PAUT Inspection Services for Plant Shutdowns
Plant shutdowns and turnarounds involve inspecting, repairing and recommissioning critical assets within a tightly controlled schedule.
Phased Array Ultrasonic Testing is suitable for many shutdown applications because it provides rapid weld-volume examination, detailed imaging and permanent digital records without using ionising radiation.
PAUT can be deployed independently or combined with TOFD, conventional UT, corrosion mapping and surface NDT methods according to the component, expected damage mechanism and applicable inspection requirements.
Successful shutdown inspection depends on technical preparation, equipment readiness, qualified personnel, safe site execution, data quality and timely reporting.
Industries Supported
Shutdown PAUT services can be provided for:
➤ Refineries
➤ Petrochemical plants
➤ Fertilizer plants
➤ Chemical-processing facilities
➤ Thermal power plants
➤ Nuclear-support facilities, subject to approval
➤ Oil and gas terminals
➤ LNG facilities
➤ Pipelines and compressor stations
➤ Offshore installations
➤ Steel and cement plants
➤ Boiler and pressure-equipment facilities
Typical Shutdown PAUT Applications
PAUT may be used to inspect:
➤ Process-piping welds
➤ Pipeline girth welds
➤ Pressure-vessel welds
➤ Boiler headers
➤ Steam-line welds
➤ Nozzle and branch connections
➤ Repair and replacement welds
➤ Heavy-wall components
➤ Flange welds
➤ Small-bore piping
➤ Corrosion-prone areas
➤ Cracking-susceptible locations
➤ Weld overlays and cladding
➤ Structural welds
Each application should be reviewed for technical feasibility before mobilization.
Why PAUT Is Suitable for Shutdown Inspection
Rapid Data Acquisition
Electronic beam steering can cover multiple inspection angles without repeatedly changing conventional angle-beam probes.
Immediate Results
PAUT data can normally be reviewed on-site, allowing repair decisions to be taken quickly.
Permanent Digital Records
Encoded PAUT creates inspection files that can be stored, reviewed and compared with future examinations.
No Radiation Exclusion Zone
PAUT does not use ionising radiation. Nearby maintenance activities can normally continue, subject to normal site-safety controls.
Detailed Defect Location
PAUT can provide indication position, depth, length and through-wall information when supported by a suitable sizing technique.
Repeatability
Encoded scanners provide positional tracking and help reproduce the examination during repair verification or future shutdowns.
PAUT and TOFD During Shutdowns
Combined PAUT and TOFD may be selected for critical butt welds.
PAUT provides directional coverage and helps detect discontinuities at different orientations. TOFD can provide through-wall sizing for suitable defects where tip-diffracted signals are clearly identified.
Combined inspection may be applied to:
➤ Heavy-wall process piping
➤ Pressure-vessel seams
➤ Critical steam piping
➤ Boiler components
➤ Repair welds
➤ New replacement spools
➤ High-pressure system welds
TOFD suitability must be confirmed for the component thickness, curvature, access and applicable code.
Pre-Shutdown Technical Planning
Shutdown success depends on completing technical preparation before the plant is taken out of service.
The client should provide:
➤ Component list
➤ Weld identification numbers
➤ Drawings and isometrics
➤ Pipe diameter and wall thickness
➤ Material specifications
➤ Weld configurations
➤ Expected damage mechanisms
➤ Inspection code
➤ Acceptance criteria
➤ Previous inspection reports
➤ Repair history
➤ Site-access information
➤ Shutdown schedule
➤ Required reporting timeline
Missing or inaccurate information can delay probe selection, calibration-block preparation and procedure approval.
Inspection Scope Classification
The shutdown worklist should be divided into clear categories.
Planned Inspection
Components identified before the shutdown with complete technical details.
Hold-Point Inspection
Examinations linked to fabrication, welding or repair stages requiring client clearance before work continues.
Repair-Weld Inspection
PAUT performed after weld repair or replacement.
Emergent Inspection
Additional components identified after opening, cleaning or visual examination.
Reinspection
Repeat scanning following repair, grinding or further engineering review.
Separating these categories helps control manpower, equipment and reporting priorities.
Procedure and Scan-Plan Preparation
Before mobilization, the inspection company should prepare:
➤ PAUT procedure
➤ TOFD procedure, where applicable
➤ Technique sheets
➤ Weld-specific scan plans
➤ Calibration instructions
➤ Data-naming protocol
➤ Indication-reporting format
➤ Acceptance and escalation process
➤ Equipment list
➤ Personnel matrix
Complex welds, small-bore pipes and unusual materials may require a procedure demonstration or feasibility trial.
Calibration-Block Readiness
Shutdown projects often contain multiple diameters, thicknesses and weld profiles.
The required reference blocks should be identified and manufactured in advance.
Calibration blocks may need to represent:
➤ Material type
➤ Diameter
➤ Wall thickness
➤ Surface curvature
➤ Weld geometry
➤ Cladding or overlay
➤ Reference reflectors
➤ Expected defect locations
A missing or unsuitable calibration block can stop the inspection even when the PAUT equipment and personnel are available.
Personnel Planning
A shutdown PAUT team may include:
➤ PAUT Level II technicians
➤ TOFD-qualified technicians
➤ NDT assistants
➤ Data analysts
➤ PAUT Level III technical support
➤ Equipment coordinator
➤ Reporting personnel
➤ Project supervisor
➤ Safety coordinator
The required number of teams depends on:
➤ Total weld quantity
➤ Shift pattern
➤ Inspection complexity
➤ Daily production target
➤ Access conditions
➤ Reporting deadlines
➤ Number of simultaneous work fronts
Adequate rest periods and shift handovers are essential for maintaining reliable data interpretation.
Equipment Planning
Shutdown equipment planning should include both primary and backup systems.
Typical requirements include:
➤ PAUT instruments
➤ TOFD-capable systems
➤ Conventional UT equipment
➤ PA probes
➤ TOFD probes
➤ Flat and contoured wedges
➤ Small-bore scanners
➤ Large-diameter scanners
➤ Position encoders
➤ Calibration blocks
➤ Couplant
➤ Batteries and chargers
➤ Cables and adaptors
➤ Data-storage devices
➤ Analysis computers
➤ Spare probes and wedges
Backup arrangements are important because equipment failure during a shutdown can delay other maintenance activities.
Site Readiness
Before inspection begins, the client and inspection team should confirm:
➤ Components are identified correctly
➤ Insulation has been removed where required
➤ Surface preparation is complete
➤ Welds are accessible
➤ Scaffolding is available
➤ Lighting is adequate
➤ Surface temperature is within limits
➤ Nearby work will not affect scanning
➤ Safe access is provided
➤ Permits are approved
➤ Calibration and analysis areas are available
➤ Electrical power is available where required
Technicians should not be mobilized to an inspection location before the component is ready.
Surface Preparation
PAUT scanning surfaces should be reasonably smooth and free from:
➤ Weld spatter
➤ Loose scale
➤ Heavy rust
➤ Flaking coating
➤ Sharp projections
➤ Excessive surface waviness
➤ Oil and contamination
Grinding and buffing requirements should be agreed in the contract because surface preparation can significantly affect inspection productivity.
Inspection Workflow
A typical shutdown workflow is:
1. Confirm weld identification and technical details.
2. Verify surface preparation and access.
3. Review the approved technique sheet.
4. Calibrate the PAUT system.
5. Perform encoded or manual scanning.
6. Check data quality and weld coverage.
7. Analyse relevant indications.
8. Communicate preliminary results.
9. Issue a weld-wise inspection report.
10. Reinspect repaired areas where required.
11. Complete final data review and reporting.
Preliminary and Final Reporting
Shutdown decisions often require rapid communication.
Preliminary Result
A preliminary result may indicate:
➤ Accepted
➤ Reportable indication observed
➤ Engineering review required
➤ Repair recommended by the responsible authority
➤ Rescan required
➤ Incomplete coverage
➤ Surface preparation required
Preliminary results should not bypass the approved evaluation and authorization process.
Final Report
The final report may contain:
➤ Component and weld identification
➤ Inspection procedure
➤ Equipment details
➤ Probe and wedge details
➤ Calibration information
➤ Scan coverage
➤ Indication table
➤ PAUT or TOFD images
➤ Sizing information
➤ Acceptance status
➤ Inspection limitations
➤ Analyst and reviewer details
Data Management
Large shutdowns can produce hundreds or thousands of scan files.
A controlled data-management system should include:
➤ Standard file-naming format
➤ Unique weld identification
➤ Daily backup
➤ Separate folders for accepted and reportable welds
➤ Calibration-file retention
➤ Repair and reinspection linkage
➤ Revision control
➤ Analyst-review status
➤ Final-report reference
➤ Secure data storage
Poor data management can create reporting errors even when field scanning is technically correct.
Quality-Control Measures
Shutdown quality controls should include:
➤ Daily equipment verification
➤ Calibration checks at required intervals
➤ Encoder checks
➤ Scan-coverage verification
➤ Random data review
➤ Level III technical support
➤ Analyst cross-checking
➤ Weld-identification verification
➤ Report-to-data traceability
➤ End-of-shift handover
Production targets should not compromise calibration, coverage or data quality.
Common Shutdown Challenges
Late Release of Components
The inspection team may remain idle while waiting for insulation removal, grinding, scaffolding or permits.
Scope Increase
Emergent inspection requirements can exceed the planned equipment and manpower capacity.
Incorrect Component Information
Actual thickness, diameter or weld configuration may differ from the supplied worklist.
Limited Access
Temporary structures, nearby piping and equipment can restrict scanner movement.
High Surface Temperature
Components may not have cooled sufficiently for standard wedges, probes or couplant.
Reporting Congestion
Data collection may exceed analysis and reporting capacity if sufficient analysts are not assigned.
Equipment Damage
Cables, wedges, probes and scanners are exposed to heavy site use. Backup equipment is essential.
Productivity Factors
Daily inspection output depends on:
➤ Component readiness
➤ Weld diameter and thickness
➤ Inspection technique
➤ Scanner installation time
➤ Surface condition
➤ Access and scaffolding
➤ Calibration changes
➤ Indication complexity
➤ Reporting requirements
➤ Shift duration
➤ Permit delays
➤ Repair and reinspection volume
A guaranteed daily weld quantity should not be quoted without reviewing these conditions.
Safety Considerations
Shutdown PAUT activities may involve:
➤ Work at height
➤ Confined-space entry
➤ Hot surfaces
➤ Temporary electrical connections
➤ Slippery couplant
➤ Simultaneous operations
➤ Heavy equipment handling
➤ Restricted escape routes
➤ Night-shift work
The inspection team must comply with the plant’s permit-to-work system, risk assessment, toolbox talk and personal protective equipment requirements.
Applicable Standards and Procedures
Shutdown inspections may be performed with reference to:
➤ ASME Boiler and Pressure Vessel Code, Section V
➤ ISO 13588
➤ ISO 16828
➤ ISO 17640
➤ ISO 20601
➤ ISO 22825
➤ Applicable construction and in-service codes
➤ Client specifications
➤ Approved PAUT and TOFD procedures
The applicable edition, technique qualification and acceptance criteria must be confirmed before inspection.
Our Shutdown PAUT Capabilities
Integrity & Advanced Inspection Solutions India Private Limited provides:
➤ PAUT and TOFD inspection teams
➤ PAUT Level II personnel
➤ Level III technical support
➤ OmniScan-class PAUT systems
➤ Small-bore and large-diameter scanners
➤ A15- and A32-type phased-array probes
➤ Flat and contoured wedges
➤ Calibration-block support
➤ Customized scan-plan development
➤ Manual and encoded scanning
➤ On-site data analysis
➤ Shift-wise reporting
➤ Repair-weld reinspection
➤ Backup equipment arrangements
➤ Domestic and international mobilization
Information Required for a Shutdown Proposal
Please provide:
➤ Plant location
➤ Shutdown dates
➤ Component worklist
➤ Weld quantities
➤ Diameter and thickness range
➤ Material specifications
➤ Weld configurations
➤ Inspection code
➤ Acceptance criteria
➤ Shift pattern
➤ Surface-preparation scope
➤ Scaffolding and access arrangements
➤ Reporting timeline
➤ Client-provided facilities
➤ Expected emergent-work percentage
Request a Shutdown Inspection Proposal
Early technical planning allows the PAUT team to prepare suitable procedures, scan plans, probes, scanners, calibration blocks, backup equipment and reporting resources.
Share the preliminary shutdown worklist with our technical team for manpower planning and a techno-commercial proposal.