Inst ToolsInst ToolsInst Tools
  • Ask
  • Courses
  • Videos
  • Q & A
    • Interview
      • Instrumentation
      • Electronics
      • Electrical
      • Practical Questions
    • MCQ
      • Instrumentation MCQ
      • Electrical MCQ
      • Electronics MCQ
      • Control Systems MCQ
      • Analog Electronics MCQ
      • Digital Electronics MCQ
      • Power Electronics MCQ
      • Microprocessor MCQ
      • Multiple Choice Questions
  • EE
    • Electronics
      • Electronics Q & A
      • Electronic Basics
      • Electronic Devices & Circuits
      • Electronics Animation
      • Digital Electronics
    • Electrical
      • Electrical Basics
      • Electrical Q & A
      • Power Electronics
      • Electrical Machines
      • Electrical Animation
      • Power Systems
      • Switchgear & Protection
      • Transmission & Distribution
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
Search
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Reading: SIS Instruments and Valves Inline Testing – Safety Instrumented System
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • PLC Tutorials
  • Control Systems
Search
  • Ask
  • Courses
  • Videos
  • Q & A
    • Interview
    • MCQ
  • EE
    • Electronics
    • Electrical
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Safety Instrumented System (SIS) > SIS Instruments and Valves Inline Testing – Safety Instrumented System

SIS Instruments and Valves Inline Testing – Safety Instrumented System

Safety Instrumented System (SIS) – Inline testing is quite useful for SIS instruments, and valves online testing for safe Operation.

Last updated: April 19, 2022 12:41 pm
Editorial Staff
Safety Instrumented System (SIS)
No Comments
Share
10 Min Read
SHARE

Safety Instrumented System (SIS) – Inline testing is quite useful for SIS instruments, and valves. Online testing enables the safe Operation & functioning of SIS.

Contents
SIS Inline TestingBenefits of Inline TestingFlowmeters Inline TestingTemperature Elements Inline TestingSIS Inline Testing of ValvesWhy is it important?How to Overcome this?Procedures to TestDigital Valve Controllers

In this article, testing refers to Proof testing of the SIS instruments/valves.

SIS Inline Testing

Inline testing implies that testing can be accomplished without a process shutdown. There are several requirements to be considered for accomplishing this.

  • Redundancy is mostly used for SIS components (especially sensors) wherever possible based on configuration.  A test of one SIS sensor can be done, while the other sensor(s) continue to function.
  • Bypasses could be installed around SIS final elements (valves) so that testing and maintenance can occur while the process is in operation. 
  • In batch plants, Inline testing might be accomplished by shutting down one train of equipment while keeping the rest of the plant running to eliminate (or reduce) any potential production loss,
  • Documenting occurrences where the required automatic action has occurred during the operation of the plant (such as a pump trip, based on the same process condition that is required by the LOPA function).
  • Automated testing and recordkeeping may be an option in some plants for a subset of the testing requirements, but all aspects of testing requirements (including visual field inspection of the installation, leak testing, etc.) must be met according to the required/calculated proof test interval.

Benefits of Inline Testing

The benefits common to all of the options above are to minimize downtime and reduce maintenance costs for SIS proof testing.

Automated inline testing (Like triggering the small movement of the valve say 2-3% using Smart Digital positioners) may bring value by extending or eliminating off-line proof testing, but may require additional instruments for comparison like Secondary flow/pressure transmitter or Master flow meters, etc.

Flowmeters Inline Testing

For simple DP cell and orifice plate types, the most common approach is to inject a differential pressure signal, simulating the flow, into the cell, however, this does not test the impulse lines and isolation or equalization valves for possible blockage.

Regular maintenance, impulse lies flushing & draining on a redundant sensor, and calibration of the sensor instrumentation enhance the inline testing and the reading from the instrument.

Flowmeter installations must include the necessary configuration to allow the proof testing of the instrument at the required testing interval.

The type of installation required will depend on the required test interval and the desired shutdown interval for the plant.

The following 1 line drawings are examples of installations that allow testing to be accomplished for single and two flow meters installations.

Meter used in SIS Testing installation

Temperature Elements Inline Testing

Temperature Elements installed in pockets of a process gas heater/furnace are tested online, as most of these installations form part of triple redundant systems with 2 out of 3 votings.

They use a thermocouple / PT100 simulator from the connection at the head and check for ingress, integrity, and connection security.

When inline, the technician check for differences in readings between the three instruments to detect drift.

To improve confidence and reliability, the maintenance team shall plan to change the thermocouples regularly in addition to simulation and check contact with the end of the pocket.

Another method of inline test is to inject a current, voltage, or resistance signal to simulate temperature and so test the operation of the safety system.

The signal can be injected into some types of probes together with the electronics and so only the sensing element is not tested.

On some other probes, the signal is injected after the electronics, particularly where the installations are on higher elevations & unreachable locations.

SIS Inline Testing of Valves

There is always a challenge to test the SIS Valves inline, as they form the critical isolation point of an equipment/process / interplant.

Why is it important?

With periods between plant shutdowns being extended, emergency shutdown valves (ESDV) may remain in the open position, without movement, for lengthy periods.

Experience has shown that after extended periods without movement, there is a tendency for the valve to stick.

This would result in the shutdown system failing to operate in the event of a genuine demand on the shutdown system, despite all other tests on the system being completed satisfactorily.

How to Overcome this?

An inline testing application such as Smart Valve Monitoring (SVM) can monitor the Emergency Shutdown Valve (ESDV) for faults based on comparing an original full closure fingerprint of the ESDV assembly and components, such as solenoid valves, against a partial stroke test.

Their system can perform all tests at the ESDV-designed closure speed without shutting the plant down.

Procedures to Test

Adding drain valves where SIS Final control elements are in place. Below typical drawing depicts the installation/requirement.

This helps to inject instrument air at the upstream and ensure no leak in the ESD valve downstream,

Smart Valve Monitoring

An alternate method is to test ESD valves in-line by blocking the solenoid vent with a pressure gauge and operating the valve.

This caused the valve to move slightly and also gave an indication of the pressure gauge of solenoid operation.

This is not a standard practice. This system may work well though the installation and subsequent removal of the gauge would need to be very carefully controlled.

Another method is that valves can often only be tested when the plant is being shut down or actually shut down.

Tests are generally limited to tripping the valve and observing that it moves to the open or closed position. This test realizes that they can only carry out limited checks on the effect on flows through the valve if there is no bypass.

Digital Valve Controllers

The most efficient way to perform SIS Valves inline testing is to install Digital Valve Controllers (DVC).

DVC enables the user to define a suitable online valve stroke value from 1% up to a maximum of 30% from its standby position to minimize the effect on the process.

The test parameters are saved in the microprocessor’s non-volatile memory, minimizing mistakes and enabling consistent test results.

Digital Valve Controllers not only provide intelligence benefits in terms of performance and safety by allowing partial stroke test online but also provides additional benefits in terms of ease, simplicity, flexibility in diagnostics, improved reliability of SIF, etc.

By eliminating expensive conventional local test mechanism, which was laborious, time-consuming, and require specific talent.

Digital Valve Controller reduces complexity and simplifies the test process. Digital Valve Controller predictive maintenance capability provides complete Final Element health analysis and reduces the amount of scheduled regular maintenance by extending the turnaround period.

The below figure depicts a digital valve controller installed in a SIF loop, where Logic Solver provides an AO (Analogue Output) 0-20mA or 4 to 20 milliamp DC current signal to DVC. The signal is generated based on sensors and logic internal by the logic solver to DVC. Digital Valve Controller is used as a safety and Diagnostics device.

The below figure shows the SIS valve test schematic with a Digital valve controller using AO (4-20mA) signal.

SIS valve test schematic with Digital valve controller

The below figure shows the SIS valve test schematic with a Digital valve controller using DO (24 VDC) signal.

Safety Instrumented System Online Testing

Images Courtesy: Emerson

If you liked this article, then please subscribe to our YouTube Channel for Electrical, Electronics, Instrumentation, PLC, and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Read Next:

  • SIS Application Program
  • How to do a Proof Test?
  • Common Cause Failures
  • SIS Verification & Validation
  • Probability of Failure on Demand
Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !
S84 / IEC 61511 Standard for Safety Instrumented Systems
Safety Instrumented System Engineer Interview Questions
SIS Safety Requirements
SIS Hardware Fault Tolerance – Methods to Overcome HFT issues
SIS Final Control Elements
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
208kSubscribersSubscribe
38kFollowersFollow

Categories

Recent Comments

  • Guifty Shimica on Top Non-PLC Certification Courses for Automation Professionals
  • Guifty Shimica on Top Non-PLC Certification Courses for Automation Professionals
  • MIHARITSOA Aina Sitraka on Top Non-PLC Certification Courses for Automation Professionals
  • Vaishnavi on Free Instrumentation Course for Trainee Engineers

Related Articles

Parts of Safety PLC

SIS Software Simulation – Safety Instrumented System

Process Shutdown

Difference between Process shutdown and Emergency Shutdown

Reliability of a Control System

Reliability of a Control System

Component De-rating

Component De-rating in Control Systems

Basic Terms used in SIL Verification

Basic Terms used in SIL Verification

safety PLC programming

SIS Logic Solver

Safety Instrumented System SIS Component Selection

SIS Component Selection – Safety Instrumented System

Purpose of Emergency Shutdown (ESD) System

Purpose of Emergency Shutdown (ESD) System

More Articles

Temperature Sensors Fault

18 Temperature Sensors Fault Leads to Plant Shutdown

Pressurizer

Pressurizer

Advantages of Hydrogen cooling in Synchronous Generators

Electronic Devices & Circuits Objective Questions

Electronic Devices & Circuits Quiz – Set 1

FIFO in STL Language in Siemens PLC

How to Code a FIFO Queue in STL Language in Siemens PLC?

Relay Types

Types of Relays – Questions and Answers

Baffle Nozzle Assembly Sensitive Mechanism

Baffle Nozzle Assembly Sensitive Mechanism

Top 50 Electrical Engineering Questions & Answers

Top 50 Electrical Engineering Questions & Answers

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?