Re-define the metering pump (with photos)

When is the metering pump no longer metering pump? Donelle Capriotti, Director of Business Development at Wanner Engineering, said that the latest technological advances have given some functions beyond the traditional range of dosing pumps. He thinks dosing pumps need a new definition. From centrifugal pumps to positive displacement pumps, many types of pumps and systems are used to control liquid flow, while long term reciprocating metering pumps are used for precise chemical dispensing. Although metering pumps are known for their accuracy, linearity and reproducibility, conventional metering pumps suffer from operational errors. Pumping inaccuracies, idling, and potential leaks are common issues in stroke regulation, and intermittent and pulsating metering flow can put pressure on the system. Pumps featuring electronic flow controllers and multiple diaphragm designs overcome these drawbacks and may even redefine metering pumps. Metering pumps have been benefiting from advances in technology since their former lubricators first appeared on steamers. Pumps with pistons and plungers can withstand a wide range of flow rates and pressures but the contact of the piston or plunger with the pumped media requires compatibility between the material of manufacture and the fluid which may result in a costly replacement And maintenance. Environmental and safety issues, including leakage, especially the leak-free advantages of diaphragm metering pumps also make the pump less universally available. Leak-free pump with precise metrology Wanner Engineering built its first Hydra-Cell leak-free pump back in the 1970s, focusing on agriculture and the rapidly evolving automotive cleaning industry. When analyzing market data, Wanner collected data on the use of the pump and they were pleasantly surprised to find that the Hydra-Cell pump has been successfully run in applications that require precise metering. In many areas, Hydra-Cell is replacing the traditional hydraulic counterbalance diaphragm metering pump. Like other metering pumps, the Hydra-Cell has a hydraulically balanced diaphragm, but it also has electronic flow control and most models have multiple diaphragms (see Figure 1). Figure 1. Hydra-Cell pumps with leak-free hydraulically balanced diaphragm designs are similar to conventional metering pumps, but they also feature electronic flow control and multi-diaphragm design. In conventional hydraulic-balanced diaphragm pumps, the diaphragm is separated in two fluids: process Balance between fluid and working medium. This balanced design ensures that the mechanical diaphragm pump can achieve higher outlet pressure and flow rate. These hydraulically balanced diaphragm metering pumps have the following features: â—† Regulate flow primarily by manually controlling stroke length changes â—† One diaphragm per fluid side â—† Pulsating, intermittent fluid â—† Combination of each plunger, diaphragm and liquid side, flow rate And the pressure range is limited â—† with the flow and pressure increases, the installation area increased significantly. Definition of dosing pumps Over the years, many institutes and associations have proposed dosing pump definitions. Some are industry-focused, such as the American Petroleum Institute's (API) 675 standard for positive displacement pumps with positive displacement control. Other definitions are broader in scope, such as those defined by members of the Hydraulics Society. Regardless of the origin of these definitions, these statements may be excluded if they do not reflect design and technical improvements, and those that achieve the same measurement accuracy and unique design characteristics have different improvements in many areas In the list of considerations. The effect of these technical improvements is obvious, for example by hydraulically driving the metering pump to regulate the flow rate. The metering pump flow is a function of plunger diameter, stroke effective length and stroke rate. Since the plunger diameter must be constant for a given pump, changing the stroke length and pump speed is the only way to adjust the flow. Many years ago, manual stroke regulators became a major feature of metering pumps. Initially, these regulators can not be used during pump operation. Later, the design improvements made the process length of the stroke can be changed. There are two ways to adjust the stroke length. The first one, commonly referred to as amplitude modulation, alters the eccentric radius of the plunger drive. In general, sliding the crank so that the stroke length can be changed by changing the length of the pivot arm is similar to that of a pendulum. This also applies to the piston, the stroke length of the piston is equivalent to the pendulum arc. The other is called idle, can also be divided into mechanical idle and hydraulic idle. In mechanical idle design, the motor rotates the worm shaft, the worm shaft drives the eccentric gear to rotate. The cam and gear rotate and the plunger is activated by the cam follower. When the plunger moves forward on the outlet stroke, it discharges the fluid behind the diaphragm, thereby discharging the pumped medium. Then the spring retracts the plunger back to its original position. Limiting the backward movement of the plunger can change the stroke length, thereby changing the flow rate. Hydraulic idling is a change in effect, not the actual stroke length. In this case, the plunger reciprocates throughout the stroke length, but a portion of the working fluid is bypassed by the bypass valve. Technological Progress With the increasing popularity of automation, pneumatic and electric actuators begin to be used as stroke adjustment devices for AM and IQ metering pumps. Despite their ease of use, low rates of change (typically 1 second / 1% stroke length) result in inaccurate pumping during conditioning. Recently, there has been a growing use of VFDs to change stroke speed rather than stroke length (see Figure 2). Figure 2. Variable speed motors (VFDs) and controllers, which are generally cheaper than electronic actuators and provide full stroke length, improve accuracy and avoid idling, eliminating possible leaks in metering and dosing applications. AC and DC motors react faster, reaching a maximum speed of 0 in 0.5-1.3 seconds. Faster flow correction achieves higher long-term accuracy. In general, variable frequency motors are much cheaper than electric actuators. Reliability, reproducibility, and linearity improvements are some of the other advantages of AC motors. Many AC motors have a turn down ratio of 1000: 1, which is as good as or better than the range ratio achievable with both electric actuators and manual stroke regulators. Since full-stroke length is the optimum metering pump performance, changing flow rates by varying speed rather than stroke length is recognized, reducing the importance of manual stroke adjustment. For example, the Hydra-Cell metering pump has been at full stroke length and uses only VFD motors and controllers to change flow. The common denominator for metering pumps is the single diaphragm configuration, which creates a nonlinear fluid, which is the "inevitable nightmare" of the metering system. The Hydra-Cell metering pump has 5 diaphragms on each liquid side, each with a corresponding valve and piston. The inherent "pulseless" nature of these multiple diaphragm pumps eliminates the problems that have long been seen to reduce acceleration loss and pipe strain. As a result, shock absorbers are no longer required in the system and their application is extended to the field of linear fluid metering. To illustrate the effects of pulsations, Wanner Engineering conducted a pilot experiment to run a Hydra-Cell multi-diaphragm metering pump and a typical hydraulically balanced single-diaphragm metering pump under ideal flow and pressure conditions to record their pressure trajectories ( See Figure 3). Figure 3. Hydra-Cell Pump with Multi-Diaphragm Design for Operation at the Same Flow and Pressure More Stable Performance Than a Traditional Single Diaphragm Metering Pump Traditional metering pumps can be reduced by using a combination of shock absorbers and several pumps Pulse, the diaphragm stroke order. However, these methods significantly increase the system cost, size and maintenance. With such metering pumps, the size of the plunger, diaphragm, and liquid end increases as flow and pressure requirements increase. Conversely, designs such as the Hydra-Cell pump have many advantages because the fluid end can be held constant and transmissions using gearboxes of different ratios are the only differential components that cover a wide range of flow rates and pressures. Changes in process requirements can be made only by changing gearboxes. This reduces the pump purchase, maintenance and downtime maintenance costs. For many manufacturers, the increased size (including the increase in motor size) may require a large mounting area at higher flow and pressure. A smaller Hydra-Cell pump delivers the same throughput as a large composite system while meeting API 675 performance standards with constant accuracy, linearity and reproducibility (see Figure 4). Figure 4. The traditional triple metering pump in the background is comparable to the Hydra-Cell pump in the foreground (smaller motor). They all have a hydraulic balance diaphragm that meets API 675 standards with constant