Beside the valuable renewable heat energy, geothermal water brings a host of undesirable substances to the surface. One of these, found in high concentrations in the water sourced from deep underground in northern Germany, is salt. And salt can present a problem in shallow and deep geothermal systems alike, as it acts abrasively on metals and can cause damage to pipework and valves. The same is true for other solids, which can crystallize due to turbulence in the flow of the medium. This so-called scaling effect is a headache for geothermal plant operators. With its Ballostar KHI, KLINGER Fluid Control has the solution.
“The less the disturbance in the flow of water through the valve, the less surface area there is for the solids to crystallize on.” The body of the Ballostar KHI from KLINGER Fluid Control features optional purging outlets, which allow the valve seat to be purged with phosphoric acid to prevent crystallized deposits accumulating in the cavity between the valve’s seating surfaces.
Valve with a long service life
With valves, the choice of material is also critical. KLINGER offers its Ballostar KHI in several versions: steel, stainless-steel, and duplex. “The choice is essentially based on the results of the chemical analysis that we run on the geothermal water. Together with the plant operator, we use these to decide which material is best suited for the local conditions,” says Gerhard. As a rule of thumb, saline water generally requires the higher-quality duplex steel to maximize the valve’s service life.
Hard as chrome
The choice of material for the ball was an obvious one: spheroidal graphite iron. Cast in a single piece, the ball is additionally chrome-plated. “The chrome surface is extremely hard, highly resistant to solids and has a low surface roughness. So particles cannot adhere to it and destroy the seal when the valve is operated,” explains Gerhard. As the ball is cast in one piece, it also has no weld seams, which would be susceptible to corrosion. The geometry, material and design of the Ballostar KHI are designed to minimize maintenance costs and thus also the operating costs of geothermal power plants.
