LDO ,FO UNLOADING AND PRESURING SYSTEM FOR A STEAM GENERATOR -ABC OF THERMAL POWER PLANT -PART-I

The fuel oil plant consists of

a.     Fuel (LFO/LDO & HFO) unloading terminal

b.     Fuel (LFO/ LDO & HFO) unloading pumps

c.     LFO and HFO Day tanks (for supplying fuel to auxiliary Boiler)

d.     LFO and HFO Storage tanks (for supplying fuel to main Boiler)

e.     LFO and HFO pressurising pumps for supplying fuel to auxiliary and main pumps.

f.      Fuel oil lines from fuel oil plant to Boilers.

LFO = light fuel oil ; HFO = Heavy Fuel Oil.

In a power station in India Main Boiler Package only contains Fuel oil Pressuring unit with

accessories like pumps , heaters ,pipelines, valves etc ( between pressuring unit and 

Boiler . Trestle comes under civil work.

Unloading station from wagon /tanker etc is a separate system generally offloaded to a

third party as a package consist of pump ,valves ,pipelines etc.  

I will give a short description of unloading system and data provided is of 500 MW unit

only.

   LFO/HFO STORAGE AND DAY TANKS:

 

Storage & Day tanks receives the fuel oil from fuel unloading terminal and serves as the

supply reservoir to Fuel oil pumps pumping oil to Main Boiler. Aux. Boiler respectively.

These tanks are provided with local and remote level indicators, arrangements for heating in

the case of HFO and interconnecting outlets with other Fuel oil tanks.

 FO unloading pumps

No. of pumps                  :       5

Capacity                          :      100 cu.m/Hr at 1.88 ksc

RPM                               :       1470 RPM

Type                                :       Screw Pump

LFO unloading pumps

No. of pumps                :        2

Capacity                        :        50 cu.m/Hr  at 1.2KSC

RPM                              :        1430 RPM

Type                             :         Screw Pump

 

Tanks

LDO Storage Tank          :     500 cu.m

LDO Day Tank                :     100 cu.m

HFO Storage Tank          :   2000 cu.m

HFO Day Tank                :      100 cu.m

Associated carbon steel pipelines valves , steam tracing lines or electrical heaters are also

supplied in the package . These lines need to be cleaned mechanically before charging . As

these lines are more than 100 mm diameter no steam blowing is envisaged for these lines.

Fuel Oil Pump House is structural and civil building having a small EOT crane on monorail

to handle the pumps and heaters in the pump house. Therefore it is to be erected before 

the erection start of Fuel Oil Handling Package. These cranes are provided for maintenance

purposes but if we erect it early it will help to reduce the erection time period considerably.

The pump house work should be completed in all respect before charging of oil . Specially

leak test individual items to be checked. Please note that once oil is charged in the system

it is very difficult to get the shut down for any rework . Welding and gas cutting etc will be 

prohibited for safety reasons and hot job welding is also some times not possible due to

traces of oil inside the pipelines. Therefore any rework will take considerable time and 

effort to line up the job. Steam tracing line ( Nb10 ) pipes also to be completed with

steam traps . Now -a -days all the pumps come as a skid with suction discharge valves

mounted with pipelines. Heaters are also coming as a skid with integral pipelines.

However we do not receive trap station in assembled condition. If we receive the same

in assembled condition or pre-fabricate it at site on lean period will reduce E&C time. 

It is to be noted that fuel oil station readiness and its associated commissioning work will

be all time under time pressure as Light Up date will be nearing and a tendency will be

there to By-pass some works . These may lead to delay in completion as shut down of 

system will not be available.

 We ignore the laying of drain lines etc up to the design point due to time pressure but it is

necessary to complete the lines with designed slopes to the drain tank. Incomplete drain

line will prolong the package completion .   

CONTINUED TO PART-II

ID ,FD ,PA FAN COMMISSIONING OF BOILER PART -X ABC OF THERMAL POWER STATION

Pre-commissioning Check List/activity to be carried out

Check the erection protocol /log sheet for foundation bolt tightness , clearance with respect to

impeller hubs ,blades casing etc.

Check fan shaft level , check the coupling arrangement , Different gaps measurement in protocol etc.

Check the calibration of power cylinder for blade pitches etc.

Once all the protocol checks are over then check the connection of water line and oil line at different

places.



Check the inlet /outlet duct position immediately before and after fan.

Check the commissioning of outlet dampers and inlet guide vanes.

Check the freeness of the rotor by hand before connecting to the motor.

Remove all temporary supports from inside the duct which comes under the flow path of fan

Agencies working in the boiler area / associated ducting system are informed about the test / cleared

from the test area (As per the actual requirement). Specially for the first time otherwise dust storm

can put any body into trouble .

All loose materials around the fan area are cleared.

Required approach stair cases, platforms and hand rails are erected prior to testing.

Erection of the following are completed.

Lube oil system

All the lube oil control oil pipe lines erected ,cleaned and flush as per procedure (acid cleaning)

described in my earlier blog 

DM.C.W lines for HT motors and oil coolers

Suction and discharge duct and their connection with fan.

L.T./H.T switch gears required for the fan.

Fan casing, Suction / Discharge ducts are cleared off men & temporary materials.

All permanent supports and guides of fan & duct  are erected.

All local  instrumentation of lube-oil system, motor and fan are erected. (Required list to be prepared

at site) )Pressure and temperature indicators are duly calibrated)

Remote indication at control room are made available (List to be prepared at site)

Recommended Blade pitch operation (for FD & PA fan) and inlet damper operation for ID fan)

verified at local and the same ensured from remote for correct opening / closing with respect to

position indicator at local and remote. Free movement of Blades & inlet dampers are ensured.

ACW lines are flushed and connected to the respective inlet points.

 ACW inlet / outlet connections to ID fan sleeve bearings are connected as per the indicated

markings.

 Ensure variable frequency Drive (VFD) system is made ready (In case of ID Fan for operation of the

Fan. (Refer to the procedure enclosed in Section 10.0.)

Insulation resistance of the motor measured and ensured that the values are at satisfactory level.

Final commissioning

Start lube-oil system and establish oil circulation at recommended oil pressures (Both lube-oil and

control oil, which ever is applicable)

After obtaining clearance from all agencies, start the motor in decoupled condition and check the

direction of rotation. If  direction found reverse, change the direction of rotation of the motor.

Refer to section 10.0 for details regarding checking and commissioning of VFD system. In addition

commissioning manual of VFD issued by supplier to be followed in the commissioning of VFD

system.

Start  the motor once again and put under 8 Hrs trial run (FD and PA motors). In the case of VFD

synchronous Machine, put the machine under 4 Hrs trial through channel I and under 4 Hrs trial

through channel II.

Performance of the motor to be monitored by logging load current, vibration and temperatures of

bearings and windings, whichever applicable.

After satisfactory completion of drive trial run, drive and the fan are coupled.

Start the fan and put under 8 Hrs trial run.

Blade pitch for FD and PA fan to be at minimum before starting the fan and after starting, fan to be

slowly loaded up to around 10-15% (Exact loading of the fan to be decided at site)

For ID Fan, keeping the inlet damper at minimum, Fan started and loading to be gradually increased

to 10-15% (Exact loading of the fan to be decided at site)

During 8 Hrs trial run, Fan performance observed by logging load current, vibration, temperatures of

the bearings, parameters of lub-oil system VFD system and draft values in PA,SA and Gas circuits

covered in single fan running condition.

Following parameters are recorded every hour in log sheet.

a. Starting time . b. Closing time (i.e time taken from running to standstill). c. Vane angle

d. Current and Voltage  e. Discharge Pressure . f. Motor Winding Temp . g. Oil level leakage of

oil. h. Cooling water flow Pressure and temperature. I. Lube oil and control oil Pressure and

temperature. j. Any other observation k. Vibration on all bearings.

All the fans commissioning process is same except the duct connection to be done . For FD and

PA suction chamber with silencer head should be available and discharge goes to furnace through

SAPH and PAPH.

For ID fan suction can be taken from ESP outlet bar or ESP can also be taken on line if ESP Air

tightness test is over . Discharge can be up to chimney. 

Above drawing shows the area to be covered during trial run. But it will be best if total ducting work

gets completed before the trial run.

 PA fan distribution up to mill including PAPH.

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ID,FD,PA FANS COMMISSIONING OF BOILER PART -X -ABC OFTHERMAL POWER

In my last blog I have discussed about the lube oil supply unit for fans ,Air heaters and Mills.

Construction features and item including control and instrument in the lube oil system is

more less same .Therefore observing one lube oil commissioning will help to learn the other.

Now we will discuss the commissioning of FANS. The commissioning of six numbers of

FANs are similar however system requirement for commissioning of FANs are different. We

will discuss the common system requirement and the individual requirement of FANs.

Induced Draft Fan

No of Fan                                :  2

Flow   (Approx)                       : 558.2 cu.m/Sec

Pressure (Approx)                  :  485 mmwc

Temperature                           :  150⁰C to 154 ⁰C

Drive                                       :  Motor

Speed                                     :  580 RPM

Motor Rating                           :  3650

Control                                    :  Inlet Damper plus variable  / Hydraulic coupling

                                                   Frequency Drive. (VFD).

Forced Draft Fan

No. of Fan                                                   :  2

Flow    (Approx)                                          :  246 cu.m/Sec

Pressure    (Approx)                                    : 351 mmwc

Temperature                                               :  50 degree C

Drive                                                            : Motor

Speed                                                           : 980 RPM

Control                                                         : Variable Blade Pitch control.

Motor Rating                                               :  1175 KW

The boiler   is also equipped with primary air fan, which form a part of the coal preparation a

and firing system.

PRIMARY AIR FAN

 

No. of Fan                                               :  2

Flow       (approx)                                   :  170.5 cu.m/Sec

Pressure   (approx)                                 :  1183 mmwc

         

Temperature                                           :  50 degreeC

Drive                                                       :  Motor

Speed                                                      :  1480 RPM

Motor Rating                                          :  2450 KW.

Control                                                   :  Variable Blade Pitch

                                                                  control.

(****- All the values given here are of 500MW set of BHEL Make.)

 

All the fan are mounted on concrete deck with suction and discharge duct. Connected to the

Fan flanges. FD Fans and PA fans are provided with Silencer at the suction duct. 

Regulation of Fan from no load to full load is performed by changing the pitch angle of blade

profile on all blades simultaneously during operation. This is achieved through a

sophisticated servo mechanism (Hydraulic Servo Motor externally actuated by a power

cylinder and forced lube-oil system.

In the case of ID Fan, the equipment is driven by variable frequency drive motor coupled

with soft coupling. The regulation of the fan is effected through the inlet dampers located at

the inlet of the fan and variable speed by VFD.

In FD and PA fans, the rotor is supported in antifriction  bearings and cooled by forced

lubricating oil. A thrust bearing is provided to absorb axial loads. Thermometers (RTD &

TI ) are provided in the bearing housing for temperature monitoring.

In ID Fan, the bearings are while metal sleeve type with forced oil lubrication. Fixed bearing

near drive end is designed to absorb the Axial forces. Thermometers are provided in the b

earing housing for temperature monitoring.

Respective O & M manuals to be referred for typical drawing of each fan.

Common Facilities Required for Fans

Safety Rules clearance certificate to be signed at site by all concerned engineers

before commissioning of the fans.
 

It is proposed to commission the fans as per the following proposals.

Oil flushing of lube-oil system is completed in all respect and fresh oil has been filled in the tank.(****)

 (***)- Presently using electronic centrifuge flushing oil can be cleaned up to required

parameter and can be reused as fresh oil. 

Trial run of H.T. Motor carried out for  8 Hrs as per agreed protocol.

Auxiliary cooling water line connected ,flushed with all instrumentation and ready for use.

LT /HT Power supply available and Minimum protection is tested and ready.

Availability of lighting, communication facility at the test area.

 Availability of portable fire extinguishers

Servo control mechanism / VFD system / Hydraulic coupling commissioned and calibrated.

Instruments for Pressure ,Temperature , Blade Pitch Position etc are commissioned and put

in place.

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