In pumps

If a situation arises whereby formation fluid or gas enters the bore bole the driller will notice an increase in the total volume of mud. Other indications such as a sudden increase in penetration rate and a decrease in pump pressure may also indicate an influx. Much depends on a quick response of the driller to close in the well before substantial volumes of formation fluid have entered the borehole. Onoe the BOP is closed, the new mud gradient required to restore balance to the system can be calculated. The heavier mud is then circulated in through the kill line and the lighter mud and influx is circulated out through the choke line. Once overbalance is restored, the BOP can be opened again and drilling operations continue. 

Balk M W and Fleming G R 1985 Dependence of the coherence spike on the material dephasIng time In pump-probe experiments J. Chem. Phys. 83 4300-7... 

Another important breaktlirough occurred with the 1974 development by Laubereau et al [24] of tunable ultrafast IR pulse generation. IR excitation is more selective and reliable than SRS, and IR can be used in pump-probe experiments or combined with anti-Stokes Raman probing (IR-Raman method) [16] Ultrashort IR pulses have been used to study simple liquids and solids, complex liquids, glasses, polymers and even biological systems. 

These can be controlled by variations in pump design in nonaerosols and by variations in valves, actuators, and concentrate/propeUant ratio in aerosols. 

Pumps are designed to give trouble-free operation for a long period of time. The ANSI B73.1M pumps are designed for a bearing life of no less than two years (29), and API 610 pumps for a minimum of five years (30). However, in real appHcations, a typical mean time between faUures (MTBF) is often found to be significantly less, and sometimes it is as short as a few weeks. Whereas in some instaUations the seals last from three to four years, in others these are replaced monthly. The reason for such wide variations in pump component life is often not poor pump design but equipment misappHcation. 

Cavitation. The subject of cavitation in pumps is of great importance. When the Hquid static pressure is reduced below its vapor pressure, vaporization takes place. This may happen because (/) the main stream fluid velocity is too high, so that static pressure becomes lower than vapor pressure (2) localized velocity increases and static pressure drops on account of vane curvature effect, especially near the inlets (J) pressure drops across the valve or is reduced by friction in front of the pump or (4) temperature increases, giving a corresponding vapor pressure increase. 

Fig. 17. Cavitation phenomenon in pumps showing cavitation bubble distribution and rate of weight loss as a function of cavitation coefficient at constant...

Trends in ED appear to be reduction in pumping and direct ED energy, increase in electric current density, and the use of EDR and hybrid processes in plants in which the manufacturer of the demineralisation plant owns and operates the plant, selling water to the user or water distributor. 

Chemical end uses employ the most exceptional property of PPS, chemical inertness. PPS is almost as chemically resistant as Teflon. It is used in pump impellers and housings and for down-od-weU end uses. New extmsion grades have been developed for potential piping end uses. Coatings of PPS are used extensively. 

On/Off Control An on/off controller is used for manipulated variables having only two states. They commonly control temperatures in homes, electric water-heaters and refrigerators, and pressure and liquid level in pumped storage systems. On7off control is satisfac-toiy where slow cychng is acceptable because it always leads to cycling when the load hes between the two states of the manipulated variable. The cycle will be positioned symmetrically about the set point only if the normal value of the load is equidistant between the two states of the manipulated variable. The period of the symmetrical cycle will be approximately 40, where 0 is the deadtime in the loop. If the load is not centered between the states of the manipulated variable, the period will tend to increase, and the cycle follows a sawtooth pattern. 

Transfer of Momentum Deceleration of one fluid (motivating fluid) in order to transfer its momentum to a second fluid (pumped fluid) is a principle commonly used in the handhng of corrosive materials, in pumping from inaccessible depths, or for evacuation. Jets and eductors are in this categoiy. 

Work Performed in Pumping To cause liquid to flow, work must be expended. A pump may raise the liquid to a higher elevation, force it into a vessel at higher pressure, provide the head to overcome pipe friction, or perform any combination of these. Regardless of the service required of a pump, all energy imparted to the liquid in performing this sei vice must be accounted for consistent units for all quantities must be employed in arriving at the work or power performed. 

Cavitation Formation of transient voids or vacuum bubbles in a liquid stream passing over a surface is called cavitation. This is often encountered arouna propellers, rudders, and struts and in pumps. When these bubbles collapse on a metal surface, there is a severe impact or explosive effec t that can cause considerable mechanical damage, and corrosion can be greatly accelerated because of the destruction of protective films. Redesign or a more resistant metal is generally required to avoid this problem. 

When the layer of graphite and corrosion products is impervious to the solution, corrosion wdl cease or slow down. If the layer is porous, corrosion will progress by galvanic behavior between graphite and iron. The rate of this attack will be approximately that for the maximum penetration of steel by pitting. The layer of graphite formed may also be effective in reducing the g vanic action between cast iron and more noble alloys such as bronze used for valve trim and impellers in pumps. 

Many copper alloys are also used in pumps as bushings, bearings, impellers, and gaskets. Bronzes, brasses, and other copper alloys are frequently used. Thus, pump components are often corroded. 

The pump manufacturers publish the NPSHr values on their pump curves. We re saying that the NPSH reading is one of the components of your pump curves. Wc ll. see this in Chapter 7 on Pump Curves. If you want to know the NPSHr of your pump, the easiest method is to read it on your pump curve. It s a number that changes normally with a change in flow. When the NPSHr is mentioned in pump literature, it is normally the value at the best efficiency point. Then, you ll be interested in knowing exactly where your pump is operating on its curve. 

In pump terminology, the approximate energy in an imploding cavitation bubble is 358,209 ft. To convert this energy into pressure ... 

Surface finish of internal surfaces - Kffieicney inerea,ses from better surface finishes are mostly attributable to the specific speed Ns (discussed in Chapter 6) of the pump. Generally, the improvements in surface finishes are economically justifiable in pumps with low specific speeds. 

Inadequate Pressure. Not enough velocity. Air or gases in pumped liquid. Impeller diameter too small Worn or damaged impeller Incorrect rotation... 

Uneven wear in parts is often due to turbulence. Bad piping designs or poorly sized valves can cause turbulence and uneven wear in pumps. Whenever possible, use straight pipe sections before and after the pump. Uneven flow creates turbulent flow and excessive wear occurs. 

A cathode cable is adequate for the return path of the protection current for individual storage tanks. In pumping stations with several storage tanks, each tank must be provided with a cable connection. If the tanks are connected to each other by electrical connections, then two cathode cable connections must be provided [2]. 

A final fuels group eontains high-ash erudes and residuals. These aeeount for 5% of installed units. Residual fuel is the high-ash by-produet of distillation. Low eost makes them attraetive however, speeial equipment must always be added to a fuel system before they ean be utilized. Crude is attraetive as a fuel, sinee in pumping applieations it is burned straight from the pipeline. Table 12-2 shows data obtained from a number of users that... 

Packing corroded away (twice). Poor separation. Pieces of packing in pump suction. Wrong metallurgy specification error. 

PPO forms one of a group of rigid, heat-resistant, more-or-less selfextinguishing polymers with a good electrical and chemical resistance, low water absorption and very good dimensional stability. This has led to a number of applications in television such as tuner strips, microwave insulation components and transformer housings. The excellent hydrolytic stability has also led to applications in water distribution and water treatment applications such as in pumps, water meters, sprinkler systems and hot water tanks. It is also used in valves of drink vending machines. 

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