High Pressure Acid Leaching (HPAL) and Pressure Oxidation (POX) are critical processes in the extraction of nickel, copper, gold, and other valuable minerals. These processes operate under some of the harshest conditions found anywhere in mining: high temperatures, extreme pressures, and highly abrasive, acidic slurries.
Within these circuits, severe service ball valves play a vital role. They are responsible for slurry isolation, pressure control, and process safety. When these valves fail, the consequences are immediate and costly: unplanned shutdowns, lost production, safety risks, and expensive component replacement.
For decades, the mining industry has relied on conventional thermal spray coatings to protect the valve trim (the internal, wetted, and replaceable parts of a valve that directly contact the process fluid) in these applications. However, according to global engineering technology leader, Score, this approach is reaching its limits.
The limitations of traditional valve trim coatings
Thermal spray ceramic coatings have been widely used to improve wear resistance on titanium valve trim. While they offer initial protection, they suffer from inherent weaknesses that are magnified in HPAL and POX service. These include:
1. Mechanical bonding only
Thermal spray coatings adhere mechanically to the substrate rather than forming a true metallurgical bond. Under high stress, this makes them prone to spalling and delamination.
2. Inherent porosity
These coatings are porous by nature. Microscopic voids allow acidic slurry to penetrate through the coating, attacking the titanium substrate underneath and accelerating corrosion.
3. Limited coating thickness
Typical thermal spray coatings are approximately 300 microns thick. Once erosion breaks through this thin layer, rapid wear of the base material follows.
4. Short service life
In many HPAL autoclave discharge applications, conventional coatings fail within 6-12 months, forcing frequent valve replacements and unplanned shutdowns.
The result is a cycle of recurring maintenance, escalating costs, and reduced plant availability; a situation that’s becoming unacceptable for high‑capital mining operations.
A step change in valve trim technology
To address these persistent issues, Callidus, a provider of high-end flow control solutions to the mining industry, developed FM-1500TM, a proprietary new approach to valve trim protection and one that moves beyond applied coatings and instead modifies the surface of the valve trim itself. Score acquired Callidus in 2025 to strengthen its offering in engineering, flow control solutions, valve management, welding, and field services, particularly in severe service environments
The acquisition has meant gaining access to Callidus advanced technology, which uses a metallurgically bonded titanium nitride‑based surface modification, transforming the outer layer of the valve trim into a fully dense, wear‑ and corrosion‑resistant structure.
“Rather than sitting on the surface, the modified layer becomes an integral part of the valve trim,” says Dr Evelyn Ng, group materials & innovation manager, at Callidus, a Score Company.
What makes this technology different
- Metallurgical bonding
The modified layer is fused to the titanium substrate, eliminating the risk of delamination. - Zero porosity
The dense structure prevents acid ingress and protects the base metal from corrosion. - Substantial thickness
At approximately 1,500 microns, the modified layer is up to five times thicker than traditional coatings. - Exceptional hardness
Surface hardness can reach up to 1,000 HV, delivering superior resistance to erosion and abrasion.
Proven performance in HPAL and POX environments
This surface‑modified valve trim technology has been subjected to extensive laboratory testing and real‑world field trials in HPAL operations.
Testing to internationally recognised ASTM standards has demonstrated:
- Outstanding erosion resistance, with wear volume reductions of up to 90% compared to untreated titanium.
- Excellent corrosion resistance, maintaining structural integrity after prolonged exposure to sulphuric acid at elevated temperatures.
Field results: breaking the six‑month shutdown cycle
In one HPAL facility, a 14‑inch Class 600 ball valve found on an autoclave discharge line had become a known weak point. Every six months, the valve required a full change‑out due to coating failure and rapid erosion of the titanium substrate.
After retrofitting the valve trim with the advanced surface‑modified technology into an OEM design, inspections were conducted at regular intervals. Inspection at 18 months of continuous service revealed:
- No delamination was observed.
- No galling or loss of sealing integrity occurred.
- Wear patterns remained minimal and stable.
Ultimately, service life extended from six months to more than two and a half years, a fivefold improvement.
Operational and commercial benefits for mining operators
For mining operations, the benefits of this technology extend well beyond longer component life.
1. Reduced unplanned downtime
By eliminating coating delamination, valve failures become predictable rather than sudden, improving overall plant reliability.
2. Lower maintenance and inventory costs
Longer service intervals reduce the frequency of valve change‑outs, spare parts holdings, and maintenance labour.
3. Retrofit friendly
The technology can be retrofitted to existing valve designs from all major OEMs, without requiring modifications to actuation systems.
4. Improved safety
Fewer shutdowns and interventions in high‑temperature, high‑pressure areas reduce exposure risks for maintenance personnel.
5. Sustainability gains
Extended service life means fewer replacements, lower material consumption, and reduced environmental impact associated with manufacturing and logistics.
In HPAL and POX circuits, valve trim is often the determining factor in whether a valve succeeds or fails. While coatings may appear cost‑effective upfront, their short service life often results in higher total cost of ownership.
Evaluating valve trim technologies based on long‑term performance, rather than initial purchase price, can unlock substantial operational savings, increased production uptime and reliability improvements.
New standards for severe service mining valves
Advanced surface‑modified valve trim technology is a genuine shift in how severe‑service valves are protected in HPAL and POX applications. By addressing the root causes of coating failure, Callidus’ FM-1500TM process, delivers the durability, reliability, and longevity that modern mining operations demand.
For operators seeking to improve uptime and reduce maintenance burden, this technology is fast becoming the new benchmark for severe‑service valve performance.
Download this report to get a clearer picture about how Callidus FM-1500TM can support your mining operation.
