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Pollution Prevention and Control Technologies for Plating Operations
Section 2 - General Waste Reduction Practices
2.3 GOOD OPERATING PRACTICES
2.3.5 Leak/Spill Prevention and Control
Chemical losses from leaks and spills can equal or outweigh the losses due to routine production operations. If small leaks from pumps, filters or tanks go unnoticed or ignored over a long time period, the overall loss can be very significant. Catastrophic losses, such as a tank failure caused by corrosion, will cause more immediate results. Several methods for reducing the potential of chemical losses from these sources were identified from the literature and Users Survey. These include:
- Conduct preventive maintenance of pumps, filters, tanks, etc., as discussed in Section 2.3.4.
- Employ a controlled method of adding make-up water to process tanks (do not permit use of unattended hoses).
- Install overflow alarms on all process tanks and especially on tanks that are heated and require regular evaporative replacement.
- Install double-walled tanks and for added protection install a sight tube that will indicate if a leak of the inner wall has occurred. Two shops indicated use of this method for cyanide baths (PS 124, PS 133) (see note).
- Implement company rules for tank additions and other chemical transfers.
- Construct secondary containment with segregation that would permit reuse of spilled material. For example, install berms around process tanks, external filter systems (PS 149) and pumps (PS 257).
- Install pH, ORP, moisture sensors, and/or conductivity sensors with an associated alarm system in bermed areas (PS 146, PS 155), sumps (PS 089, PS 165, PS 172), drain lines, or around treatment tanks (PS 036). Example: shops PS 089 and PS 165 installed moisture sensing alarms in sumps that under normal operation are dry. Of the 318 plating shops responding to the Users Survey, 50 (or 15.7%) indicated that they have installed overflow alarms on process tanks and 47 (or 14.8%) have installed other spill or leak detection systems (see questions 13 and 14 in Exhibit 2-6).
Note: One of these shops fabricated double walled tanks themselves and installed sight glasses (PS 133). During a follow-up conversation, this shop warned that brass sight glasses, which are most commonly used, are not applicable to cyanide-containing tanks. They suggest using either stainless steel or PVC (PVC sight glass available from U.S. Plastic Corp., Lima, Ohio). PS 133 also suggests placing the sight glass in a protected, front corner of the tank (i.e., should be readily visible but protected from damage).