MWV Air Purification
CASE STUDY CORROSION PROTECTION AT WSACC CONCORD, NC MWV Air Purification Group 5255 Virginia Avenue North Charleston, SC 29406 1.800.348.7196 mwv.com/apg
Air Purification
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Background The Rocky River Regional Wastewater Treatment Plant (RRRWWTP) is a two stage 24 MGD biological wastewater treatment facility that is owned and operated by the Water and Sewer Authority of Cabarrus County (WSACC). In 1995, an upgraded sludge processing system was completed. This system included high solid centrifuges for dewatering and eight control panels. Within six months of start-up, WSACC started to experience PLC card and Centrifuge Back Drive card failure due to corrosion caused by H2S gas. Failure Rates were at one to two failures per month, a costly problem that caused equipment down time. An attempt was made to purge the cabinets with outside air, but this did not help. WSACC even tried coating the boards. Unfortunately, all of their attempts to fix the problem were unsuccessful. WSACC lived with the failures for some time, dealing with card repairs and numerous costly replacements.
“We had battled corrosion previously with spray on products and with vapor releasing in cabinet products, but with unmeasured success.� -Everett Stotesbury, Maintenance Manager
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The Solution Coincidentally, Black & Veach was the engineer on another project on site. This project was to add two MCC buildings and refurbish a 3rd room. Recognizing the potential for corrosion problems with this facility and their experience with another MWV customer (North Charleston, SC), Black & Veach specified adsorber technology to protect these three facilities from corrosion due to corrosive gases. Immediately, WSACC personnel recognized the possibility of using the MWV technology being specified in this new project as a potential solution for their existing control panel problems.
MWV monitored temperature, humidity and room pressurization with our Room Sentry.
MWV did a corrosion study using our coupons to quantify the corrosion rates.
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The exposed coupons were sent to our lab for detailed analysis, and a comprehensive report was generated. 2.0
corrosion rate in microns/year
*This is a SAMPLE report - not project specific
1.5
1.0
0.5 .1 microns/year
0.0
5 Room 1 Room 2
10
15
20
Room Number Room 3 Room 4
Room 5 Room 6
25
30
35
target corrosion rate
Room 7
WSACC decided to add the sourcing and installation of vapor adsorbers for these (8) control panels to the new Black & Veatch project scope of supply. The control cabinets that got MWV adsorbers were: • • • • •
Centrifuge Control Panel (2) Bunker Control Panel (2) Waste Activated Sludge Control Panel Primary Pump Control Panel (2) Thickened Sludge Station Control Panel
The Results Failure rates went from one to two per month to less than two per year immediately, and have become less than one per year as previously damaged equipment has been cycled through.
“....compared to the savings from eliminating the failures, they are worth it” -Everett Stotesbury, Maintenance Manager
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Black & Veatch Based on the success of the project, Black & Veatch presented a paper entitled “Considerations for Adverse/Corrosive Environments in Wastewater Treatment Plants”. The presentation was a case study of this situation at WSACC. Following are some highlights from the Black & Veatch presentation. Please contact MWV if you would like a copy of the actual presentation.
Protection Measures for Electrical Equipment Considerations for Adverse/Corrosive Environments in Wastewater Treatment Plants Matthew Marbois Black & Veatch
Predominant Corrosives
Failure Rate
Equipment Affected
Recommendations
• • • • • •
Hydrogen Sulfide Sulfur Dioxide and Trioxide Ammonia Chlorine Chlorinated Compounds Moisture/Water
All electrical equipment including: • Motor Control Equipment • Switchboards • Panel Boards • Safety Switches • Switchgear and other
• Pre-corrosion protection implementation • 1-2 component failures per month • PLC I/0 cards, processor, & power supply • Nematron LCD Display • Branch circuit breaker (mechanical) • Post-corrosion protection implementation • <2 component failure per year
Recognize electrical equipment is not intended for exposure to corrosive environments.
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MWV Vapor Adsorbers-Equipment for any application Series HM® Cabinet Vapor Adsorber
Carbon Pellet Systems
Ideal for protecting expensive electronic equipment in control cabinets. Available in 40 and 90 CFM models. Series HM® Vapor Adsorber Systems
In certain applications, pellet based systems may be the best choice. The MWV pellet based adsorber systems offer rugged SS 316L construction and are available in capacities from 100 to 6,000 cfm.
Series HM® Recirculation Systems
Available in numerous configurations for new installations or retrofit applications, in sizes from 100 to 30,000+ cfm. Provides corrosion protection, odor removal and contaminant removal in a wide variety of applications. Room Sentry® II
Recirculation type systems offer a certain degree of protection and are suitable in certain applications, especially for retrofit projects. The MWV recirculation systems offer the Versacomb™ technology in a budget conscious package. Fans can be added easily if required by the application. Continuously monitor any space for gases that may cause corrosion or odors. The Room Sentry® II detects corrosion caused by gases such as H2S, SO2, SO3, Cl2, NO, NO2, O3, HF and NH3.
*Series HM products contain Versacomb™ media. 7
Corrosion problem solved.
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MWV Air Purification Group 5255 Virginia Avenue North Charleston, SC 29406 1.800.348.7196 mwv.com/apg