Pressure static

All that can be done is to make a reasonable initial assessment of the number of stages. Having made a decision for the number of stages, the heat flow through the system is temporarily fixed so that the design can proceed. Generally, the maximum temperature in evaporators is set by product decomposition and fouling. Therefore, the highest-pressure stage is operated at a pressure low enough to be below this maximum temperature. The pressure of the lowest-pressure stage is normally chosen to allow heat rejection to cooling water or air cooling. If decomposition and fouling are not a problem, then the stage pressures should be chosen such that the highest-pressure stage is below steam temperature and the lowest-pressure stage above cooling water or air cooling temperature.  [c.87]

Transfer Molding. Valve and fitting liners are made by a transfer-molding process (33), with the valve or fitting serving as the mold. Melted resin is forced into the fitting at a temperature above the melting point of the resin. The melt may be produced by an extmder or an injection mol ding machine or melted cubes contained in a melt pot and transferred by applying pressure to a piston in the pot. After the resin transfer is completed, the fitting is cooled under pressure. Stock temperatures of 350—380°C and fitting temperatures of 350—370°C are used to process PFA 350. A slight adjustment in the cooling cycles may be required for transfer mol ding PFA 350 because it has higher melting and freezing points than FEP.  [c.377]

It is difficult to determine exactly the areas of localized pressure reductions inside the pump, although much research has been focused on this field. It is easy, however, to measure the total fluid pressure (static plus dynamic) at some convenient point, such as pump inlet flange, and adjust it in reference to the pump centerline location. By testing, it is possible to determine the point when the pump loses performance appreciably, such as 3% head drop, and to define the NPSH at that point, which is referred to as a required NPSH (NPSHR). The available NPSH (NPSHA) indicates how much suction head  [c.290]

Automatic filters are made with either viscous-coated or dry filter media. However, the cleaning or disposal of the loaded medium is essentially continuous and automatic. In most such devices the air passes horizontally through a movable filter curtain. As the filter loads with dust, the curtain is continuously or intermittently advanced to expose clean media to the air flow and to clean or dispose of the loaded medium. Movement of the curtain can be provided by a hand crank or a motor drive. Movement of a motor-driven curtain can be actuated automatically by a differential-pressure switch connected across the filter.  [c.1608]

An interlock is provided through a centrifugal type of pressure switch (PS) to trip the engine in the case of low lube (lubricating) oil pressure during a run. Since during a. start oil pre.s.sure has not built up, a timer, 7 j is introduced to bypass the trip interlock and avoid a false trip. A relay (contactor), d], is used to provide lube oil pressure interlock.  [c.507]

Two level pressure switch -1st level contact for alarm  [c.641]

In the last chapter we saw how a basic knowledge of the mechanisms of creep was an important aid to the development of materials with good creep properties. An impressive example is in the development of materials for the high-pressure stage of a modern aircraft gas turbine. Here we examine the properties such materials must have, the way in which the present generation of materials has evolved, and the likely direction of their future development.  [c.197]

The alloy used for turbine blades in the high pressure stage of aircraft turbo fan is a classic example of a material designed to be resistant to dislocation (power-law) creep at high stresses and temperatures. At take-off, the blade is subjected to stresses approaching 250 MN m , and the design specification requires that this stress shall be supported for 30 hours at 850°C without more than a 0.1% irreversible creep strain. In order to meet these stringent requirements, an alloy based on nickel has evolved with the rather mind-boggling specification given in Table 20.2.  [c.199]

The feed line runs through a surge check valve (also called a flow limiting valve) to the reactor. This is a safety device that stops flow completely if flow exceeds a certain high value. Excess flow can be caused by failure of a fitting or by breakage in any instrument that would cause sudden release of a large quantity of gas. Flooding of the experimental unit with combustible gas can be dangerous and the surge check valve protects against this event. Another protection against ignition of combustible gas is the pressure switch in case of a sudden drop in operating pressure to below a given limit, it shuts off electric power for the heater and the motor. Once the surge check valve is closed, and the cause for the action is identified and corrected, it can be opened. For this the bypass valve is needed to equalize the pressure around the surge check valve.  [c.84]

Pressure Switch SOR, Inc. OMNI  [c.85]

The compressors in the train arrangement are equipped with antisurge controls operating a blow-off (air compressor) or bypass valve (nitrous gas compressor). If dual-casing turbocompressors are used, the ideal technical solution is to equip each machine with its own blow-off or bypass valve. This allows the installation to operate within a stable range and deliver any useful quantities between maximum and virtually zero. Where a two-casing set for air and nitrous gas is operated at more or less constant load, sometimes only the low-pressure air compressor is equipped with anti-surge control and a blow-off valve. The high-pressure compressor is then protected by a simple open-closed outlet valve controlled by a thermostat and differential pressure switch.  [c.124]

Radiosonde balloons are released twice daily, near 00 and 12 GMT. Measurements of temperature and humidity, alternated by a pressure switch, are transmitted by radio signals from the instrument package, which is also tracked by ground-based radio direction-finding equipment at the point of release. This allows computation of wind direction and wind speed at numerous heights above ground. Figure 21-1 shows the locations of radiosonde stations throughout the world, including over 60 locations in the contiguous United States.  [c.346]

A pressure switch located so as to sense falling pressure at the earliest moment should be used to activate the standby pump. The switch should be so connected to the system as to permit testing the startup circuit without shutting down the compressor. Figure 8-8 shows four piping arrangements. The figure at b would be the recommended method.  [c.313]

Figure 8-8. Pressure gauge and pressure switch piping arrangements [1], Figure 8-8. Pressure gauge and pressure switch piping arrangements [1],
Provision must be made in the wiring to maintain power to the standby pump driver. This will prevent power interruption due to the pressure switch contacts opening when lubricant pressure is restored. Cycling of the standby pump will occur if the circuit is not maintained. A reset will have to be furnished to permit shutting down the standby pump when the main pump is back on stream.  [c.314]

Many large petrochemical projects involve considerable investment. Plant output value can be measured in staggering amounts of money if value of lost production is calculated. An incorrect pressure switch installed on a compressor may have very little direct financial impact to a compressor manufacturer, but it can cause a loss to the user far in excess of the total value of the compressor package itself. Extra care must therefore be taken in compressor performance tests. In the planning of a pro- ject, testing has to be reviewed to  [c.404]

The pressure switch that permits squeezing of the membranes only when the plate pack is compressed with the hydraulic closing system.  [c.191]

Low-pressure stage casings and interstage circuits on both centrifugal and positive displacement multi-stage compressors are not normally designed for full discharge pressure and must also be provided with overpressure protection.  [c.139]

The same system, but with an on-off pressure switch set to activate the emergency shutdown system if the pressure reaches the predetermined point. The pressure switch remains inactive as long as the pressure is below its trip point.  [c.14]

In Europe, the gas safety controls must meet the requirements of CEN standards, including flame failure devices, solenoid control valve, pilot con trols, ignition and governor. Overheat-type thermostats and either a pressure switch or an airflow-proving device are fitted to ensure that the burner will cut off in the event of no air flowing through the heater, such as occurs with fan failure.  [c.714]

For safe operation, the heater should have an overheat thermostat and either a pressure switch or airflow-proving device. This control device ensures that tlie burner will isolate in the event of restricted or no airflow through the heater.  [c.715]

In such openings, bidirectional flow driven by temperature differences between the two rooms can occur. If a total pressure (static pressure plus dynamic pressure) is specified, this phenomenon can be accounted for. For higher accuracy in the neighborhood of this opening, it is, however, recommended to expand the calculation domain beyond this opening.  [c.1037]

Automatic roll A roll filter that constantly or intermittently provides a clean portion of filter in the air stream by means of a pressure switch activating an electric motor, which winds the filter from a clean spool to a dirty spool.  [c.1440]

Pressure, static The potential pressure that is exerted in all directions by a fluid at rest.  [c.1469]

It is very important that the inert gas be available from a reliable source and that the proper pressure and flow rate are always provided. A low-pressure switch and alarm are sometimes installed in the inert gas supply line to the equipment and piping. The alarm will warn the operator that a problem may be occurring with the inert gas supply. The switch is also sometimes interlocked to open up a valve in piping from a backup inert gas cylinder bank.  [c.34]

Various workers have suggested modifications of this useful equipment (26,79). One such modification, which can be adopted to any reactor, is Incorporation of a pressure switch that slops agitation when a predetermined  [c.19]

Pressure Gauge or Pressure Switch  [c.423]

Several pockets may be in each cylinder, depending upon volume needed and cylinder design. When all pockets (equal to cylinder volume) are open at one end of a cylinder, no gas enters. In the by-pass control scheme. Figure 12-29B, a pressure switch activates a solenoid valve when the system discharge pressure reaches a preset value. Activating air then causes the unloaders to open the suction valve (s). Figure 12-28, allowing suction pressure to pass freely in and out of the cylinder. No compression takes place. The unloaders may be manually operated, although automatic operation usually gives better control.  [c.444]

Regular in-situ testing of various parameters can be an aid to maintaining plant in an optimum condition regarding both efficiency and safety. Commissioning data, which should be on record, must be compared with measurements made on a regular basis for such parameters as gas and air pressures, pressure switch settings, limit switch settings, timer settings, flue gas analyses, etc. Adjustments should be made as necessary.  [c.285]

In this form, a continuously running centrifugal pump maintains the pressure. A second pump under the control of a pressure switch is provided to come into operation at a predetermined pressure differential and as an automatic standby to the duty pump. Surplus water is delivered to or taken from a spill tank or cylinder as described previously.  [c.410]

This is really a simple form of axial fan but with its impeller mounted in a ring or diaphragm which permits it to discharge air with both axial and radial components. Duties covered are high volume and low pressure. Static efficiency is normally under 40 per cent.  [c.423]

The unloading function in rotary positive-displacement compressors is automatic and not under operator control. Generally, a set of limit switches, one monitoring internal temperature and one monitoring discharge pressure, are used to trigger the unload process. By design, the limit switch that monitors the compressor s internal temperature is the primary control. The secondary control, or discharge-pressure switch, is a fail-safe design to prevent overloading the compressor.  [c.561]

The law states that any pressurized air system must be fitted with a pressure relief valve. This valve prevents the system from being over pressurized and becoming a hazard to personnel or damaging equipment. A pressure switch is an electro/pneumatic control device that is installed on the air receiver to regulate the output of the air compressor. When the air pressure reaches its maximum set point, the regulator is activated and transmits a signal to a solenoid valve on the air compressor. This solenoid valve opens to direct lubricating oil to hydraulically keep the suction valves shut on both the low and high-pressure cylinders on the air compressor. The air compressor will remain in this mode until the pressure drops to the lower set point and deactivates the pressure regulator. This, in turn, de-energizes the solenoid valve on the air compressor causing it to release the lubricating oil pressure on the low- and high-pressure suction valves. The air compressor returns to normal operation pumping air into the receiver until the maximum pressure set point is reached when this happens, the control cycle starts again. Using a pressure switch prevents the air compressor from mnning continuously.  [c.631]

Pressure switch - Turns the air compressor on and off.  [c.631]

The determining factor in the frequency of cleaning is the pressure drop. A differential-pressure switch can serve as the actuator in automatic cleaning applications. Cyclone pre-cleaners are sometimes used to reduce the dust load on the filter or to remove large particles before they enter the bag.  [c.778]

Air-cooled condensers having two or more fans (Figure 6.2) may have a pressure switch or thermostatic control to stop the fans one by one. This method is simple, cheap, and effective.  [c.78]

The gas demand dictates the rate of acetylene generation which is satisfied by the rate of carbide feed. One method of feed of properly si2ed carbide, which is used in medium pressure generators, employs gravity flow controlled by a valve activated by a spring-loaded mbber diaphragm. The motion of the diaphragm reflects the change of internal generator pressure and is transmitted to the carbide feed valve which, in turn, either opens or closes as the pressure decreases or increases the generator operating pressure is set by the spring load appHed to the mbber diaphragm. High capacity generators are equipped with screw conveyors for carbide feed with either constant speed on-off operation or of the variable-speed close-pressure control type. The on-off type is controlled by a simple electric pressure switch which pneumatically signals the required feed-screw operation to match the gas demand and can have pressure fluctuations up to 128.9 kPa (18.7 psi) or less.  [c.379]

Generally, the higher stabiUty of the generated alkyl radical compared to that of the starting radical provides the driving force and determines the course of a propagating reaction. The radical, R-, formed in the -scission reaction is the most stable alkyl radical among the three possible radicals, R-, R -, and R"-. Propagating reactions are also affected by temperature, pressure, stetic, and electronic effects. In a termination reaction, two radicals interact in a mutually destmctive reaction in which both radicals form covalent bonds and reaction ceases. The two most common termination reactions are coupling (eq. 4) and disproportionation (eq. 5).  [c.101]

Chile [Prog. Aerosp. Sc7, 16, 147-223 (1975)] reviews the use of the pitot tube and allied pressure probes for impact pressure, static pressure, dynamic pressure, flow direction and local velocity, sldn friction, and flow measurements.  [c.885]

Ordinary shaker-cleaned filters may be shaken every 14 to 8 h, depending on the service. A manometer connected across the filter is useful in determining when the filter should be shaken. Fully automatic filters may be shaken as frequently as every 2 min, but bag maintenance will be greatly reduced if the time between shakings can be increased to 15 or 20 min without developing excessive pressure drop. Cleaning may be actuated automatically by a differential-pressure switch. It is essential that the gas flow through the filter be stopped when shaking in order to permit the dust to fall off. With very fine dust, it may even be necessaiy to equalize the pressure across the cloth [Mumford, Markson, and Ravese, Trans. Am. Soc. Mech. E/ig., 62, 271 (1940)]. In practice this can be accomplished without interrupting the operation by cutting one section out of service at a time, as shown in Fig. 17-59. In automatic filters this operation involves closing the dampers, shaking the filter units either pneumatically or mechanically, sometimes with the addition of a reverse flow of cleaned gas through the filter, and lastly reopening the dampers. For com-pressed-air-operated automatic filters, this entire operation may take only 2 to 10 s. For ordinaiy mechanical filters equipped for automatic control, the operation may take as long as 3 min.  [c.1601]

A differential pressure switch set to alarm when the pressure drop reaches a predetermined point protects against the loss of oil flow. In addition to the differential pressure switch, a two-way, three-port valve with a pressure gauge is piped in parallel with the differential pressure switch for accurate indication of inlet and outlet oil filter pressure. When a single transflow valve is used with a cooler-filter installation, the differential pressure switch and pressure gauge assembly should span the cooler-filter system.  [c.551]

LOW OIL PRESSURE 1. Oil pump failure. 2. Oil foaming from counterweights striking oil surface. 3. Cold oil. 4. Ditty oil filter. 5. Interior frame oil leaks. 6. Excessive leakage at bearing shim tabs and/or bearings. 7. improper low oil pressure switch setting. 8. Low gear oil pump bypass/relief valve setting.  [c.323]

Cartridge Filters Cartridge filters are used in a multitude of solid-liquid filtration applications ranging from laboratory scale operations to industrial flows in excess of 5,000 gpm. These units are typically operated in the countercurrent mode. Common configurations consist of a series of thin metal disks that are 3 to 10 inches in diameter, set in a vertical stack with very narrow uniform spaces between them. The disks are supported on a vertical hollow shaft, and fit into a closed cylindrical casing. Liquid is fed to the casing under pressure, whence it flows inward between the disks to openings in the central shaft and out through the top of the casing. Solid particles are captured between the disks and remain on the filter media. Since most of the solids are removed at the periphery of the disks, the unit is referred to as an edge filter. The accumulated solids are periodically removed from the cartridge. As with any filter, careful media selection is critical. Media that are too coarse, for example, will not provide the needed protection. However, specifying finer media than necessary can add substantially to both equipment and operating costs. Factors to be considered in media selection include the solids loading, the nature and properties of the particles, particle size, shape and size distribution, the amount of solids to be filtered, fluid viscosity, slurry corrosiveness, abrasiveness, adhesive qualities, liquid temperature, and flowrate. Typical filter media are wire mesh (typically 10 to 700 mesh), fabric (30 mesh - 1 /i), slotted screens (10 mesh to 25 fi) and perforated stainless steel screens (10 to 30 mesh). Multiple filters are also common, consisting of two or more single filter units valved in parallel to common headers. The distinguishing feature of these filters is the ability to sequentially backwash each unit in place while the others remain on stream. Hence, these systems are continuous filters. These units can be fully automated to eliminate manual backwashing. Backwashing can be eontrolled by changes in differential pressure between the inlet and outlet headers. One possible arrangement consists of a controller and solenoid valves that supply air signals to pneumatic valve actuators on each individual filter unit. As solids eollect on the filter elements, flow resistance increases. This increases the pressure differential across the elements and, thus, between the inlet and outlet headers on the system. When the pressure drop reaches a preset level, an adjustable differential pressure switch relays information through a programmer to a set of solenoid valves, which in turn sends a signal to the valve actuator. This rotates the necessary valve(s) to backwash the first filter element. When the first element is cleaned and back on stream, each successive filter element  [c.359]

The synthesis of ammonia is divided into four stages. In stage 1, the natural gas undergoes eatalytie reforming to produee hydrogen from methane and steam. The nitrogen required for ammonia pro-duetion is introdueed at this stage. Stage 2 involves the "synthesis gas" (syngas) that is purified by removing both earbon monoxide and earbon dioxide. Stage 3 is the eompression of the syngas to the required pressure. Stage 4 is the ammonia loop. A typieal feed stoek for ammonia synthesis is 0.17 million standard eubie meter per day (6 Msefd) of natural gas at a temperature of 16°C and a pressure of 23.4 barg. Table 4 shows its eomposition.  [c.1124]

Rupture discs are also used below relief valves to protect them from corrosion due to ves.sel fluids. The rupture disc bursts first and the relief valve immediately opens. The relief valve reseals, limiting flow when the pressure declines. When this configuration is used, it is necessary to monitor the pressure in the space between the rupture disk and the relief valve, either with a pressure indicator or a high pressure switch. Othei-wise, if a pinhole leak develops in the rupture disk, the pressure would equalize on both sides, and the rupture disk would not rupture at its set pressure because it works on differential pressure.  [c.367]

Tower Operating Pressure Static Slot Seal [15], In. Dynanuc Slot Seal [5],In.  [c.158]

Figure 12-103C. In a compound pump, the gas is compressed in two stages. First, the gas is compressed in the larger low pressure section and then transferred through the cross-over and internal passageways to be compressed in the smaller, high pressure stage. (Used by permission Form 4114. Kinney Vacuum Division, Tuthill Corporation.) Figure 12-103C. In a compound pump, the gas is compressed in two stages. First, the gas is compressed in the larger low pressure section and then transferred through the cross-over and internal passageways to be compressed in the smaller, high pressure stage. (Used by permission Form 4114. Kinney Vacuum Division, Tuthill Corporation.)

See pages that mention the term Pressure static : [c.476]    [c.78]    [c.524]   
Gas turbine engineering handbook (2002) -- [ c.23 , c.114 ]