Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: RCA – Compressor Did Not Trip on Suction Pressure Low Low
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Process > RCA – Compressor Did Not Trip on Suction Pressure Low Low

RCA – Compressor Did Not Trip on Suction Pressure Low Low

In this article, you will learn the Root Cause Analysis for Compressor did not trip on the suction pressure low-low.

Last updated: February 4, 2023 9:04 pm
Editorial Staff
Process Root Cause Analysis (RCA)
1 Comment
Share
6 Min Read
SHARE

In this article, you will learn the Root Cause Analysis for Compressor did not trip on the suction pressure low low.

Contents
Compressor Did Not TripRoot Cause Analysis of Compressor Trip

Here we will discuss about one incident related to the Interlock bypass procedure. Due to the incorrect interlock bypass procedure followed, the Compressor could have been damaged. But due to the Panel Engineer’s timely action, the Compressor was stopped which avoided damage to the Compressor. 

Compressor Did Not Trip

A Centrifugal Compressor with a single stage was installed in one of the plants in a refinery. This centrifugal Compressor was a kind of booster Compressor.

The inlet to the Compressor was 5 kg/cm2 and the outlet of the Compressor was 9 kg/cm2. While the Compressor was running, the Panel Engineer observed that the Compressor’s Suction Pressure Low alarm was generated for all 3-pressure transmitters.

Within a few seconds, Compressor’s Suction Pressure Low Low alarm was also generated for all 3 Suction Pressure Transmitters. Immediately the Panel Engineer pressed the emergency shutdown button and stopped the Compressor. 

Some background information about the Compressor: The Compressor is a single-stage centrifugal Compressor for boosting the inlet gas from 5 kg/cm2 to 9 kg/cm2.

Important Interlocks are given on Low Low Suction Pressure, High High Inlet Temperature, Low Low Suction Flow, High High Outlet Temperature, and High High Discharge Pressure. Tripping is given for all these parameters at low-low and high-high values.

Compressor Did Not Trip

Root Cause Analysis of Compressor Trip

So why the Compressor did not trip on Suction Pressure Low Low?

Let us have a Root Cause Analysis for the Compressor which did not trip on Suction Pressure Low Low

Probable Cause 1: Pressure transmitter malfunction

All 3 pressure transmitters had a low-low alarm. All 3-pressure transmitters cannot malfunction at the same point of time.

Probable Cause 2: Analog Input card malfunction

All 3-pressure transmitters were connected to 3 different analog input cards. Hence this cause also is not possible.

Probable Cause 3: No Interlock configured for Suction Pressure Low Low.

The Compressor has tripped many times on Suction Pressure Low Low due to upstream disturbances.

Also, Cause and Effect shows Compressor tripping on Suction Pressure Low Low.

Probable Cause 4: Interlocks of Suction Pressure Low Low bypassed

On checking, found that the Interlocks of the Suction Pressure Low Low were in bypass condition.

So, what went wrong?

Let us have a detailed analysis of this incident in which the Compressor did not trip on Suction Pressure Low Low.

1 day before the incident, a preventive maintenance job on the pressure transmitter was done. During the job, all the 3 pressure transmitters were bypassed by the Instrumentation engineer. The job was done on all 3 pressure transmitters one by one.

After job completion, the Interlocks were restored by the common shift engineer as the job got completed during the end of the General shift, and Operation Department asked the Instrumentation department to keep the Interlocks bypassed for a few more minutes to observe the pressure transmitter after the job.

All the 3 Interlocks were restored by the Instrumentation Shift Engineer later.

On further checking, it was found that the Instrumentation Shift Engineer only restored alarms (low-low, low, high, and high-high) which were taken from the value.

Generally, in all PLC, there is one bit for tripping the Compressor, and the alarm is also generated using that bit only. But in this case, one other bit was used for tripping the Compressor. This was a special case for this Compressor. The Instrumentation Shift Engineer was unaware of this.

Hence, he did not restore the bit which was used to trip the compressor on Suction Pressure Low Low. Due to this bit present in bypass conditions, only alarms were generated but the Compressor did not trip.

So, it is always best practice to write all the locations of bypass in the Interlock Bypass Request as well as in the Interlock bypass register.

Also, if the Interlock is very critical, then a screenshot before the bypass and a screenshot after the bypass should be saved on the Server.

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:

  • Heat Exchangers
  • Filters in Compressors
  • Desuperheater Design
  • Control Loop Testing
  • Ball Float Steam Trap
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 !

Continue Reading

Turbo-Compressor Problem – Root Cause Analysis
Reformer Fan Bearing Change Times cut by 90%
A Large Gate Valve’s Failed Motorized Operation
Root Cause Analysis for Tank Overflow due to Valve Problem
Reciprocating Compressors
Pump 3-monthly Seal Leaks threaten entire Plant Shut down Indefinitely
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
1 Comment
  • Anil Dass says:
    October 4, 2022 at 5:49 pm

    Excellent learning, communication and shared knowledge by all within a department is key, also verifications and double checking anything and everything should be completed in the manner it was supposed to be. Never take it for granted that job well done, without verification.

    Reply

Leave a Reply Cancel reply

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

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Pipeline Shakes Torn apart Valve Positioners
Primary Reformer RFG main Hot Spots threaten Indefinite Outage
Repeat Control Valve Plug Stem and Gland Leaks
Solenoid Valve Failure in Plant Start-Up: Identifying the Root Cause
Blowout preventer (BOP) Principle
Centrifugal Compressor near ½-RPM Frequency High Magnitude Shaft Vibrations
Passing Control Valves Cause Yearly Losses in Production Plant
Instrument Steam Pressure Taps Primary Block Valves Glands and Bonnets Leaks

Keep Learning

Plant Shutdown Analysis: Valve Closed and SOV Coil Failure

Plant Shutdown Analysis: Valve Closed and SOV Coil Failure

High-pressure Service Level Transmitters Misunderstood Zero Drifts

High-pressure Service Level Transmitters Misunderstood Zero Drifts

Doubtful Temperature Readings

Doubtful Temperature Readings threatens Soaking Pit Wrecks 

An Indian Plants all turbines’ low Vacuum

An Indian Plants all turbines’ low Vacuum & Saudi Plant turbo-compressor only

Sprocket Assembly and Bolting Segments

Bucket elevators Chain and teeth wear Problems

What is Pump Redundancy

What is Pump Redundancy?

Boiler Feed Water Heater Shell Flange Leaks

Boiler Feed Water Heater Shell Flange Leaks

Reactor Top lid lapped

Urea Reactor Top Bolted Plug developed Leaks

Learn More

actuated-valve-schematic

Components of Shutdown Valve

Fieldbus Segment

Basics of Foundation Fieldbus

Types of Transfomer Cooling Methods

Hydrogen Sulfide Accident

The Aghorn Hydrogen Sulfide Accident – H2S Gas

Top 50 Electrical Engineering Questions & Answers

Top 50 Electrical Engineering Questions & Answers

What is NEST loading=

What is Nest Loading? – DCS and PLC Control Systems

Motor ladder Logic

Draw a ladder logic circuit for the electric motor of an air compressor ?

how-a-plc-do-the-scaling-for-a-sensor

How a PLC do the Scaling for a Sensor ?

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

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?