is fully function. All pressure vessels and pressurized facility remain safe.

REASONS FOR SAFETY IN CHEMICAL INDUSTRYIt is no doubt that workers who are working in chemical plant potentially suffering from illness, injuries even death. In fact, chemical plants are full of potential hazards and could cause accidents and disasters if they are not treated properly. Hazards may come from hazardous chemicals, electrical, high temperature, high pressure, unsafe acts and conditions, work at elevated area, etc. Hence, safety in a chemical plant holds an important role.There may be hundreds of reason why safety in chemical plant is vitally important. And the list below is only a part of them. Indeed, I intend to remind about importance of safety and why we have to make safety become the first consideration in mind.1. Safety protects workers, employers and all people in the plant including strangers from illness, injuries or death.2. Ensuring survival of company's business.3. It prevents company's property and facility from damage.4. It enhances company's reputation.5. It teaches people in the plant how to work safely.6. It helps company to achieve its targets and objective.7. Keeping company away from law suits and penalties.8. It keeps workers to feel comport, happy and safe.9. Company will be avoided from unnecessary cost.10. It keeps workers awareness alive.11. Safety teaches everyone in the plant to pay attention to their workplaces and surrounding.12. It keeps customer's confidence to do business with the company.13. Safety program is a cost-effective decision for the company.14. Safety is able to reduce employee's turn over and increase productivity.15. Safety can prevent production process interruption and shut down.

Compressed AirWhat is Compressed Air? Compressed air, commonly called Industry's Fourth Utility, is air that is condensed and contained at a pressure that is greater than the atmosphere. The process takes a given mass of air, which occupies a given volume of space, and reduces it into a smaller space. In that space, greater air mass produces greater pressure. The pressure comes from this air trying to return to its original volume. It is used in many different manufacturing operations. A typical compressed air system operating at 100 psig (7 bar) will compress the air down to 1/8 of its original volume. (figure CA1-1)Why Use Compressed Air?Compressed air supplies power for many different manufacturing operations. At a pressure of 100 psig (7 bar), compressed air serves as a utility. It supplies motive force, and is preferred to electricity because it is safer and more convenient. There are numerous industries that use compressed air for various applications.Industrial Plant Maintenance: Air tools, such as paving breakers, are used to fix cement floors, to open up brick walls for assorted service lines, and other comparable work. Caulking and chipping (fig. CA1-2) can be done using smaller air hammers.For other maintenance work, plants can use air-operated drills, screwdrivers, and wrenches, provided that the air outlets are well placed throughout the plant. Painting can be done using paint-spraying systems.Sprinkler systems are controlled by air pressure, which keeps water from entering the pipes until heat breaks the seal and releases the pressure. Air jets speed up the process of cleaning machines, floors, remote ceiling areas, move heavy loads and overhead pipes. Air pressure also efficiently cleans boiler tubes. Tuck pointing of brick walls and metalizing of worn parts are two other compressed air uses.On the Production Line: Pneumatic tools are convenient for industrial production because they have a low weight-to-power ratio, and they may be used for long periods of time without overheating and with low maintenance costs. Chipping and scaling hammers are used in railroads, oil refineries, chemical refineries, shipyards, and many other industries for general application. They are also used in the foundry for cleaning large castings, and to remove weld scale, rust, and paint in other industries. Additionally, these hammers are good for cutting and sculpturing stone.Pneumatic drills can be used for all classes of reaming, tapping, and drilling anytime that the work cannot easily be carried to the drill press and for all classes of breast drill work. These air-powered drills (fig. CA1-3) are also often used for operating special boring bars, and in emergencies, for independent drive of a machine tool where required horsepower is within their capacity.Grinding, wire brushing, polishing, sanding, shot blasting and buffing are performed efficiently with compressed air in the automotive, aircraft, rail car, locomotive, vessel shops, shipbuilding, other heavy machinery, and other industries. The primary goals are to finish surfaces and prepare them for finishing operations. Two of the most basic assembly operations, driving screws and turning up nuts, are performed more efficiently because of pneumatic screwdrivers and nut runners.Air Motors, Vacuum, & Other Auxiliary Devices: Air motors are often used as a power source in operations involving flammable or explosive liquids, vapor, or dust, and can operate in hot, corrosive, or wet atmospheres without damage. Their speeds may be easily changed; they will start and stop rapidly and are not damaged by stalling and overloading. Air motors power (fig. CA1-4) many hand-held air tools and air hoists. They are used in various applications in underground tunnels and mines and in industrial areas where there are flammable liquids or gas. They also drive many pumps used in construction and many positioning apparatuses used in manufacturing.Vacuum has numerous applications in production. A vacuum pump is a compressor in which the desired effect is the intake vacuum, not the pressurized air. For vacuum chucking, the pump holds a vacuum in a tank located close to the machine, while bleeder holes under the part to be machined are opened to hold the part in place.Pneumatic auxiliary production equipment is used extensively. Positioners, feeders, clamps, air chucks, presses, air knives and many other devices powered by air cylinders increase production efficiency. Pneumatic cylinders plus ratchets or stops provide reciprocating or rotating interrupted motions much more economically than by traditional mechanical tools. In finishing and packaging areas, pneumatic devices are used for many applications, such as dry powder transporting and fluidizing, liquid padding, carton stapling, and appliance sanding. Blast cleaning and finishing are other widely used compressed air applications.AutomationThe field of automation has been impacted by pneumatics. For instance, air circuitry and pneumatic controls allow the integration of traditional and special air tools and auxiliary devices into single automatic machines. One system has a high degree of interchangeability of pneumatic tools and controls. Because of fluidics, we have simple devices for pneumatic control at lower pressures and with almost no moving parts. Pneumatic positioners have been created that are capable of positioning parts to within 1/1000" without the use of mechanical stops.Compressed air is also used for the pneumatic transportation of materials, such as substances in granular, chip, pelletized, or powdered form and liquids where inertness is not required. Painting is another frequently automated application that uses air circuitry and pneumatic controls in robotic machines and paint spray systems. Compressed air is often used in automatic packaging machinery for sealing, locating the work, and actuating arms that fold paper to wrap the work. Vacuuming machines also perform similar tasks, such as picking up and transferring materials.Automated Assembly StationsCompressed air is speeding up operations in the automotive, appliance, electronics, communications, and business machines industries. Common air-powered tasks in automatic machines include the following: tightening threaded fasteners to specified torque; pressing of hammering plugs, pins, and rivets with air; feeding fasteners or parts; actuating positioning cylinders, slides, or work heads, blow-offs, operating indicator lights; and transmitting signals to recording computers.Common compressed air applications:

The Levels of Compressed Air Quality

LevelApplicationAir Treatment ComponentsFunction

1Shop AirFiltered Centrifugal SeparatorRemoves solids 3 microns & larger, 99% of water droplets,& 40% of oil aerosols

2Air Tools, Sand Blasting, Pneumatic Control SystemsRefrigerated Compressed Air Dryer, Air Line FilterRemoves moisture producing a 35 to 50F (-1.67 to 10C) pressure dew point, removes 70% of oil aerosols, and all particles 1 micron and larger

3Instrument Air, Paint Spraying, Powder Coating,Packing MachinesRefrigerated Compressed Air Dryer, Oil Removal FilterRemoves moisture & produces a 35 to 50F (-1.67 to 10C) pressure dew point, removes 99.999% of oil aerosols, and all particles .025 microns and larger

4Indoor Applications,Food Industry, Dairy Industry, LaboratoriesRefrigerated Compressed Air Dryer, Oil Removal Filter, & Oil Vapor AdsorberRemoves moisture & produces a 35 to 50F (-1.67 to 10C) pressure dew point, removes 99.999% of oil aerosols, all particles .025 microns and larger, oily vapor, oily smell, & oily taste

5Outdoor Pipelines, Pneumatic Transport of Hygroscopic Material, Breweries, Chemical & Pharmaceutical Industry, Electronics IndustryAir Line Filter, Oil Removal Filter, Low Dew Point Desiccant Dryer, Air Line FilterRemoves moisture producing a -40 to -150F (-40 to -101C) pressure dew point, removes 99.999% of oil aerosols, and all particles .025 microns and larger

6Breathing AirBreathing Air System (Continuous or Portable)Removes harmful compressed air contaminants and will produce Grade D breathing air

Rules of thumb:compressed air. These rules apply to the design and installation of the system:There are several rules of thumb regarding All compressors produce heat during the compression process. This heat must be removed from the compressor room for proper operation of the compressor. Be sure to provide sufficient ventilation for all equipment that may be installed in the compressor room. All compressor manufacturers publish allowable operating temperatures. Leave sufficient space around the compressor to permit routine maintenance. It is also suggested to provide space for the removal of major components during compressor overhauls. An air receiver near the compressor should be located to provide a steady source of control air, additional air cooling, and moisture separation. In the distribution system, there may periodically be large volume demands, which will rapidly drain the air from surrounding areas, and cause pressure levels to fall for surrounding users. However, strategically located receivers in the system can supply these abrupt demands and still provide a consistent air flow and pressure to the affected areas. Select piping systems that have low pressure drop and provide corrosion free operation. When selecting the main air header, size for a maximum pressure drop of 1 to 2 psi (.07 to .14 bar). A good rule is to use a header pipe size at least one size larger than calculated. This will provide additional air storage capacity and allow for future expansion. It is suggested that all piping in a loop system (fig. CA1-5) be sloped to accessible drain points. Air outlets should be taken from the top of the main line to keep possible moisture from entering the outlet. Drip legs or drain valves should be installed at all low points in the system where it is possible for moisture to accumulate. One gallon per CFM of capacity is the minimum amount of storage recommended. Systems with sharp changes in demand should have a minimum amount of storage of three gallons per CFM of capacity. An efficient control system will help to accommodate these abrupt changes in demand. A Load/No Load control will help system efficiency because it operates the compressor at either full load or no load. The motors continue to run in the unloaded state, but the inlet valves to the compression chamber are left open, keeping air from being compressed. The motor still does a small amount of work even when no air is compressed. Position filters and dryers in the air line before any pressure-reducing valve (highest pressure) and after air is cooled to 100F (38C) or less (lowest temperature). (fig. CA1-6)These rules give measurements at which a standard system operates: Every 1 psig pressure drop increases compressor power required by .5%. At discharge pressures of 100 psig, most water-cooled aftercoolers will need about 3 gpm per 100 CFM of compressed air. The water vapor content at 100F (37.78C) of saturated compressed air is equal to about two gallons per hour for each 100 CFM of compressor output. In saturated compressed air, for every 20F (-6.67C) temperature drop the water content of the air drops by 50%. (fig. CA1-7) Every 100 CFM of air compressed to 100 psig produces 20 gallons of condensate per day under normal conditions.

PUMPA pump is a device used to move fluids, such as liquids or slurries. A pump displaces a volume by physical or mechanical action. Pumps fall into five major groups: direct lift, displacement, velocity, buoyancy and gravity pumps. Their names describe the method for moving a fluid.TYPE OF PUMP(1)POSITIVE DISPLACEMENT PUMPS A positive displacement pump causes a fluid to move by trapping a fixed amount of it then forcing (displacing) that trapped volume into the discharge pipe. A positive displacement pump can be further classified according to the mechanism used to move the fluid: Rotary-type, [internal gear], screw, shuttle block, flexible vane or sliding vane, helical twisted roots (e.g. the Wendelkolben pump) or liquid ring vacuum pumps.Positive displacement rotary pumps are pumps that move fluid using the principles of rotation. The vacuum created by the rotation of the pump captures and draws in the liquid. Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually. Positive displacement rotary pumps also have their weaknesses. Because of the nature of the pump, the clearance between the rotating pump and the outer edge must be very close, requiring that the pumps rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids will cause erosion, much as ocean waves polish stones or erode rock into sand. Rotary pumps that experience such erosion eventually show signs of enlarged clearances, which allow liquid to slip through and detract from the efficiency of the pump. Positive displacement rotary pumps can be grouped into three main types. Gear pumps are the simplest type of rotary pumps, consisting of two gears laid out side-by-side with their teeth enmeshed. The gears turn away from each other, creating a current that traps fluid between the teeth on the gears and the outer casing, eventually releasing the fluid on the discharge side of the pump as the teeth mesh and go around again. Many small teeth maintain a constant flow of fluid, while fewer, larger teeth create a tendency for the pump to discharge fluids in short, pulsing gushes. Screw pumps are a more complicated type of rotary pumps, featuring two screws with opposing thread - that is, one screw turns clockwise, and the other counterclockwise. The screws are each mounted on shafts that run parallel to each other; the shafts also have gears on them that mesh with each other in order to turn the shafts together and keep everything in place. The turning of the screws, and consequently the shafts to which they are mounted, draws the fluid through the pump. As with other forms of rotary pumps, the clearance between moving parts and the pump's casing is minimal. Moving vane pumps are the third type of rotary pumps, consisting of a cylindrical rotor encased in a similarly shaped housing. As the rotor turns, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump. Reciprocating-type, for example, piston or diaphragm pumps.Positive Displacement Pumps has an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. The volume is constant given each cycle of operation.The positive displacement pumps can be divided into two main classes reciprocating rotaryThe positive displacement principle applies whether the pump is a rotary lobe pump progressing cavity pump rotary gear pump piston pump diaphragm pump screw pump gear pump Hydraulic pump vane pump regenerative (peripheral) pump peristalticPositive Displacement Pumps, unlike Centrifugal or Roto-dynamic Pumps, will produce the same flow at a given speed (RPM) no matter the discharge pressure. Positive Displacement Pumps are "constant flow machines"A Positive Displacement Pump must not be operated against a closed valve on the discharge side of the pump because it has no shut-off head like Centrifugal Pumps. A Positive Displacement Pump operating against a closed discharge valve, will continue to produce flow until the pressure in the discharge line are increased until the line bursts or the pump is severely damaged - or both.A relief or safety valve on the discharge side of the Positive Displacement Pump is therefore absolutely necessary. The relief valve can be internal or external. The pump manufacturer normally has the option to supply internal relief or safety valves. The internal valve should in general only be used as a safety precaution, an external relief valve installed in the discharge line with a return line back to the suction line or supply tank is recommended. Reciprocating PumpsTypical reciprocating pumps are plunger pumps diaphragm pumpsA plunger pump consists of a cylinder with a reciprocating plunger in it. The suction and discharge valves are mounted in the head of the cylinder. In the suction stroke the plunger retracts and the suction valves open causing suction of fluid into the cylinder. In the forward stroke the plunger pushes the liquid out of the discharge valve.With only one cylinder the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when the plunger is at the end positions. A lot of energy is wasted when the fluid is accelerated in the piping system. Vibration and "water hammer" may be a serious problem. In general the problems are compensated for by using two or more cylinders not working in phase with each other. In diaphragm pumps, the plunger pressurizes hydraulic oil which is used to flex a diaphragm in the pumping cylinder. Diaphragm valves are used to pump hazardous and toxic fluids.Gear pumpThis uses two meshed gears rotating in a closely fitted casing. Fluid is pumped around the outer periphery by being trapped in the tooth spaces. It does not travel back on the meshed part, since the teeth mesh closely in the centre. Widely used on car engine oil pumps. it is also used in various hydraulic power packsProgressing cavity pumpWidely used for pumping difficult materials such as sewage sludge contaminated with large particles, this pump consists of a helical shaped rotor, about 10 times as long as its width. This can be visualized as a central core of diameter x, with typically a curved spiral wound around of thickness half x, although of course in reality it is made from one casting. This shaft fits inside a heavy duty rubber sleeve, of wall thickness typically x also. As the shaft rotates, fluid is gradually forced up the rubber sleeve. Such pumps can develop very high pressure at quite low volumes.Roots-type pumpsThe low pulsation rate and gentle performance of this Roots-type positive displacement pump is achieved due to a combination of its two 90 helical twisted rotors, and a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous and non-vorticuless flow with equal volume. High capacity industrial "air compressors" have been designed to employ this principle, as well as most "superchargers" used on internal combustion engines, and even a brand of civil defense siren, the Federal Signal Corporation's Thunderbolt.Peristaltic pumpA peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes" or "wipers" attached to the external circumference compresses the flexible tube. As the rotor turns, the part of the tube under compression closes (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution") fluid flow is induced to the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract.Reciprocating-type pumpsHand-operated, reciprocating, positive displacement, water pump in Koice-ahanovce, Slovakia (walking beam pump).Reciprocating pumps are those which cause the fluid to move using one or more oscillating pistons, plungers or membranes (diaphragms).Reciprocating-type pumps require a system of suction and discharge valves to ensure that the fluid moves in a positive direction. Pumps in this category range from having "simplex" one cylinder, to in some cases "quad" four cylinders or more. Most reciprocating-type pumps are "duplex" (two) or "triplex" (three) cylinder. Furthermore, they can be either "single acting" independent suction and discharge strokes or "double acting" suction and discharge in both directions. The pumps can be powered by air, steam or through a belt drive from an engine or motor. This type of pump was used extensively in the early days of steam propulsion (19th century) as boiler feed water pumps. Though still used today, reciprocating pumps are typically used for pumping highly viscous fluids including concrete and heavy oils and special applications demanding low flow rates against high resistance..BUOYANCY PUMPCompressed-air-powered double-diaphragm pumpsOne modern application of positive displacement diaphragm pumps is compressed-air-powered double-diaphragm pumps. Run on compressed air these pumps are intrinsically safe by design, although all manufacturers offer ATEX certified models to comply with industry regulation. Commonly seen in all areas of industry from shipping to processing, SandPiper, Wilden Pumps or ARO are generally the larger of the brands. They are relatively inexpensive and can be used for almost any duty from pumping water out of bunds, to pumping hydrochloric acid from secure storage (dependent on how the pump is manufactured - elastomers / body construction). Lift is normally limited to roughly 6m although heads can reach almost 200 Psi.[citation needed]Hydraulic ram pumpsA hydraulic ram is a water pump powered by hydropower. It functions as a hydraulic transformer that takes in water at one "hydraulic head" (pressure) and flow-rate, and outputs water at a higher hydraulic-head and lower flow-rate. The device utilizes the water hammer effect to develop pressure that allows a portion of the input water that powers the pump to be lifted to a point higher than where the water originally started.The hydraulic ram is sometimes used in remote areas, where there is both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation, the ram is often useful, since it requires no outside source of power other than the kinetic energy of flowing water.Velocity pumpsRotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe. This conversion of kinetic energy to pressure can be explained by the First law of thermodynamics or more specifically by Bernoulli's principle. Dynamic pumps can be further subdivided according to the means in which the velocity gain is achieved.These types of pumps have a number of characteristics:1. Continuous energy2. Conversion of added energy to increase in kinetic energy (increase in velocity)3. Conversion of increased velocity (kinetic energy) to an increase in pressure headOne practical difference between dynamic and positive displacement pumps is their ability to operate under closed valve conditions. Positive displacement pumps physically displace the fluid; hence closing a valve downstream of a positive displacement pump will result in a continual build up in pressure resulting in mechanical failure of either pipeline or pump. Dynamic pumps differ in that they can be safely operated under closed valve conditions (for short periods of time).APPLICATIONSPumps are used throughout society for a variety of purposes. Early applications includes the use of the windmill or watermill to pump water. Today, the pump is used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewage movement, flood control, marine services, etc.Because of the wide variety of applications, pumps have a plethora of shapes and sizes: from very large to very small, from handling gas to handling liquid, from high pressure to low pressure, and from high volume to low volume.CENTRIFUGAL PUMPA centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exits into the downstream piping system. Centrifugal pumps are used for large discharge through smaller heads. According to Reti, the Brazilian soldier and historian of science, the first machine that could be characterized as a centrifugal pump was a mud lifting machine which appeared as early as 1475 in a treatise by the Italian Renaissance engineer Francesco di Giorgio Martini. True centrifugal pumps were not developed until the late 1600's, when Denis Papin made one with straight vanes. The curved vane was introduced by British inventor John Appold in 1851.Vertical centrifugal pumps are also referred to as cantilever pumps. They utilize a unique shaft and bearing support configuration that allows the volute to hang in the sump while the bearings are outside of the sump. This style of pump uses no stuffing box to seal the shaft but instead utilizes a "throttle Bushing". A common application for this style of pump is in a parts washer. A centrifugal pump containing two or more impellers is called a multistage centrifugal pump. The impellers may be mounted on the same shaft or on different shafts. If we need higher pressure at the outlet we can connect impellers in series. If we need a higher flow output we can connect impellers in parallel. All energy added to the fluid comes from the power of the electric or other motor force driving the impeller.ENERGY USAGEThe energy usage in a pumping installation is determined by the flow required, the height lifted and the length and friction characteristics of the pipeline. The power required to drive a pump (Pi), is defined simply using SI units by:

where:Pi is the input power required (W) is the fluid density (kg/m3)g is the standard acceleration of gravity (9.80665 m/s2)H is the energy Head added to the flow (m)Q is the flow rate (m3/s) is the efficiency of the pump plant as a decimalThe head added by the pump (H) is a sum of the static lift, the head loss due to friction and any losses due to valves or pipe bends all expressed in metres of fluid. Power is more commonly expressed as kilowatts (103 W) or horsepower (multiply kilowatts by 0.746). The value for the pump efficiency may be stated for the pump itself or as a combined efficiency of the pump and motor system.The energy usage is determined by multiplying the power requirement by the length of time the pump is operating.

PROBLEMS OF CENTRIFUGAL PUMPS Cavitationthe NPSH of the system is too low for the selected pump. Wear of the Impellercan be worsened by suspended solids. Corrosion inside the pump caused by the fluid properties. Overheating due to low flow. Leakage along rotating shaft. Lack of primecentrifugal pumps must be filled (with the fluid to be pumped) in order to operate. Surge.OPERATION OF CENTRIFUGAL PUMPThe operating manual of any centrifugal pump often starts with a general statement, Your centrifugal pump will give you completely trouble free and satisfactory service only on the condition that it is installed and operated with due care and is properly maintained. Despite all the care in operation and maintenance, engineers often face the statement the pump has failed i.e. it can no longer be kept in service. Inability to deliver the desired flow and head is just one of the most common conditions for taking a pump out of service. There are other many conditions in which a pump, despite suffering no loss in flow or head, is considered to have failed and has to be pulled out of service as soon as possible. These include seal related problems (leakages, loss of flushing, cooling, quenching systems, etc), pump and motor bearings related problems (loss of lubrication, cooling, contamination of oil, abnormal noise, etc), leakages from pump casing, very high noise and vibration levels, or driver (motor or turbine) related problems. The list of pump failure conditions mentioned above is neither exhaustive nor are the conditions mutually exclusive. Often the root causes of failure are the same but the symptoms are different. A little care when first symptoms of a problem appear can save the pumps from permanent failures. Thus the most important task in such situations is to find out whether the pump has failed mechanically or if there is some process deficiency, or both. Many times when the pumps are sent to the workshop, the maintenance people do not find anything wrong on disassembling it. Thus the decision to pull a pump out of service for maintenance / repair should be made after a detailed analysis of the symptoms and root causes of the pump failure. Also, in case of any mechanical failure or physical damage of pump internals, the operating engineer should be able to relate the failure to the process units operating problems.Any operating engineer, who typically has a chemical engineering background and who desires to protect his pumps from frequent failures must develop not only a good understanding of the process but also thorough knowledge of the mechanics of the pump. Effective troubleshooting requires an ability to observe changes in performance over time, and in the event of a failure, the capacity to thoroughly investigate the cause of the failure and take measures to prevent the problem from re-occurring.The fact of the matter is that there are three types of problems mostly encountered with centrifugal pumps: design errors poor operation poor maintenance practicesTHE AXIAL PISTON PUMPAn axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a cylinder block. It can be used as a stand-alone pump, a hydraulic motor or an automotive air conditioning compressor.An axial piston pump has a number of pistons (usually an odd number) arranged in a circular array within a housing which is commonly referred to as a cylinder block, rotor or barrel. This cylinder block is driven to rotate about its axis of symmetry by an integral shaft that is, more or less, aligned with the pumping pistons (usually parallel but not necessarily). Mating surfaces. One end of the cylinder block is convex and wears against a mating surface on a stationary valve plate. The inlet and outlet fluid of the pump pass through different parts of the sliding interface between the cylinder block and valve plate. The valve plate has two semi-circular ports that allow inlet of the operating fluid and exhaust of the outlet fluid respectively. Protruding pistons. The pumping pistons protrude from the opposite end of the cylinder block. There are numerous configurations used for the exposed ends of the pistons but in all cases they bear against a cam. In variable displacement units, the cam is movable and commonly referred to as a swash plate, yoke or hanger. For conceptual purposes, the cam can be represented by a plane, the orientation of which, in combination with shaft rotation, provides the cam action that leads to piston reciprocation and thus pumping. The angle between a vector normal to the cam plane and the cylinder block axis of rotation, called the cam angle, is one variable that determines the displacement of the pump or the amount of fluid pumped per shaft revolution. Variable displacement units have the ability to vary the cam angle during operation whereas fixed displacement units do not. Reciprocating pistons. As the cylinder block rotates, the exposed ends of the pistons are constrained to follow the surface of the cam plane. Since the cam plane is at an angle to the axis of rotation, the pistons must reciprocate axially as they precess about the cylinder block axis. The axial motion of the pistons is sinusoidal. During the rising portion of the piston's reciprocation cycle, the piston moves toward the valve plate. Also, during this time, the fluid trapped between the buried end of the piston and the valve plate is vented to the pump's discharge port through one of the valve plate's semi-circular ports - the discharge port. As the piston moves toward the valve plate, fluid is pushed or displaced through the discharge port of the valve plate. Effect of precession. When the piston is at the top of the reciprocation cycle (commonly referred to as top-dead-center or just TDC), the connection between the trapped fluid chamber and the pump's discharge port is closed. Shortly thereafter, that same chamber becomes open to the pump's inlet port. As the piston continues to precess about the cylinder block axis, it moves away from the valve plate thereby increasing the volume of the trapped chamber. As this occurs, fluid enters the chamber from the pump's inlet to fill the void. This process continues until the piston reaches the bottom of the reciprocation cycle - commonly referred to as bottom-dead-center or BDC. At BDC, the connection between the pumping chamber and inlet port is closed. Shortly thereafter, the chamber becomes open to the discharge port again and the pumping cycle starts over. Variable displacement. In a variable displacement unit, if the vector normal to the cam plane (swash plate) is set parallel to the axis of rotation, there is no movement of the pistons in their cylinders. Thus there is no output. Movement of the swash plate controls pump output from zero to maximum. Pressure. In a typical pressure-compensated pump, the swash plate angle is adjusted through the action of a valve which uses pressure feedback so that the instantaneous pump output flow is exactly enough to maintain a designated pressure. If the load flow increases, pressure will momentarily decrease but the pressure-compensation valve will sense the decrease and then increase the swash plate angle to increase pump output flow so that the desired pressure is restored. In reality most systems use pressure as a control for this type of pump. The operating pressure reaches, say, 200 bar (20 MPa or 2900 psi) and the swash plate is driven towards zero angle (piston stroke nearly zero) and with the inherent leaks in the system allows the pump to stabilise at the delivery volume that maintains the set pressure. As demand increases the swash plate is moved to a greater angle, piston stroke increases and the volume of fluid increases; if the demand slackens the pressure will rise, and the pumped volume diminishes as the pressure rises. At maximum system pressure the output is once again almost zero. If the fluid demand increases beyond the capacity of the pump to deliver, the system pressure will drop to near zero. The swash plate angle will remain at the maximum allowed, and the pistons will operate at full stroke. This continues until system flow-demand eases and the pump's capacity is greater than demand. As the pressure rises the swash-plate angle modulates to try to not exceed the maximum pressure while meeting the flow demand.USESDespite the problems indicated above this type of pump can contain most of the necessary circuit controls integrally (the swash-plate angle control) to regulate flow and pressure, be very reliable and allow the rest of the hydraulic system to be very simple and inexpensive. Axial reciprocating motors are also used to power many machines. They operate on the same principle as described above, except that the circulating fluid is provided under considerable pressure and the piston housing is made to rotate and provide shaft power to another machine. A common use of an axial reciprocating motor is to power small earthmoving plant such as skid loader machines. Another use is to drive the screws of torpedoes.

EFFECTIVE PREDICTIVE AND PRO-ACTIVE MAINTENANCE FOR PUMPSKeeping pumps operating successfully for long periods of time requires careful pump design selection, proper installation, careful operation, the ability to observe changes in performance over time, and in the event of a failure, the capacity to thoroughly investigate the cause of the failure and take measures to prevent the problem from re-occurring. Pumps that have been: properly sized, are dynamically balanced, that sit on stable foundations with good shaft alignment, with proper lubrication, where operators start, run, and stop the machinery with care and where the maintenance personnel observe for unhealthy trends that begin to appear and act on them usually never experience a catastrophic failure.This is true with a large percentage of pumping systems but, it is definitely not true with all of them. Frequently pumps are asked to operate way off their best efficiency point, or are perched on unstable baseplates, or run under moderate to severe misalignment conditions, or were lubricated at the factory and never see another drop until the bearings seize, and vibrate to the point where bolts come loose. When the unit finally stops pumping, new parts are thrown on the machine and the deterioration process starts again with no conjecture as to why the failure occurred. Recently a supervisor at a pharmaceutical company who has been trained in root cause failure analysis stated that when a failure occurs on a piece of machinery it should be treated as a police crime scene where corrective action is not initiated until all the evidence is gathered by the scientific crime lab personnel to find the primary source of the malady. Until the real criminal is apprehended and banished, the crime is most likely to occur again and again. Take a moment to reflect on how many times you and your organization have thoroughly investigated a failure until you found the primary cause(s).

Pump maintenancePump MaintenanceDenis Sparrow, Senior Irrigation Officer, ICMS, PIRSA, LoxtonThe efficiency of pump units relates directly to dollars. Either dollars into your pocket or out of it. The correct selection, operation and maintenance of pump units is essential if maximum efficiency and operational life is to be achieved. Pump units not operated on their most efficient points suffer from extra mechanical damage through additional stress being applied and in some cases cavitation damage to impellers and pump parts. The cost per kilolitre of water pumped is increased and correct coverage or application rates from sprinklers may not be achieved resulting in crop loss. The efficiency of pump units can be maintained and in some cases increased by employing modern overhaul methods, the use of mechanical seals and internal glazing.Why perform maintenance?Maintenance of mechanical and electrical plant is essential if equipment is to remain in a safe and reliable condition and perform the duty it was designed to do and in a cost effective manner.We maintain equipment, to ensure: Reliability Efficiency Extend the assets service life Maintenance levels vary depending on the complexity of equipment and the consequence of failure. We must ensure our pumps and motors are maintained in a safe and reliable condition. The level of maintenance and expenditure can be evaluated by considering the cost of failure. Evaluate the risk to personal safety and environment damage Crop loss Cost of emergency arrangements Cost of emergency repairs Total loss of asset What type of maintenance is applicable for a block pump?Maintenance can be performed by having procedures based on:Reactive Maintenance Maintenance is performed only when it has failed and you are required to act immediately. This form of maintenance can be supported by spare parts or in some cases a spare pump so that down time is kept to a minimum. Reactive maintenance is not a good method. Preventative Maintenance This form of maintenance requires you to act just prior to failure. Deciding on what has to be performed and when is it a major problem. Predictive Maintenance By recording selected readings, noting operational conditions you can try to predict when the unit may fail and of course act prior to this point being reached. Predictive maintenance is the best method. There are other preventative maintenance programs such as Continuous Diagnostic Maintenance which takes constant readings and notes any significant change in the readings. Machine history is also a good tool to predict the life of a pump. It is based upon "like" operation in that it relies upon the history of the previous unit relating to the present unit. Since the taking of readings and observations form a vital part of most maintenance programs what should be looked for? Heat in bearings and glands Pressure pump discharge pressure Noise cavitation, bearings Flow a drop off in flow Leakage glands piping oil or grease Power consumption Vibration an increase could indicate problems Regardless of type of maintenance program practiced problems will still be experienced. The aim of a maintenance program should be to reduce failure and operational expenditure while still maintaining an efficient unit.Monthly Preventative MaintenanceProcedure Ensure safety of plant and equipment before performing any work Record all meter readings. Calculate efficiency Check all valves, glands and supports Test run unit, check for correct running, noise, heat, vibration Adjust gland if required Check oil levels if applicable Check sump drain pump if applicable Clean inside and outside of station Check condition of electrical components for hot spots

IMPORTANT if electrical work is to be performed ensure it is carried out by licensed persons Act on any findingsThe Irrigated Crop Management Service provides an irrigation management consultancy service. This service assists irrigators to interpret soils, plantings and irrigation systems information. To enquire about this service, call (08) 85959100 or email Sparrow.Denis@saugov.sa.gov.au.

Difference Between Reciprocating & Centrifugal PumpI want to do this! What's This?

Image by Flickr.com, courtesy of Louise Docker Reciprocating and centrifugal pumps serve different purposes and operate with separate functions. Centrifugal pumps transport huge amounts of liquid at a time, but the level at which the centrifugal pump operates is reduced as pressure rises. Reciprocating pumps push liquid out through a check valve, but the amount of liquid that is released is limited. Due to the differences in how they operate, they are ideally suited for dissimilar functions.

Reciprocating Pumps1. Reciprocating pumps operate by moving a plunger back and forth through a cylinder. The plunger provides pulses of pressure as it moves. Reciprocating pumps can be single action or double action (pump provides pressure as the piston advances and as it retracts). Reciprocating Uses2. Reciprocating pumps are ideal for providing short bursts of high pressure. Examples include bicycle pumps and well pumps. Centrifugal Pumps3. Centrifugal pumps operate by rotating a central impeller. Intake fluid is provided at the center of the impeller and the spinning acceleration sends it out of the sides of the impeller to provide pressure. Centrifugal Uses4. Centrifugal pumps are ideally suited for constant lower pressures, such as that found in pool filters. Pump Comparison5. For pneumatic tools, a centrifugal pump is better suited due to the constant pressure it can provide. For filling a pressurized container, the higher peak pressures of a reciprocating pump is preferred.

Plant LayoutThis Technical Measures Document refers to Plant Layout. .General principlesPlant layout is often a compromise between a number of factors such as: The need to keep distances for transfer of materials between plant/storage units to a minimum to reduce costs and risks; The geographical limitations of the site; Interaction with existing or planned facilities on site such as existing roadways, drainage and utilities routings; Interaction with other plants on site; The need for plant operability and maintainability; The need to locate hazardous materials facilities as far as possible from site boundaries and people living in the local neighbourhood; The need to prevent confinement where release of flammable substances may occur; The need to provide access for emergency services; The need to provide emergency escape routes for on-site personnel; The need to provide acceptable working conditions for operators. The most important factors of plant layout as far as safety aspects are concerned are those to: Prevent, limit and/or mitigate escalation of adjacent events (domino); Ensure safety within on-site occupied buildings; Control access of unauthorised personnel; Facilitate access for emergency services. In determining plant layout designers should consider the factors in outlined in the following sections.Inherent safetyThe major principle in Inherent Safety is to remove the hazard altogether. The best method to achieve this is to reduce the inventory of hazardous substances such that a major hazard is no longer presented. However, this is not often readily achievable and by definition no COMAH facility will have done so. Other possible methods to achieve an Inherently Safer design are: Intensification to reduce inventories; Substitution of hazardous substances by less hazardous alternatives; Attenuation to reduce hazardous process conditions i.e. temperature, pressure; Simpler systems/processes to reduce potential loss of containment or possibility of errors causing a hazardous event; Fail-safe design e.g. valve position on failure. Plant layout considerations to achieve Inherent Safety are mainly those concerned with domino effects (see below).The Dow / Mond IndicesThese hazard indices are useful for evaluating processes or projects, ranking them against existing facilities, and assigning incident classifications. They provides a comparative measure of the overall risk of fire and explosion of a process, and are useful tools in the plant layout development stage since they enable objective spacing distances to be taken into account at all stages.The methodology for undertaking a rapid ranking method that is based on the Dow / Mond index is detailed in ILO, PIACT, Major Hazard Control: A practical manual, 1988.Although these are useful rule-of thumb methodologies for first consideration of plant layout, they do not replace risk assessment. The distances derived between plant units using these systems are based upon engineering judgement and some degree of experience rather than any detailed analysis.Domino effectsHazard assessment of site layout is critical to ensure consequences of loss of containment and chances of escalation are minimised. Domino may be by fire, explosion (pressure wave and missiles) or toxic gas cloud causing loss of control of operations in another location.FireA fire can spread in four ways: Direct burning (including running liquid fires); Convection; Radiation; Conduction. The spread of fire from its origin to other parts of the premises can be prevented by vertical and horizontal compartmentation using fire-resisting walls and floors. Further information may be found in BS 5908 : 1990. Consideration should also be given to the spread of flammable material via drains, ducts and ventilation systems. Delayed ignition following a release may result in spread of flames through such systems via dispersed flammable gases and vapours.Protection against domino effects by convection, conduction and radiation can be achieved by inherent safety principles i.e. ensuring that the distances between plant items are sufficient to prevent overheating of adjacent plants compromising safety of those plants also. Where this is not possible due to other restrictions, other methods such as fire walls, active or passive fire protection may be considered.ExplosionExplosion propagation may be directly by pressure waves or indirectly by missiles. As for fires, inherently safe methods that should be considered are: arranging separation distances such that damage to adjacent plants will not occur even in the worst case; provision of barriers e.g. blast walls, location in strong buildings; protecting plant against damage e.g. provision of thicker walls on vessels; directing explosion relief vents away from vulnerable areas e.g. other plants or buildings, roadways near site boundaries. However, the latter may not provide practical solutions, particularly against missiles, and risk analysis may be required to prove adequate safety.Toxic gas releasesToxic gas releases may cause domino effects by rendering adjacent plants inoperable and injuring operators. Prevention/mitigation of such effects may be affected by provision of automatic control systems using inherently safer principles and a suitable control room (see section below on Occupied Buildings).Reduction of consequences of event on and off SiteIn addition to the measures described in the sections above, Plant Layout design techniques applicable to the reduction of the risks from release of flammable or toxic materials include: Locating all high-volume storage of flammable / toxic material well outside process areas; Locating hazardous plant away from main roadways through the site; Fitting remote-actuated isolation valves where high inventories of hazardous materials may be released into vulnerable areas; Provision of ditches, dykes, embankments, sloping terrain to contain and control releases and limit the safety and environmental effects; Siting of plants within buildings as secondary containment; Siting of plants in the open air to ensure rapid dispersion of minor releases of flammable gases and vapours and thus prevent concentrations building up which may lead to flash fires and explosions; Hazardous area classification for flammable gases, vapours and dusts to designate areas where ignition sources should be eliminated. Risk management techniques should be used to identify control measures that can be adopted to reduce the consequences of on or off site events. See references cited in further reading material.Positioning of occupied buildingsThe distance between occupied buildings and plant buildings will be governed by the need to reduce the dangers of explosion, fire and toxicity. In particular, evacuation routes should not be blocked by poor plant layout, and personnel with more general site responsibilities should usually be housed in buildings sited in a non-hazard area near the main entrance. Consideration should be given to siting of occupied buildings outside the main fence. In all cases occupied buildings should not be sited downwind of hazardous plant areas. Further guidance is available in standard references.Aggregation / trapping of flammable vapoursTo avoid aggregation and trapping of flammable / toxic vapours which could lead to a hazardous event, buildings should be designed so that all parts of the building are well ventilated by natural or forced ventilation. Flammable storages should be sited in the open air so that minor leaks or thermal outbreathing can be dissipated by natural ventilation. Maintenance procedures should include the displacement of vapours from hazardous areas before work begins (see Technical Measures Document on Permit to Work Systems).Segregation of incompatible substances (particularly in warehouses / storage areas)This is detailed in the Technical Measures Document on Segregation of Hazardous Materials.Status of guidanceAdditional material providing much insight into analysis of offsite consequences through a risk management program is now available from the United States Environmental Protection Agency. This provides guidance on offsite consequence analysis for toxic gases, toxic liquids, and flammable substances.Codes of Practice relating to Plant Layout Process plant hazard and control building design: An approach to categorisation', Chemical Industries Association, 1990. CIA Guidance for the location and design of occupied building on chemical manufacturing sites, CIA/CISHEC, 1998. BS 5908 : 1990 Code of practice for fire precautions in the chemical and allied industries, British Standards Institution.Section 5, Paragraph 21 provides guidance on the minimum distance that the building can be placed from the site boundary. For some specific substances, HSE guidance notes or industry codes of practice are available, giving separation distances such as those from plant to site boundaries.Section 10, Paragraph 54.3 provides guidance on methods to reduce any flammable gas concentrations below the lower limit, including the use of fixed water sprays or monitors positioned in such a way as to aid the dispersion of the gas into the atmosphere. HS(G)176 The storage of flammable liquids in tanks, HSE, 1998.Paragraphs 46 to 55 provide guidance on the siting of tanks. HS(G)50 The storage of flammable liquids in fixed tanks (up to 10000 cu. m in total capacity), HSE, 1990.Superseded by HS(G)176, Paragraph 12 provides guidance on the siting of tanks. HS(G)51 Storage of flammable liquids in containers, HSE, 1990. HS(G)52 The storage of flammable liquids in fixed tanks (exceeding 10000 cu. m in total capacity), HSE, 1991.Superseded by HS(G)176. HS(G)28 Safety advice for bulk chlorine installations, HSE, 1999.Paragraphs 21-30 provide guidance on siting of bulk chlorine installations. HS(G)30 Storage of anhydrous ammonia under pressure in the UK : spherical and cylindrical vessels, HSE,1986.Paragraph 155-160 provide guidance on siting of vessels for receiving tanker deliveries of anhydrous ammonia. LPGA CoP 1 Bulk LPG storage at fixed installations. Part 1 : Design, installation and operation of vessels located above ground, LP Gas Association, Revised Edition July 1998 (includes Amendment 1, January 1999).Supersedes HS(G)34 Storage of LPG at fixed installations.Part 1 gives guidance on plant layout. HS(G)34 Storage of LPG at fixed installations, HSE, 1987.Superseded by the above.Paragraphs 15 to 36 give guidance on plant layou

ReferencesWater treatment handbook Vol. 1-2, Degremont, 1991Industrial water conditioning, BeltsDearborn, 1991http://www.thermidaire.on.ca/boiler-feed.html