PACKAGE : I Bid Document VOLUME : II - Public Health Engineering

The design of bearing should be such that the bearing lubricating element does not
contaminate the liquid being pumped. Where there is a possibility of liquid entering
the bearings suitable arrangement in the form of deflectors or any other suitable
arrangement must be provided ahead of bearing assembly.
Bearing shall be easily accessible without disturbing the pump assembly. A drain
plug shall be provided at the bottom of each bearing housing.
Features of Construction:
Impeller:
The impeller shall be an enclosed impeller, made in one piece and securely keyed
on the shaft. The installation will include means to prevent loosening of the impeller
during operation, including rotating in the reverse direction. The impeller shall be
statistically and dynamically balanced to prevent vibration, as per ISO Standards.
Casing Ring:
The pump shall be provided with a renewable type casing ring, to offer wearing
resistance. Hardness of the casing ring shall be 50 BHN (Brinell Hardness Number
Units), lower than the impeller.
Shaft :
Single integral shaft, shall be designed to withstand the torque loads throughout the
whole range of operating conditions, for the selected particular impeller diameter as
well as all the impeller diameters covered between minimum and maximum
impeller diameters when coupled to the motor shaft through flexible coupling. The
shaft design should also include the possibility of running the pump with a electric
motor of higher power rating meant for future expansion with increases impeller
diameters.
Shaft Sleeves:
Replaceable shaft sleeves shall be provided to protect the shaft where it passes
through stuffing boxes. The end for the shaft sleeve assembly shall extend through
the packing gland. Shaft sleeves shall be securely locked or keyed to the shaft to
prevent loosening. Shaft and shaft sleeve assembly shall ensure concentric rotation.
GTS : General Technical Specification. Page 149