In industries such as mining, cement, power generation, steelmaking, chemical processing, and biomass energy, screw conveyors are often regarded as auxiliary equipment. However, maintenance data shows that they are among the most frequent causes of unplanned production downtime.
The primary reason for these failures is usually not motor malfunction or gearbox damage, but continuous wear of the screw flights. As the flights wear down, conveying efficiency decreases, material blockages occur more frequently, vibration increases, and the entire system becomes unbalanced.
When severe wear is discovered, many companies immediately consider purchasing a new screw conveyor assembly. However, for large industrial conveying systems, replacing components often means high procurement costs, long lead times, and additional production losses caused by downtime.
As a result, more and more companies are turning to PTA Welding (Plasma Transferred Arc Welding) technology for screw conveyor refurbishment and remanufacturing.
With the correct repair strategy, PTA not only restores worn dimensions but also provides wear resistance that significantly exceeds original equipment performance. In high-abrasion applications, refurbished components can achieve a service life that is typically 3 to 8 times longer than new parts.
Why Do Screw Conveyors Always Wear in the Same Areas?
From an engineering perspective, screw conveyor wear is not random.
More than 80% of wear typically occurs in specific locations:
Flight Outer Edge
The outer edge operates at the highest linear speed and therefore experiences the greatest frictional load.
Feed Inlet Section
Bulk materials continuously impact the leading edge of the flights, resulting in severe impact-abrasion wear.
Discharge Area
As material density and conveying resistance increase, wear rates become significantly higher near the discharge end.
Center Shaft Surface
In systems conveying fly ash, mineral powders, and chemical materials, the center shaft is often exposed to both abrasion and corrosion.
Simply rebuilding these areas with conventional welding electrodes usually results in the same failure recurring within a few months.
The real challenge is addressing the wear mechanism rather than merely restoring dimensions.
Why Has PTA Welding Become the Preferred Technology for Screw Conveyor Repair?
Over the past two decades, industries have experimented with numerous wear protection methods, including:
• Manual hardfacing
• Submerged arc welding
• MIG hardfacing
• Thermal spraying
• Laser cladding
Among these technologies, PTA has become the preferred repair solution for many heavy industries because it effectively solves three critical challenges.
Superior Metallurgical Bonding
PTA produces a true metallurgical bond rather than a mechanical coating.
The deposited layer becomes an integral part of the substrate, greatly reducing the risk of coating delamination.
Exceptional Wear Resistance
PTA can deposit high-performance materials such as:
• Tungsten carbide reinforced alloys
• Nickel-based alloys
• Cobalt-based alloys
These materials provide wear resistance far beyond that of conventional welding consumables.
Excellent Dimensional Control
Because the plasma arc is highly concentrated, heat input remains low and distortion is minimized.
This advantage is especially important when repairing long screw shafts that require strict dimensional accuracy.
How to Repair a Screw Conveyor Using PTA Welding: Standard Engineering Procedure
1. Wear Assessment and Inspection
Every successful repair project begins with accurate inspection.
Experienced engineers never start hardfacing immediately. Instead, they first analyze the wear pattern and overall component condition.
Typical inspection items include:
• Remaining flight thickness
• Screw outer diameter reduction
• Shaft wear measurement
• Concentricity deviation
• Dynamic balance condition
• Crack detection
In many cases, visible wear is only part of the problem.
Ignoring fatigue cracks or structural damage can significantly reduce the effectiveness of the repair.
2. Surface Preparation
Surface preparation is one of the most critical factors affecting repair quality.
Before hardfacing begins, the following contaminants must be completely removed:
• Oxide layers
• Oil and grease
• Corrosion products
• Fatigue-affected material
• Existing weld deposits
Severely worn areas may require dimensional restoration before wear-resistant hardfacing is applied.
This creates a consistent foundation for uniform weld deposition.
3. Wear Material Selection
There is no universal hardfacing alloy suitable for every application.
The best solution depends entirely on operating conditions.
• For limestone and cement clinker conveying systems, tungsten carbide composite materials are commonly selected.
• For fly ash and coal powder applications, nickel-based wear-resistant alloys are often preferred.
• For high-temperature environments, cobalt-based alloys provide excellent performance.
Material selection expertise is often more important than the equipment itself.
This is one of the key differences between professional PTA solution providers and ordinary welding contractors.
4. Automated PTA Welding Process
Modern PTA refurbishment has entered the era of automation.
Advanced PLC-controlled systems enable:
• Automatic workpiece rotation
• Synchronized torch movement
• Precise powder feeding
• Real-time current adjustment
• Closed-loop temperature control
These features ensure consistent deposition quality and repeatable repair performance, even in large-scale production environments.
5. Post-Weld Machining and Inspection
Hardfacing is only part of the refurbishment process.
High-quality repairs require comprehensive post-weld inspection, including:
• Overlay thickness measurement
• Hardness testing
• Dimensional inspection
• Concentricity verification
• Bond quality evaluation
• Dynamic balancing
Only after all quality requirements have been met should the screw conveyor be returned to service.
How Much Longer Can PTA-Repaired Screw Conveyors Last?
Based on our experience in mining, cement, power generation, and steel industries, typical service-life improvements include:
• Limestone conveying systems: over 300% improvement
• Mineral powder conveying systems: over 500% improvement
• Fly ash conveying systems: over 400% improvement
• High-abrasion slag conveying systems: up to 800% improvement
For large industrial conveying systems, these improvements often translate into maintenance cost savings worth tens or even hundreds of thousands of dollars.
PTA Repair vs. Purchasing a New Screw Conveyor: Which Is More Cost-Effective?
For procurement managers, return on investment is often more important than technology itself.
When the conveyor structure remains intact and only wear damage is present, PTA refurbishment can typically reduce total costs by 30% to 70% compared with purchasing new components.
At the same time, lead times are often reduced by more than 50%.
Even more importantly, wear-resistant reinforcement frequently enables the repaired component to outperform the original design life.
This is why many international mining companies, cement manufacturers, and energy groups have integrated PTA refurbishment into their standard maintenance strategies.
Frequently Asked Questions
1. How long can a PTA-repaired screw conveyor last?
Depending on operating conditions, service life is typically 3 to 8 times longer than the original component.
2. Will the PTA welding overlay peel off?
No. PTA Welding creates a metallurgical bond with the substrate, providing significantly stronger adhesion than thermal spray coatings.
3. Which material is best for severe mining abrasion?
Tungsten carbide reinforced alloys generally provide the highest wear resistance in highly abrasive mining environments.
4. Can stainless steel screw conveyors be repaired using PTA?
Yes. PTA is suitable for 304 stainless steel, 316 stainless steel, duplex stainless steel, and many other stainless materials.
5. Is PTA repair more economical than purchasing new equipment?
For most industrial applications, PTA refurbishment delivers a substantially higher return on investment.
Why Do Global Industrial Companies Choose Our PTA Solutions?
For more than 20 years, we have focused on PTA hardfacing equipment development and wear-resistant engineering solutions.
We do more than supply equipment—we help customers solve real-world wear problems.
From mines and cement plants to power stations and steel mills, we have delivered thousands of PTA hardfacing solutions worldwide.
Whether you need to repair screw conveyors, enhance wear resistance of critical components, or establish a fully automated PTA production line, our engineering team can provide complete technical support.
Contact us today for a free wear analysis and service-life assessment report. Based on your conveyed material, wear mechanisms, and production requirements, we will develop a customized PTA hardfacing solution tailored to your operation.
Post time: Jun-12-2026