Application of twin-screw pump in butadiene rubber device

glue pump, twin screw pump

This article introduces the current use situation of the original rotary piston glue pump in butadiene rubber equipment and the structural characteristics of the twin-screw pump. It also analyzes the use of the twin-screw pump to replace the original rotary piston pump for conveying glue, and its use in conveying high-viscosity glue. The effect shows that the twin-screw pump can deliver glue in butadiene rubber devices with reliable operation and good economic benefits.

The butadiene rubber plant of a chemical company has 12 glue pumps, which are key equipment in production. Among them, there are 6 glue pumps. Their main function is to mix the glue between the two glue tanks, which have different qualities. The purpose of thorough mixing of physical glue liquid. There are 6 glue spray pumps. Their main function is to transport the glue stored in the glue tank to the coagulation kettle for glue spraying. Before the glue pump was replaced with a twin-screw pump, the rotary piston pump was used. However, during the production operation of these pumps, due to the feeding pulsation, the pipeline system vibrated seriously and even affected the normal use of the instrument. It also caused frequent failures and heavy maintenance work. And the phenomenon of high maintenance costs is becoming increasingly prominent. Therefore, after careful analysis and research on the above problems, it was believed that this type of rotary piston pump was structurally unsuitable for transporting butadiene rubber glue, and it was decided to update and replace these pumps. Through research and comparison, it was decided to choose the 2HS500-80 twin-screw pump to replace the original rotary piston pump, which achieved good results in production operations.

 

1. Current status and existing problems of the original rotary piston glue pump

 

The original glue pump used in the device is a rotary piston pump. The rotation of the pump is driven by the rotation of the driving shaft and a pair of synchronous gears at the rear of the pump, driving the driven shaft to rotate, causing the two rotating rotors to bite each other and pump the glue. Inhale from the suction port and discharge from the discharge port. The axial seal of the driving shaft is a single-end mechanical seal. The lubrication of the sealing surface and the lubrication of the synchronization gear rely on the glue itself as the lubricating medium.

When the pump is running, the glue is stirred by the rotation of the synchronized gear in the rear end cover of the pump, and the solvent in the glue gradually evaporates. Due to the high viscosity of the glue, it is difficult to replenish fresh glue into the rear end cover of the pump. During long-term operation of the pump, after the solvent in the glue evaporates, the viscosity of the glue will also increase, which will lead to poor lubrication of the gear operation, or even lack of lubrication, resulting in dry friction between the gears, causing the temperature of the rear end cover to rise, and in severe cases, lead to Gears and bearings burned. After the solvent in the glue liquid evaporates, the glue liquid between the sealing surfaces of the mechanical seal in the front end cover of the pump will turn into fine rubber particles, making the sealing surface poorly lubricated and making it difficult for a sealing film to form between the seals, causing leakage of the mechanical seal.

In response to this problem, the relevant personnel took corresponding measures and drilled a ф12mm hole in the bearing seat to increase the circulation amount of glue in the gear part, but the effect was not obvious. To ensure the smooth production of the device, mandatory maintenance is adopted, that is, it is disassembled, inspected and cleaned every 15 days of operation to prevent damage and cause greater losses.

 

2. Structure of 2HS500-80 twin-screw pump

 

The twin-screw pump has a double-suction structure. Both ends of the screw are in the same pressure chamber. The axial force of the screw can balance itself. The bearings at both ends are externally mounted and separately lubricated with grease, so they are not affected by the transport medium. It relies on the synchronous gear in the gearbox to transmit power. The driving screw drives the synchronous gear to rotate, thereby driving the driven screw to run, causing the two screws to bite each other, sucking the glue from the suction port and discharging it from the discharge port. There is no direct contact between the two screws, but there is a certain meshing gap. The meshing gap is adjusted according to the viscosity so that different flow rates and pressures can be obtained. Impurities in the medium will not cause direct wear (except erosion) to the screw, and the pump will not damage related parts when idling for a short time.

The 2HS500-80 twin-screw pump uses double-end mechanical seals for the main and driven axial seals and the seals between the driven shaft and the synchronization gear. The sealing lubrication between the double-end faces relies on sealing oil supplied from an independent set of sealing oil stations outside the pump.

Because there is a mechanical seal between the synchronization gear and the pump body, gear oil is added separately into the cavity of the synchronization gear to ensure good lubrication of the synchronization gear. As for the glue in the pump body, the double-end mechanical seal is used at the shaft end of the dynamic seal of the pump, which effectively seals the glue in the pump body, making the glue less likely to dry out.

 

3. Characteristics of 2HS500-80 twin-screw pump

 

1) The bearings of the pump are externally lubricated separately, so they can transport high-viscosity media, such as high-viscosity glue.

2) A separate lubricated synchronous gear is used to transmit the torque from the driving screw to the driven screw to ensure that there is no metal contact and power transmission between the driving and driven screws, no wear of the screw and long service life.

3) It adopts a double-suction structure, and the axial forces at both ends of the main and driven screws are balanced with each other.

4) The double-end mechanical seal used for lubrication and flushing at the lubricating oil station ensures that the pump can deliver high-viscosity rubber glue.

5) Adopt a special spiral surface form to ensure minimal shear damage to the polymer rubber glue.

6) The pump is equipped with a circulation valve. When the pressure exceeds the rated pressure of the pump, the circulation valve opens and a part of the liquid flows back to ensure that the pressure of the pump is not too high.

 

4. Application and effect of 2HS500-80 twin-screw pump

 

This kind of screw pump transports materials uniformly and stably, with high pressure, large flow, small vibration, low noise, high efficiency, low energy consumption and wide application range. It is suitable for transporting high-temperature or low-temperature liquid media, viscous media, transporting flammable, explosive or toxic and harmful liquid media, and is especially suitable for transporting various glues with poor lubricity and high viscosity. Of course, different seals must be selected for different media, and corresponding measures must be taken.

After all the glue pumps of this device were replaced with twin-screw pumps, the pumps have been running for more than 20 months. During this period, no abnormalities or leaks were found, which solved the problem of severe vibration of the pump outlet pipeline due to the large pulsation of the original glue pump. Problems, and many problems such as burning bearings and damaged seals due to poor lubrication of the conveying medium. The twin-screw pump satisfies the transportation of high-viscosity glue, improves the equipment operation cycle and the stability of the device operation, reduces the labour intensity of the operator, reduces the maintenance cost of the device, saves costs, and reduces the impact of waste glue discharge. Environmental pollution has improved the working environment.

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