Low flow flowmeter for corrosion inhibitor

Application of low flow positive displacement flow meter in corrosion inhibitor injection system

In the petrochemical industry, precise addition of corrosion inhibitor chemical has always been a technical activity. For example the flow can be very small, such as only 1-2 GPM or even lower, and it normally operate under high pressure around 300pis .Excessive investment wastes money, while insufficient investment in equipment can lead to scaling and blockage, so flow control must be precise. Recently, many companies have started using low flow PD flow meters to solve this problem, and the effect is indeed good.

Actual demand for corrosion inhibitor injection

For common reverse osmosis systems, the amount of corrosion inhibitor (CI) added is usually between 0.13 and 2.92 liters per hour, with some systems even as low as 0.02 liters per hour. Such a small flow rate, ordinary flow meters cannot measure it at all. Moreover, the viscosity of corrosion inhibitors varies greatly, and temperature also has a significant impact on them. Generally, the error of using a flow meter will increase.

A common situation in factories is that operators adjust the dosing pump based on experience, check the liquid level of the medicine tank at regular intervals, and estimate the dosage using this "dirty method". The result of doing this is either an increase in the cost of medication or a decrease in the amount of scale, there will always be something unpleasant.

The advantages of micro positive displacement flowmeter

The biggest advantage of this flowmeter is its high accuracy, which can reach an accuracy of 0.5% or even higher, and can measure a minimum flow rate of 0.5 milliliters per minute (0.5ml/min). More importantly, it is not afraid of changes in liquid viscosity. Whether it is thin water or thick liquid, as long as the gear can be pushed, the measured results are accurate.

High pressure flow meter: The flow measurement of corrosion inhibitors is often carried out under high pressure, such as 280psi or 100bar. Small PD flow meters can be made into high-pressure flow meters, and the pressure can even reach up to 400bar.

Small flow sensors for ultra low corrosion inhibitors can be made in very small sizes, such as 1/8 ", 1/4", 1/2 ", 3/4", 1” which meets the low flow measurement.

For corrosion inhibitor injection systems, these characteristics are too practical. Firstly, the flow range covers a wide range, ranging from tens of milliliters to tens of liters per hour; Secondly, the measurement accuracy is high, and the dosage of the medication can be precisely controlled; finally, it has good stability and requires minimal maintenance after installation.

What should be paid attention to in practical applications?

Although the small oval gear flowmeter is easy to use, there are still some requirements for installation and use.

• Filters must be installed. Although the corrosion inhibitor looks clear, there are inevitably some impurities. If a filter is not installed, impurities will get stuck in the gears over time, and the flow meter will become inaccurate. It is generally recommended to install filters with a mesh size of 200 or more, which are cost-effective but worry free.

• The installation direction should be correct. This type of flowmeter has requirements for installation direction, the inlet and outlet cannot be reversed, and it is best to maintain a certain back pressure for more stable measurement. The specific installation instructions are provided in the manual, just follow the rules.

• The temperature range should be monitored. The standard model operates at temperatures ranging from -30 to 80 degrees Celsius. If the on-site temperature is particularly high, a high-temperature model should be selected. Don't save money on this, otherwise the flow meter won't last long and will break down.

• Careful handling of joints is necessary. When twisting the joint, do not wrap too much raw material tape, as it may cause trouble if it gets stuck inside the flowmeter. This small flowmeter has a small diameter, and even a small amount of debris can cause problems.

Several key parameters during selection

Min flow it can detect is  0.5ml/min

The range of traffic should be selected according to actual needs. For example, if the dosage of your system is 0.5 to 5 liters per hour, then choose the LC-M6 model, which has a measurement range of 0.5 to 100 liters per hour, which is completely sufficient and has enough margins.

Material is also important. the corrosion inhibitor is corrosive, 316 stainless steel should be chosen, which is more expensive but durable.

The output signal from flow transmitter should match the control system. Current flow meters generally have pulse or current 4-20mA outputs, which can be directly connected to PLC or DCS systems for automatic control. If it's just simple monitoring, a mechanical flow meter is enough; it's cheap and doesn't require external power supply.

Practical experience in maintenance and upkeep

Check the filter once a quarter and replace it if it gets clogged. Filter blockage can affect flow measurement and increase the burden on the pump.

Perform an accuracy check regularly, connect a measuring cylinder to the outlet, and measure the flow rate to see if it matches the displayed value. If the error is large, it may need to be recalibrated in nearby workshop.

Economic accounts need to be calculated clearly

The price of micro oval gear flowmeter is indeed not cheap, ranging from several thousand to tens of thousands of dollars per set. But in the long run, this money is worth it.

Firstly, it's about saving medication. Accurately controlling the dosage and adding according to actual needs can save a lot of medication costs every year. Especially for imported corrosive inhibitors, the price is very expensive; saving 10% of the usage can recoup the cost in one year.

Secondly, it is to reduce equipment failures. Accurate dosing reduces equipment scaling, lowers cleaning frequency, and reduces downtime, all of which have significant indirect benefits.

Finally, there is the cost of labor. Automatic monitoring and control, operators do not need to stare at the medicine box every day, nor do they need to frequently adjust the dosing pump, saving them time and effort.

The use of a miniature positive displacement flowmeter for corrosion inhibitor injection system is indeed a good solution. High precision, good stability, and simple maintenance. Although the initial investment is a bit large, in the long run, the cost-effectiveness is very high. Of course, the selection and installation should be done correctly, and daily maintenance should not be careless, so as to fully utilize the true function of the flowmeter.

If your system is still using the "estimation" method to add scale inhibitors, you may consider upgrading your measurement methods. After all, refined management is the trend, and the money that should be spent still needs to be spent. Stable operation of equipment is the key principle.