It’s the dosage that counts
A holistic approach to metering pumps – systems solutions are currently very popular

There are very few industrial applications where a centrifugal a pump is inherently a bad choice. However, the metering pump is one example where this is in fact the case. Positive displacement pumps are the most popular solution in these applications. Manufacturers are obviously now paying more attention to the peripherals. A look at current products on the market reveals a move towards system solutions.

The metering system specialist ProMinent reports that modular, pre-mounted metering systems have proven to be a very good solution in typical applications such as injection of disinfection, neutralization, precipitation or cleaning agents. Users get a complete customized solution which eliminates interface problems and reduces planning and installation effort. Other suppliers offer comparable system solutions, and it appears that the market is ready to embrace individual modules. The reason for this is that the properties of the medium and the degree of precision needed for the process are important criteria in any given application. Even metering applications which appear to be simple always have a holistic aspect, making a system approach superior to installation of separate components. It is instructive to look at a solution provided by sera.
The task at hand was to develop a system to automatically transport batches of liquid chemicals from storage containers to a mixing reactor while maintaining an accuracy of +/- 0.5%. The major design criteria were operational reliability, high precision and ease of handling.

The solution which the company developed was a compact system consisting of a membrane metering pump including all of the necessary fittings, magnetic inductive flowmeters and automatic shutoff mechanisms. The system was built around a PLC. The operator only has to enter the recipe number and then press the start button to initiate the fully automatic mixing process. If a malfunction occurs, the system detects the problem (insufficient volume of chemicals, metering pump failure), displays a clear text message and shuts the system down. In addition to correcting the fault, the program will continue where from the point where it was interrupted, and the batch will be finished properly.
Operational reliability, high precision and ease of handling
Pump specialist Lutz-Jesco also offers complete sets consisting of a metering pump, tube, injection point and suction line. The company supplies the Magdos LC as a low-cost alternative for continuous metering applications. The pumps are ideal for water treatment and the process industry at ambient temperatures up to 45°C. The metering pump features a newly designed solenoid which operates at a natural rate of 120 strokes/min. The pump is available in three performance ranges, and the stroke length can be adjusted between 20 percent and 100 percent to produce the desired flow rate.
“Gentle” dosing is the solution
The Grundfos DME is a piston diaphragm pump, and the design alone makes it suitable for high-precision metering applications. This type of pump has the highest volumetric efficiency and a non pressure-sensitive performance characteristic, which means that the pressure has virtually no effect on the flow/dosage rate. Pumps at the low end of the range are designed to handle very small flow rates (2.5 ml/h). The largest models can handle a flow rate of 940 l/h with an accuracy of +/- 1%. Before it releases a new pump for volume production and sales, Grundfos tests the product at selected customer sites. One of the earliest field tests was conducted at Buckman Laboratories, which produces chemicals for aqueous industrial systems including microbicides, corrosion inhibitors, defoamers and other chemical agents. Eddy Scott from Buckman is very satisfied with the design of the new pumps. “We used one of the large DME pumps at a customer site, and the performance was outstanding. Dosing was very gentle, which is just what we needed in that particular application.” Scott also cited ease of use as a key advantage. “The large pumps are adjusted in exactly the same way as the smaller models. This means that users do not have to learn how to use a new pump. They already know what to do.“
Alltech is another supplier which offers piston diaphragm metering pumps for chemical applications. The modular design of the FKM gives users great flexibility and allows them to select the right model for their specific application. Customers also have a choice of metering head and the valve materials to handle a variety of different chemicals. A choice of flow rates and pressure levels increase the options available to users. The manufacturer is confident that the integrated pressure relief valve ensures safe operation.
Diaphragm protection system included
The Lewa ecoflow series is a new generation of metering pumps which is based on the Lewa modular range. The company says that new drive units, a totally redesigned M900 diaphragm pump head with PTFE diaphragm and the DPS diaphragm protection system significantly expand the application horizon and enhance efficiency and operational reliability. The ecoflow product range also includes pump heads with metal membranes and piston pump heads (flow rates between 1 l/h and 10 m3/h per pump head). The DPS (Diaphragm Protection System) features a new mechanism to control the position of the diaphragm.
Lewa claims that DPS always keeps the diaphragm within the optimum operating range. Regardless of external influences (problematic operating conditions, gross operator error), the diaphragm remains within defined limits, eliminating the possibility of early failure caused by overextension of the diaphragm. The DPS also features a diaphragm monitoring system combined with a pre-shaped, multi-layer PTFE diaphragm. The protection system is designed to provide early warning when a diaphragm layer has suffered damage due to excessive wear.
API and Atex compliant solutions
An optional version of the KM 250 and KM 280 series piston diaphragm pumps can be supplied with an API certificate. These rugged versions are suitable for use in refinery applications, for example
-in petrochemical refineries: dosing of chemicals used to treat and condition refinery drinking water, service water and cooling water
-in the oil pipeline process: dosing of inhibitors
-in the natural gas production and transportation process: dosing of polyelectrolytes for gas/water separation and dosing of additives which makes it easier to detect leaks (distinctive smell).
In addition to its Novados and Novaplex pump series, Bran+Luebbe supplies the ProCam series of piston and membrane pumps for explosive zones (1 and 2). Stainless steel versions are available, and the company also offers a plastic version of the diaphragm pumps. There are a few important points to note on the plastic version. The standard DP15 and DP50 diaphragm pumps, which deliver flow rates up to
50 l/h, can be used without modification. Minor changes have to be made to the pump heads on models with flow rates up to 500 l/h. The simple addition of a front plate on models DP100, DP200 and DP500 is sufficient to comply with Atex regulations. Existing plastic ProCam diaphragm pumps can be retrofitted at low cost. This is only a small sample of what the pump market has to offer. The market summary on the following pages lists the pump types and technical data for products from other manufacturers.