Chapter Four Black Zone Process 4.6 Negative Pressure System

With that, we'll talk about the necessary equipment for casting-negative pressure system.

Everyone knows that the pouring of the lost foam is carried out in the state of negative pressure vacuum,Its main function: it has a secondary tightening effect on vibrating and compacting molding sand, improves the static friction between sand particles, makes dry sand set under the action of atmospheric pressure, and at the same time sucks away the gas generated in the gasification process of foam model to avoid porosity in castings; Increase the flow speed of molten iron, accelerate punching, greatly improve the qualified rate of castings, and ensure smooth and orderly pouring.

The vacuum pump we are equipped with is a water ring vacuum pump, which creates a vacuum and pressure in a closed container by pumping water-insoluble, non-corrosive gases. Provide the negative pressure required during the pouring process and create a stable negative pressure field for the sand box.

The burning gas passes through three-stage filtration, dust removal, purification, and discharge to the atmosphere .

Commonly used negative pressure system according to different pumping volume, every minute20 cubic, 25 cubic, 35 cubic, 43 cubic. The choice of negative pressure system is mainly based on the size of your sand box, the volume of the product and the number of sand boxes vacuumed at the same time, and the appropriate negative pressure system is selected by calculation.

After years of experience, we found that the larger the composite tank is, the more stable the negative pressure casting system is. Therefore, in some fields, we have equipped some large tanks in the composite tank to stabilize and maintain the pressure.

In actual production, in order to prevent everyone's misoperation, we have added some control valves in the negative pressure system control to prevent water backflow caused by sudden power failure or misoperation.

In the use of negative pressure, we should pay attention to several points:

1.Start according to the starting time specified in the manual, remember not to be used for frequent starting.

2.Wiring shall be carried out according to the identification of the control schematic diagram (self-provided circuit breaker), and the test machine can be powered on after confirming that the wiring is correct. Determine the direction of motor rotation to prevent reverse rotation.

3.All equipment must be reliably grounded, safety first, in case of accidents.

4.Check the water level of the separation tank in the negative pressure system before the pump is started, and change the water frequently to ensure the height of the water level.

5.Adjust the negative pressure valve to make the system negative pressure zero, and then close the vacuum pump to prevent water backflow.

6.Always check the operation and lubrication of the bearing. Normal working bearings should be loaded with oil 3-4 times/year. Clean the bearing at least once a year and replace the lubricating oil.

7.Maintain normal water level in the tank and discharge sewage regularly.

Long-term shutdown of the pump before the start, the coupling must be turned by hand for several weeks to verify that the pump is not stuck or other damage phenomenon.

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