Why can’t the ultimate vacuum level of a water-jet vacuum pump reach 2–3 Hg?

There might be a problem with the nozzle design; simply replace it with another one or increase the water pressure

It’s due to the compression ratio; at high vacuum, water itself vaporizes as well

Can replacing water with a medium that has a higher vaporization point increase the vacuum level, and by how much? For example, using mineral oil.

If the circulating water temperature is controlled at 4-5 degrees, can the water jet pump achieve 2-3 mmHg? Please have a vacuum pump expert do the calculation

Common faults and troubleshooting methods for W-type hydraulic ejectors (vacuum pumps, water jet pumps) Fault Cause Troubleshooting method Insufficient vacuum level Decrease in vacuum level Unstable vacuum level Increased alkalinity or acidity of the circulating water, or scaling that reduces the diameter of the holes in the porous plate or diffuser. Clean with acid or replace the parts. Adjust the pH level of the circulating water. The temperature of the circulating water in the pool rises. Replace or add some circulating water to lower the water temperature. The water pump is faulty; pressure drops suddenly and flow rate decreases. Replace the water pump. Remove scale or debris from the impeller and inner shell of the water pump. System leakage. Inspect the system to find and fix leaks. The circulating water contains a large number of bubbles. A baffle is installed between the drain pipe and the water pump inlet pipe. The circulating water contains a large number of bubbles; replace the circulating water. Corrosion and deformation of the nozzle orifice and the perforations in the porous plate occur during water discharge (that is, when the circulating water flows out through the inlet). Replace the nozzle or porous plate. Adjust the pH level in the regulating tank. The nozzles and perforated plates are not accurately manufactured. Proper processing meets the accuracy standards specified in the drawings. The mixing pipe was processed inaccurately, resulting in surface corrosion. Proper processing ensures concentricity and surface finish, meeting the standards. The porous plate is blocked by foreign objects. Remove foreign objects. Clean the pool. The water pump pressure suddenly decreased. Inspect the water pump, and replace or repair it. Improper operating procedure. Turn off the water pump to balance the drainage with the atmosphere. Circulating water flows back into the system. Install a check valve in the system; fluctuations in atmospheric pressure affect the back pressure. Attach a one-meter-long tail pipe below the drain pipe.

For the multi-tube water jet vacuum pump we used in the past, without altering the equipment itself, the only way to make adjustments was by reducing the water temperature and increasing the outlet pressure.

The 6th floor covered it quite comprehensively; I learned from it

It could be caused by a blockage in the nozzle area, or it might be due to an insufficient flow rate of the cooling water

This type of pump inherently has a relatively low vacuum level; it is a primary rough vacuum pump

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