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Why do I need to shroud my submersible bore pump or install a sleeve?
PVC pump shrouds are installed over the body of the pump and motor so that the water flow past the motor is sufficient to achieve adequate cooling of the motor. Easy to fit and definitely required if you are installing the submersible pump in a well or bore with a diameter of 200mm or greater. You can buy ready to use shrouds or sleeves of standard pump sizes, alternatively a shroud or sleeve can be made from PVC Pipe.
A shroud is always required in an open body of water eg. a dam or river, or a cascading bore. A pump shroud should also be used if the pump is to be installed below water inlet level. This protects the pump from damage from falling sand and ensures correct velocity of water over motor for cooling purposes.
Fitting a shroud over the pump intake and motor casing will ensure that cool underground water flows upwards over the motor casing on its way to the intake, ensuring that the motor stays cool. The shroud is a tube open only at its base enclosing the submersible pump. Water can only reach the pump intake by flowing over the motor helping to keep it cool. It should be sized to provide sufficient flow past the motor for proper cooling, as per manufacturer’s specifications
A pump shroud for a 4-inch pump can be made from a piece of thin-wall 4-inch PVC pipe about a foot longer than the pump and motor. By simply cutting five or six slots longitudinally about 6 inches down one end of the pipe, the diameter of the shroud at the attachment point can be reduced to fit tightly over the pump housing. Attach it to the top of the pump with a stainless steel clamp so the flow of water to the pump inlet is forced to pass by the motor. Tape the attachment point with heavy-duty PVC tape or pipe wrap to make a good seal. It also is a good idea to install three screws in the lower portion of the shroud to center the shroud on the motor, which will provide an even flow of cooling water around the motor.
The 4H Motor, if installed inside a 4″ well, can operate in water with a temperature not exceeding 40 degrees celcius. If the well dimensions are larger, the maximum tolerated water temperature is 30 degrees celcius. The minimum volocity is 88 cm per second. 40 degrees celcius is tolerated only if the water velocity past the motor is no less than 0.3 meters per second. In order to determine the water speed with a good degree of approximation apply the following formula:
|10,6 x Q|
|Dp2 – 9025|
|Where||V =||water speed in m/c|
|Q =||delivery in l/m|
|Dp =||well internal diameter in mm|