Oil lubrication control system keeps deep well pumps operating

Mekorot’s oil lubrication control system is installed in all of the country’s 400 deep wells to prevent pump failures due to lubrication failures.

The national water company of Israel, Mekorot, and the local electronics lab, Hoffman & Hoffman, developed an oil lubrication control system that prevents pump failures created by lubrication malfunctions in deep wells.

Mekorot operates more than 1,200 pumps in shallow wells (800) and deep wells more than 250 meters deep (400 wells). In shallow wells pumped water can be used to lubricate shaft bearings for two reasons: shaft bearings are made of rubber and only a short period of time elapses between the energizing of the motor and rising of the water up the pressure tube. Consequently, the pump operates without lubrication for a short time (dry running).

In a deep well where the turbine is installed at a depth of more than 250 meters, the time required to reach ground level is longer and pumped water cannot be used as a lubricant. In order to prevent heating of the rubber bearings, they are replaced by bronze bearings (Tube bearing), which require constant lubrication for avoiding seizing, wear, and tear.

The oil lubrication system consists of enclosed oil tubes that are connected by steel bushings with inlaid tube bearings that contain the line-shaft within. The bearing itself is made of bronze to maximize the surface qualities and precision, with grooves to ensure uniform lubrication of the shaft. The enclosed tubes are held in place within the pressure tube by stabilizing spiders made of rubber.

The purpose of the oil-lubrication control system for deep wells is to prevent pump failures created by lubrication malfunctions. Dripping oil through the bearings and enclosed tube along the shaft lubricates the long shafts. Lack of lubrication or an insufficient supply of lubricant causes accelerated wearing of the bearings that could lead to seizing of the shaft. The control system allows continuous oiling with remote monitoring and tuning, giving ultimate protection against lack of lubrication and regulates the lubricant quantity, according to the predetermined amount. Mekorot installed this lubrication control system in all of its oil-lubricated wells.

According to Mekorot’s maintenance procedures, the oil-dripping rate during well operation is set at 20 to 40 drops per minute depending on well depth. The oil-dripping rate while the well is not in operation is set to 10 drops per minute. The role of the lubrication control system is to regulate the drops in order to create a constant dripping rate in accordance with the predetermined values.

Should the dripping rate fall below 15 drops per minute while the motor is operating, the control shuts down the motor automatically. The dripping rate is regulated through an automated control system based on a servomotor-regulating valve that changes its condition. according to the actual dripping rate that is measured every minute. A manual regulating option for the valve can be used to check the device.

The oil container has an oil-level viewer and is installed on a mount near the wells. The oil tube is connected from the containers through the oil controller and a filter. The container should be situated at least 30cm above the oil cup in order to maintain a constant downward slope of the oil tubing. The oil controller regulates the oil drops that drip through the tube into the enclosed tube and bearings.

All of Mekorot’s 400 well are equipped with this system, which have worked continuously for about 12 years with zero failures and minimal maintenance.

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Author’s Note

Eng. Dotan Druker is a mechanical engineer for Mekorot Water Company, Email: [email protected].

Enquiry No. 103