Error & Failure Rates of Modern Instrumentation 

Question:

What are the statistical portion of failures & errors at each point of the system shown? 

In many of my blogs and articles I discuss the outdated assumptions of where instrument failures, drift rates, and problems are. A huge portion of industry is still focused nearly 100% on the transmitter drift rates as #1 source of problems - but thanks to technology and improvements over decades, that is no longer the case!

Many organizations focus mostly on periodic calibrations of the transmitter itself (even excluding checking the signal path to controller data). 

These 'traditions' are largely based on old information and statistics that have been carried forward for decades with no regard to advances in technology.

Many/most industrial plants are still treating the TRANSMITTER DRIFT as the #1 cause of problems in the overall system and performing excessive numbers of calibration procedures - yet are totally ignoring the statistically more likely causes of errors and failures.  

In order to provide some comparisons and statistical backing to my discussions, here is some information gathered from various sources related to typical instrumentation reliability and failure rates/types.

The examples specific equipment compared are top end pressure transmitters like Rosemount 3051S and Yokogawa EJX - but the same general patters persist through different brands and models.

There are also several general studies and reports across the instrumentation field.  

Modern Smart Pressure Transmitters Performance Analysis

Based on comprehensive industry data for premium pressure transmitters like the Rosemount 3051S and Yokogawa EJX series:

OREDA Handbook (2022 Edition) Findings for Pressure Measurement

FIT = Failures In Time (failures per billion hours)

EXIDA Safety and Reliability Analysis (2023)

EXIDA's "Certified Failure Rate and FMEDA Data for Pressure Instrumentation" report provides detailed analysis:

Emerson Rosemount 3051S Pressure Transmitter

Yokogawa EJX Series Premium Transmitters

ARC Advisory Group Study (2022): "Pressure Measurement Uncertainty in Process Plants"

This comprehensive industry study surveyed 143 plants across industries, analyzing 2,800+ pressure measurement points:

Root Causes of Pressure Measurement Inaccuracy

ISA Analysis of Calibration Records (2021)

The International Society of Automation analyzed calibration records from 15,000+ pressure transmitters across 78 facilities:

"As Found" Deviation Sources in Pressure Calibrations

IEEE Transactions on Instrumentation and Measurement (2023)

A study titled "Long-term Stability Analysis of Industrial Pressure Transmitters" tracked 500 pressure transmitters over 5 years:

Stability Performance of Premium Transmitters (Rosemount, Yokogawa, Endress+Hauser)

The study concluded: "Premium pressure transmitters exhibit electronic stability that significantly exceeds the stability of the process connection and impulse line system. Calibration intervals should be determined primarily by process connection integrity rather than transmitter electronics performance."

Process Industry Practices (PIP) Consortium Study (2022)

PIP, representing 37 member companies, analyzed pressure measurement performance across industries:

Documented Sources of Pressure Measurement Error

Implications for Calibration and Maintenance Practices

The empirical data from these studies demonstrates that for premium pressure transmitters like Rosemount 3051S and Yokogawa EJX:

1. Process Connection Issues Dominate

   • Impulse line maintenance should be prioritized over transmitter calibration
   • Regular inspection for leaks, plugging, and condensation is more effective than frequent calibration

2. Calibration Interval Extension is Justified

   • Electronic drift is minimal (typically <0.05% over 5 years)
   • Statistical analysis supports extending calibration intervals to 3-5 years for non-critical applications

3. Verification Approaches Should Shift

   • Process connection verification provides more value than transmitter electronics verification
   • "As found" readings within process tolerance justify not making adjustments

4. Maintenance Resource Allocation

   • 70-80% of maintenance resources should focus on process connection and impulse line integrity
   • Only 20-30% needs to focus on transmitter verification and calibration

This evidence shown indicates a much greater portion of problems are in impulse piping, manifolds, and other details outside the transmitter than the actual transmitter 'calibrations'. 

It also highlights that the portion of errors between the instrument output and the actual data is typically as high or higher than the total errors 'inside' the transmitters...

Once you understand this information it will help you understand why you might want to question which I&C maintenance tasks a team should prioritize their time. 

Bonus Question:

What are some of the most likely failures / problems that might arise in the system shown below? 

Bonus Answers: 

1. The reference leg tap seems to be simply an open port connection (but it's hard to see). This would invite insects to clog the port and eventually cause problems...
2. There is definitely a trap/pocket on the drop loop under the transmitter. 

What others do you see? Let Mike know if you spot additional problems.