SP 8/6 Submersible Pump Rubber Lining Aging Inspection: From Hardness Test to Ultrasonic Thickness Measurement

Subtitle: Shore hardness, ultrasonic thickness, visual inspection – a 3‑step method to accurately assess rubber lining aging and prevent casing corrosion

Introduction

The SP 8/6 submersible slurry pump (200mm discharge, 150mm inlet) is widely used in slurry pits, tailings sumps, and chemical wastewater applications. Its wet end is often rubber‑lined to resist chemical corrosion from acidic media and erosive wear from fine particles. However, rubber is an organic polymer that gradually ages due to temperature, chemical attack, and mechanical stress. Aged rubber becomes hard, cracked, and loses elasticity, eventually leading to lining detachment. The pump casing is then directly exposed to corrosive slurry, resulting in perforation and scrap.

Field maintenance personnel often rely on visual inspection alone, which is insufficient to accurately determine remaining rubber life. This article introduces three field‑applicable methods: visual inspection, Shore hardness testing, and ultrasonic thickness measurement, with replacement thresholds and step‑by‑step procedures. As a professional slurry pump manufacturer, we aim to help users make data‑driven decisions.

1. Signs and Hazards of Rubber Lining Aging

Key point: Rubber aging is gradual. Replacing at the moderate stage has the lowest cost. Waiting until the severe stage damages the casing, multiplying repair costs.

2. Method 1: Visual Inspection (Rapid Screening)

Visual inspection is the simplest initial method, recommended monthly.

Tip: Use a flashlight at an oblique angle to highlight fine cracks. Focus on high‑velocity areas such as the inlet and volute.

3. Method 2: Shore Hardness Test (Quantify Aging)

The most direct physical change during rubber aging is hardening. Fresh rubber lining typically has a Shore hardness of 55–65 Shore A. As aging progresses, hardness rises to 70–80 Shore A or higher.

3.1 Tools

3.2 Procedure

3.3 Interpretation

Note: Different rubber compounds (natural, butyl, neoprene) have different initial hardness. Use measured values from new lining as baseline.

4. Method 3: Ultrasonic Thickness Measurement (Quantify Remaining Thickness)

Rubber lining thickness gradually decreases due to wear and aging. An ultrasonic thickness gauge can non‑destructively measure remaining thickness – the most accurate quantitative method.

4.1 Tools

4.2 Procedure

4.3 Interpretation

Original thickness: Design thickness of new lining (typically 10–25 mm depending on pump size). For SP 8/6, inlet lining ~20 mm, volute area ~15 mm.

5. Combined Decision Matrix

Use all three methods together for replacement decisions:

6. Daily Maintenance Recommendations

Conclusion

Assessing rubber lining aging in SP 8/6 submersible pumps cannot rely on visual inspection alone. Combining visual inspection, Shore hardness testing, and ultrasonic thickness measurement provides a scientific evaluation of remaining lining life, avoiding both premature replacement (waste) and delayed replacement (casing corrosion). Establish a regular inspection schedule and record data for trend analysis.

As a professional slurry pump manufacturer, we offer rubber lining replacement services and on‑site inspection training. For lining aging diagnostics or replacement solutions, please contact our technical team.