FLOW METER BUYERS GUIDE

INTRODUCTION

With all of the flow meter technology available on the market today, selecting a flow meter can be a daunting task. Believe it or not, incorrect selection happens more often than you might think. In fact, studies report 90% of flow meter measurement problems are due to incorrect meter selection! Keep reading our flow meter buyers guide to learn more.

Choosing the wrong meter can result in serious problems such as constant maintenance, expensive repairs, safety concerns, and other issues that can effect overall operations and profit. In addition to choosing the right meter for the job, proper use, maintenance, calibration, and care are all huge factors in flow meter longevity and ensuring you are getting accurate readings.

This guide outlines best practices in selecting the right flow meter, caring for your flow meter, how to go about regular maintenance without having to shut down operations, and other factors that help to extend the life of your flow meter.


There is no such thing as a “one size fits all” flow meter, and it is important to understand that you should not be choosing a meter based on the technology, you need to choose a meter based on your application. It is much easier to first analyze your application’s requirements and then choose the technology that fits rather than buying the meter first and forcing it to work in your application.

There are a number of things to consider as you evaluate your application and technology options including:

Things to keep in mind during flow meter selection:

The answers to the questions below will help you narrow down the many choices you have at the beginning of your flow meter selection process.

1. What type of fluid is to be metered?

2. What are the flow conditions?

3. What are the installation conditions?

4. What are the performance requirements?

The next step we will cover in the flow meter buyers guide is application. When selecting a flow meter, it is important to consider exactly where and how the device will be installed. The installation location can significantly affect both accuracy and efficiency. Obstructions in the pipeline can all cause distortions in flow, affecting flow meter accuracy and repeatability. To ensure best results, flow meters should be installed in locations where there are several straight-lengths of unobstructed pipeline both upstream and downstream. Also consider the following:

There are a number of things that can go wrong with the actual installation. Common issues include:

Be sure to inspect your installation carefully. Research the manufacturer installation recommendations before buying a flow meter, particularly where installation space is limited.The proper use of your flow meter is one of the best ways you can cut down on the need for maintenance, calibration and repair. Rules for use will change from meter to meter. Ask the manufacturer and refer to your owner’s manual to ensure proper use of your meter in your specific application. The top three most important things you can do to ensure proper use and quality measurement include:

  1. Ensure your meter possesses a valid calibration at the time of use
  2. Calibration conditions should mirror the same conditions in which the meter will be used – compensate if necessary
  3. Make sure your calibration laboratory can meet accuracy requirements

Flow meter calibration and maintenance frequency vary based on  industry, application, and flow meter operating environment. The flow meter buyers guide outlines considerations below. What causes the changes in meter performance that require service?

Of course every situation is different, but flow meters have been around for a long time and we all know history has a tendency of repeating itself. Below is a table of common flow meter types and common reasons they require maintenance, calibration, or repair.

Type Reason for Service
Differential Pressure
  • The wearing of orifice plates, cones, and venturies change the geometry of the meter and behavior of flow
  • Dirty pilot tubes
  • Transmitter failure
Magnetic
  • Electrode coating
  • Linear damage
  • Electronic failure
Coriolis
  • Wear and coating of flow tubes
  • Electronic failure of the transmitter
Open Channel
  • Accumulation of debris
  • Level transmitter calibration
  • Electronic failure of transmitter
Positive-displacement
  • Volume changed by dirty liquids, corrosion, and abrasion
  • Bearing wear affects accuracy
  • Solids cause plugging in the meter
  • Gear service is affecting calibration
Thermal Mass
  • Wearing of the sensor
  • Sensor failure
  • Leaks
Ultrasonic
  • Calibrate before putting in service
  • Changes in fluid sonic properties
  • Electronic failure
Turbine
  • Dirty bearings
  • Bearings are affected by chemicals or rotors wear
  • Bearing service affects calibration
  • Electronic failure
Variable Area
  • Plugging
  • Material buildup
  • Metering tube failure
Vortex
  • Vibration
  • Expansion due to temp. variation
  • Meter off-center in pipe
  • Electronic failure

Regular flow meter calibration is necessary. But how should you calibrate a flow meter? Time in use and maintenance schedules are a major factor in the performance a flow meter. Gradual and imperceptible changes occur in the meter due to environment, use, and other factors. Flow meters issues aren’t visible externally. To identify possible issues, the flow meter must be taken apart. This process will happen if issues are found during flow meter calibration testing.

The flow meter buyers guide includes manufacturer guidance. In general, the manufacturer recommendation is that new flow meters should have a six month calibration cycle. Flow meters that are used in unfamiliar applications are also recommended to have calibration after six months. As those calibrations are performed you can analyze the results to adjust your schedule accordingly. Recommendations may differ by manufacturer. Check the flow meter manual, contact the manufacturer, or ask your ISO/IEC 17025 accredited calibration lab for help establishing calibration intervals.Flow meter calibration, repair, and maintenance should not interfere with work. To verify equipment reliability and keep operations running smoothly at the same time, consider the following:

Your maintenance, repairs, and calibration are only as good as your service provider, right? Depending on your company, you may require certain certifications, documentation, and proof that your equipment is being properly maintained. Choosing the right service provider is a significant part of being able to comply with regulations. How do you know you are getting the best possible service? Look for the following:NIST (National Institute of Standards and Technology) is one of the oldest physical science laboratories in the US. NIST calibration services are the highest quality services available. According to the NIST website, “Traceability can be defined as an unbroken record of documentation or an unbroken chain of measurements and associated uncertainties.”  A NIST Certificate of Calibration means that the instrument has been tested and approved to be on a certain level of accuracy. Having NIST calibrate your equipment can be extremely expensive and time intensive. Working with a calibration lab that can provide NIST traceability is your best bet.  The following criteria must be met in order to meet the qualifications of being completely NIST traceable:

  1. The instrument’s calibrated indications have to be traced along an unbroken chain, going back to a national or international standard.
  2. The measurement uncertainty for each link in the traceability chain must be calculated or estimated, in a way that is quantifiable. Allowing the overall uncertainty for the whole chain to be calculated or estimated based on the initial test.
  3. Each link in the traceable chain must be preformed according to previously documented and agreed upon procedures.
  4. All those who are participating in the traceable chain must supply proof of their technical competence.
  5. By the end of the comparison chain, there must be principal standards for realization of the International System of Units.
  6. Calibration must take place at regularly repeated intervals.

ISO stands for International Organization for Standardization. The ISO website states, “ISO is the world’s largest developer of voluntary International Standards. International Standards give state of the art specifications for products, services and good practice, helping to make industry more efficient and effective. Developed through global consensus, they help to break down barriers to international trade.” Although ISO is the body that develops the rules by which accreditation is granted, they do not perform certification auditing. Companies become ISO accredited after completing an audit, performed by an external ISO accreditation body. A calibration laboratory that holds an ISO 17025 accreditation has successfully demonstrated valid calibration testing procedures, adhered to quality principles, and provided accurate documentation. You can feel confident that you are getting the best possible service for your instruments..An ISO 17025 accredited calibration lab goes through a strict annual audit. An auditor observes technicians as they perform procedures, reviews laboratory documentation for standards and customer certifications, and verifies that the lab meets all requirements necessary. The auditor also ensures that proper test equipment is being used to perform calibration. Any lab can be compliant, but that does not mean they are accredited. Labs that are compliant do not go through this auditing process and are not recognized by the ISO accreditation body. This means the lab has not proven they have the competence, expertise, equipment required, or the proper procedures to perform valid calibrations. Any lab can claim compliance, an ISO 17025 accredited lab has actually demonstrated it.Onsite calibration is a cost effective option for companies that have a large quantity of flow meters, and other equipment, to calibrate. Not all service providers have this option. Be sure to ask about this while searching for a provider. Using onsite calibration can help you get your flow meters services quickly, efficiently, and save you money on shipping.

We hope that the flow meter buyers guide has answered all of your questions. Feel free to share the flow meter buyers guide with a friend or coworker that may need help choosing flow meters.Contact the team at e2b calibration for a quote HERE or via email at [email protected]