TBM / Shield Tunneling Slurry

PAM for TBM Slurry Treatment

Tunnel boring machine (TBM) slurry contains ultra-fine clay and silt. PAM enables 70-85% slurry recycling, reducing disposal costs by $50,000-$200,000 per project.

How PAM Works

TBM Slurry Conditioning

APAM at 10-25 ppm conditions TBM slurry for separation. Ultra-high MW APAM (20-28M) is often needed for fine particles.

• Molecular weight: 20-28 million Da
• Hydrolysis degree: 25-30%
• Settling time: 2-4 hours

Case Study

Metro Tunnel: 5 km length, 80% slurry recycling, $180,000 disposal cost savings

Product Selection Guide

Dosing Tips

1. Always jar test first. Application-specific wastewater requires optimization. A 30-minute jar test saves weeks of field trial.
2. Prepare fresh solution daily. PAM solution degrades after 24-48 hours. Use chlorine-free water.
3. Gentle mixing. High shear breaks polymer chains. Use 30-50 RPM for 5-10 minutes after PAM addition.
4. Monitor for overdosing. Too much PAM causes charge reversal — flocs redisperse and turbidity increases.
5. Batch consistency matters. We test every batch for MW (±0.5M tolerance) and retain samples for 24 months. If performance varies, it's a supplier problem, not a PAM problem.

Frequently Asked Questions

Why does my PAM performance vary batch to batch?

This is almost always a supplier consistency problem. Trading companies source from whoever is cheapest each month. We are the factory. Every batch is tested for MW and charge density. If you have a performance issue, we can compare your batch against retained samples.

Can I use the same PAM for clarification and dewatering?

Not optimal. Clarification needs APAM (anionic) at low dosage. Dewatering needs CPAM (cationic) at much higher dosage. Using one grade for both is a compromise — you'll either over-dose or under-perform.

What is the shelf life of PAM?

Properly stored (sealed bags, dry warehouse, below 35°C), PAM powder lasts 2-3 years. Once opened, use within 6 months. Emulsion PAM: 6-12 months sealed, 3 months after opening.