Slurry valves are the unsung heroes that keep things flowing in heavy-duty industries such as mining, wastewater treatment, power generation, and pulp and paper.
Controlling abrasive, high-density mixtures of solids and liquids under harsh conditions that ordinary valves could not stand for more than a few weeks, slurry valves are expected to hold up. But even the toughest of slurry ball valves and knife gate valves will be subjected to wear and tear if not correctly selected, installed, and maintained.
Knowing common slurry valve problems — and how to prevent them — can save you thousands in repair and replacement costs by prolonging the life of your system while reducing downtime.
Here are three of the most common problems that regularly plague slurry valves, along with some proven strategies to avoid them.
1. Erosion and Wear by Abrasive Slurries
The worst enemy of slurry valves is the erosive nature of abrasive particles in the slurry mixture. In mining applications, common slurries can consist of broken rock, sand, and tailings that serve like sandpaper on valve surfaces.
Over long periods, erosion thins out valve bodies, trims, and seats until leaks or loss of performance. One way to extend longevity is to buy quality slurry ball valves.
The principle of wear prevention starts with proper material selection. Components intended for applications under heavy abrasion should be hardened or coated with tungsten carbide, chrome carbide, or have ceramic linings on their critical wear areas.
The final important design consideration is the minimization of turbulence. Erosion is accelerated by changes in either velocity or direction in slurry flow. So, valves should be sized appropriately and installed in a straight run of pipe wherever possible.
2. Clogging of Valves and Blockage
Slurry mixes have the tendency to settle whenever the flow slows down or stops. The abrasive solids build up inside the valve cavity, seat, or around the ball or gate mechanism and create blockages that can prohibit valves from fully opening or closing.
Given an appropriately designed valve and operated system, clogging can be avoided. Valves designed for slurry service, such as cavity-free ball valves or pinch valves, don’t have any dead areas in which the solids can collect.
It’s also necessary to maintain uniform flow velocity, typically above the critical settling velocity of the slurry. Still another method of preventing settling of solids within is by installing the valves in horizontal lines instead of vertical ones.
Periodic flushing systems or purge ports can clean the valve internals. Most new slurry valve designs are available to offer several built-in options for flushing blockages out with water, air, or process fluid compatible with the slurry.
3. Seal and Seat Leakage
Slurry applications are subject to leaking seals or valve seats because of high pressure, combined with temperature variation, and sometimes abrasive particles that can degrade elastomers. If a valve develops a leak, the result could be hazardous working conditions.
You can avoid this by using a seal that is compatible with the chemistry and temperature of your slurry. For instance, in an abrasive application, a metal or ceramic seat resists wear much better than a soft one.
Slurry valves face some of the most hostile conditions found in industry — abrasive flow, high pressure, and corrosion potential. Yet, with the right product and strategy, you can ensure good reliability and longevity.
Slurry valves endure some of the most hostile conditions in industry, balancing abrasive flow, high pressure, and corrosion. But with the right combination of design, materials, maintenance, and operation, you can significantly boost their reliability and lifespan.
It starts with getting the right slurry ball valves in the first place and going from there.
