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: Pressure Switch Frozen Screwed Cover Extends the Plant Shutdown
Share
Notification Show More
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 > Root Cause Analysis (RCA) > Pressure Switch Frozen Screwed Cover Extends the Plant Shutdown

Pressure Switch Frozen Screwed Cover Extends the Plant Shutdown

Instrumentation engineering root cause analysis of pressure switch (PS) frozen screwed cover which extends the plant shutdown time.

Last updated: September 28, 2022 2:55 pm
S Raghava Chari
Root Cause Analysis (RCA)
No Comments
Share
4 Min Read
SHARE

Instrumentation engineering root cause analysis of pressure switch (PS) frozen screwed cover which extends the plant shutdown time.

Contents
Pressure Switch Frozen Screwed CoverShop EffortsField Instrument Crew Done JobsRecurrence Prevention
Article Type:Root Cause Analysis (RCA)
Category:Instrumentation
Equipment Type:Switches
Author:S. Raghava Chari

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

Pressure Switch Frozen Screwed Cover

K-901 NH3 Refrigeration Compressor tripped on Low-Low lube oil pressure though the oil header pressure was the set 1.4 bars. A large Al screwed cover housing contains the pressure switch (PS). The crew identified the PS’s micro-switch as defective and proceeded to change it.

The corrosion and oxides frozen stubborn Aluminium (Al) cover defied two hours long all possible violent unscrewing efforts including not permitted.

Finally, the crew took the below-listed steps:

  1. Cut the cable entering the housing
  2. Chisel out the 6 mm Carbon Steel mounting bolts
  3. Send the entire assembly to the shop

Shop Efforts

Shop efforts are:

  1. Shop crew too failed cover unscrewing after an hour long more violent ‘expert’ efforts
  2. Finally the ‘experts’ machined off the cover, cleaned the body threads and took necessary measurements and sent the coverless casing to install in the field 
  3. They turned out a CI cover and fitted a cut from automobile windshield rush bought window
  4. They delivered to the field instrument crew
old Pressure Switches
This is an example image, not related to this article.

Field Instrument Crew Done Jobs

While the above shop tasks progressed, field Inst crew done jobs are:

  1. They bolted the pressure switch (PS) assembly less cover at its location using threads greased SS bolts & nuts
  2.  They replaced the defective micro-switch and set the PS for proper trip pressure
  3.  They connected the cable
  4. Using this opportunity, the simulation tested the trip system
  5. As soon as the shop delivered the new CI cover, they greased the threads profusely and screwed it in .

Thus, a simple ½-hour task extended to 12 hours of lost ammonia production, despite well-coordinated done several tasks.

Recurrence Prevention

The above hard-way learning prompted taking the below-given recurrence prevention steps:

  1. Grease all fasteners and screwed covers before bolting / screwing in
  2. Check all field instruments
  3. Unscrew / unbolt one stand fastener at time, grease and screw back to avoid future stubborn fasteners caused delays
  4. Spray WD-40 or other loosening sprays on stubborn fasteners and complete step-a. Chisel out still stubborn fasteners and fit new fasteners. Use stainless for ≤ 6mm and CS for larger all greased
  5. Unscrew and grease screwed covers
  6. Free stuck instrument door hinges and latches, and oil them

Thanks to these pro-active steps stuck screws and covers became history.

Author: S. Raghava Chari

Do you face any similar issues? Share with us through the below comments section.

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

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

Read Next:

  • Target Flow Transmitters Failed
  • Multistage Flash Drums Readings
  • Rotameter Caused Pipe Weld Cracks
  • Level Instruments Stopped Working
  • Differential Pressure Transmitter Problem
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

Reformer Fan Bearing Change Times cut by 90%
Process Air Compressor too Frequent & too Lengthy Overhauls Eliminated
Inability to Test Repaired HT Motors in Workshop Posed Problems
Compressor Anti-Surge Control near-miss incident
Stuck Segment Orifice Dimensions Calculations
Pulverizer Electrical Problem Solved
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
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

CO2 Absorber Corroded Wall Thickness & Weld Building
Ammonia Flash Vessel All Level Instruments Stopped Working
Discharge Head 3‑monthly leaks of Steam Turbine Driven Centrifugal Compressors
Arc Fault Breaker (AFB) Electrical Problem Solved
Primary Reformer RFG main Hot Spots threaten Indefinite Outage
Instrument Steam Pressure Taps Primary Block Valves Glands and Bonnets Leaks
Compressor Cracked Shaft Spacers
Welding Machine Fail in Dusty and Corrosive Areas

Keep Learning

Refrigeration Compressor Turbine Not-tripping when needed Trip

Refrigeration Compressor Turbine Not-tripping when needed Trip

Failed Letdown Valve

Failed Letdown Valve Shuts down a Urea Plant Several Hours

Phosphate Dozing System

Phosphate Dozing System Problems

Multistage Flash Drums Erratic Level Readings

Multistage Flash Drums Erratic Level Readings

Damaged Magnetic Flow Meter Flow Tube

None Could Repair Slightly Damaged Magnetic Flow Meter Flow Tube

Aluminum Cable Terminations

Aluminum Cable Terminations Repeat Failures

Fan Motor Frequent Journal Bearing Failures

Fan Motor Frequent Journal Bearing Failures Posed Plant Outages

Steam Letdown Station Problems

Steam Letdown Station Problems and their Solutions

Learn More

Working of Proximitor

Different Types of Turbine Protective Devices

Wood Sawing and Blower System PLC Control Design

Wood Sawing and Blower System: PLC Control Design

Typical process control loop

How Process Control Loop Works

Air Circuit Breaker Principle

High Voltage Circuit Breaker Principle

Bio Sensors Objective Questions

Bio Sensors Objective Questions

Importance of Fire & Gas Detection System

Importance of Fire & Gas Detection System

PLC Structured Text Program for Output Generation via Equations

PLC Structured Text Program for Output Generation via Equations

Pressure Safety Valve Leak Test Procedure

Pressure Safety Valve Leak Test Procedure (PSV Testing)

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?