Keeping Up with Chromium MACT Standards

Article From: Products Finishing, , from Hixson, Inc.

Posted on: 6/1/2003

In review of the June 5, 2002 Federal Register, U.S.

In review of the June 5, 2002 Federal Register, U.S. EPA is “proposing” changes to the current Chrome MACT Standard (40 CFR Part 63) that will have a “positive” influence on the plating industry. The four proposed changes include 1) the use of fume suppressant by hard chromium platers; 2) the use of enclosing tank hoods; 3) the definition of a tank; and 4) the pressure drop for systems with composite mesh pads (CMP). The following is a brief summary of each proposed change.

Fume Suppressants

This proposal would allow hard chromium electroplaters using fume suppressants for emission control to meet a U.S. EPA “set” surface tension limit similar to the requirements for decorative chromium electroplaters and anodizing facilities. Facilities choosing this method would be required to monitor the surface tension at the same frequency (once every four operational hours to once every 40 operational hours after one week) as that currently of the decorative electroplaters to demonstrate compliance. The proposed “set” surface tensions limits using a stalagmometer would be 45 dynes/cm and using a tensiometer would be 35 dynes/cm.

Enclosing Tank Hoods

The current standard does not recognize enclosing tank hood, that is, hoods that discharge into workspace as a control technology. Hard chromium electroplating tanks using this method of chromium mist control would have the option of meeting an alternative and equivalent site specific mass rate emission limit instead of the present concentration limit of 0.03 mg/dscm for small facilities and 0.015 mg/dscm for large facilities. In order to take this route, the ventilation rate cannot exceed 1/2 the ventilation rate of a comparable open surface tank with the same surface area of 250 cfm/ft2 equipped with conventional hooding and ventilation.

Tank Definition

The current standard has been interpreted that the replacement of an existing chromium-plating tank (i.e., due to wear and tear) with a new tank of exact same size and construction would constitute a “new source”; therefore they would be subjected to the new tank total air pollution rules and regulations such as Permit-to-Install, Permit-to-Operate, Chrome MACT Standard and possible lower emission limitation. U.S. EPA has come to realize that enforcing this rule would cause many facilities to avoid necessary tank replacement and increase the potential harm to the environment due to possible spills.

The proposed standard’s tank definition would be expanded to include ancillary components, such as rectifiers, anodes, heat exchanger equipment, circulation pumps and air agitation systems. These components would then be included in the 50% fixed capital cost calculation for determining reconstruction.

Pressure Drop for CMP Systems. The current standard requires these systems to be operated at all times within +/- one inch of water column of the pressure drop values established during the initial or subsequent performance stack test. U.S. EPA has collected information to demonstrate that CMP systems operating outside the +/- one inch of water column are still meeting the required emission limit. Therefore, U.S. EPA is proposing to change this operation limit to +/- two inches of water column.

U.S. EPA is expected to make the rule changes effective in June of 2003.

 

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