Steam Turbines, particularly in corrosive or harsh environments, often need main throttle valve replacement or retrofit. Olsen Actuators use its expertise to ensure the latest technology allows more efficient reliable production and processes, with actuators that are more resilient and reliable and can give complete control.
Achema is the largest privately owned company in Lithuania and the largest fertiliser producer in the Baltic states. It exports 79% of its 2.7 million tonnes a year from the 3km2 plant in Jonava, central Lithuania, where 1,300 people are employed.
Achema’s plant was built in the 1960s. Natural gas is imported from Russia and ignited to drive steam turbines to drive compressors pumps, fans and generate power. Nitric acid and ammonia are produced and in the atmosphere, where ambient temperatures can reach 40-50oC. If the actuators fail the turbines stop as the actuators control the main throttle valve for steam with no emergency stop valve. Every turbine stop halts production and costs 3 million Euros. Actuators need to work reliably in these harsh conditions.
Olsen Actuators was contacted because of its experience in power and steam generation retrofits. It quoted to a specification within a week, receiving the order a few weeks later, to finalise 10 weeks of manufacturing time and the inclusion of engineer commissioning, servicing plan and management.
Since then, six years ago, Achema order actuators once a year, to their budget and upgrade a turbine once a year on shut down. Olsen has just completed a technical presentation to their 20 engineers and technical director as part of this year’s installation.
Olsen recommended Exlar GSX50 and GSX60 with Exlar SV and Control Techniques M700 drives. The drive electronics are separate as larger drives are needed because the actuators are high power, operating at about 3-5 tonnes worth of thrust with an actuation distance of 150-250mm. The actuators need to be extremely reliable and explosion-proof to Class 1 Division 2 in Zones ABCD as there is ammonia in the atmosphere and nitric acid in another plant nearby.
There are some special features to ensure the long life of the actuators. This includes stainless steel trunnion mounts with double anti-rotate guide arms, stainless steel main rods, front protective bellows an EXD terminal box (to ATEX standards) and 60-metre high-temperature cables in case they touch the turbine case; it can be very hot. They also have a type 3 hard coat to avoid any corrosive casing damage from the acid and alkaline environments.
Originally SV drives from Exlar were supplied which had easy Windows-based front end software. For the latest sets, Olsen has supplied the Unidrive M700 with some bespoke Olsen software which allows Visual Basic, easy to use front end software. The valves can be configured and calibrated for the open and close positions without programming skills. Each actuator has a 4-20mA input to Olsen’s control system, unique for an actuator of this size, which we convert for the drive system.
The drive system is backed up by a battery UPS system such that if the mains power fails they have got a backup.
Improved Product Output
Reduced Maintenance Costs
To date, Olsen Actuators has supplied six actuators with the seventh due.
Now Achema can control the turbine speed regulation to 0.1 rpm which allows them to control very accurately, which is unique and helps plant efficiency.
Piers Olsen, who recently visited Achema and ammonia plant No2 where there are three Olsen specified actuators said; “Olsen Actuators are known in the industry for offering quality reliable solutions that can easily be installed or retrofitted into existing small turbines rated under 50MW. These are the cantilever design turbines with a fulcrum where the actuator controls the steam valve directly. These relatively small turbines are produced by companies like Siemens, Alstom, Peter Brotherhood, Dresser-Rand, Escher & Wyss also Mitsu, or the Russian St Petersburg company LMZ. Exlar solutions have been installed in over 1,000 turbines as retrofits in Eastern Europe and are also used for gas turbines by other large OEMs; over 5,000 globally for turbine valve control. Olsen Actuators can help.”