MINI-CASE the coupling cover sections are joined by two bolts. There are Cover-S
ID: 367705 • Letter: M
Question
MINI-CASE the coupling cover sections are joined by two bolts. There are Cover-Shield Failure and Falling o nuts used. Incident at R. H. Saunders Hydroelectric Generating (Abridged) At approximately 11:00 a.m. on Saturday, October 30, 1999 a maintenance technician started to open the erection bay door Station from the inside push-buton station on the south side of the door The door had raised approximately 2 metres when he heard a noise at the north side of the door and saw something fall to the erection bay floor. He stopped the door and went to investigate The technician found two halves of a drive-shaft coupling cover and two bolts for securing the coupling cover on the floor. The Marc A. Rosen, UOIT ntario Power Generation's R. H.Saunders Station, located on a dam on the St. Lawrence River near Cornwall, coupling cover was from the north drive-shaft coupling Ontario, is the second-largest hydro power station in Ontario. After the incident, the door was isolated. The coupling cover It contains typical hydroelectric equipment such as turbines, was bolted back on the coupling. Also, the covers on the two generators, a repair shop (called the erection bay), and a 300 other drive shaft couplings were inspected. Two bolts on the ton gantry crane (a moving, four-legged overhead structure) south coupling cover had to be tightened 1/8 turn each. One bolt R. H. Saunders is an outdoor type of generating station, where on the centre coupling cover was tight and the other bolt had to the 16 generators are located across the dam, side by side, and be tightened 1/8 turn. The door was returned to service. are easily accessible by the gantry crane. The crane is used to handle generators in need of repair. It moves on rails and can be moved into the erection bay. The erection bay is a closed structure near shore on the dam, with a huge door that can be opened to let the crane in The incident was reported to the station manager, who rated the incident as "potentially high risk."The level of investigation is more detailed for the high-risk incidents. The door opening measures 20 metres by 20 metres. The door is powered by a motor. A drive shaft runs across the top of the door opening. The drive shaft has sections joined by three chain-type couplings (see Exhibit 1). The cast-aluminum covers that are mounted over the couplings (see Exhibit 2) rotate with The erection bay door is original to the station and mainte nance responsibilities were turned over to the station in January 1960. The 1960 document includes manufacturer servicing instructions. Inspections of door components should be scheduled on a monthly to six-month basis. The inspections should include checks of oil levels, chains, brakes, cables, and gear cases. The maintenance file on the bay door was not complete. It showed that mechanical maintenance was done on the door in 1983, 1984, 1989, and 1996. The work in 1989 was described as "emergency inspection and repair" and was performed by an the couplings as the drive shaft turns to operate the door. The coupling covers are made up of two sections. Each sec- tion weighs approximately 3 kg. The two mating surfaces ofExplanation / Answer
After reading the mini case study following conclusions can be made regarding the incidence happened:
Answer No. 1:
The reason behind erection bay door lead to breakdown during maintenance is clear indication of not following the manufacturer recommendation of the preventive maintenance i.e. "Manufacturer Servicing Instructions". The manufacturer of any machinery or part is the originator of that particular thing and knows better about the wear and tear of the parts or machinery they manufacture. It is always necessary to follow their guideline for the preventive maintenance to avoid any kind of malfunctioning during the course of the machinery run time. The OPG did not develop their own maintenance policy which could be stringent to the manufacturer recommendation or could have at least followed manufacturer's instruction for maintenance schedule, failure to which lead to the breakdown of the erection bay door.
Answer No. 2:
There was not a design problem in particular because the same assembly was working perfectly since a long period of time so that it ruled out the design issue in the cover shield assembly.
However, as defined in the case that the technician was opening the erection bay door from inside the push button on the south side the door and the same time problem occurred in the north side of the door where drive shaft and the coupling cover and two bolts which were securing the coupling cover were got damaged from the north side of the door which indicate that the technician have not followed the "Manufacturer Servicing Instructions" for opening the erection bay door completely which may have lead to the incident.
Answer No. 3:
As per the given details about the incident it seems that there was no adequate documents or guidelines were designed and available readily with the maintenance technician to refer i.e. "Manufacturer Servicing Instructions". There was no adequate emergency breakdown maintenance plan was in place during the day of incidence due to which the incidence happened.
Answer No. 4:
As examining the incidence details, it can be suggested to OPG that first of all they should develop a written document keeping in view manufacturer recommendation for maintenance of the erection door so that it will be easy for any maintenance operator to follow the written procedure while doing the maintenance activity.
It is also suggested that the OPG should have a adequate preventive maintenance schedule to mitigate the risk of any unexpected breakdown and while preparing this PM schedule they should keep the frequency of schedule as per manufacturer recommendation of monthly to six month basis for inspection of door components i.e. Oil level, brakes, chains, cables and gear cases.
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