Attachment B JD Bridge Crane Load Cell Investigation - 4_27_21_Redacted.pdf

HYDROELECTRIC DESIGN CENTER

MEMORANDUM FOR RECORD

SUBJECT: Bridge Crane Overloading Investigation

PURPOSE: The trip was conducted to investigate high load readings on the bridge crane during the Unit 12 turbine lift.

DATE ON SITE: April 27, 2021

HDC Personnel:

John Day Personnel:

Executive Summary traveled to John Day to witness the Unit 12 turbine lift performed by on April 27, 2021. A meeting at 0700 with and Corps personnel was held to discuss safety and the procedure for the lift, the expected weight of the turbine assembly was stated to be 375 tons. At 1000 the turbine lift began, and Corps personnel boarded the north bridge crane with operator to investigate the overloading issue. The load was maneuvered from being staged near Unit 10 and into the hole of Unit 12. The load cell readings were recorded during the entire lift and collected on a laptop through the PLC and saved in an excel file for processing. Each of the two load cells were reading (approximate values) 208 tons while the load was suspended, 205 tons while raising the load, and 212 tons while lowering the load. The rating of the bridge crane is 385 tons and the observed load readings were around 9% above the rated load. Project staff reported that load cell readings were similar on the South bridge crane as well.

HDC recommends load testing both the north and south bridge cranes with a known test weight (water bags, concrete blocks, etc.) to check if the load cells are accurate. Further recommendations will depend on the results of the load test.

Figure 1: North Bridge Crane Lowering Turbine into Unit 12 Pit

Figure 2: Crane HMI While Lowering Load

Figure 3: PLC Display While Lowering Load

Turbine Lift Procedure The turbine was attached to both the upstream and downstream trolleys with the turbine assembly lifting links for tandem operation. The load was slowly applied to the crane until the turbine was five inches off the ground. This position was held for a five-minutes to ensure the brakes were able to hold the load. The load was then lifted enough to install the nose cone at the bottom of the turbine. Once the nose cone was installed, the turbine was lifted above Units 10 and 11 and bridged over to Unit 12 where it was lowered into the hole. See Figures 2 and 3 for PLC and HMI display readouts while lowing the turbine into the pit.

Load Cell Reading Data During the lift, was in the operator cab monitoring the human machine interface (HMI) readings while were on the bridge walkway monitoring the laptop collecting load cell data from the programable logic controller (PLC). These are the following maneuvers that were being monitored:

Suspended Load

This is the stabilized weight reading while the turbine is just hanging from the crane and not raising, lowering, or stabilizing from stopping. While the load was suspended, each load cell reading was roughly 208 tons which is a total load of 416 tons.

Raising/Lowering

The load cell reading while raising or lowering was a few tons below or above the suspended weight reading. This is because the PLC only scales the 4-20mA input from the load cells to tons (output to HMI) and does not account for any reeving friction affects while raising or lowering.

The load cells were reading 205 tons while raising and 212 tons while lowering.

Stop

After the load was being raised or lowered and came to a stop by moving the master switch to the neutral position, the load cell readings would adjust quickly with little oscillation. After lowering operation, the load cells would adjust from 212 tons back to 208-209 within a few seconds. Also, after a raising operation the load cells would adjust from 205 tons back to 208- 209 within a few seconds.

HDC Recommendation HDC recommends load testing the north bridge crane with a known test weight (water bags, concrete blocks, etc.) to verify if the load cells are accurate or if they are reading high. It is a possibility that the actual weight of the turbine assembly is the 420 tons that was measured on 4/27/21 and that the documented value of 375 tons is incorrect. If the crane is load tested to 100% rated capacity (385 tons) and the load cells are reading correct, then the documented turbine assembly weight of 375 tons is inaccurate. If a 100% load test of 385 tons is still reading ~416 tons, the load block sheave bearings and shafts will need to be inspected for damage and/or load cells will need to be recalibrated. It would also be possible to perform a load test on each trolley separately with a lighter known weight to check the load cell calibrations. Although not as conclusive as a 100% load test it would provide good confidence in the observed higher load readings. Further recommendations will be considered based on the results of the load test.

Conclusion and traveled to John Day to witness the Unit 12 turbine lift performed by on April 27, 2021. The expected turbine assembly weight was 375 tons and the weight observed on the load cells was around 416-420 tons which is 9% over the rated load of the crane.

HDC recommends load testing the north and south bridge cranes with a known weight to check if the load cells are accurate. Further recommendations will depend on the results of the load tests.

The load cell data files and photos/videos taken during the trip on 4/27/21 are in the following folder:

Y:\Projects\John Day-CENWP\_ArchivedJobs\Crane-Bridge Cranes Rehab-2005\Overloading Investigation 2021\Site Visit 4.27.21 - Turbine pick