[Time-Limited Quick Response Contest, Round 3] 004 (Completed) (2 users won prizes + 30 wealth points)

Transporting volatile substances such as ethylene and propylene requires pumps with minimal or no leakage. In terms of structure, magnetic drive pumps and shielded pumps have only static seals and no dynamic seals, ensuring that not a single drop of liquid is lost during transportation. The main measures to prevent cavitation in pumps are: (1) For pumps operating under conditions prone to cavitation, it is advisable to choose pumps with good cavitation resistance; if necessary, these pumps should have a low NPSH and materials that are resistant to cavitation ； (2) When selecting and arranging the suction pipeline system of the pump, it is necessary to ensure a sufficiently large effective net positive suction head, such that a >. Furthermore, the flow friction loss in the suction pipeline should be minimized as much as possible to increase the effective net positive suction head. (3) When adjusting the flow rate while the pump is in operation, only the valves on the discharge pipeline may be used for this purpose; it is not allowed to use valves on the suction pipeline. Because throttling in the suction pipeline causes a to decrease and r to increase. This post was last edited by tekchina on 2009-4-14 17:08]

When transporting volatile media such as ethylene and propylene, double mechanical seals (whether pressurized or non-pressurized depends on process requirements) or leak-proof pumps (magnetic pumps or shielded pumps) are used

Magnetic pumps and shielded pumps can ensure no leakage. To prevent the vaporization of the liquid inside the pump, it is necessary to properly control the physical parameters of the fluid, such as temperature and pressure, and the pump should be installed in a suitable location. In practical operation, it is necessary to strictly control the process parameter values; when starting the pump, it must be fully filled with fluid and thoroughly degassed, and flow rate can only be adjusted by controlling the pump’s outlet valve. Magnetic pumps and shielded pumps must never be run without load, as the presence of gas inside will accelerate wear.

Magnetic pumps or shielded pumps are usually chosen to ensure that the material does not leak. Measures in process design: 1. When selecting a pump, it is necessary to do so based on the performance curve, ensuring that the pump’s operating point falls within the acceptable range; this is the key measure to ensure the proper operation of the pump ； 2. The installation height of the pump needs to be verified after the equipment layout sketch is prepared; this is the main measure to prevent cavitation in the pump ； 3. The diameters of the inlet and outlet pipes of the pump need to be determined reasonably based on the flow rate from material balance calculations and the optimal flow velocity ； 4. The inlet pipeline of the pump must have a straight section at the inlet end during design, in order to achieve stable flow. 5. When a reducer is connected at the pump inlet, it should be installed in accordance with the principle that \"for top-fed types the bottom should be level, for bottom-sucked types the top should be level, and in cases of straight pipe sections, the bottom should always be level.\" 6. A check valve must be installed on the pump’s outlet pipe. A pressure gauge should be placed between the check valve and the outlet valve, and a drain valve should be installed at the bottom of the pressure gauge. 7. A minimum flow line needs to be installed on the pump’s outlet pipe. Operational measures: 1. The pump must be primed before starting it. 2. When operating the pump, flow rate adjustment can only be done using the outlet valve; the inlet valve must not be used for this purpose. 3. If any abnormal noises are heard inside the pump chamber during operation, the pump should be stopped immediately, the outlet valve should be closed, and the pump should be refilled. (The above are my humble opinions; please point out any errors, and those with experience may wish to add suggestions regarding the operational aspects.) ）

When transporting volatile substances such as ethylene and propylene, pumps with high sealing performance are usually chosen, such as shielded pumps and magnetic drive pumps； In the process design, it should be ensured that the filling head is above the allowable suction vacuum level of the pump ； During operation, the pump’s outlet valve cannot be used to regulate its flow rate; it is better to use an inverter-driven motor to adjust the pump’s speed in order to control its flow rate.

004: What type of pump is usually chosen for transporting volatile substances such as ethylene and propylene? Vertical centrifugal pumps and horizontal centrifugal pumps are both available; the choice depends on the required outlet pressure, as well as temperature and capacity considerations. To prevent the vaporization of the liquid inside the pump from affecting its normal operation, what measures should generally be taken in process design and actual operation to ensure this? It is designed with exhaust lines and liquid discharge lines for gas-phase and liquid-phase pre-cooling. Thermal insulation must be done properly.

Ethylene and propylene are not highly toxic substances, so ordinary multi-stage centrifugal pumps are sufficient to meet the requirements. To prevent the pump from being emptied, care must be taken to remove any gas from within the pump body and the inlet pipelines before starting the pump. The inlet tank must maintain a specified pressure (usually, means for pressurizing it are available). Before starting the pump, it is necessary to rotate the shaft evenly; moreover, the seals and the pump body must be preheated before this rotation takes place, in order to avoid damaging the seals during rotation.

When transporting volatile substances such as ethylene and propylene, pumps with high sealing performance such as shielded pumps and magnetic drive pumps are usually chosen. In process design, it should be ensured that the liquid level of the medium being pumped is above the allowable suction vacuum level of the pump. In operation, it is best to use a frequency-controlled motor to adjust the pump’s speed in order to control its flow rate; the pump’s outlet valve should not be used for this purpose.