Pump
The pumps used shall be in general & conform to the following specification and applies to Centrifugal pumps only.Casing
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The casing shall be of heavy close grained cast iron, to withstand high tensile strength with smooth waterways and fitted with bronze wear ring. It shall be of vertically split design with streamlined volute and integral suction vertical position to facilitate piping. Casing shall have tapped openings for perming, vent, drain and gauge connections.
Horizontally Split Case Centrifugal Pumps
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The casing shall be of heavy close grained cast iron of high tensile strength, and shall be split parallel to the shaft. Bearing housing supports, suction and discharge flanges shall be cast, bored and machined generally with the lower half and bolted together. This removable upper half casing and bearing caps should permit inspection or removal of the entire rotation assembly without disturbing the piping. The flanges shall be to BS4504-1968.
Impellers
The impellers on end suction pumps shall be semi-open type carefully balanced for smooth operation. Balancing openings shall be provided near hub of the impeller to reduce pressure on the stuffing box to approximately suction pressure. The impeller shall be secured to the shaft by feather and nut.
The impeller on horizontally split case pumps shall be enclosed, double suction type, cast in one piece and balanced to minimise thrust and to ensure longer bearing life and smooth operation. Impeller shall be keyed to the shaft and locked in position by threaded shaft sleeves.
Wearing Rings
Wearing rings are provided to maintain close running clearance and to minimise pressure leakage between suction and discharge chambers of the casing. The casing wearing rings shall protect the casing against wear and shall be locked in pump casing to prevent rotation.
Shaft
The shaft shall be of high strength steel with optimum diameter to provide maximum strength with minimum shaft deflection. The shaft shall be fully protected by renewable shaft sleeve.
Bearings
The bearings shall be precision ball bearings. The bearings shall be located and positioned on to shaft by means of lock nut.
The outdoor bearing shall be double row bearings, to take the radial and thrust loads. The inboard bearing shall be single row bearing taking the shaft radial load and shall be free to move axially in the bearing housing to compensate for shaft expansion due to temperature changes. Labyrinth deflectors shall be provided to exclude dirt and moisture from the bearing housing. Facilities shall be provided for grease lubrication. Grease relief shall be provided to prevent over-lubrication.
Shaft Seal
The pump shall have mechanical shaft seals of extra hard carbon ceramic type. Details of the Mechanical seal provided shall be submitted with the tender.
Baseplate
The pumps and driver shall be factory mounted by the pump manufacturer on either cast iron base or fabricated steel base plate.
i.Cast Iron Base
The cast iron base shall be reinforced against, deflection with raised lips for drain collection.
ii.Fabricated Steel Base
The fabricated steel base plate shall be reinforced against deflection. It shall be furnished with fabricated drip rim and drain connection.
Drive Motor
The drive for the pump shall be by means of electric motor. The motor shall be suitable for operation on 440 volts, 3 phase 50 cycles power supply. The motor shall be squirrel cage induction (drip proof Totally Enclosed Fan Cooled TEFC explosion proof) type. The motor size shall be sufficient to prevent overloading at the operating conditions or at the lowest listed head conditions, whichever point requires the greater horsepower.
Alignment
The pump and motor shall be aligned by the pump manufacturer. The pump manufacturer shall provide certification to the effect that the pump and motor coupling has been carried out by them and checked by them.
On completion of the installation, grouting and connection of all piping, the pump and motor shall be rechecked for alignment by means of accepted methods, by the pump manufacturer/sole agent.
Suction And Delivery Flanges
The suction and delivery branch flanges shall be to British Standard Table 'D'.
Performance Tests
The Contractor shall after installation carry out commissioning tests and ensure that the specified flow rate and head are achieved, by means of Direct Reading Flow meter.
The performance tests shall alternatively be carried out at factory test rig of the pump supplier in the presence of the Consulting Engineer.
The Contractor shall submit detailed performance curves for the pumps supplied along with the tender.
Variable Speed Pumping Systems
Where variable speed pumps are indicated in the Specification Drawings, the pumps shall be provided with adjustable frequency drives and pump controllers for the automatic adjustment of the pump speed to achieve the desired pumping conditions whenever a change in demand is experienced.
The pump controller shall incorporate the adjustable frequency device and shall be of the microprocessor based programmable type dedicated for the pumping system.
The frequency drive shall employ sine wave pulse width modulation control and shall be suitable for operation on a three phase, 415 Volts, 50 Hertz input supply with an input voltage variation of +10% and -15% and frequency variation of +1 Hertz.
The drive shall be capable of providing a variable frequency output of 0 to 50 Hertz proportional to a 4 to 20 mA or 0 to 10V input signal obtained from a field sensor/transmitter. The field sensors / transmitters required for pump control shall be supplied as part of the variable speed pumping system. The sensors/transmitters shall be suitable for measuring the appropriate process parameters (i.e. pressure, differential pressure, temperature, flow etc.,).
The drive shall incorporate the following minimum features:-
a) Operating output frequency range of 0.5Hz to 200Hz
b) Rated output voltage of 415 volts
c) Power factor 0.9 or better
d) Adjustable acceleration/deceleration times of 0.1 to 1600 seconds (programmable)
e) Auto/Off/Manual speed selector switch
f) Facility for local setting of frequency manually in the event of control signal failure
g) Facility for local and remote controlled start/stop of the motor
h) LED display for indication of output frequency control settings and fault conditions
i) Summary alarm volt free contacts for remote alarm monitoring
j) Adjustable start boost to suite the required starting torque of the load
k) Protection against short circuit, ground faults, input mains over-voltage, under-voltage, overload, high temperature and motor stall prevention during acceleration and deceleration
l) Adjustable upper and lower limit settings to keep the frequency output within the allowable rotating speed of the motor
m) Noise improvement reactors to decrease the motor noise when motor is under the frequency drive operation
n) Auto / manual by-pass facilities in the event the frequency drive has failed
o) Auxiliary power supply units which may be required for the operation of the pump controller and drive
The pump controller with the adjustable frequency drive shall be housed in a IP20 enclosure when mounted inside a motor control centre or in a IP43 enclosure if mounted independently in the pump room. Adequate ventilation shall be ensured for continuous operation at the maximum ambient temperature specified by the manufacturer.
All power, control and instrument cabling shall be provided and installed as described elsewhere in this specification.