Foam property tests to evaluate the potential for longwall shield dust control

Area of Science:

• Mining Engineering
• Occupational Safety and Health
• Materials Science

Background:

• Respirable dust in coal mines poses a significant health hazard to workers.
• The Mine Safety and Health Administration (MSHA) has set a lower respirable dust standard of 1.5 mg/m³.
• Foam agents are being reconsidered for dust control in underground coal longwall operations to meet these standards.

Purpose of the Study:

• To evaluate the properties of four foam agents for their suitability in longwall mining dust control.
• To classify foam agents based on their expansion ratio and water drainage characteristics.
• To identify foam agents that can help mines comply with MSHA's respirable dust regulations.

Main Methods:

• Foams were generated using two distinct methods: compressed air and water pressure, and low-pressure blower air with water pressure (using a NIOSH-developed generator).
• Foam properties were assessed through expansion ratio tests and water drainage tests.
• Foam agents were classified based on their performance in these tests.

Main Results:

• Compressed-air-generated foams exhibited low expansion ratios (10-19) and high water drainage.
• Blower-air-generated foams demonstrated higher expansion ratios (30-60) and lower water drainage.
• Two foam agents were eliminated due to poor expansion ratios; the remaining two showed adequate properties for dust control.

Conclusions:

• Foam agents with expansion ratios between 30 and 60, and lower water drainage, are stable and suitable for longwall dust control.
• The tested material property assessments are effective in classifying foams for mining applications.
• Further testing of the two promising foam agents is warranted for practical dust control implementation.