r. selva kumar – sr. engineer, quality control a ravi...
TRANSCRIPT
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ROOT CAUSE ANALYSIS FOR COMPLAINT OF
LESS WALL THICKNESS FOUND IN PUP PIECE – TRUNNION MOUNTED BALL VALVES
Team Members:
Date: 27.04.2018
N Kesavan – Manufacturing
S Kannan – Quality contr
M. Balasubramanian – Manufacturing
Senthil Kumar - Service Engg.
R. Selva Kumar – Sr. Engineer, Quality Control
A Ravi. – Sr. Engineer, Quality
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CONTENTS
1.0) Background of the complaint
2.0) Preliminary Investigation done at LTVL on receipt of complaint
3.0) Root Cause Analysis: To identify the underlying cause
a) Problem Description
b) Cause and Effect Diagram
c) Significant Causes
d) Why- Why analysis
4.0) Correction
5.0) Corrective Actions
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1. Background of the complaint:
We have supplied the Manual Valves with pup piece of 72 Nos to M/s. L&T Hydrocarbon Engineering Limited, from Dec’2017 to March -2018. They have received and found less
wall thickness in pup piece of 12” # 600 welded valve – 1 No. They have communicated
same to LTVL, to submit the repair procedure for rectification at site itself.
Sl No Valve Serial No Size Class
Supply Date Type of Non-Conformity
1 17G706143 12” #600
24/01/2018
2. Preliminary Investigation done at LTVL on receipt of complaint
a) The following documents were verified and found in order:
Internal Valve Test Report (VTR) Verified & Found OK.
Final inspection report (SCN) Verified & Found Not ok. (i.e. we noticed the land height in the range of 4 to 7 mm in one end of pup piece against the maximum of 1.5mm, during pre-dispatch inspection. Hence, the inner surface of pup piece was grounded to make the land height uniform thorough the circumference. Therefor cleared as such.)
b) Following stages were verified w.r.t the reported complaint
Verified the process conditions of other valves tested during the same date of complaint.
Site photos:
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3.0 Root Cause Analysis: To identify the underlying cause
a) Problem Description
DESCRIPTION AREA
DESCRIPTION
WHAT
What object has the defect Trunnion Mounted Ball Valve
What is the defect? Grinding marks observed in one end of the pup piece
WHERE
Where specifically on the valve do you see the defect? On the pup piece
Where geographically is the object observed? At customer end
WHEN
First seen - By the customer? Yes
When seen since? April -2018
When is the observation seen in the valve- while testing @ site, operation (i.e. when the valve is used)?
It was observed during their inspection
When is the observation seen in the life of the object?(eg. when new or after few years of service)
After two monthes
HOW BIG How many objects have noticed this observation? one Valve
Similar Parts
How many/much observation(s) per object One
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b) Cause & Effect Diagram:
c) Stratification of causes
No
Possible Causes Verification Significant / Insignificant
1.1 Method of inspection incorrect RIS-17 for Inspection IN-SIGNIFICANT
1.2 Method of packing wrong during transit Received with cut piece and ok IN- SIGNIFICANT
1.3 Method of machining incorrect Verified with supplier and they have done in VTL
IN- SIGNIFICANT
2.1 Visual & Dimensions were not as per requirements
Verified Inspection report and found ok
IN-SIGNIFICANT
2.2 Pup piece got orality due to high input during welding
Heat input verified by using thermal IN-SIGNIFICANT
3.MAN 4.MATERIALS
1.METHODS / PROCESSES 2.MACHINE
Grinding marks observed in end of the pup piece
1.1 method of inspection incorrect
3.1 Pup piece bulged due to collar welding at edge of pipe.
3.2 Wrongly measured the dimensions in inspection
1.2 Method of packing wrong during transit
2.1. Visual & Dimensions were not as per requirements.
3.3 Pup piece handled improperly
4.1. Wrong materials used
3.4 Butt weld end preparation done by taken wrong reference
3.5 Excess clamping done during setting in machine
1.3 Method of machining incorrect
1.2 Pup piece got orality due to high input during welding
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chock and ok
3.1 Pup piece bulged due to collar welding at edge of pipe.
- IN-SIGNIFICANT
3.2 Wrongly measured the dimensions in inspection
Qualified operator inspected IN-SIGNIFICANT
3.3 Pup piece handled improperly - IN-SIGNIFICANT
3.4 Butt weld end preparation done by taken wrong reference
- SIGNIFICANT
3.5 Excess clamping done during setting in machine
- IN-SIGNIFICANT
4.1 Wrong materials used Materials found as per e- bom IN-SIGNIFICANT
d) Consideration for Why-Why analysis
1.1 Why – Why Analysis
1.1.1 Why– Butt weld end preparation done by taken wrong reference
Why– Operator not measured the full circumference of pipe ID
Root cause: Operator not measured the full circumference of pipe ID. Because of this one of the pup piece made with orality by 4-7mm
4.0 Correction:
Repair procedure has been submitted on 27.04.2018 to M/s.LTHE for rectification at site itself.
5.0 Corrective actions:
1. We have given the awareness to the supplier to take the 100% measurement of pipe ID circumference before starting the Edge preparation.
2. 100% Pup piece to be inspected in receipt stages.