Local valves manufacturer Aveng Manufacturing DFC has delivered a nozzle check valve – the largest yet manufactured by Dynamic Fluid Control (DFC) – for installation in a pipeline project in a neighbouring State in February, DFC mining and water executive director Pat Stander tells Engineering News.

“The 1 200 mm nominal bore Vent-O-Mat model B nozzle check valve weighs about 5 t and has a flow range of 800 ∙/s to 4 500 ∙/s and will form a key part of pipeline-pressure management,” he says, adding that its design as a safety mechanism prevents any possible damage to the pipeline and its pumps by water surge and water hammer that might be caused by conventional check-valves.

The design engineers for this pipeline project decided to use a nozzle check valve in the pressure management system as an alternative to air valves. Nozzle check valves are designed to use water flow, rather than air, to protect the pipes and pumps from damage by surge and water hammer, Stander notes.

“Pipeline surge and water hammer are caused by separation of the water column when a pump trips or is switched off. The water column separates, with potentially damaging volumes of water beginning to surge back and forth within the pipeline.”

Stander says damage is usually prevented by DFC’s air valves, which allow air to be drawn into or be ejected from the pipeline to compensate for pressure build-up and vacuum caused by movement of the water column.

However, the amount of time needed to refill the pipeline against the pressure of indrawn air for this particular pipeline project was viewed as undesirable, he adds.

“An alternative solution was designed to use the vacuum cre- ated by the water column separation to draw additional water into the pipeline from a feeder tank at the top of the pipeline profile,” Stander says, adding that the nozzle check valve is the ideal product to aid this process.

The valve is designed to readily open for forward flow under normal conditions, to backseat firmly at low flow and to close fully and rapidly on reverse flow without any of the shock associated with standard check valves as they slam shut, he explains, further noting that minimal seat leakage occurs in the closed position.

“Further, the valve’s annular ring design is used to reduce disc weight, enabling the valve to switch from fully open to fully closed in a fraction of a second. The annular ring also prevents jamming under conditions of unevenly distributed flow,” he says.

Another advantage includes head-loss performance, owing to the low disc mass and superior pressure recovery capabilities of this annulus configuration.

DFC was awarded the contract as the Vent-O-Mat nozzle check valve was the only valve to meet the project application parameters, which require that the valve be in the closed position at the lowest system static head of 7 m and reopen under a differential head of between 2.5 m and 5 m.

“The completed nozzle check valve passed all performance tests after manufacture was complete, with leakage in the closed position well within the required specifications,” Stander adds.

Meanwhile, he notes, although the nozzle check valve was specifically developed for bulk water transfer schemes, with sizes ranging from 450mm to 1 200 mm for large bore systems, DFC has received orders for the 200 mm nozzle check valves used in water reticulation systems, with several municipalities expressing interest in the valve.

The company has received additional multimillion-rand orders for at least 18 nozzle check valves in the past three months, Stander notes, adding that the valves are destined for projects throughout Africa, the Middle East and the Far East in the following three months.

While the company is currently involved in several projects in North West, Limpopo and KwaZulu-Natal, Stander adds, DFC has registered an increase in demand for automated act- uated valves, particularly hydraulic automated valves, as they have become “critical for industry to fine-tune industrial processes and production and reduce human error”.

He concludes that sales of automated electric and pneuma- tic actuated valves have increased by about 20% to 25% over the last year.