Most popular metering pumps for chemical industry

While metering pumps are widely used in chemical plants, selecting the right pump for the given application can be a daunting task. To help the user find the right pump, Rakesh Rao has put together a list of some of the most popular metering pumps for chemical industry.
Most popular metering pumps for chemical industry
Chemicals, having various properties and characteristics, find applications in all industries. However, if used without adequate control, chemicals (which are often procured and stored in high concentrations) can cause harm to people and environment. Hence, it is important to ensure that chemicals are precisely dispersed in manufacturing process. 

There are various types of pumps used by chemical plants. However, when manufacturers want to dose chemicals in precise amount, they use metering pump. Metering pumps - a type of positive displacement pump - move precise volumes of liquid in predetermined increments within specific time frames. Metering pumps are designed to pump liquids like chemicals, solvents, syrups, solutions, oils, etc. As metering pumps move a precise volume of liquid in a specified time period, they provide an accurate volumetric flow rate. Metering pumps are also designed to pump into a high discharge pressure.

Standards for metering pumps
Proportioning pumps, controlled-volume pumps and dispensing pumps are other common names for metering pumps. When used in chemical process industry to transfer liquids like slurries, acids, bases, and corrosives solutions, metering pumps are also alternatively referred to as chemical dosing pumps.

Users rely on metering pumps as they produce extraordinarily accurate and repeatable results, and also send out a liquid cyclically on a consistent basis. Today's metering pumps offer benefits of advanced technology like precision, control, and accuracy.

For high quality requirements, metering pumps must meet the standard guidelines of one or more organisations such as ATEX, NEMA, and/or ANSI. Besides, depending on end-user industries and the application areas, metering pumps have to meet additional quality standards. For example, for military applications, metering pumps need to meet Mil-Spec standards. Similarly, metering pumps used in food & beverages and pharmaceutical industries must adhere to FDA standards.

How to select the right metering pump
No two chemicals are similar in terms of their pH, viscosity, volatility, corrosiveness, etc. Thus, handling chemicals can be tricky (and sometime risky). For picking the right metering pump for chemical industry application, the user needs to look into a number of factors. Given below are some of the parameters:

Material of construction: Chemicals can be corrosive in nature and, hence, pumps need to be designed and constructed from materials which can withstand substances with varying levels of viscosity, corrosiveness, and abrasiveness. Metering pumps provide flow measurement and control for applications that require precise volumes of chemicals. Standard materials (such as cast irons, bronzes and low-carbon steels) are less costly and replacement of them will be readily available. However, these materials can cause premature failure, leading to unexpected service and replacement; thus, costing more in the long run. Generally, for corrosive chemicals, pumps made of plastics (like PP, PE-HD or PVDF) or alloys are used, while for non-corrosive chemicals, metal pumps are used. Factors like pumping of hazardous or toxic liquids, condition of the liquid, expected pump life, intermittent or continuous duty, etc must be considered for selecting materials for wetted pump parts.
Nature of the chemicals to be pumped: Dosing or transporting chemicals with aggressive, acidic or otherwise challenging properties places special demands on the know-how of chemical pumps. “Volatile liquid may generate vapour while pumping process is on, which may affect the pump. Similarly, temperature and pressure of the chemical also need to be looked into before selecting a pump. Thus, it is important for the user to share properties of the chemical (which needs to be pumped) with the OEM for them to suggest and design the right pump to the user,” said Vijay Vaz, Sales Manager, Samtech Engineering Services Pvt Ltd.

The choice of pump mainly depends on the chemical properties of the pumped medium and the operational safety aspects. Acids such as sulfuric acid and hydrochloric acid are especially corrosive. In addition to acids, chemicals that pose corrosion problems to varying degrees are chlorine, alkaline solutions, and water. Care must be taken to select a pump manufactured from a material that is compatible with the chemical media.

Chemical compatibility for all wetted parts (and parts in contact with the medium in case of a breach of the primary containment method) should be looked at when choosing a pump to handle hazardous chemicals and solvents. It is important to make an in-depth risk analysis of the work environment and pumping systems for ensuring safe and reliable transfer of dangerous liquids.

Accuracy: It is the most important criteria to pick a pump for any stated application. “Diaphragm or plunger pump (both are positive displacement pumps) give high accuracy compared to centrifugal pumps. OEM issues a certificate to the customer about accuracy. If the process is critical, then it is important to have pumps with high accuracy for the consistency of the process,” said Jaysukh Boda, Maintenance Manager, Covestro (India) Pvt Ltd

As mentioned earlier, metering pumps are known to dose accurate volume of liquid because the pump head displacement moves only a known volume over a known time. However, in practice, it never achieves a high level of accuracy because of changing process conditions, such as temperature, pressure shifting, air entrapment and wear of components. For example, any change to the system pressure can result in deviation of dosed volume and lead to incorrect addition of metered chemicals to the process; thus, reducing accuracy and quality. To solve this problem, the pump should accurately decrease speed when the system pressure falls. This will ensure dosing accuracy in accordance to the set point that the operator programmed into the pump. According to Milton Roy company, although a metering pump can generally be adjusted to pump at any flow rate between 0 and its maximum capacity, its accuracy is measured over a range determined by the pump's turndown ratio. Most metering pumps have a turndown ratio of 10:1, which simply means that the pump is within its accuracy rating anywhere between 10 per cent and 100 per cent of capacity.

Capacity/flow rate: Flow rate - measured in litre per hour (LPH) - is one of the most important things to consider while selecting a pump. A higher flow rate means a larger pump size is required. However, there are some factors that affect a metering pump’s resulting flow rate. For example, at an operating pressure of 50 psi, a metering pump is dosing 20 LPH of a chemical. If the same system had to operate at a pressure of 150 psi, the flow rate will drop slightly to something like 17 LPH. Though the drop is small, in case of critical application, this may prove costly. A good rule of thumb is to make your maximum expected flow rate not more than 90 per cent of the pump’s capacity. This way the user will have room for small increases if needed. 

Cost factor: Wide range of metering pumps are available in the market and their cost ranges from Rs 15,000 to few lakhs. As flow rate/capacity increases, price also increases accordingly. Typically, Indian made pumps cost less than the imported (or global) brands. Besides upfront cost, cost of maintenance, servicing cost, availability of spare parts, etc should also be considered while selecting a pump. Many offer additional features such as IIoT based monitoring system to understand the working condition of the pump. These features, which are useful for big plants where pumps are needed for continuous operations, add to the cost.   

Other factors: In addition, factors like head, pump drivers, suction condition, pH, leak protection mechanisms, viscosity, etc should be considered while buying a pump. For example, a chemical metering pump with a system to alert the user about a leak can help in avoiding accidental discharge of excess amounts of chemicals during the operation of the pump. This can potentially prevent an accident, if the chemical is volatile and explosive. Most of the known brands (Indian or imported) offer one-year warranty on the product.

Select from the Most Popular Metering Pumps 
While metering pumps are very useful, selecting the right pump for your application can be a daunting task. To help you find the right supplier for your need, we have put together a list of some of the most popular metering pump brands made by Indian companies based on our discussions with the pump experts and the users from chemical industry in no specific order of ranking.

Indo Pump: The Nashik (Maharashtra) based Indo Pump is known for designing and manufacturing dosing pumps for process industries. Capacity of these plunger type dosing pumps ranges from 0 to 500 LPH and can operate with pressure of 5 kg/cm2 to 100 kg/cm². Wetted parts are made of stainless steel. These pumps find applications in industries like fertiliser, pharmaceutical, detergent, chlorine, etc.

Minimax Pumps Pvt Ltd: Minimax Pumps - the Nashik (Maharashtra) based company that designs and develops pumps using high-grade components in accordance to the API-675 standards - offers technically advanced Plunger Type Pump MP60 to ensure smooth performance at low operating cost. This pump has high flow rates of 0-700 LPH, is easily compatible with most of the fluids, and offers steady state metering accuracy of +/-1 % of pump output. It can handle high pressures of 200 Kg per sq. cm. Positive return of plunger and variable stroke mechanism allows linear relationship between control stroke setting and stroke length.

Positive Metering Pumps: Positive Metering Pumps' plunger-type dosing pump is precise metering device and its performance conforms to API 675. Plunger is hard chrome plated and flow rate is linear to stroke length variations. External arrangement for flushing the gland packing to increase its life is also possible. Metering accuracy is almost independent of back pressure. There are 4 models of this pump having flow rate ranging from 0-513 LPH to 0-22800 LPH and can operate under pressure ranging from 133 bar to 796 bar. It comes with options of jacketed head for heating or cooling the liquid been pumped. Materials of construction offered by the company are SS304/ SS304L, SS316/ SS316L, Carbon Steels, Alloy20, Hastalloy, etc.

Sandur Fluid Control: The Bangalore based Sandur Fluid Control, the first Indian company to obtain ISO Certification for dosing/metering pumps, offers Dostec 50 dosing pumps which are heavy duty, high precession, motor driven diaphragm pumps for dosing liquid products. This series allows many injection possibilities depending on the head being chosen. The available heads are 330 to 1000 LPH. Dostec 50 dosing pumps are manufactured with materials that can resist most chemicals. They are designed for all sorts of processes where it is necessary to dose a product into a hydraulic network, such as food, textile, chemical industry, water treatment etc. This maintenance-free pump has aluminium die-cast body. Up to four different modules can be added, which can be piston, diaphragm or both. There is an option to connect Variable Frequency Drive for providing 4-20 mA.

Shapotools: Shapotools' metering pumps are high precision positive displacement pumps, made as per API 675 International code, for dosing a controlled volume of liquid. The discharge can be varied from zero to maximum capacity while pumps are running or at rest. The pump's design makes it an ideal flow control element in chemical process, for the feeding of chemicals with a high degree of accuracy, even under very high discharge pressure conditions. These pumps are robust and of unmatched quality, and offer considerable savings to customer on account of compactness, low installation, operational cost and minimum maintenance.

Swelore Engineering Pvt Ltd: Ahmedabad-based Swelore Engineering Pvt Ltd offers comprehensive range of chemical metering pumps with robust design. Its VX series is hydraulically flexed diaphragm metering pump that comes in single and double diaphragm type. It offers flow rate of 0-6000 LPH in simplex design. Higher capacity can be achieved by multiplexing. This pump can operate in pressure upto 250 kg/cm2 (in standard design) and upto 350 kg/cm2 (in case of special design). It has features like leak-free design, diaphragm rupture monitoring system, high metering accuracy, in-built relief valve in hydraulic circuit, and diaphragm life of more than 20,000 working hours. All moving parts including plunger is running in oil. It has automatic capacity control via pneumatic or electric signal on demand. It is versatile and suitable for any liquid including toxic and hazardous.

Unique Dosing Systems: Unique Dosing Systems' chemical dosing pump is membrane type pump which has good suction lift character. This pump ensures free flow performance in high capacity and high pressures situations. The pump is specially designed for corrosive liquids like sulfuric acid, slurries, etc. These are straightened with easy maintenance cartridge type check valves, Hypalont and Vitont diaphragms and Single and double ball check valves to ensure better performance. PTFE coated diaphragm is supported by a steel core & temperature resistant material simplex. Accuracy at repeatability of +3%. The pump is well suitable for continuous duty to handle most corrosive fluids.

VK Pump Industries Pvt Ltd: VK Pump Industries provides solutions for high pressure metering and dosing systems. Its plunger type metering pump offers flow rate of up to 7,000 LPH on single head, and meets API 675 standards. It offers, as option, spare parts kit for 2 years normal operation. It can perform at process temperature from -20°C to 120°C and comes with sandwich diaphragm pressure leak detection. Wetted parts standard is AISI-304/AISI -316 Stainless Steel. Wetted parts are also available in Alloy 20, Hastelloy ‘B’ or ‘C’ or PP, UHMWPE/PTEF. Capacity is continuously adjustable from zero to maximum, both while pump is stopped or running. Metering accuracy of ± 1% of pump output at any single setting from 10% to 100% of capacity. Multiplexing facility allows coupling of several pumps, driven by one common motor.

Make a wise choice
In addition to the above mentioned Indian-made pumps, there are number of global players in the Indian metering pumps market. Some of them are Milton Roy India, WILO Mather and Platt Pumps Pvt Ltd, IDEX India, SEKO, Bran+Luebbe (a SPX FLOW brand), Grundfos, LEWA, Cole-Parmer and Tuthill Pump. As discussed, choosing a right pump for a particular application in chemical industry is tricky. While knowing the properties of the chemical to be pumped is useful, working closely with the pump OEM helps in selecting the right pump suitable for the given application. In addition to upfront price, the buyer also needs to take into account the running cost, service support & its charges, availability of spare parts, etc before finalising the purchase.  

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