Standard Operating Procedures For Multistage Vertical Centrifugal Pumps
Before attempting to start any vertical centrifugal pump, check the water level in the well to be sure that the first impeller of the pump is submerged.
It is important not to operate the pump if the first impeller is above the standing water level, in this condition, the pump cannot be expected to pump water.
Severe damage to the pump may become the result. Another point is that the following must be checked when trying to start the pump:
Pre-lubrication piping is important for pumps over 50 feet long.
Grease fitting at packing.
Lubrication of the driver.
Oil-cooling connections for the driver.
Wiring of an electric motor.
Impeller adjustment.
Discharge piping connections.
The shut-off valve in the discharge pipe must be open.
If the standing water level is 50 feet or more below the surface, never start the pump without pre-lubricating the line shaft bearings. Pre-lubrication is necessary even if the pump is started after a short shutdown.
Another precaution is that the tank-to-pump valve should be closed while the tank should be filled with clean water if the manually controlled storage tank is used for pre-lubrication.
Before starting the pump, allow 75% of the water in the tank to drain into the pump column. If an external water supply is used for pre-lubrication, allow water to pour into the column for several minutes before starting the pump.
Start the pump. The remainder of the water in the pre-lubrication tank will lubricate the bearings until the column fills. If there is excessive vibration or if the driver overheats, stop the pump. Determine the cause and correct the problem before restarting.
Leave the tank-to-pump valve open. When the pump fills the discharge head, water will flow back into the tank. Shut off the valve when the tank is filled to the required level. Pre-lubrication will then be available for the next time the pump is started.
If the pressure at the discharge head is not sufficient to raise water to the required level in the pre-lubrication tank, obstruct the pump discharge line to increase the pressure until the tank is adequately filled.
The proper installation of the pump will contribute to maximum efficiency and long trouble-free life.
The following precautions are necessary when adjusting the packing gland, do not tight the packing gland during adjustment otherwise, it will wear out the packing quickly when it operates for a few minutes. Such can lead to damage of the shaft.
With the pump in operation, there will be some leakage at the top shaft packing. The packing gland must now be adjusted to allow a controlled amount of leakage while maintaining the required pressure at the discharge head.
The correct leakage rate is approximately one drop per second. This amount of water passing through the packing will act as a lubricant and will carry off excessive heat of friction.
Turn down the gland nut only one-sixth to one-quarter turn at a time. After adjustment, allow the packing to equalize against the increased pressure and the leakage to gradually reduce to a steady rate before making the next adjustment.
The amount of adjustment required will vary with the pressure developed by the pump at the discharge head. Never rush the break-in of the packing, even if it requires several days of attention to accomplish.
On models furnished with a grease fitting for lubrication of the packing, use a lightweight grease that will not tend to harden when in contact with water.
A list of acceptable greases, by brand name and manufacturer is usually attached to the pump handbook manual for specific reasons.
In addition to its lubrication value, the grease will act as a water barrier thereby reducing the packing required.
