28 September 2023

Steam Turbine Catenary / Slop Adjustments | Turbine Fundamentals and Basics | Basic Aspects of Steam Turbine Maintenance | Part#3 | Content-8 |

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Catenary / Slop Adjustment

Steam Turbine Catenary / Slop Adjustments for Turbine Fundamentals & Basics and Aspects of Steam Turbine Maintenance.

Steam Turbine Catenary / Slop :-
  • When rotors are resting in free condition on their bearings, there will be individual sags in them due to its dead weight and dimensions.
  • Due to above the mating coupling faces of the rotors shall be at an angle. In this condition it is very difficult to couple the rotors.
  • To align the coupling faces the rotors are given vertical adjustment through bearing or pedestal adjustment so that they become parallel and coupling becomes easier. One rotor normally LP rotor is kept as MASTER.
From above adjustment the deflected lines of rotors  also approaches the Center line which reduces the Centrifugal forces on the rotor.

Steam Turbine Catenary / Slop Adjustment:-
  • Correction / Adjustment in the Slope is carried out by making changes in the Pads / Keys of the bottom half of the bearing  .
  • In New design it is carried out by Spring Deck Correction whereby the whole pedestal lift is affected by means of adding/ removing plates/Sheets in the spring deck foundation.


Steam Turbine Catenary / Slop Procedure:-
  • Slope is measured by Water Micro level.
   A.) Precautions:- Before taking slope readings , MICRO LEVEL should be calibrated. It should be calibrated on a Known surface like Lathe machine Bed and then sealed  with lacquer to avoid any disturbance.
   B.) Water Micro Level:- Water Micro level having two water level, one small level perpendicular to shaft axis for setting of Gauge on shaft and other main level for taking reading . Set the reading of micro level to zero –zero datum Place micro level on the Shaft and by a adjusting screw bring the main level position in the Center. Record the reading on the circular scale.
  • To nullify the errors above slopes reading should be taken in the two direction (to minimize the any error of the level), Second one in 180 degree opposite to first position but at the same location( As shown in figure) For this ensure the vertical level is in the center. Before taking second reading again set the micro level to zero-zero datum.
  • Slopes are measured by a micro level one division of which corresponds to slope of 0.1 mm per mtr length
  • Slope to be taken in uncoupled position of rotors.
  • At some sites Slope is directly measured by the water jar gauges kept on bearing pedestals directly connected to each other in series and differential reading is noted.

Steam Turbine Catenary / Slop Check List:- 

Steam Turbine Catenary / Slop Protocal :-

Checking the slope & catenary using Optical composite image leveler


Bearing -1 0.93 Towards MOP
Bearing -2 0.37 Towards MOP
Bearing -3 0.04 Towards MOP

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