Enhancing Reliability & Precision of Chemical Dosing Solutions

Two of the most important factors to consider in designing a chemical feed system have always been precision and reliability.  With increasing costs of chemicals and longer & unpredictable lead times for chemical delivery, these factors have only become even more important to consider.  Implementing a chemical dosing strategy that is as precise as it is reliable can offer significant savings on chemicals, improve asset protection, ensure safety of operators, and prevent time and frustration spent on frequent maintenance. 

Two of the most common metering pump choices are solenoid driven diaphragm pumps and peristaltic pumps.  Both can offer reliable, cost-effective, and accurate control of chemical feed for a wide variety of water treatment applications.  However, each have weaknesses that can present problems depending on the application.  Primarily, solenoid-driven diaphragm pumps can have trouble maintaining prime with off-gassing chemicals (such as bleach), while peristaltic pumps present greater risk of leaks and can require more frequent maintenance in the form of tube-replacements.

Recent advances in metering pump technology can overcome these challenges, providing solutions that significantly enhance dosing precision at an even greater degree of reliability.  IWAKI’s IX Series pumps are direct-drive, digitally controlled pumps that combine both accuracy and flexibility into a low-power, energy efficient design.  These ‘smart-dosing’ metering pumps use sophisticated motor control technology to maintain precise control of flow over a wide output range, while reducing power consumption by up to 70% compared to conventional mechanical diaphragm metering pumps.


The accuracy of a metering pump’s dosing capabilities is typically considered by evaluating a pump’s ability to deliver chemical at prescribed flow rates.  The IX Series pump’s precise motor control combined with an efficient valve design achieves a high accuracy of ±1% over full scale.

Two other important considerations for accuracy are the pump’s ‘turn-down ratio’, and the smoothness of the pump’s dispensing rate. 

Turn-down ratio is the ratio of a pump’s maximum rated flow to its lowest flow output while still within its defined accuracy range.  In other words, if a pump is rated for 100 GPH and can be reduced to 20 GPH while maintaining accuracy, the turn-down ratio would be stated as 5:1.  This is important to a pump’s performance as many applications may require different flow rates depending on the season, system conditions, and other factors.  While typical metering pumps may offer turn-down ratios of 180:1 or 360:1, the IX series pump enables control and discreet adjustment of the discharge and suction speeds, providing a high turndown ratio up to 1000:1.  You can accurately deliver 7.5 mL/hour on a pump that is rated for up to 7.5 L/hour.

The ‘smoothness’ of a pump’s dispensing rate can be viewed as the length of the gap between pump strokes, especially as you reduce a pump’s flow output.  As you turn-down a typical solenoid driven diaphragm metering pump, the gap between pump strokes will lengthen as the time taken for the suction stroke will slow equally to the time taken to complete a discharge stroke.  This can result in ‘slug feeding’ of chemical. 

On an IX Series pump, suction stroke speed always remains at full pump speed. As pump flow rate is decreased, discharge stroke speed is reduced, maximizing discharge time and helping to reduce pressure spikes, overall pulsation and inertial forces on the piping.  Maintaining a smooth dispensing rate ensures that the system sees a steady supply of chemical, even at low flow rates – avoiding this ‘slug feeding’ that can occur with other metering pumps. 

Figure 1 – Dispensing Rate of IX Series vs. Conventional Metering Pumps


Reliability of a metering pump is not only determined by how long the pump may be able to run without requiring maintenance, but also how reliable the pump is in delivering uninterrupted chemical feed, and how the pump responds to scenarios where maintenance may be required, or where continued operation may present a safety hazard. 

One of the biggest challenges when feeding off-gassing chemicals (such as bleach) is losing prime.  Peristaltic pumps are often the pump of choice for these applications to overcome this challenge, however the potential for leaks and frequent tube replacements can present challenges of their own.  One of the most advantageous features of the IWAKI IX Series Metering Pumps is the excellent degassing ability – a proprietary head design and fixed stroke length maintain a high compression ratio throughout each stroke, resulting in fast priming and no gas-lock conditions at any flow rate or pressures.

As a diaphragm pump, IX series pumps are less prone to leaks than the tubes of a peristaltic pump.  In the event that a leak does occur, the pump comes standard with a diaphragm leak detection sensor.  Detection of a leak will halt pump operation and trigger an alarm output that can be communicated to a control system, ensuring that repair can be done quickly and safely. 

Figure 2 – Diaphragm Leak Detection standard in IX Series pumps

Further protective features include abnormal operation detection – this protects the pump and piping during discharge pressure spikes (valve closure) or increases (clogging).  Sophisticated electronics and monitoring of the motor power consumption allow for monitoring & detection of safe versus abnormal operating conditions. If the system backpressure increases above the safe capability of the pump, the pump will shut itself down. It will attempt several restarts, but if the pressure remains high, the pump will shut off, the display will indicate an overload condition/check plumbing, the LEDs will change to RED, and the pump will output an alarm condition as programmed.

Overall, IWAKI’s careful consideration of precision and reliability in all aspects of design, result in a pumping technology that is uniquely ready to meet today’s demands for automated chemical delivery, satisfying a broad range of application flow requirements.  Common applications range from pre and post-treatment of water from municipalities to process water; pH neutralization, polymer addition, bleach feed, and a variety of other applications requiring chemical additions. 

For more information, view this video on the IX Series Pump: https://www.youtube.com/watch?v=-h9uWqaEx2U