Characteristics and Requirements for Horizontal Centrifugal Pumps offered by Everest Industries

The ash slurry pumps for combined B.A. and F.A. disposal, B.A. Cooling water over flow pumps, BAHP pumps, BALP pumps, flushing water pumps seal water pumps, for ash slurry pumps, dust suppression, ash conditioning and seal water pumps in main storage silo area and cooling water pumps for cooling various equipments of ash handling plant shall essentially be horizontal and centrifugal type. The equipment shall be capable of developing the required head at rated capacity for continuous operation.

All Centrifugal Pumps shall have a drooping characteristics curve, with the head continuously increasing with decreasing flow to maximum head at zero flow and the pumps shall preferably be non-overloading type beyond rated duty point. The characteristics curves of each set of pumps shall match each other for equal load sharing in case of parallel operation and such pumps shall be identical and all parts shall be fully interchangeable.

The ash slurry sump geometry and configuration shall be such as to minimise ash settlement, formation of vortices and air entrainment in the slurry as this may affect the operation of the slurry disposal pumps. To minimise the ash settlement adequate number of high velocity water jetting nozzles shall be provided in the slurry sumps.

The fly ash slurry concentrations under this mode of operation shall be decided, considering the rated capacity of the extraction system. To maintain the concentration limit and to run the ash slurry disposal pumps efficiently a provision shall be made for make-up water pipe connections complete with motor operated gate valves and manual gate valves.

Minimum 10% margin shall be considered for ash slurry pump sizing over and above the total slurry disposal head requirement comprising the straight pipe line frictional loss and bends loss. The value of the constant ‘C’ in William-Hazen equation shall be considered as 140 for calculating the system head.

An additional flow of 100 m³/hr (continuous) shall be considered on ash slurry pump capacity to take into account sludge disposal from clarifier units to be pumped by ash slurry disposal pumps to the disposal area. Bidder may take advantage of this additional quantity of sludge (the density of solids in sludge may be taken as 1.1 and the concentration as 5%) while arriving at ash slurry concentration for the combined ash disposal pumps. Apart from the working streams one standby and one maintenance standby shall be provided for the ash slurry disposal system.

The slurry pumps shall essentially be slow rpm pumps. The rotational speed of the impeller at design point shall not exceed 1000 rpm. The first stage of slurry disposal and transportation pumps shall be provided with variable speed hydraulic coupling of robust design for setting the optimum operating speed of the pumps based on actual site requirements after the system is installed. Minimum (+) 10% and (-) 45% speed variation with respect to speed at rated design point shall be provided in the first stage of combined ash slurry disposal pumps and ± 20% for bottom ash transportation and BA overflow water pumps. The slurry pump motor speed shall not exceed 1500 rpm.

To minimise the drive losses in the first stage of slurry disposal and transportation pumps, a constant speed reduction gear box shall be provided. The gear boxes to be employed shall be suitable for heavy duty application and of such reputed make which have proven established record of trouble free service under heavy load transmission duties.

For the subsequent slurry disposal and transportation pump stages, the drive shall be transmitted through belt drive arrangement. If in future, the operating speed of these pumps is also required to be changed, the Owner intends to carry out this change by replacing the existing belt-pulley with a pulley of different diameter to allow a future variation of ± 10%. Pump and motor layouts in the pump house shall be accordingly decided to take care of this requirement.

Continuous motor rating (name plate rating) at 50°C for ash slurry pumps shall have at least 20% margin above the maximum load demand of the driven equipment at the rated duty point. The maximum load demand shall be calculated considering slurry density, efficiency of pump when handling slurry and the complete drive losses in the transmission (fluid coupling, gear box, etc.). For selecting the motor, the maximum pump efficiency to be considered shall be 70%. To ensure interchange ability, all the pumps & motors of the pumping streams shall be of similar rating and the pumps shall be designed for + 10% and – 45% speed variation.

Pumps shall be single stage, end suction design provided with heavy duty impellers suitable for highly abrasive duty application. All the wear parts of pumps, impellers and liners etc. shall have a minimum guaranteed life of 8000 hrs. of operation. Provision shall be made for adjustment to take up wear by axial movement of the shaft. The seals shall be water flushed packed glands, fed from an external clean water supply source. The impeller tip speed at the rated parameters shall not be more than 1676 metres/min. Bidders shall make selection of the pump size such as to limit the tip speeds to above specified limits. The passages and clearances in pump components shall be properly designed, considering the size of ash and clinker to be handled.

The pumps shall have flooded suction inlet and shall be located indoors. However, pumps shall be suitable for operating with up to 2 metres suction lift. The glands of the pumps should be suitably designed to prevent clogging of ash particles.

About Us :

Everest Industries is a leading Centrifugal Pump and Plate Lifting Clamp supplier and manufacturer in Ahmedabad, Gujarat, India. Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.

Contact Detail :

Telephone: +9179-22902552

E-mail: everestind2552@yahoo.co.in

FAX: +91-9427710684

For more information, please visit Everest Industries Website everestindustries.co.in