One of the biggest issues that steel mills need to control for is the overheating of their pumps so they aren’t damaged. Many mills use a continuous bypass flow to keep their pumps cool. But, this solution wastes a lot of energy and it’s expensive. A better way is pump bypass control.
Instead of a continuous flow, minimum flow is delivered to cool the pump only when it’s needed. This method also allows you to direct higher flows and pressures to improve the descale efficiency and product surface quality, or shut down a pump by eliminating continuous header prefill and pump bypass flows from multiple pumps for significant energy cost savings.
There are three components that play a role in this system:
Pump Bypass Check Valve
Most centrifugal pump manufacturers specify Automatic Recirculation Valves (ARC) to provide the minimum flow required for pump cooling. These valves utilize an orifice assembly that is mechanically controlled as the check valve opens and closes. But, they typically do not perform well in descale system applications due to the high rate of cycling on and off combined with the contamination level of the water in most systems.
Hunt’s solution modifies the existing ARC valve by replacing the linkage and orifice with a Hunt pump bypass valve, multistage pressure breakdown orifice and control method. This typically consists of a magnetic flow meter on the suction side of the pump. The accumulator level can also control the system.
Pump Bypass Valve
The pump bypass valves deliver the minimum flow for pump cooling only when needed—providing the capability to direct 100% of the flow to the descale header when required.
Hunt’s pump bypass valves are designed to be bias open via the pump pressure to ensure pump protection in the event of electrical, pneumatic or hydraulic pressure loss.
The proportional control of the EMA actuation or proportional hydraulic control enables users to tune the system and virtually eliminate water hammer.
Pressure Breakdown Orifice
The pressure breakdown orifices handle the pressure drop and pressure/flow rate requirements of each pump. A series of heat-treated stainless-steel orifice plates reduce the pressure from the inlet to the outlet. The orifice plates are designed to provide a small pressure drop that spreads the wear throughout the components.
Hunt Valve can design a pump bypass valve system customized to your specific plant and its needs. Our experience with field application problems associated with the fully mechanical protection valves of other manufacturers has led us to adapt and customize our poppet and plunger style descale product range to fit the most critical centrifugal pump applications. Contact us or call 800-321-2757 with any questions or to request a quote.