Problem Solving Article: ROOF WALKWAY KAIZEN

Eighth Article in a Series of Problem Solving Articles in an Industrial Setting

The roof of the main cannery building where I worked had 20 large exhaust fans installed. The roof exhaust fans were driven by 3 Horsepower, 460 VAC electric motors.

The painted, steel housings had a self closing set of doors that opened from the air pressure exerted when the fan was running. Olive oil and dust collected on the fan equipment and housing walls from the large amounts of air pulled through the fan opening.

The oil would collect to the point that, if not cleaned, the oil would drip down onto whatever was underneath the fan. The roof exhaust fans were located over areas that made it impossible to reach the fans to work on or clean them.

I decided that the fans would have to be pulled from the roof, with their housings, and brought to ground level for cleaning and repairs. There were no walkways on the roof and walking on the thin sheet metal was scary. From below, you could watch where a person was walking on the roof from the depressions in the ceiling.

Part of the crew had just completed replacing a large number of worn and unneeded planking from the Process Plant tank farm. These planks could be used on the cannery roof for a walkway.

The planks were raised to the roof using our large, 5-ton forklift. There were enough planks to run the length of the area where the fans were installed and to reach the fan locations.

We laid out the planks and, one-by-one, removed the fans in their housings to the roof edge. The big 5-ton forklift was used to pick up the the fans and lower them to the ground level.

The roof exhaust fan and housings were steam cleaned. The motors were removed to the shop for further cleaning and bearing replacement. The gearbox and drive shaft were removed.

The oil in the gearboxes was removed and the bearings replaced. The gears were checked for wear, but they were in good condition. The oil was low and in bad condition.

Each roof exhaust fan was thoroughly overhauled and repaired. After everything was replaced in the housing, the fan was test ran on the ground. 

The motor amperage was checked against nameplate ratings; noise was okay; and motor, gearbox, and fan blade were checked for vibration. Each unit was checked out and then replaced on the roof and reinstalled. After reinstallation, the fan was again tested for correct rotation and vibration.

We returned to the plank walkways when all the fans had been cleaned and overhauled. The planks were good lumber, ten feet long, 2" X 12". The roof supports underneath the metal skin were every 5 feet. 

We could build a support to be fastened through the roof every ten feet with a middle support attached to the center of the plank at five feet. The end support would have to fit the curvature of the roof and support two planks.

The roof that the fans were located on was 300 feet long. We would need to fabricate 30 of both type of supports and install them. The planks installed to and around the fan housings were bolted directly to the supports.

The contractor and his crew jumped on the planks and installed them rapidly. The whole setup looked good when completed.

The electricians were tasked with installing conduit and wires for 120 VAC outlets on the roof. The mechanics installed air and cleaning water to the roof so most of the work could be done on the roof. Periodically, the fans would still need to be removed for cleaning.

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Author: Larry Bush 
Profile: Electrician in industrial, construction, marine, and food industries for 47 years, with 22 of those years in management.
URL: http://www.reliability-consultant.com