How to Calibrate Flowmeters:
laboratory vs in line calibration

In every production facility, from water utilities to pharmaceutical manufacturing, flow is an essential measurement parameter used to control the process. Whether flow is used to monitor production performance or to dose the correct amount of product into a batch, it is crucial that the measured values are reliable and within specification.

Discrepancies in measurement can result in unnecessary use of ingredients, but they can also affect final product quality and production consistency. Product quality is especially critical in pharmaceutical manufacturing, which is why legislation requires frequent calibration of measuring points to ensure compliance and product quality.

To maintain accurate and reliable measurements, flowmeters typically need to be calibrated one to two times per year. This article explains the differences between traditional laboratory calibration and on-site, in-line calibration, and outlines the challenges and benefits associated with each approach.

Why Flow Calibration is Required

Over time, flowmeters drift due to mechanical wear, environmental conditions, and changes in the production process. Even small deviations in measurement can lead to incorrect batching, increased waste, and reduced production consistency.

Reliable flow measurement is therefore essential not only for process control, but also for protecting product quality and ensuring compliance with regulatory requirements. As a result, frequent calibration of flowmeters is required in many industries to maintain accurate and traceable measurements.

Challenges with Traditional Laboratory Calibration

Traditional laboratory calibration can be a time-consuming and disruptive process. In order to calibrate a flowmeter, it must first be physically removed from the process line, which often requires parts of the production to be shut down. 

Key challenges include

• Production downtime during removal and reinstallation
• Risk of mechanical damage during handling and transport
• Waiting times and logistical delays when using external laboratories
• Increased risk of contamination if cleaning and reinstallation are insufficient
• Additional validation efforts after reinstalling the instrument

Together, these factors can significantly extend calibration time and increase the operational impact on prodution.

What is in-line Flow Calibration?

In-line flow calibration is a method where calibration is performed directly in the production process without removing the flowmeter from the pipework.

Instead of dismounting the instrument and sending it to a laboratory, calibration is carried out on-site by comparing the measured values under actual process conditions.

This approach eliminates the need to remove and reinstall the flowmeter, which reduces downtime and avoids the uncertainties that can be introduced when an instrument is reinstalled in a process. By performing calibration in-line, measurements are verified under the same conditions in which the flowmeter is normally operating.

When Does In-Line Flow Calibration Make Sense?

In-line flow calibration is particularly relevant in production environments where frequent calibration is required and production downtime must be kept to a minimum. In many facilities, flowmeters need to be calibrated one to two times per year, making repeated removal and reinstallation both time-consuming and disruptive.

Processes that involve continuous production, batching, or dosing can be especially affected by downtime associated with laboratory calibration. In such cases, performing calibration directly in the process allows production to continue with minimal interruption.

In-line calibration is also well suited for regulated industries, where product quality and compliance are critical. By calibrating under actual process conditions, measurement results better reflect real operation and reduce uncertainties introduced by removing and reinstalling instruments.