A Pioneer in Power Joins Hands with an Innovator in Valve Technology

A pioneer in the Indian power sector, Tata Power has been an eminent private utility in India since 1922. With total installed capacity of 2,300 MW (including Hydro and Thermal) Tata Power is among India ’s largest private sector power companies.

A true trailblazer, Tata Power was the first in India to introduce a 63 MW unit in the 50s, the first to introduce a 150 MW unit in the 60s and again the first to introduce a 500 MW unit in 1984. Tata Electric Companies (TEC), a subsidiary of Tata Power, currently operates 4 thermal units at Trombay. TEC has been providing power to Mumbai (formerly Bombay ), the most industrialized city and commercial hub of India , for the last 80 years.

High reliability, continuous availability and the highest operating efficiency are the hallmark of TEC. Before CCI DRAG® technology was introduced to the Trombay plant in 1996, TEC engineers had experienced many problems with control valves in a variety of critical applications. These applications included boiler feedpump recirculation, SH and RH steam desuperheating spray control, startup feedwater regulator, soot blower pressure control, CC pump seal injection control, fuel oil flow control etc. Maintenance engineers at the plant were looking for a permanent solution to control valve problems. These problems were causing continuous maintenance headaches, involving unwarranted expenses for spare parts, manhours and plant/equipment downtime.

Introducing DRAG® Technology in 1996

TEC found the permanent solution in CCI’s DRAG® technology in 1996. The first introduction was a startup feedwater regulator in Unit 4 (150 MW). Operation and maintenance engineers were pleased with the performance of this CCI valve right after the unit restarted smoothly following an outage.

This was followed by an installation of a superheat spraywater valve at Unit 6; the existing valve was Copes Vulcan. CCI offered a solution with customized DRAG® trim of 12 pressure reducing stages to replace the existing super cascade trim. CCI DRAG® trim controls high fluid velocities at the trim exit, which prevents damaging effects such as erosion of the plug and seat and consequent leakage. In addition, with long stroke and fine resolution, CCI’s spraywater valve offered fine control at all flow levels.

Based on excellent performance of the first spraywater valve, TEC ordered another spraywater valve in 1997. This was followed by a succession of DRAG® valves in different critical applications such as full load feedwater control, SH spraywater control, fuel oil flow control etc

Meeting Feedwater Demands in 1999

TEC had a successful experience with CCI DRAG® valves in the main feedwater regulator application too. In January 1999, CCI provided a main feedwater regulator for Unit 7 of the Trombay plant. This feedwater regulator was a replacement for a motorized inching bypass in the 180 MW combined cycle unit commissioned in 1993. Since its installation, the customer had experienced problems with the locally supplied inching bypass valve, namely heavy leakage due to trim erosion. CCI provided a replacement that would operate from startup to full load in what has proven to be a successfully operating valve. Benefits of a combined startup and main feedwater regulator include reliability of startup, elimination of problems experienced during transition from startup to main valve, increased production due to faster startup, and prolonged time between maintenance.

Additionally, Unit 7 also ordered CCI DRAG® valves in 2000 to replace existing spraywater valves that were leaking heavily and were posing control problems.

Spraywater Header Pressure Control in 2001

Spraywater header pressure control is a tricky control valve application. In this application a valve experiences a very high differential pressure when used during startup. This results in very high vibration, destruction of the valve seat and plug and lack of control.

The original valve (Unit 5, installed in 1984), a Copes Vulcan make, vibrated so violently that plant operation engineers never used it after the first startup. This had a detrimental effect on the steam temperature control during startup and operators had to be extra cautious controlling the steam temperature. This obviously complicated the startup and caused many inefficiencies and difficulties.

In 2001, TEC engineers approached CCI for a solution to this difficult application. After careful analysis of the situation, CCI offered a valve with 16 stage trim to handle the pressure drop of 4250 psi (300 kg/cm2) across the valve. In addition a piston actuator, a smart positioner and fast response controls were provided for quick response to any changes in control signals.

CCI’s header pressure control valve was successfully installed in February of 2002 and to great pleasure of Tata engineers, the valve operated very smoothly without any vibration. Along with the spraywater header pressure control valve, Unit 5 also commissioned 100% feedwater regulator in motor driven BFP discharge and a fuel oil flow control valve in February of 2002. Since the installation of these valves, Trombay has reported very smooth operation with no sign of vibration at all.

All severe service applications are not the same: this makes the details of each application all the more important. By customizing the control valves to the application, operating conditions and characteristics, CCI offers solutions that optimize performance.

In a short period of six years since the first CCI valve was installed at Unit 4, the name “CCI” has become synonymous with “severe service” at the Trombay site and “velocity control” has become a mantra of TEC maintenance engineers.

Published in SOLUTIONS Spring 2002