Pressure normal operating

K pipeline failure data tj,j= 1, 2,. .., 28, — piping operation time till rupture (years), at 5 Bar pressure (normal operation condition). 

During a hydrotest the additional weight of the water superimposes the normal operational stress by steam pressure. The big advantage of the pneumatic test is now, that it is the best imitation of the normal service condition. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

As described above, the mobile phase carrying mixture components along a gas chromatographic column is a gas, usually nitrogen or helium. This gas flows at or near atmospheric pressure at a rate generally about 0,5 to 3.0 ml/min and evenmally flows out of the end of the capillary column into the ion source of the mass spectrometer. The ion sources in GC/MS systems normally operate at about 10 mbar for electron ionization to about 10 mbar for chemical ionization. This large pressure... 

Normal Operation. The designer of a chemical plant must provide an adequate interface between the process and the operating employees. This is usually accompHshed by providing instmments to sense pressures, temperatures, flows, etc, and automatic or remote-operated valves to control the process and utility streams. Alarms and interlock systems provide warnings of process upsets and automatic shutdown for excessive deviations from the desired ranges of control, respectively. Periodic intermption of operations is necessary to ensure that instmments are properly caUbrated and that emergency devices would operate if needed (see Flow measurement Temperaturemeasurement). 

Sulfur burners are normally operated at moderate pressures, in the range of 135.8—170.3 kPa (5—10 psig), using air suppHed by the main blower for the plant. 

Complete removal of water from the pyrolysis gas is achieved with molecular sieve dryers. Typically, there are two dryers one is in normal operation while the other is being regenerated. The dryers are designed for 24 to 48 hours between successive regenerations and high pressure methane heated with steam at 225°C is the preferred regeneration medium. Activated alumina was used in older plants, but it is less selective than molecular sieves (qv). 

Pressure thrust, which is the product of the effective thrust area times the maximum pressure to which the joint will be subjected during normal operation. (For shp joints the effective thrust area shall be computed by using the outside diameter of the pipe. For corrugated, omega, or disk-type joints, the effective thrust area shall be that area recommended by the joint manufacturer. If this information is unobtainable, the effective area shall be computed by using the maximum inside diameter of the expansion-joint bellows.)... 

Gas Distrihutor The gas distributor has a considerable effect on proper operation of the flmdized bed. Basically there are two types (1) For use when the inlet gas contains solids and (2) for use when the inlet gas is clean. In the latter case, the distributor is designed to prevent Back flow of sohds during normal operation, and in many cases it is designed to prevent back flow during shutdown. In order to provide distribution, it is necessary to restrict the gas or gas and solids flow so that pressure drops across the restriction amount to from 0.5 kPa (2 in of water) to 20 kPa (3 Ibf/iu ). 

Ocean water has an osmotic pressure of about 2.6 MPa, with some locations as high as 3.5 MPa. Recovery (/ ) is normally around 45 percent, occasionally higher. Osmotic pressure in the concentrate rises as 1/(1 — / ) and significant overpressure (at least 1 MPa) is required to maintain good-quality permeate. Normal operating pressures are 6-8 MPa. 

Vessel Filled with Reactive Gas Mixtures Most cases of damage arise not from the vessel failing at its normal operating pressure but because of an unexpected exothermic reaction occurring within the vessel. This usually is a decomposition, polymerization, deflagration, runaway reaction, or oxidation reaction. In assessing the damage... 

Thermal expan sion. Equipment and pipehues which are liquid-full under normal operating conditions are subject to hydrauhc expansion if the temperature increases. Common sources of heat that can result in high pressures due to thermal expansion include solar radiation, steam or other heated tracing, heating coils, and heat transfer from other pieces of equipment. 

Operating Temperature and Pressure Arresters are certified subject to maximum operating temperatures and absolute pressures normally seen at the arrester location. Arrester placement in relation to heat sources, such as incinerators, must be selected so that the allowable temperature is not exceeded, with due consideration for the detonation potential as run-up distance is increased. 

In many applications a pressure vessel may be tested for safety simply by hydraulic testing to a pressure that is higher - typically 1.5 to 2 times higher - than the normal operating pressure. Steam boilers (Fig. 16.7) are tested in this way, usually once a year. If failure does not occur at twice the working pressure, then the normal operating stress is at most one-half that required to produce fast fracture. If failure does occur under... 

Now for the snag of a soft bearing material - will it not fail to support the normal operating forces imposed on it by the crankshaft All bearing materials have a certain p - v envelope within which they function safely (Fig. 26.3). The maximum pressure, p, that the bearing can accept is determined by the hardness of the surface the maximum velocity, v, is determined by heating, and thus by the thermal conductivity... 

An expander performanee map of shaft power versus mass flow with lines of eonstant inlet temperature and pressure shall be provided. There shall be a minimum of four eonstant pressure lines with inerements of approximately 5 psi and a minimum of four eonstant temperature lines with inerements of approximately 100°F. The map shall be valid for rated speed with normal exhaust pressure and gas eomposition. The normal operating point shall be indieated on the map. 

The expander shall be guaranteed to deliver the shaft horsepower at the normal operating eonditions (pressures, temperatures, flowrate, speed, and gas analysis) with a toleranee of -0 and -1-4%. 

Fluetuations in the flue gas flowrate (typieally less than 3% of nominal) are deteeted by the differential pressure eontroller and eompensated for by adjusting the small bypass valve. The main bypass valve is eompletely elosed during normal operations, but ean open in the event of sharp inereases in the flue gas flowrate. Similarly, in the event the flue gas flowrate deereases, the small bypass valve eloses to a meehanieally preset minimal opening, and the inlet eontrol valve also partially eloses. The minimum opening is neeessary to keep the bypass lines to the minimum requisite operating temperature. 

Under normal operations, the existing differential pressure governor is switehed to manual and the double slide valve is wide open. This valve must be suffieiently opened so that, even in the event of an emergeney expander trip, the entire flue gas flow ean pass through the double slide valve without the regenerator diseharge pressure inereasing to nonpermissible levels. 

The regenerator pressure fell by 28 mbar. This value was within the eontraetually agreed limits. Nevertheless, two further tests were performed with modified parameters. Five hours after beginning the optimization proeess, a test was performed in whieh the regenerator pressure dropped by just 8 mbar. This value is within the normal operating spread of the regenerator output pressure. 

Turboexpander sensitivity to process gas inlet pressure. As previously mentioned, variable speed turboexpanders are more sensitive to changes in normal operating conditions. Tlie pattern of TTE degradation, however, is the same as for constant speed turboexpanders (Figure 7-13a). In other words, TTE is more sensitive to pressure drop than to pressure rise. For instance, a 20% drop in gas inlet pressure will reduce TTE to 90% of the design value, whereas a 20% increase in gas inlet pressure reduces TTE to 99% of the design value. 

Consideration must be given to the pressure and temperature that the seal will see during normal operation, startup, shutdown, and upset conditions. 

The depth-type filter elements are used when the oil is free from water, and when particles sizes to be removed are in the five-micron and greater range. Generally, the depth-type element is water-sensitive, and when oil is contaminated with moisture, this element type will absorb the water and produce a rapid increase in differential pressure across the filter. The desired maximum differential pressure across a filter with clean elements is five psig at normal operating temperature. 

While working in a plant, a troubleshooter read a pressure gauge daily for several weeks and only realized it was inaccurate when one day the blower was down. The gauge still read about normal operating pressure. Had this have been a distillation unit, it could have been more serious. In distillation service, pressure is a more important variable than in many other unit operations. Relative volatility is a function of pressure. Pressure, or more accurately delta-P, is the best indication of the tower hydraulics. 

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