Wear observed upon failure of the original valve, with leak path to atmosphere (site photo – standard knife gate valve – 2004).
The Beginning

In the early 2000’s, a Canadian Oil Sands facility was using knife gate valves to modulate slurry from their Primary Separation Cells. At that time, the service life of these heavy-duty valves was measured in days (typically 2-3 weeks).

When throttling a knife gate valve, higher flow velocities will occur within the acute angles formed at gate to body interface. Upon failure, the system was shutdown, the valves removed, and new units were installed.

These expenditures in labor and product were significant; however, they were minimal compared to the lost production revenue. The frequent shutdowns were costing the company millions annually. There had to be a better way.

Prototype 1.0

To improve valve performance, we initially manufactured a metal seated valve with gate and seat ring made of Hardox® wear plate (55 HRC). The new/harder material improved service life by 50%, to 4.5 weeks.

The client noted that turbulence from the seat ring likely caused the wear observed on the valve’s body.

Knife gate valve manufactured with Hardox® 500 gate and seat ring.
Valve with smooth bore, flush with pipe ID.
Ni-Hard deflector ring.
Prototype 2.0

To reduce turbulence, we manufactured a valve without the seat ring, providing a smooth bore that was flush with the pipe ID. The gate and bore were again made with Hardox®, and we included an additional Ni-Hard deflector ring.

Service life now tripled the original valve; pushing the benchmark to 9 weeks with this latest iteration.

Prototype 3.0

The third valve we worked on incorporated the same basic design, but with replaceable Hardox® bore liners and gate. Service life remained at 9 weeks, however the client’s replacement expenditures were reduced, as the body could be re-used upon failure of the Hardox® wear components.

Valve with replaceable Hardox® bore liners and gate.  
Narrow gate with convex tip protects the valve body from erosive flow.
Acute angles formed at the gate to bore liner interface were areas of high velocity flow.
Prototype 4.0

By narrowing the gate width, and modifying the tip from convex to concave, only the replaceable Hardox® gate and bore liners were exposed to abrasive flow. This was a design breakthrough for the team, and a feature we later Patented.

Although service life was bumped to 12 weeks, the acute angles between the gate and bore liners remained. These areas were ultimately the point of failure.  

Prototype 5.0

Upon failure of the latest Hardox® gate and seat plate, we manufactured the replacement parts with stainless steel, which we hard coated with a Tungsten Carbide overlay.

The client inspected the valve after 12 weeks in service. This site photo clearly shows the excellent wear resistance of tungsten carbide. This latest material upgrade provided an impressive 26 weeks of service, with the mode of failure being high velocity flow within the acute angles.

Bore liner with Tungsten Carbide welded overlay, applied via PTAW process (75 HRC).
Concave gate tip and bore liner during a performance inspection (12 week milestone).
A new ‘seat plate’ design eliminates the acute angles.
Negligible wear to the tungsten carbide overlay. The six holes (intended to increase Cv) were removed on subsequent seat plate designs.
Prototype 6.0

To eliminate the acute angles, we modified the bore liner to incorporate a seat plate. This design filled the gap on the sides of the gate, leaving a centered orifice with linear control. Again, these trim components were manufactured with stainless steel, and coated with a tungsten carbide overlay.

This latest prototype was inspected upon 26 weeks of service. We observed negligible wear to the tungsten carbide wear coating, however the six holes (within the seat plate) were enlarged due to erosion. Impressed with the performance, the client retuned the valve to service, and a trim kit was installed at the 52 week mark.


SlurryFlo Valve Corp opened its doors in 2007, with a patented new linear control valve for abrasive mining applications. During the past 14 years, our valve technology has been installed at every major oilsands facility in Alberta, and in hundreds of applications throughout the world.

Installed primarily at mining facilities, it is common for SlurryFlo control valves to remain in operation 10x longer than the heavy-duty control valves they replace.

SlurryFlo Control Valve
SlurryFlo's patented design centers flow like no other control valve. Our variable orifice technology will outlast anything you've ever used.

Patented Design

SlurryFlo Modulating Control Valve