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: A Large Gate Valve’s Failed Motorized Operation
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 > Root Cause Analysis (RCA) > A Large Gate Valve’s Failed Motorized Operation

A Large Gate Valve’s Failed Motorized Operation

A large gate valve’s failed motorized operation threatens NH3 plant guarantee test completion.

Last updated: September 28, 2022 3:08 pm
S Raghava Chari
Root Cause Analysis (RCA)
No Comments
Share
6 Min Read
SHARE

A large gate valve’s failed motorized operation threatens NH3 plant guarantee test completion.

Contents
Molecular Sieve Brief IntroductionGate Valve Failed Motorized OperationMore DetailsBush RepairNew Idea
Article Type:Root Cause Analysis (RCA)
Category:Mechanical
Equipment Type:Pipelines and Miscellaneous Problems
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.

Molecular Sieve Brief Introduction

Molecular Sieves (MS) are granules of specific size and shape pores having affinity to absorb specific chemicals from fluid streams.

CO is a poison to ammonia catalysts. MS charged vessel 1 (V1) adsorbs the CO a poison to ammonia convertor catalyst from the 250-bars pressure synthesis gas (SG 75% H2, 25% N2 gas mixture) entering the NH3 Convertor for synthesis into NH3.

4-hours later a programmable logic controller (PLC) diverts the SG flow to Vessel 2 for adsorption, de-pressures V1  slowly, and admits heated small quantities low pressure SG into V1 for 2 for two hours to strip the CO from the MS;

The hot impure gas joins the fuel gas stream. V1 cools for 1½ hours and becomes ready for adsorption. The PLC alternates the adsorption and regeneration between V1 and V2 at 4-hourly intervals.

Various sized several motorized gate valves open and close according to the PLC commands to purify the gas entering the convertor.

Gate Valve Failed Motorized Operation

The 12” 1500 # butt welded to the pipe line gas inlet to V1 motorized gate valve (MGV 1) spindle bush damage prevented the changeover between V1 and V2.

The only option was continuing V1 adsorption as long as possible and devising a way to open and close MGV1 at least manually.

More Details

Mechanics identified that the valve gear toothed stem bush (GTSB) stripped threads prevented the MGV was the reason for MGV 1 inoperability and the failed V1-V2-V1 automatic changeovers. The valve vendor quoted GTSB delivery time was 3-months and price exorbitant.

The commissioning crew overlooked MGV gear boxes was the reason for the MGV1 stripped threads. Hence, the crew filled grease in all GBs and saved further damages. Fortunately the steam bush gear teeth escaped damages.

The instrument crew adjusted the PLC to hoot and flash a lamp 1 hour before MGV 1 close / open needs. Mechanics standing by responding to the operator’s telephone call reached the MGV 1 and closed it using a hydraulic jack / opened using the already suspended chain pulley block and operated the valve close / open limit switches as MGV 1 would do on PLC operation.

Thus, the PLC recognizing proper MGV1 position completed the rest of the changeover tasks. Thus, the PLC completed the V1-V2-V1 changeovers automatically aided by manual MGV1 close / open steps and the guarantee test progressed to successful completion.

During the few days it took to restore the MGV 1 motorized operation, the instrument crew set V1-V2-V1 changeovers to 8-hours instead of the usual 4-hours to avoid too frequent crew call outs.

Bush Repair

The author got the gear toothed stem bush (GTSB) repaired thus:

  1. A machinist made a 10-mm wall thickness CI bush (CIB),  enlarged the GTSB bore and shrink fitted the CIB to the  GTSB
  2. He cut ACME threads in the CIB bore to suit that on the MGV1 stem
  3. As no sample stem was available the machinist walked to V1, ascended the platform several times and walked back to the workshop to try the bush on the valve stem till the stem accepted it smoothly.
  4. His determined and patient efforts yielded a smoothly screwing in / out GTSB, restored MGV 1 open / close and fully automatic V1-V2-V1 changeovers and the Guaranteed Test Completion.

New Idea

The innovative idea and the machinist’s fine job immensely benefitted the company thus:

  1. Enabled the hard won export orders and boosted the company image in the international market
  2. The company’s financial gain too was enormous
  3. Restored Molecular Sieves full automatic operation – a boon in tightly staffed units
  4. Saved the enormous expenses of buying a GTSB and several months human aided V1-v2-V1 changeovers
  5. The valve repair saved sending back the vendor engineers to Japan and calling them back for a repeat guarantee test – an infructuous enormous expense.

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:

  • CO2 Stripper Collapsed Internals
  • Roof Hot Spots eliminated forever
  • Absorber Corroded Wall Thickness
  • Rotary Drier Shell to Split Gear drive
  • RFG main Hot Spots threaten Outage
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

Butterfly Valve Failure Caused Serious vicinity Heavy Fire
Repeat Failures of Letdown Valves
Doubtful Temperature Readings threatens Soaking Pit Wrecks 
Root Cause Analysis – Burst Transformers and 11 kV Input Breakers
Gas Cooler Re-tubing Done Successfully (Root Cause Analysis)
RCA – Compressor Did Not Trip on Suction Pressure Low Low
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

Less than 40% available Plant Air Compressors made available 100% for Operations
Carbamate Plunger Pump Packing Problems Eliminated
Control Panel Instruments Problem Threatened Plant Shutdown
Incident Investigation: Motor Operated Valve Lesson
Root Cause Analysis of Differential Pressure Level Transmitter
Cooling Tower fan FRP fan blades saves and saves
Within Few Weeks Failing Acid Dozing Pumps
Thermocouple Extension Lead Problem

Keep Learning

Failed Letdown Valve

Failed Letdown Valve Shuts down a Urea Plant Several Hours

Fired Boiler Induced Draft Fan (IDF) Failures

Fired Boiler Induced Draft Fan (IDF) Failures Upset all Plants Operations

Rupture Disc

Rupture Discs bursts caused too many Urea Plant Shutdowns

Thermowell Shank to Flange Repeat Weld Leaks

Thermowell Shank to Flange Repeat Weld Leaks

Turbine to Gearbox Alignment Drifts Caused Pump Transfers Problems

Turbine to Gearbox Alignment Drifts Caused Pump Transfers Problems

Turbo-Compressor Problem

Turbo-Compressor Problem – Root Cause Analysis

Weigh Feeder Drive

Failing Weigh Feeders and Mechanical Variable Speed Drives (VSD)

Piston No-Diaphragm Seal Instrument

Seal Pressure Instruments Root Cause Analysis

Learn More

PLC Program for Positive edge pulse output for one scan cycle

PLC Program for Positive Edge Pulse Output for One Scan Cycle

PLC ON DELAY TIMER FUNCTION

#6 PLC Best Practices – Validate Timers and Counters

Types of Failures in Industrial Automation Systems

Types of Failures in Industrial Automation Systems

Two Wire Transmitter Working Principle

Basics of Two, Three & Four Wire Transmitters

PID Simulator

PID Simulator Download

Power Electronics Objective Questions

3 Phase Bridge Inverters Quiz

9 Best E-Book Apps for Students

9 Best E-Book Apps for Students

ControlLogix 5580 Controllers

Rockwell PLCs for Large Scale Applications

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?