CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

One method used blasts of high-pressure air. This cleaning process, known as “shaking the bags,” was
initiated by pushing a button on a control panel in the blend room; however, this could be done only when
the mat-former was not processing material. The blast of high-pressure air dislodged the dust from the
bags, and it settled in the bottom of the baghouse.
The second method, performed daily during shift line cleaning (Section 4.2), required CTA employees to
manually strike the bags with a stick to remove the dust cake. This cleaning procedure was covered in a
written Job Safety Analysis, which provided instruction on the hazards associated with cleaning the
baghouse, including the risk of explosion.
The residue that collected in the bottom of the baghouse could be either automatically recycled to the
process or manually removed as waste during shift cleaning. If the material was recycled, it was returned
to the processing line via a conveyor and then dropped through a vertical pipe containing a rotary airlock 8
before being deposited into the residue feeder. In December 2002, the use of the residue feeder on line
405 was discontinued because of a process change, and the baghouse residue was manually removed by
dropping it through a chute. The residue fell into a cardboard box placed under the chute on the blend
room floor.
4.1.3 Curing Oven
The mat exited the mat-former on a conveyor. Facing 9 was applied above and below the mat just prior to
it entering the curing oven. Chain-driven oven flights sandwiched the mat and guided it through the oven.
To reduce friction, a pneumatic pump dispensed oil rated for high-temperature use to lubricate the chains
and sprockets.
8 A rotary airlock is a valve that contains a set of rotating pockets that mechanically pass solids while preventing
excessive return flow of air or gases. This device was necessary for the baghouse to maintain its suction.
9 Facing is thin plastic nylon sheeting, which arrived at the facility on a spindle. One roll of facing was positioned
above and another underneath the discharge conveyor of the mat-former.
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