| Turbine developments
Vortex products so that they perform optimally in each individual steam turbine.
Tip seal leakage
Apply Vortex Shedder® here
Tip & shaft leakage ~ 1/3 of typical stage
Apply
Guardian® here
Above: Where Vortex Shedder®
leakages
tip seals and Guardian®
about to occur, the posts of the Guardian packing ring will push the seal teeth away from the rotor. This protects the delicate teeth from potential damage and maintains the efficiency and integrity of the seal. Unlike other packing designs, Guardian packing rings maintain a positive radial seal during start-up, shutdown, turning gear operation, and unit operation. Since seal efficiency and longevity are increased, the unit heat rate between overhauls is better maintained.
Vortex Shedder tip seals work by creating vortices at the admission side of the seal. These vortices create a pressure barrier at the tooth, lowering the change in pressure across it, which reduces leakage and increases seal efficiency and longevity. These seals can be installed in any location on any OEM steam turbine. The Vortex Shedder has been proven to increase unit efficiency above design by 1.5% to 4.5%. It also helps lower EPA regulated emissions per megawatt and the overall increased unit efficiency results in lower operating costs. The Vortex Shedder can be employed in reaction steam path designs where it can be applied to the rotating seal strip and the stationary seal strip. This reduces the pressure drop, resulting in lower flow and less leakage across the seal. This also means improved stage heat rate performance for the turbine.
Two case studies ● Case 1: Guardian/Vortex installed in HP/
IP, GE D11 steam turbine, 1050°F/1800 psia, nominal 200 MW
For this installation, the expected HP efficiency increase with new conventional seals was 2.1%. After installation of the Guardian packing rings and Vortex Shedder tip seals the efficiency gain was measured to be 3.5%, giving the plant owner an additional 1.4%.
● Case 2: Guardian/Vortex Installed in HP/IP, Toshiba steam turbine, nominal 200 MW With this system, the expected HP efficiency increase with new conventional seals was 1.9%. After installation of the Guardian packing rings and Vortex Shedder tip seals, the efficiency gain was measured at 2.8%, achieving a 0.9% efficiency improvement relative to retrofit with conventional seals.
rotor
packing rings are applied
On-site installation The installation process begins with a comprehensive measurement and assessment phase.
Performance data is also collected, so that the new seals can be designed, manufactured and installed to meet the exact specifications required.
All of the collected information is reviewed, and the data used to modify the MD&A Guardian and
rotor
less loss
The MD&A installation team fits the new seals and, thanks to its containerised machine shop, can correct out-of-round conditions. The goal is to have the steam turbine up and running at a performance level that exceeds where the machine was prior to the retrofit. A major benefit of having custom on-site installation is that the team can go above and beyond just replacing the seals. For example, they will make adjustments during design or installation to compensate for issues such as holder distortion, dished diaphragms, mis- alignment issues and bowed rotors.
Significant performance improvement
MD&A’s innovative Guardian and Vortex advanced sealing systems have been installed in over 350 units to date, representing all the major steam turbine manufacturers, and the result has been significant efficiency increases, reduced performance degradation, and, overall, lower operating costs.
For further information contact MD&A Parts Division, +1 (518) 885-3199,
info@MDAturbines.com
Guardian®
Without Guardian®
cause immediate damage to
Guardian®
Guardian®
Guardian® posts
protect teeth
Above: Guardian® packing ring, how it works
www.modernpowersystems.com | July/August 2022 | 33
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