Orifice plate flowmeters are one of the most versatile and popular types of flowmeters available today. In fact, it accounts for 77% of all differential pressure installations. This meter imparts a constraint to the flow to make the needed differential pressure.
Just like all differential pressure measurement systems, the orifice plate flowmeter systems comprise of three elements.
- A primary element that makes the differential pressure signal;
- A differential pressure transmitter that gauges the DP and turns it into a digital or electronic signal;
- A tertiary component that computes, transmits, stores, and displays the measured flow rate based on the values.
In this post, you’ll learn some of the best practices and options for using orifice plate flowmeters to their maximum potential. Read on!
Selecting the Correct Specifications
Any orifice flowmeter operation relies much on setting up the correct specifications and making sure that the meter is in the right size for the particular flow application. When it comes to custody transfer applications, a full and comprehensive list of specs is needed.
Some of the questions that must be dealt with include: what’s the allowable pressure drop and desired flow turndown, and what flow conditions and process attributes are prone in the flow application.
Moreover, gas amounts, liquid, and other variables must be considered, as well. Take note that orifice plate flowmeter accuracy sustained in liquid flows that have at least 2.2% by weight of liquids in gas and 5.5% by volume of gas in liquids. The accuracy of the meter might be affected if the numbers are higher.
There are a lot of online sellers, like SmartMeasurement, that sells such a device. Just keep in mind to check the specs before you decide to buy it.
Picking the Correct Holding Device
Choosing the correct orifice holding device is yet another important matter to consider. The right fittings are crucial to the performance and accuracy of the meter. Plus, the need for flexibility when replacing plates or removing plates.
The most common holding device for plate flowmeters is the orifice flange union. This device is known for its affordability and simplicity. Additionally, this type of flange union is especially appropriate to these meters that don’t require periodic inspections.
Taking out an orifice plate from the such flange union, when necessary, requires the separation of the flanges and line depressurization. With that, there’s a high chance of the liquids spilling.
Another great holding device is a single-chamber device. The main advantage of using this fitting is that it can accurately find the orifice plate in the pipeline. Also, flange separation isn’t necessary, but the pipe must be depressurized when removing the plates.
Furthermore, it’s extremely vital to keep in mind that the orifice plate bore should depend on the flow range. When determining the nominal plate bore’s diameter, you must consider the maximum and minimum quantities of gas to be dealt with over long and short periods. And the values estimates for the 1st, 3rd, and 10th year.
Turndown and Beta Ratio
There are plenty of other steps that must be considered to guarantee the maximum accuracy of orifice meters. The first one is the beta ratio. It’s advised to opt for an orifice beta ratio ranging from 0.2 and 0.7, for best accuracy.
Values beyond or lower that range are likely to have inaccuracies. The capability to change the orifice meter to a different one beta ratio gives the flowmeter the limited ability to be leveraged long-term over massive flow ranges. Additionally, it’s an essential factor in its effectiveness.
Also, you need to consider the necessity for a wide turndown. Unlike other flowmeters, orifice meters will give a quantitative signal to low flow rates. So, if a wide turndown is needed, then it’s best to install two differential pressure transmitters on the device to measure both low and high flow range.
Periodic maintenance and inspections of the flowmeters must always be done to minimize unaccounted and lost for corresponding gas or liquid. Also, the frequent operation of all senior orifice holding devices is recommended.
It entails opening, lubrication, closing the slide valve, cleaning drain plug holes, and rotating the gear shafts. These steps must be performed when the fittings have been depressurized.
Transmitters have an essential part in the orifice plate metering today. Over the years, differential pressure transmitter performance has made better. The ease of use and low cost of modern differential pressure transmitters have made it economically viable.
And stacking differential pressure transmitters have become practical. You can lower the differential pressure reading uncertainty by adjusting the transmitters to particular flow conditions.
Orifice flowmeters are versatile and advanced meters. From selecting the correct specs to using transmitters effectively, orifice flowmeters can provide results beyond expectations and will stay as a chief element of flow applications in the long run.
Ultimately, orifice flowmeters can enhance flow measurement across industries and deliver precise measurements for any flow applications like custody transfer and closed-loop control applications.