Using pipe pigs to remove dusty deposits from pressurised pipelines (DN47 - DN50)

Case Study: Removing Hygroscopic Powder Residues from a Stainless Steel Pipeline

In a number of industrial production processes, powdered materials are transported through pipelines using air pressure. Over time, things can build up on the inner pipe wall, especially when you're moving materials that soak up moisture. These deposits can cause problems, like contamination, reduced efficiency or more maintenance.

A recent customer project demonstrates how such challenges can be solved efficiently using a carefully designed pipe pig cleaning strategy and a combination of specialised pipe cleaning pigs from MOWOTAS.

In general, pipe pigs—often manufactured as flexible foam pigs—are cylindrical cleaning tools that travel through pipelines. As they move through the pipe, the pipe cleaning pig presses against the inner wall, removing deposits and pushing the loosened material out of the system.

Pneumatic conveying in the food industry

Our customer operates a pneumatic pressure conveying pipeline made of stainless steel with the following specifications:

• Nominal diameter: DN 50
• Internal pipe diameter: DN 47
• Pipeline length: approx. 25–30 m
• Height difference: approx. 12 m
• Pipe condition: slightly contaminated
• Pipeline layout: several bends

The system transports a powdered product – dried pea fibre. This hygroscopic material absorbs moisture from the surrounding air, which gradually leads to deposits forming on the inner pipe wall.

Characteristics of the Residues

• Particle size of the removed material: approx. 30–60 µm
• Deposit thickness: approx. 1–3 mm
• Several bends within the pipeline

Over time, a continuous dust layer forms along the pipe wall. This layer can be removed effectively using a pipe cleaning pig that is inserted into the pipeline and propelled through it using air, water or vacuum.

Cleaning Objectives

• Complete removal of powder residues
• Mechanical cleaning of the pipe wall
• Cleaning of the entire 25–30 m pipeline including bends
• Insertion of the foam pig via vacuum suction (-0.22 bar)
• Retrieval of the pipe pig using a rope core with eyelet

Challenges in Cleaning Pneumatic Conveying Pipelines

• Hygroscopic powders can clump together and adhere strongly to the pipe wall
• Long pipelines with significant vertical height differences
• Pipe bends require flexible foam pigs capable of navigating curves
• Deposits must be removed completely to prevent contamination

In many cases, simple air flushing is not sufficient. Instead, a mechanical solution using a suitable pipe cleaning pig is required.

The MOWOTAS Solution: A Multi-Stage Pipe Pig Cleaning System

To achieve thorough cleaning, a multi-stage pipe pigging process was implemented. Each cleaning pig performs a specific function during the cleaning sequence.

1. Pre-Cleaning – Loosening Deposits

The first stage loosens stubborn deposits from the pipe wall.

• Pipe pig B-S – Ø 45 mm
• Equipped with a stainless steel wire brush
• Medium-strength rope with eyelet

Function:

• Mechanical breaking of compacted dust layers
• Loosening of adhered particles
• Preparation of the pipeline for the main cleaning stage

2. Main Cleaning – Removing Powder Residues

• Pipe cleaning pig LM – Ø 50 mm
• Partially coated foam pig design
• Two circumferential sealing discs (lamellae)
• Rope with eyelet

Function:

• Complete wiping of the pipe’s inner surface
• Transport of loosened powder residues
• Reliable movement through pipe bends

3. Final Cleaning – Removing Residual Dust

• Foam pig SW-UB – Ø 50 mm
• Foam pig SW-UB – Ø 60 mm
• Soft, uncoated foam structure
• Waterproof base plate
• Rope with eyelet

Function:

• Absorption of remaining dust particles
• Fine cleaning of the pipe wall
• Removal of residual powder deposits

Advantages of the Pipe Pig Cleaning Solution

• Complete removal of powder residues
• Reduction of dust build-up inside the pipeline
• Reliable cleaning even in pipelines with bends and height differences
• Controlled movement of the pipe pig via rope core and eyelet
• Effective yet gentle mechanical cleaning

Conclusion

Powdered, hygroscopic products such as dried pea fibre place specific demands on pipeline cleaning in pneumatic conveying systems. Conventional air flushing is often insufficient to remove persistent deposits.

By using a multi-stage pipe pig cleaning system—combining a brush pipe pig, a lamella cleaning pig, and soft foam pigs for final cleaning—even stubborn dust deposits can be removed reliably.

The result: clean pipelines, stable production processes and reduced maintenance requirements.

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