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Reverse flow through pumps

If a pump trips (or is shut down and not isolated), it can be driven backward by the pressure in the delivery line and damaged. Check valves are usually fitted to prevent reverse flow, but they sometimes fail. [Pg.331]

When the consequences of reverse flow are serious, then the check valve should be scheduled for regular inspection. The use of two, preferably of different types, in series, should be considered. The use of reverse rotation locks should also be considered. [Pg.331]

When lines are being emptied by steaming or by blowing with compressed air or nitrogen, care should be taken that pumps are not turned so fast in reverse (or even forward) that they are damaged. [Pg.331]

This is a good example of an accident waiting to happen. Sooner or later the check valve was bound to fail, and a spillage was then inevitable. [Pg.331]

In this case the design was not at fault. The operators did not understand the design philosophy. Would this have been foreseen in a hazard and operability study (Section 18.7), and would special attention have been paid to the point in operator training  [Pg.331]


The oil system should be equipped with a main oil pump, a standby and, for eritieal maehines, an emergeney pump. Eaeh pump must have its own driver, and eheek valves must be installed on eaeh pump diseharge to prevent reverse flow through idle pumps. The pump eapaeity of the main and standby pumps should be 10-15% greater than maximum system usage. The pumps should be provided with different prime movers. [Pg.544]

Figure 5.22 — Reversible flow-through fluorimetric sensor for the determination of potassium in human blood plasma based on the mechanism shown in Fig. 5.21.3. (A) Flow-cell containing the lipophilic membrane. (B) Flow injection conflguration. P pump IV injection valve W waste. For details, see text. (Reproduced from [86] with permission of Elsevier Science Publishers). Figure 5.22 — Reversible flow-through fluorimetric sensor for the determination of potassium in human blood plasma based on the mechanism shown in Fig. 5.21.3. (A) Flow-cell containing the lipophilic membrane. (B) Flow injection conflguration. P pump IV injection valve W waste. For details, see text. (Reproduced from [86] with permission of Elsevier Science Publishers).
A set of pumps in a pit recirculates the cooled water. Submerged vertical pumps are standard in this service. When using multiple pumps with large capacities, it is necessary to space them properly and to design the pit to allow unimpeded access of the water flow to the suction of the pumps. The requirements of the pump vendors will fix this aspect of design. Any reverse flow through idle pumps recycles to the basin and reduces the efficiency of the process. Check valves and anti-reverse mechanisms help to prevent this. [Pg.1184]

Each motor is provided with an anti-reverse rotation device. The device is designed to prevent impeller rotation in the reverse direction due to each of the following conditions motor starting torque, if the motor was incorrectly wired for reverse rotation and, reactor coolant flow through the pump in the reverse direction due to the largest remaining pipe break after application of leak before break as described in Section 3.6, which could result in reverse flow through the pump. [Pg.132]

In the event of a break which is not eliminated by leak before break which would result in reverse flow through the pump, the anti-reverse rotation device prevents impeller rotation in the reverse direction. In the event of a break which is not eliminated by leak before break and which could result in increased flow through the pump tending to accelerate the pump impeller,the highest predicted pipe break induced overspeed is less than the lowest critical speed of the flywheel. [Pg.133]

When pumps are connected in parallel, more than three of them would be required in such ULOF because there may be some reverse flow through the pump at fault. In a serially arranged two-pump system of the 4S-LMR, the core flow rate can be sustained at more than 50% of the rated flow, because there is no reverse flow and the functioning pump could be able to sustain a higher flow due to its flow-head curve. The analytical results obtained for the 4S-LMR indicate that this more severe ULOF pushes the temperatures up by about 10°C only, which is acceptable. They also point to certain margins in core pressure drop and... [Pg.436]

While working a HAZOP of a water distribution system, we found that reversing flow for emergency reasons created additional hazards to our process. One of the new hazards was critical safety valves and pumping stations could be blocked from contamination from dirt picked up from reverse flow through our filters. [Pg.185]

Many accidents occur because process materials flow in the wrong direction. Eor example, ethylene oxide and ammonia were reacted to make ethanolamine. Some ammonia flowed from the reactor in the opposite direction, along the ethylene oxide transfer line into the ethylene oxide tank, past several non-return valves and a positive displacement pump. It got past the pump through the relief valve, which discharged into the pump suction line. The ammonia reacted with 30m of ethylene oxide in the tank, which ruptured violently. The released ethylene oxide vapor exploded causing damage and destruction over a wide area [5]. A hazard and operability study might have disclosed the fact that reverse flow could occur. [Pg.996]

The scheme in Figure 9.19 shows a simplification of the separation unit, using a 2-position valve to reverse the flow through the column for load/wash and elute steps, and an additional 2-position valve as a detector diverter valve. The system also incorporated several zero-dead volume syringe pumps and several additional valves to route sample and reagents through the system. [Pg.550]

Concentration of 1-micron-size micro-organisms from about 100 ml of liquid, whether drawn from a bio-aerosol collector or from an environmental water source, into a volume of 1 to 2 ml. is achieved by a liquid flow system including a reversible filter through which filtered liquid can be recirculated or disposed of and from which a concentrated sample is recovered by opening a solenoid valve leading to a detector or to a collection container and reversing the pump for a short time. The reversing action flushes the collected particles off the filter and into the detector or container. [Pg.111]


See other pages where Reverse flow through pumps is mentioned: [Pg.331]    [Pg.331]    [Pg.544]    [Pg.141]    [Pg.110]    [Pg.648]    [Pg.332]    [Pg.52]    [Pg.828]    [Pg.217]    [Pg.1045]    [Pg.211]    [Pg.210]    [Pg.65]    [Pg.93]    [Pg.277]    [Pg.278]    [Pg.105]    [Pg.118]    [Pg.110]    [Pg.617]    [Pg.156]    [Pg.141]    [Pg.68]    [Pg.384]    [Pg.996]    [Pg.75]    [Pg.293]    [Pg.387]    [Pg.157]    [Pg.1665]    [Pg.112]    [Pg.299]    [Pg.128]    [Pg.278]    [Pg.391]    [Pg.723]    [Pg.174]    [Pg.278]    [Pg.54]    [Pg.324]   


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