The last requirement of any specification for wastewater systems should be a system "Start-up". This last step will assure all parties that the system has been properly installed and all plumbing and electrical connections have been are functioning as specified. When wastewater pumps fail, the results are usually costly and a proper start-up is the best way to avoid these situations.
A factory start-up should include:
Piping inspections to make sure the check valves have been installed prperly and a weep hole has been drilled in the discharge pipe below the check valve. ( To avoid an "air-lock condition.)
Confirm that the pump voltage matches the available voltage.
confirm that the pumps are responding to the H-O-A switches.
Establish that the pumps are rotating in the correct direction.
Check for excessive voltage drop while the pumps are under load.
Compare the amp readings of the pump under load to the FLA rating of the pump.
On three phase controls, the safety overloads must be set to the FLA rating of the pump. (overloads are not set at the factory and are usually shipped at the lowest setting).
Check the setting of the control floats ( or other control sensing device) to make sure they are at the correct depth and arranged in the proper sequence of operation.
In order to assure a proper start-up the following conditions must be present at the job site:
All electrical connections must be completed and power supplied to the controls.
There must be a sufficient amount of water in the basin for the pumps to operate.
An electrician and a representative of the mechanical contractor should be present.
Any documents that have been shipped with the pumps should be available.
If the shipping documents are not available, then the information on the pump tag should be recorded and made available. This should include pump part number and serial number.
The start-up should be done by factory authorized personnel.
Over the years we have observed that the majority of premature pump failures and operating problems could have been avoided with a proper start-up. The largest reason for problems with three phase pumps is the failure to check for proper rotation. `Wastewater pumps will pump when rotating in the wrong direction, so the fact that they are pumping does not assure that they are rotating correctly. Because pumps running backwards draw 50% higher amps, there will be nuisance tripping of the overloads. If they continue to rotate backwards, the impeller will eventually fail and excessive vibration can cause the premarue failure of the shaft bearings which will allow the rotor to strike the stator and cause the motor to short out.
Many pump manufacturers now require start-up to activate the warranty on the pump
A record of the conditions at start-up can help determine is any changes were made to the system that caused failure at any future date.
A proper start-up will give peace of mind to the engineer, the manufacturer, the installer and the owner. and it should be required on all commercial project specifications.
Comentários