For the first time in India, Desein had designed and constructed single pass tower type design boilers to produce 690 tonnes per hour of steam at a temperature of 540°C and a pressure of 156 ata. The drum type boiler is equipped with horizontal drainable heating surfaces.
The entire boiler including the platforms at various levels is suspended from the steel ceiling girders. A passenger lift and freight lift is provided in the pylons for access to various platform levels. Pylons are suspended on well foundations sunk and anchored to hard rock.
This design is particularly suitable for Indian Thermal Power Plants because of the high ash content in coal available for burning in Thermal Power Stations and of the highly corrosive nature of the ash. The type of design allowed location of coil bends and headers away from the flue gas path prevents directional change of flue gas in the high dense areas of tube locations and lower flue gas velocities - all contributing to much reduced ash erosion on tubes.
This design contributes to cleanliness of the station. It reduces import of high quality steel required for the heavy columns of the Boiler and utilizes locally available cement instead. The cost of structures is also reduced by about 10%.
DESEIN is amongst the first Engineering Consultants which introduced the concept of Coal Mills at the backside of the Boiler and in between Boiler and ESP. This arrangement enabled Turbine House to be free from coal dust and ensured cleanliness of Turbine House, Control Room, Switchgear Gallery, etc.
DESEIN has adopted such Mills in Thermal Power Station with the objective of reducing coal mill outage for maintenance and elimination of Mill Rejects Handling System altogether.
The source of substantial expenditure in thermal power stations is found to be the use of oil during boiler light-up. Use of DIPC burners help instant start-up of boiler using pulverized coal and these burners are ignited by spark ignition. Dependence on oil for start-up, stabilization and loading is eliminated resulting in drastic reduction in use of fuel oil. This system has been adopted in Vijayawada Thermal Power Station Units # 3 & 4.
This type of system was also introduced in the Vijayawada Thermal Power Station units engineered by DESEIN. This system enables reduction in the auxiliary power consumption because of high efficiency over a wide range of speed, smooth start-up of motors and no limitation in the number of starts, results in the increase of life of motors and integration with the main Instrumentation System.
Spring mounted vibration isolation systems were adopted for the foundation of TG sets, Coal mills, FD, PA and ID fan foundations. The provision of vibration isolation system isolates the equipment vibrations from the sub-structure and foundation and reduces the loading on it to static loading, thus providing for considerable saving in cost and time required for design.
The vibration isolation system consists of provision of a number of spring units along with visco-dampers, under the foundation deck slab. The vibrations of the machine and the deck slab are absorbed by the spring units and only static loads are transferred to the supporting sub-structure. With this system, the vertical alignment of the machine can also be adjusted, if required, while in operation, without stopping the machine. A techno-economic study carried out for a 500 MW TG foundation, showed that the cost of the foundation with vibration isolation system worked out less than the conventional foundation, even after allowing for the cost of spring units.
Use of light weight colour precoated galvalume metallic sheets for external cladding for the main power plant building, instead of the brick/block masonry walls, is a new concept in cladding which is being extensively used for the wall and roof cladding of power plant buildings.
The metallic cladding comes in two types (viz.) single sheet cladding, and double or sandwich cladding which has outer inner sheets with a layer of insulation in between. The double skin cladding is provided wherever the inside temperature of the building is to be maintained at a constant level especially in areas where extreme ambient temperatures are experienced due to seasonal changes.
The metallic cladding gives a neat aesthetic appearance to the building. This cladding is easy, clean and fast to install and does not require any maintenance. The colour coated sheets are ultraviolet stabilized and do not need any repainting during the entire plant life of 20 to 25 years.
Brushless excitation with rotating diodes is provided eliminating the problem associated with slip rings due to vibration, wear of brushes etc. as is the case with the conventional static excitation.
Single pass condensers are installed with cupro-nickel tubes. High pressure and low pressure heaters in the regenerative cycle are provided with horizontal U-tube construction for effective drainage.
A highly sophisticated electronic system is provided for Automatic Turbine Run up System (ATRS). This is integrated with turbine stress evaluator to compute stress margins for permitting a safe loading of the turbine.
Instrumentation Controls are based on the highly sophisticated Digital Distributed Control (DDC) system with computers etc.
DESEIN has built up since the last several years rich experience in engineering of Digital Distributed Control system for power station applications. It has also engineered a number of Microprocessor based Programmable Logic Controllers (PLC) for plant interlocks and sequential controls as well as for control of auxiliary plants such as coal handling plant, ash handling plant, etc.