Made for the Yogurt of the Oil Sands

Middlings Withdrawal Control Valves regulate the slurry drawn from primary separation vessels and cells in oil sands mining. Stable middlings flow is required to maintain bitumen froth quality and provide consistent feed to downstream flotation circuits. Since ore grade fluctuates over time, these control valves must accommodate wide swings in throughput while maintaining predictable control.

The Challenge

Middlings is a dense mixture of fine solids, clays, and unaerated bitumen, forming a thick, yogurt-like consistency similar to mature fine tailings. Typical conditions include inlet pressures near 50 kPa, temperatures around 70 °C, specific gravity close to 1.35, and solids loading between 25 and 40 percent by weight. The high solids content makes this a highly erosive service for throttling valves.

Performance with Conventional Valves

V-port rotary valves, pinch valves, and knife gates used for modulating duty often have a short service life during middlings withdrawal. Erosion usually occurs where the throttling geometry constricts the flow, creating localized velocity peaks that focus abrasive fines against the valve body or downstream piping.

In many cases, these valves need replacement within months, especially during periods of higher ore quality when low-flow operation is common.
View Valve COmparison
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Ball Valve CFD
V-Port Ball Valve
Knife Gate Valve

The SlurryFlo Solution

SlurryFlo’s linear control gate features a centred flow path and engineered trim geometry to direct the slurry through the valve without impingement on the body.

This design ensures a more even distribution of velocity across the stroke, reducing the high-energy zones that typically cause wear in conventional designs. The valve is capable of handling wide flow variability associated with changes in ore quality while maintaining predictable control.
SlurryFlo Control Valves centralize flow which protects the valve body and downstream piping.

The Result

For nearly twenty years, operators in the oil sands have relied on the SlurryFlo design for middlings withdrawal and mature fine tailings service.

Installations consistently report multi-year intervals between trim changeouts, enhanced control stability, and a notable decrease in maintenance interventions compared to traditional throttling valve types.

ReCent Development

SlurryFlo developed an ‘H1B1’ trim concept for a middlings withdrawal service because the existing B1 trim was not achieving the predicted flow rates. Intermittent plugging in the middlings piping and uncertainties around inlet pressure and slurry viscosity made it difficult to verify actual operating conditions, leading the process team to request a full-port knife gate valve to achieve the highest possible Cv.
At the same time, the maintenance group noted the strong service life they had observed with SlurryFlo designs in similar applications and emphasized the importance of maintaining a centred flow path to protect downstream piping. The H1B1 configuration was created to reconcile both perspectives, providing increased flow capacity while preserving the flow alignment preferred for long-term reliability. A purchase order is anticipated following final review.
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