Industrial Utility Efficiency

# Foundry Air Compressors Out of Control

Quite a number of worst-case compressed air scenarios have been encountered over the years but none may compare to the conditions that existed in a metal foundry somewhere in North America. For reasons you are about to discover, we will not reveal the name of this factory or its location, in order to protect the innocent from embarrassment.

##### This poorly maintained air dryer operated for many years even though it had no load.

This manufacturer historically had a great deal of difficulty keeping their air compressors and air dryers running. Typically, after a number of compressed air system shutdowns were experienced the compressed air service provider would get the blame and be fired only to be replaced with a new firm. This had continued over the years, with each local vendor trying numerous solutions to attempt to keep the system running. Each competing vendor rarely communicated any maintenance history to the other.

After attending a Compressed Air Challenge® seminar the maintenance staff at this foundry decided to hire a compressed air auditor to look into their system and suggest solutions. The audit discovered poor compressor control, poor operating conditions and high system waste were costing this manufacturer thousands of dollars per year in wasted energy and maintenance. What follows is a general description of what was found and what was done to improve the system.

### Ambient Conditions

The ambient conditions in this factory were terrible for air compressors. A layer of soot and metal dust deposits was on anything stationary, quickly turning the cleanest of new equipment to shades of black. Since large electric arc furnaces are used to melt steel for the product, the heat expelled raises the building temperature in some areas to very high levels, even on cold winter days. Since the dust was everywhere, formed by the vapors rising from the molten metal being poured into molds, and generated by the grinding operations, any air cooled equipment cooling surfaces would be quickly clogged. Because of this, the air compressors and dryers were liquid cooled. Unfortunately, the cooling water used for this equipment was also used to cool other processes and was full of contaminants.

### System Configuration and Baseline

This manufacturer had a system of four 150 hp water-cooled lubricated rotary screw compressors grouped in two separate compressor areas, which were separated by about 600 feet. These compressors were operating in modulation control mode, partly due to the poor condition of the units, and partly because it was difficult to coordinate any other type of control across the plant and the significant pressure differential across the filters and dryers. This system used water-cooled non-cycling refrigerated dryers experiencing shutdowns due to water contamination and high inlet temperatures.

### Benefits of System Analysis

The plant was obviously having problems than needed attention, but it took a compressed air system audit to come up with a list of issues to improve. Because an audit was done, plant management received documentation of their baseline energy consumption, and a list of potential improvements that could be used to apply for external energy efficiency funding. As a result, the project was implemented and the system greatly improved, not only increasing the reliability and pressure stability, but also reducing the cost of operation.

For more information visit the Compressed Air Challenge® website or contact Ron Marshall, Marshall Compressed Air Consulting, tel: 204-806-2085, email: ronm@mts.net.

To read more Air Compressor System Assessment articles, visit www.airbestpractices.com/system-assessments.