Pumps & Systems staff spoke with SEEPEX President Michael L. Dillon about the major trends to anticipate in 2017 related to instrumentation, controls and monitoring, as well as the pump market
What trends and challenges do you foresee for 2017 and beyond?
Most customers do not realize it but the majority of applications for progressive cavity pumps involve flow control and they are often used for multiple component blending applications. We know that the reciprocating pump community does not like for us to refer to a PC pump as a “metering” pump. But, in truth, most of our applications are used to “meter” a specific amount of fluid into a process.
Some users think only of a PC pump for abrasive, water-borne applications. It is true that a PC pump can reliably handle abrasive slurries with a very thin carrier liquid, and this is unlike most rotary PD pumps with a tolerance fit between the rotating and stationary parts. They need a viscous carrier to form a seal where this gap occurs. Still, in the wastewater industry, where a PCP pumps water-based sludge, the most common applications are where two flows are being combined and precisely controlled to enhance a process. Think of feeding a centrifuge or a belt filter press or a plate and frame filter press when the flow of the sludge and the polymer to the device needs to be precisely controlled. Failure to maintain this control can either mean a fine from the EPA for being outside the plant’s operating permit or using so much flocculent that the process becomes incredibly expensive. In one case, where advanced instrumentation was used to precisely measure the entrained solids as the sludge blanket was drawn down, the wastewater plant was able to save $3 million per year in chemical consumption.
PC pumps do this is many industries across a broad spectrum. We pump yogurt with one pump and fruit with a second pump for applications where a product blended with an in-line mixer is sent to an aseptic packaging machine. We pump vitamins and minerals into extruders that are forming dry pet food products or cereals. We pump colors and other additives into various paper products, especially tissue. We pump both aqueous ammonia and sodium hypochlorite for chloramine disinfection in drinking water plants. They are used in the chemical and food industries for numerous catalysts. Everything from noble metals in an oil refinery to renate in a dairy making cheese. Yeast recovery in breweries, chocolate spray applications and spray driers where velocities must be held constant despite varying viscosities are also common.
For the over 40 years of this author’s experience with PC pumps, variable speed drives have always been the norm. Back in the 1970s and '80s, the most common drive was the mechanical variable speed drive with variable pitch pulleys. Hydrostatic drives became popular because of their durability and inability to “wear-in” to a single speed setting. The only available electronic drive that was affordable was a DC motor with a silicone-controlled rectified (SCR). This all changed in the late 1980s as variable frequency drives dropped in price, became more common and improved in reliability. Now they are the industry standard and dominate the motion control industry. This eliminated clumsy and erratic mechanical actuation equipment needed to vary speeds on mechanical variable speed drives. Electric motors were being used to bring those variable pitch pulleys together or apart. The feedback mechanism was a DC generator with a volt meter, like the lights on the bicycle I rode to middle school.
Now with VFDs and digital feedback systems, rotary pumps can be controlled completely with electronics. Without brushes on motors and generators, they can operate reliably and simply for years on end. Integration of instrumentation with analog or digital signals is easy and inexpensive. This has opened up the opportunity for pump suppliers to no longer be equipment suppliers but real problem solvers. SEEPEX is now offering complete skid-based metering and dosing skids, our Alpha Systems. These integrate the motor controls, instrumentation and calibration tools. In some cases the motor controls are integrated with the pumps. The SEEPEX Integrated Metering Pump operates with a 30:1 electric turndown that can translate into a 100:1 or greater flow turndown ratio. The unit will accept 4-20 ma signals to follow a flow meter for the injection of disinfectants or any other water treatment chemical into a system.
For more sophisticated requirements, SEEPEX offers its TOUCH controller. This unit incorporates a programmable logic controller where numerous signals can be controlled and monitored. For instance, in addition to following a signal from a flow meter or an extruder or a conveyor speed, it can also change the ratio of the dosing. For example, as sodium hypochlorite ages it can easily lose potency. Operators may not only want to have the dosing rate follow a flow meter reading the water flow rate, but also increase the dosing ratio based on the free chlorine ions in the system. The TOUCH system can make those changes. The system can also measure loss in weight to control the pump flow rate. It can work with any style of level control and it can accept numerous safety shut off signals: absence of liquid, capacitance, thermal limits, high or low pressure, even proximity sensors for filling operations.