Published Sep 10, 2020
We at Lalitpur Power Generation Company Limited (LPGCL) believe in constant innovations for continuously improving the existing system in terms of reliability & efficiency in the plant. If this can be done with minimum expenditure and with available resources, so much the better. With this initiative, we at LPGCL have executed some innovative work for improvements, which are as follows…
In Generator Stators, water boxes play a vital role and have the dual function of carrying current as well as water. Due to the way they are designed, these water boxes run the risk of leakage from time to time. Such leakages result in a drop in insulation resistance that can lead to a flashover inside the generator stator.
Conventionally, such a water leak is arrested by the brazing method that requires heating of that particular water box. This is done with utmost care as it involves the use of liquid piped gas and one needs to ensure that the winding bar and other parts do not get affected. In fact, under the brazing method of stopping the leak, water boxes from both sides of the leak point need to be removed to make enough space to tackle the problem. Thus, this can only be done by experts and using the heating arrangement from OEM.
Taking cognisance of the tedious nature of this solution, the team at LPGCL came up with an innovative solution of pouring resin at the leak point under vacuum. In this method, the affected water box, which is connected to the particular winding bar, is kept under vacuum by connecting a vacuum pump from one end of the bar while the other end is dummied. The atmospheric air is then sucked from the leak point and liquid resin is poured in. In a few hours, the liquid resin becomes hard, thus sealing the leak point. Thereafter, the leak point is checked by N2 pressurisation of the particular winding bar followed by hydro test.
This method does not involve any risk as there is no heating process involved. Neither does the team need to remove the surrounding water boxes. Additional equipment like special burners for heating LPG cylinders and heat-resistant insulation is also not required. This can be done by any member of the team. This method was first used in 2018 and has been completely successful.
During the monsoon season, the Coal Bunkers at our LPGCL plant would frequently get choked with wet coal. This would result in tripping of the coal feeder/pulveriser on our ‘no-coal on belt’ section. This regular challenge, along with the non-availability of a coal pulveriser, was impacting the overall declared generation capacity (DC) of the unit. In several instances, oil guns were also used to clear the blockages in the coal bunker.
To counter the damage to generation, the Boiler Maintenance Division (BMD) would hire additional manpower every year during the monsoon season. This additional manpower was deployed at the coal feeder floor to hammer the bunker outlet portion located at a height of 12 meters from the feeder floor. The efficacy of the pulveriser system relied completely on this additional manpower, the flow of coal, and the operation requirement at the time. The additional manpower had to manually clear the chokes caused by the coal by using extremely heavy hammers (each tool weighed almost 10 kgs). Due to this manual intervention, it often took much longer to clear the blockages. Safety was also a major concern as the action of hammering with the heavy tools had to happen at the bunker outlet which is situated at a height of 12 meters. The unit was also incurring an additional expenditure of Rs 18 lakh every year for this additional manpower.
To provide a more cost-effective and safe solution, the team at LPGCL developed an innovative hammering arrangement. On a trial basis, a hammering device was installed at one coal bunker. It essentially consisted of a 100mm MS rod that weighed around 65 Kgs, suspended from a wire rope from the bunker itself. The arrangement aimed to eliminate the manual hammering requirement at the coal bunker outlet chute. The suspended hammer was now guided into a back-and-forth motion to mimic the action of hammering. This did help clear the chokes without the use of too much additional labour. However, delays and safety continued to still be a concern, as manpower still needed to climb up the coal feeder to the bunker outlet gate platform using a monkey ladder.
To address this remaining challenge, and to make the system more user-friendly, it was decided to provide an additional latch arrangement to the suspended hammering bar with the other end extending to the feeder floor. This latch arrangement was done using a pulley system and wire rope with a handle. With this adjustment, the issue of coal flow disturbance is now being responded to faster and with minimal manpower, and more safely.
The LPGCL team is very proud of this innovation which helped save the company approximately Rs 18 lakh per annum and improved operations of the unit.
Real-time plant performance monitoring in term of GHR & THR have been developed in-house and made available to the operator for taking proper and necessary action for proper operation of the unit.
THR & GHR is shown in operator graphics page as below.
In Axial Fans (ID, FD & PA Fans), Hydraulic actuating Device (HAD) is like the human brain that controls fans functions during operation. For testing of the repaired HAD, it was necessary to stop any Fan and after installation, the function of HAD can only be checked. Therefore, to save time in replacement of defective HAD with a tested and repaired HAD, a testing kit has been developed in-house at our Power Station. By doing this, it is possible to make the Fan availed of in minimum time, thereby reducing generation and DC loss.
For efficient operation of the power plant, the cooling towers must be maintained as per design parameters. The condition of the fills in the cooling tower plays an especially important role. To repair and fabricate the fills at the site, an innovative fill pack cutting machine has been designed & fabricated in-house at the site. This has not only saved the procurement cost of damaged fill packs but also increased the availability of cooling towers in the required condition.
Redundancy of CW pumps has been ensured by the interconnection of discharge line of all units by in-house design, fabrication, installation and commissioning. This CW Pump Discharge Line Interconnection Modification has increased reliability and availability of CW pumps, reduction in APC & Maintenance cost.
Main BFP DE and NDE mechanical seals were observed with frequent failures during running and standstill condition. The modification was carried out for DMCW inlet and outlet for both DE and NDE
By this modification seal cooling water temperature is maintained at designed values during BFP running, therefore no frequent mechanical seal failure is observed and has resulted in huge cost saving.
It is needless to cite the importance of the coal handling plant in a thermal power plant. Smooth and reliable operation of CHP is very much required for the availability of the plant. Therefore, a lot of innovative jobs have been carried out at CHP for reliable operation of the systems. Such as capacity enhancement of VGF from 500 TPH to design capacity of 1500 TPH, modification in cooling system of heavy-duty gear boxes of belt conveyor, various innovative ways to restrict coal spillage and dust suppression in belts.