Condensate Extraction Pump
1. DESCRIPTION:
The capacity of each CEP at GNDTP, Bathinda is 160m3/hr with 50% capacity at full
load. The pump takes water from hot well and supplies to Deaerator through Ejectors and
LP heaters. There are 3 CEP pumps installed at each init of GNDTP, Bathinda. Two
pumps will be required at full load and third pump is standby.
2. PARTICULARS OF CEP AND ITS MAIN MOTOR:
The rated parameters are as below
CONDENSATE EXTRACTION PUMP
Type
150-CJNV vertical pump
Make
BHEL Hyderabad
No. of stages
6 nos.
Delivery capacity
160m3/hr
Water temperature
40°C
Head at design capacity
215mwc
Shut off head
275mwc
Speed
1480rpm
Stuffing box
Mechanical seal
Lubrication of the pump
By oil under at thrust bearing and by
grease at guide bearing
Consumption of cooling water
Approx. 10 L/min for cooling of thrust
bearing oil
Quantity of water for minimum take off
60m3/hr
Quantity of water for maximum flow
190m3/hr
Direction of rotation
Clockwise-Looking from DE of Pump
Manufacturer
Type
Output
Rated voltage
Maximum rated Current
Speed
Frequency
Power factor
Manufacturer
Type
Output
Rated voltage
Maximum rated Current
Speed
Frequency
Power factor
Main Motor Stage-1
Kirloskar
KVD-400
175 KW
6.6 KV
21.0 Amps
1490
50 C/S
0.862
Main Motor Stage-2
NGEF
AM-450
175 KW
6.6 KV
19.5 Amps
1490
50 C/S
0.85
3. DESCRIPTION OF IMPORTANT PARTS
This pump is of M/s BHEL make, Model-150-CJNV and is a 6-stage pump. This pump
consists of following main parts
a)
b)
c)
d)
e)
f)
Pump assembly and shaft
Rising main tube
Pump frame and discharge elbow
Condensate chamber called canister
Motor stool
Suction strainer
It is a six-stage pump. Water from hot well enters the canister through the suction
branch after passing through the suction strainer. Water enters the suction impeller
through suction cover. Suction impeller is high capacity inlet impeller and after leaving
suction impeller it passes through the distributing passages of the diffuser where its
kinetic energy is converted into potential energy and to next set of impeller. This
procedure is repeated till water passes through the last impeller and the end diffuser.
Thrust of the pump is partially taken care by impellers and balance thrust is taken by
thrust bearing.
Water after leaving the last stage impeller enters the rising main tube which is
connected by bolts to the pump frame and is this water is delivered to the discharge pipe
through discharge elbow. Shaft of pump exits through stuffing box, where mechanical
seal is provided. Further above guide bearing is located in the motor stool above which
oil pan is located. In this oil pan thrust bearing is poisoned which is oil lubricated and oil;
level should be monitored through glass window provide to check oil level. Oil level
should be at half of oil gauge and in no case below oil gauge. This oil is cooled by
BCW. Pump is connected to motor by pin-bush type flexible
Water from second stage of pump is taken for sealing system of the unit and outlet is
connected to main sealing water header. Water from this header is taken for mechanical
seal flushing line. Also water from stuffing box is delivered to second stage of pump
through pressure release valve. In case stuffing box pressure increases a set value it will
be delivered through this line to second stage of pump.
A balancing line is provided from the canister tank top cover to condenser to
equalize pressure in the canister and condenser. Without this equalizing line CEP can
not deliver water as suction head will only be created when both canister and
condenser are at equal pressure. To ensure proper sealing of pump from atmosphere,
water sealing is provided between canister and pump frame. Frame seal line outlet valve
should be closed after deaeration of this line so that pressure is build up in the sealing
area.
CEP has very minimum clearance between rotating and stationary parts and any
small foreign material, if allowed to pass, will damage the pump. To avoid damage, a
suction strainer is provided in the suction pipe. Suction strainer is made steel cone with
3.0mm holes. Fine size hole can not be used due to restriction in allowable pressure drop
after strainer.
4. STARTING PROCEDURE OF PUMP
Following checks to be kept before stating a pump
i. All PTW’s are cancelled on CEP and connected circuit.
ii. Oil level at thrust bearing pan should be at half of oil gauge and in no case below
oil gauge.
iii. All valves are in open position except discharge valve. Discharge valve should
be open by about 10-15% position, so that only minimum flow should take pace.
iv. Hot well level should preferably be around 1000mm.
v. Fully open the vent at ejector.
vi. BCW pumps are running
vii. Open recirculation line at hot well by about 25%
viii. Supply is OK and Voltage of bus is normal
ix. Pump is free in movement
i. Start the pump and release air in the pipes by air vents at ejector. When full water
starts coming start closing the air vent and as the pressure iat the pump discharge
gauge starts increasing, start opening the discharge valve. Such that pressure does
not exceed 22 kg/cm2 and does not decrease 14 kg/cm2 . In case low pressure is
maintained, there is possibility of damage to impeller and other parts of pump due to
cavitations and also inadequate water supply to sealing system.
ii. Maximum and minimum flow should remain within design limits.
iii. Second pump should also be started in the same way and venting is not required
while running the second pump. Valves at hot well are to be operated to keep flow
requirements.
iv. Check the operating parameters, vibration, and sound etc of the pump for any
abnormality.
v. In case the pump does not develop pressure within 20 sec. then it should be
stopped from push button failing which bushes of CEP assembly may siege.
5. STOPPING THE CEP
i. Start closing the discharge valve such that pressure starts increasing and flow of the
pump reduces by about 75%.This will be achieved at about 85-90% of discharge valve
close position.Immidiatly stop the pump from push button. This procedure is desired
to have minimum thrust of stopping the pump .The pump has thrust bearing to protect
thrust in down direction, which is direction of thrust of running/starting pump. Stopping
thrust acts in upward diction and if discharge valve is in full open position, excessive
stopping thrust will act on guide bearing and may damage it. This procedure is to be
followed whether stopping first or second CEP.
ii. All valves should be in closed position when any PTW is issued for working on
strainer, mechanical seal, overhauling and assembly change.
6. COMMON PROBLEMS OF CEP
a) Suction strainer choke: The flow and current will reduce. Mild hammering and thereafter
cleaning is the solution. It should be ensured that hammering is done with soft object like
hollow pipe, wood etc.
b) Abnormal vibration/sound: The most probable cause is damage to guide/thrust bearing.
So pump may be changed over. If the problem is serious then immediately stop the pump.
c) Hunting of current: Hunting of current will occur in case of air ingress, mechanical
touching of rotating and stationary parts or other mechanical damage. If no abnormality of
sound is there then main possible cause is air ingress. So check air ingress from running as
well as from stand still pump. Check isolation if PTW is issued on one pump. Check CSE
level, it should be above 400mm and check it from site.
d) Thrust bearing temp. High: Possible causes are due to BCW blocking, oil level low or
bearing damaged. Check accordingly. Stop the pump if bearing is giving abnormal sound.
7. ALARMS AND PROTECTIONS
Following protections and alarms are required
a)
Hot well level low- Alarm at 500mm
b)
Hot well level low-low- Trip at 200mm one CEP and second CEP should
trip at 30 sec. time delay.
c)
Discharge pressure low before discharge valve-Alarm and stand by pump
should auto start
d)
Flow low -Alarm at flow less than 60m3/hr for each pump
e)
Flow high-Alarm at flow more than 190m3/hr for each pump
f)
Vibration should be less than- 80 micron
MOTOR protections: PROTECTION
Thermal Over Load (Alarm)
Thermal Over Load (Trip)
VALUE
REMARKS
Kindly mention tripping value
& if any delay is there
Instantaneous Over Current
Unbalance/Incorrect Phase Sequence
Locked Rotor
Earth Fault
Instantaneous Over Current (All 3φ)
Instantaneous Over Current (2φ, With
timer)
NOTE: Some of above alarms/protections does not exist at GNDTP