Bypass valve


Pumps are usually located under the piperack. An open slot in the piperack has to be provided at the location of the pump suction and pump discharge lines so that the piping can make a straight mn down to the pump suction and then the discharge line can be mn directly back up to the piperack. Pumps commonly have an end suction and top discharge but they can also have a top suction and top discharge. The location of these nozzles on the pump can affect the piping configuration. The pump discharge line usually has some type of flow control valve that requires a piping drop from the piperack down to the control valve. The control loop usually has a control valve, a double-block valve around the control valve, and a hand bypass valve so that the valve can be replaced or repaired while the hand bypass is used for temporary control. Double-block and bypass valves should be located at an elevation where the valve and the controller can be accessed without a ladder.  [c.80]

Hand-crimp the hose in back of the test leaf, and then turn on the vacuum pump and regulate the bypass valve on the pump to give the desired vacuum level in the receiver.  [c.1697]

FIG. 24-3 Conventional batch fermenter. A = agitator motor B = speed-reduction unit C = air inlet D = air outlet E = air bypass valve F = shaft seal G = sight glass with light H = sight-glass clean-off line I = manhole with sight glass ] = agitator shaft K = paddle to break foam L = cooling-water outlet M = baffle N = cooling coils O = cooling-water inlet P = mixer Q = sparger R = shaft bearing and bracket S = outlet (steam seal not shown) T = sample valve (steam seal not shown).  [c.2136]

Any set of guidelines must be tempered by the analysts experience. This is an investigative process. The explanations are rarely simple. However, many exhaustive tests have been run to identify that a bypass valve or alternative feed valve had been mistakenly left open. Plant resources were misused because the simple was overlooked  [c.2564]

Operations The QRA team will need specific data on how the system is actually operated. For example, are the bypass valves normally left open to increase throughput, what happens when the high level alarm sounds, or do operators bypass interlocks to continue production Human actions/errors are usually dominant contributors to the real-world risks, and truthful data on actual process operations are vital to credible QRA results. Expect to commit one full-time equivalent for the life of the project.  [c.30]

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]

At high pressure experiments the reactor should be installed in a pressure cell. All check valves before it, and the filter with the flow controller after it, can be kept in the vented operating room. As a minimum, the bypass valve and the flow controller must be accessible to the operator. This can be done by extended valve stems that reach through the protecting wall. Both the operating room and the pressure cell should be well ventilated and equipped by CO alarm instruments.  [c.86]

Bypass Valve Surge Check Valve  [c.90]

The unit was built in a loop because the needed 85 standard m /hour gas exceeded the laboratory capabilities. In addition, by controlling the recycle loop-to-makeup ratio, various quantities of product could be fed for the experiments. The adiabatic reactor was a 1.8 m long, 7.5 cm diameter stainless steel pipe (3 sch. 40 pipe) with thermocouples at every 5 centimeter distance. After a SS was reached at the desired condition, the bypass valve around the preheater was suddenly closed, forcing all the gas through the preheater. This generated a step change increase in the feed temperature that started the runaway. The 20 thermocouples were displayed on an oscilloscope to see the transient changes. This was also recorded on a videotape to play back later for detailed observation.  [c.158]

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]

Regenerator pressure is fixed by the design and eontrol of the dilute phase regenerator operation. The effeet of the regenerator pressure eontroller set point is shown in Figure 4-61. This pressure determines when the expander bypass valve begins to open. Thus, an inerease in regenerator pressure will eause the expander to deliver more power than is required by the slightly inereased power requirements of the air blower. The exeess horsepower B inereases to C. The Brown Root eomputer program assumes that this pressure is known and fixed by eontrolling the regenerator.  [c.163]

Temperature ehanges for the flue gas to the expander produee the effeets shown in Figure 4-63. The expander inlet temperature at design is 1,200°F. As the expander inlet temperature rises, the expander horsepower eurve moves to the left and upward while the ehange in the blower eurve is insignifieant. The results are that the lower horsepower balanee point moves to the left and down, the peak of the expander eurve moves to the left and up, the peak generator load inereases to G, and the expander bypass valve opens at a lower feed rate.  [c.167]

Instead of using the expander main bypass valve for regenerator pressure eontrol, it is also possible to install a small bypass valve, say 30%, downstream of the expander inlet butterfly valve, bypassing to tlie expander exhaust line as shown in Figure 4-73. Although tills valve may not appear neeessary, it ean provide additional flexibility and proteetion.  [c.181]

Once the switchgear and other electrical facilities are ready, the steam ahead of the expander inlet butterfly valve is increased so that the speed is slightly above the synchronous speed. This ensures that the expander exhaust casing temperature rating is not exceeded during synchronization. As shown in Figure 4-75, the small bypass valve located downstream of the expander inlet butterfly valve is gradually opened until the speed of the string exactly coincides with the synchronous speed. The generator is then synchronized with the power grid. Full load should then be placed on the generator by increasing the flue gas and backing out the control steam consistent with the expander heating rate. With the expander at full load, regenerator pressure control is maintained by the expander inlet butterfly valve.  [c.183]

If the breakers that connect the generator to the grid are suddenly opened, there is an instantaneous loss of total load on the expander. Immediately, the TPG string will increase in speed. When the breakers open, a signal is sent to the controller, and the controller directs the expander inlet butterfly valve to close and the small expander bypass valve to snap open. Simultaneously, regenerator pressure control transfers to the main expander bypass valve. With the expander inlet butterfly valve closed, flue gas energy no long enters the expander. When the fast-acting, small expander bypass valve opens it is equally important that the stored energy between the inlet butterfly valve and  [c.184]

The first aetion required during this situation is to sense the overspeed eondition. Well-engineered eontrols eontinuously monitor the expander speed rate-of-ehange and eonsider it the signal that indieates an emergeney eondition. As a baekup, modern eontrols also ineorporate an eleetronie two-out-of-three voting trip system. Upon sensing that an overspeed eondition exists, the trip logie direets the expander inlet butterfly valve to elose and the main expander bypass valve assumes the regenerator pressure eontrol funetion. During an overspeed eondition, it is even more important that the small expander bypass valve be available so that the stored energy ahead of the expander is dissipated as quiekly as possible. The small bypass valve diverts flue gas from the expander so that it will not enter the expander and be used to develop power. It also eauses the expander inlet pressure to rapidly deerease, thus redueing the energy available in the flue gas that does enter the expander. Therefore, the small bypass valve loeated between the expander and the inlet butterfly valve reduees the expander power in not one, but two ways.  [c.185]

Axial compressor performance is modeled using a normalized operating map of pressure rise versus inlet volume flow. Lines of constant guide vane position and normalized efficiency are included. For given inlet air conditions, guide vane position, and calculated system resistance, the operating point on the compressor map is established. The guide vanes are typically positioned by a controller (Figure 4-81) to hold constant mass flow and the antisurge system controller prevents the compressor from operating to the left of the surge control line by modulating the blow-off (bypass) valve.  [c.189]

An example is shown in Figure 4-84, whieh represents the regenerator pressure following a malfunetion of the expander bypass valve. The bypass valve trips open in 1 see while the expander inlet valve maintains eontrol. Tlie regenerator pressure drops approximately 2.0 psi before starting to reeover. The inlet valve stroking time was 10 see and the eontroller settings were 5% proportional band and 30 see reset.  [c.191]

Figure 4-84. Regenerator pressure deviation during expander bypass valve malfunction. Figure 4-84. Regenerator pressure deviation during expander bypass valve malfunction.
Figure 4-85. Power balance between string components during malfunction of bypass valve. Figure 4-85. Power balance between string components during malfunction of bypass valve.
A TPG block diagram is shown in Figure 4-86. It is similar to the FCC diagram except a second inlet valve is added to assure trip action and a bypass valve is added to reduce overspeed and aid in startup. The only rotating elements are the expander and generator and, possibly, gear (Figure 4-87).  [c.193]

An expander coupling break on the TPG string (Figure 4-88) is similar to that on the PRS string. The only difference is the use of a bypass valve between the expander inlet valve and the expander. This bypass valve significantly effects the dissipating energy around the expander. The predicted overspeed in this example was 12% compared to a 33% overspeed for a similar transient shown earlier in Figure 4-82, which did not have the downstream bypass valve.  [c.193]

It is important to recognize that with an instantaneous shedding of the load in a power recovery string, acceleration is imminent. This condition is caused by the large volume of trapped gas in the piping upstream of the expander. The gas contains a significant amount of available energy, which must be dissipated by the expander or a bypass valve arrangement. Unfortunately, the specific volume of this gas demands large control valves and these tend to have slow reaction times. Therefore, much of the trapped gas will still pass through the expander and will, thus, provide undesirable driving torque. In the conventional FCC string shown in Figure 4-140, the compressor acts as a constant source of load. If the compressor were removed from the string, an alternative load source would be required. This load source would have to accommodate the following modes of operation  [c.262]

The lube oil pumps are now ready to be turned on. The pump and filter bypass valves should be open to avoid pressure pulses in the filter eartridges. Strong pressure pulses may eause filter eartridges to eollapse. Typieal filter elements will withstand 35-100 psi differential. If the pumps are turned on with eaeh bypass elosed, an instantaneous pressure of approximately 150 psi will hit the filters. This is due to the setting of the relief valves. For this reason, it is important to have on hand several extra seal gas and lube oil eartridges.  [c.294]

The expander train supplier shall assist with the selection of the expander inlet and bypass valve configurations and closure rates by performing an open loop dynamic simulation study. For a main air blower train dais could be closed loop.  [c.319]

The gas quality feeding the dry faee seal should be elean and dry. Due to the possibility of eondensation of the proeess gas in the seal eavity, it was deeided to use a seal gas heater. The heater eontrol was set to provide warm gas at 15°C above the dew point to ensure no eondensate entered the seal eavity. Also, a dual filter in series with 5 and 2 p filtration elements was ehosen to provide an ideal sealing environment and maintain the optimum performanee of the seal. To reduee the risk of seal damage during reverse rotation of the turboexpander, programming logie was set to open the eompressor bypass valve whenever a shutdown impulse was initiated.  [c.341]

The addition of a seeond valve that permits the flue gas to bypass the expander and move direetly to the waste heat reeovery system enhanees the flexibility of FCC operation eompared to the single valve arrangement. Shown in Figure 6-35, the large single bypass valve ean pass all the flow if the expander is out of serviee. It ean proteet the regenerator and reaetor if an overpressure situation should develop. This valve ean also provide regenerator pressure eontrol if the throughput is inereased beyond the expander eapability.  [c.374]

The addition of a seeond expander main bypass valve (Figure 6-38) in parallel with the initial valve ean provide eloser proeess eontrol and flexibility. Both valves may be identieal 50% eapaeity valves or, one valve may be a 100% eapaeity main bypass valve and the other a smaller 30% eapaeity valve. Either approaeh inereases flexibility and provides more preeise regenerator pressure eontrol.  [c.377]

An elaborate system may have as many as six valves (Figure 6-40). A small 30% eapaeity valve, whieh enables for flue gas to pass direetly from the expander inlet to the expander exhaust, will enhanee startup, synehronization, and safety proteetion for the train. This small inlet bypass valve is modulated to eontrol the ramp-up speed and fine synehronizing of the TPG train. It is also benefieial during emergeney situations to divert stored flue gas direetly to the expander exhaust, instead of all the flue gas passing through the expander. The six valve arrangement may be used for the main air blower train, as well as the TPG train.  [c.378]

A typieal TPG valve arrangement is the five valve system (Figure 6-41). The two expander inlet valves provide regenerator pressure eontrol, overspeed proteetion, and flue gas shut-off to the expander. The expander exhaust valve enables expander isolation. The full and partial expander bypass valves permit aeeurate eontrol of the FCC proeess when the expander is not in operation.  [c.378]

The three valve aiTangement (Figure 6-42), using one expander inlet valve, one expander exhaust valve, and one expander bypass valve, has been tried with disappointing results. Some users have had to add  [c.378]

The bypass valves control the differential pressure between the reactor and regenerator by varying the flowrate in the expander bypass.  [c.383]

A differential pressure controller acts in split range on the inlet control valve and the bypass valves. The differential pressure governor is retained as the standby and backup system.  [c.383]

All valves are equipped with hydraulic actuators, electronic positioning controllers for precise positioning, and solenoid valves for rapid (trip) opening of bypass valves and emergency closure tripping of trip and inlet control valves.  [c.383]

The actuating time for a quick-closing/quick-opening operation effected by the solenoid valves is 0.6 sec, and the actuating time under normal control is 5 sec for the inlet valves and 0.6 sec for the bypass valves. These actuating times apply to the full valve stroke outside the end position damping range.  [c.383]

At the rated duty point, the differential pressure eontroller is aetive. The inlet eontrol valve and trip valve are eompletely open. The main bypass valve is eompletely elosed and the small bypass valve eontrols the differential pressure. Approximately 96%-98% of the flue gas flows through the expander, with the rest passing through the small bypass valve, orifiee ehamber, and double slide valve to the expander outlet to rejoin the main flue gas flow.  [c.384]

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.  [c.384]

The ECC unit operating requirements make it neeessary for the bypass eontrol valves to open as soon as the expander inlet valves start to elose. Optimum eontrol response is aehieved if the bypass valves open so that the pressure at the outlet of the regenerator remains eompletely unaffeeted by the expander shutdown.  [c.387]

The inlet valves and the bypass valves are operated in a split range mode (i.e., in a staggered sequenee). Rising regenerator pressure eauses the inlet valves to open first, followed by the small bypass valve, and then the main bypass valve. Without additional eontrol interventions, regenerator pressure (and thus differential pressure) automatieally rises if the expander is shut down. The pressure eontroller reaets to this pressure inerease and opens the bypass valves. The regenerator pressure inereases by 122 mbar. Although this pressure rise may be undesirable for many FCC units, it nevertheless represents a generally aeeeptable value.  [c.388]

The manufaeturer of this system has developed a eontrol strategy by whieh the bypass valves are eontrolled in the event of an expander trip. This enables the valves to preeisely assume the position in whieh, in eonjunetion with the downstream orifiee ehambers, they preeisely emulate the flow loss eaused by the expander prior to the trip event. A properly adjusted and ealibrated eontrol output jump funetion is applied so that the pressure fluetuations that oeeur at a given duty point are kept to a minimum.  [c.388]

If, however, the FCC unit should be operated at a different duty point, whether this is due to a different flue gas flowrate or a different regenerator pressure, the bypass valves would either open too wide or not wide enough. The result is fluetuation in the regenerator outlet pressure.  [c.388]

All MWD tools have both a power supply and data transmission system often combined in one purpose built collar and usually located above the measurement sensors as shown in Figure 5.40 (a Teleco directional/gamma/resistivity tool). Data transmission may be within the downhole assembly from the sensors to a memory device or from the sensors to surface. The latter is usually achieved by mud pulse telemetry, a method by which data is transmitted from the tool in real time, i.e. as data is being acquired. Positive or negative pressure pulses created in the mudstream downhole travel through the mud (inside the drill pipe) to surface and are detected by a pressure transducer in the flowline. Positive pressure pulses are created by extending a plunger into a choke orifice, momentarily restricting flow (as shown in the top of Figure 5.40), an operation which is repeated to create a binary data string. Negative pulses are created by opening a bypass valve and venting mud to the annulus, momentarily reducing the drill pipe pressure.  [c.135]

Generally, butterfly valves are used for the inlet eontrol and bypass valves. Tliey are inexpensive to manufaemre, and their aemators are able to operate in aeeordanee witli tlie requisite response times. Butterfly valves do, however, have the disadvantage of a tightly eurved eharaeteristie.  [c.388]


See pages that mention the term Bypass valve : [c.785]    [c.965]    [c.2135]    [c.85]    [c.66]    [c.191]    [c.193]    [c.389]   
Turboexpanders and Process Applications (0) -- [ c.66 , c.163 , c.181 , c.184 , c.185 , c.191 , c.193 ]