Problem Solving Article: INDUSTRIAL EXHAUST FAN 

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

The main cook room at the olive cannery where I worked had three rotary cookers manufactured by FMC. All three of the cookers were double pass so there were three rotary chambers for cooking and cooling for each of the three lines.

Two of the lines were 300 cans and the other was for gallon cans. All three cookers were indoors. We had four stationary retorts outside.

The nature of the cookers requires a fairly stable atmosphere. The ambient temperature should be a steady 80 to 100 degrees Fahrenheit.

The industrial exhaust fans on the roof should have been designed to replace the air at such a pace that the temperature remained at around the 90 degree F. range, year around. 

Instead, when the cook room was created in the existing building, dividing walls were installed in such positions that only one industrial exhaust fan was in the roof section over the cook room. When all three cookers were running, the heat would always go over 100 deg. F and steam would collect at the ceiling.

The steam/humidity would rapidly increase till a person would almost need fog lights to navigate around the room. The heat and humidity were extremely unpleasant to work in, especially for the operator/mechanics who spent most of their work day in the room.

The area on the other side of the cook room had three industrial exhaust fans and only needed one. I got our General Contractor, Tony, and we climbed up an access ladder to the top of the roof.

We walked down the crown of the roof to the section over the cook room. There was a place where an industrial exhaust fan had been installed but the exhaust fan had been removed and not replaced.

Two of the industrial exhaust fans from the opposite side to the cook room could be relocated to the cook room rather easily. The conduit and wires could be flipped over the crown of the roof and installed where they landed.

The opening in the roof for the fan was in one section of a metal sheet. It was the same size as a sheet of metal roofing without the fan hole.

The fan would be removed, the fan cover removed, the fan base removed, and then the metal sheet removed. We roped of the opening in the roof. Anyone working in the area had to have a safety belt and line attached to safety d-rings.

The section where the fan would be installed was removed and the area roped off. That section was installed in the hole on the other side.

All the pieces were reinstalled on the cook room roof and the fan was tested. Air rushed out of the housing and pulled steam out of the cook room as well.

We relocated another fan the same way. There was already a closed off fan housing in place over the cook room with no fan installed. I would need to locate an additional fan or purchase a new one.

We searched through our "boneyard" of old equipment and found the old fan and motor. The bearings were bad on the fan drive shaft and in the motor.

The fan assembly was taken to the maintenance shop for overhaul. All four bearings were replaced and new drive belts were installed. The fan tested OK.

Tony's crew installed the rebuilt fan assembly in the empty fan housing over the cook room. That gave us four operating fans in the roof over the cook room.

An electrical crew had been busy installing power and control wiring and conduit from the cook room Motor Control Center.

When all four fans were started at the same time, the cook room steam and heat were pulled up to the ceiling and through the fan housings and discharged into the atmosphere. What a difference. 

The cook room manager and workers were amazed. The manager and some of the crew had worked in the cook room for years and had to put up with all the steam and heat because no one thought to relocate the fans.

The cost of the project was 95% labor and compared to the eliminated downtime, reduced electrical problems from the steam and humidity, and physical comfort of the cook room work crews, the cost was almost nothing.

Almost no one had wanted to do anything in the cook room due to the heat and humidity. Now the cook room was not so off limits.

Each of the cookers had a large, stainless steel collection hood installed over the cooker end where the can entrance was located. Each hood had a high speed (3600 RPM) exhaust fan installed on the roof to pull the collected steam and heat from the cooker up through a steel pipe and through the roof. 

On the roof, a housing held stainless steel, mesh filters to trap and remove olive oil from the exhaust air as it passed through. Oil was dripping onto the roof from places where oil shouldn't have been dripping.

The housing was opened and the filters and housing had not been cleaned in years. All the filters were removed to ground level where they were steam cleaned and then reinstalled.

The housings were wiped down to remove as much of the old oil as possible. The housings had baffles to hold the filters and little troughs to collect the oil and drain the oil to a drain pipe outside each of the three housings.

Everything was wiped down and cleaned as good as it could be cleaned under the circumstances. The filters were reinstalled and the fans started. 

More of the steam and heat was removed from the cook room. If we weren't careful, people would be lining up for work assignments in the cook room.

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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