Author: Jim McVay, Mechanical Integrity Team Leader, Principal Engineer II
“Mechanical Integrity means the process of ensuring that process equipment is fabricated from the proper materials of construction and is properly installed, maintained, and replaced to prevent failures and accidental releases.”
Reference: 19 CCR 2735.3 (US)
The Mechanical Integrity element within a Process Safety Management (PSM) program is critical to safe and reliable operation of critical assets in industrial operations handling hazardous materials. Your mechanical integrity program ensures the process continues to perform in a safe and reliable manner in operation by supporting the full lifecycle of all equipment and piping in the process through designing, building, installing and operating a process. Mechanical integrity programs utilize engineering standards, process safety information (PSI), standard operating procedures (SOPs), process hazard analysis (PHA), and in-service monitoring and inspections to achieve success.
When well implemented, good mechanical integrity programs act to:
- Reduce the likelihood that equipment will unexpectedly fail due to a lack of maintenance, thereby also reducing the likelihood of a sudden release of hazardous materials, as well as the damage and injury that the release may cause.
- Extend the life of equipment by establishing an informed preventative maintenance (PM), predictive maintenance (PdM), and inspection program.
- Predict and budget for equipment and process equipment and piping replacement in the most orderly and economic manner because you should be able to predict end of life of equipment and piping at least two operation run lengths out (in most cases at least four years in advance).
- Customize PM and PdM schedules to an individual facility and process(es), rather than relying on often overly conservative or inadequate standard equipment specification sheets.
- Optimize resources, which often reduces costs for testing in mature programs.
- In many cases, increase operating limits and provide more flexibility on maintenance practices, bringing to light unnecessary conservative and costly controls.
Assets typically covered in a comprehensive mechanical integrity program include:
- Pressure vessels and storage tanks
- Piping systems (including piping components such as valves)
- Relief and vent systems and devices
- Emergency shutdown systems
- Controls (including monitoring devices and sensors, alarms, and interlocks)
- Pumps
Critical components of mechanical integrity programming include written procedures; training for maintenance activities, inspection, testing, and equipment monitoring; equipment deficiency handling; and quality assurance. Operators should establish and implement written procedures for all critical tasks to maintain the ongoing integrity of process equipment and appurtenances. Written procedures discourage personnel from operating equipment outside the conditions for which it was originally designed. They help ensure that tasks are performed adequately and consistently. Procedures are an important part of personnel training as they reduce human error. They are also important during and after ownership, organizational and personnel changes to ensure continuity of the program and safe and reliable operation.
Inspections, tests, and condition monitoring shall be performed on process equipment, instrumentation, and piping. Inspection and testing procedures shall follow recognized industry standards and generally accepted good engineering practices. Corrosion experts conduct damage mechanism reviews (DMRs) on fixed equipment and other assets to determine credible damage mechanisms and establish effective inspection and testing procedures. Developing corrosion control documents (CCDs) and establishing integrity operating windows (IOWs) for critical process units as well as implementing risk-based inspection (RBI) for fixed equipment are crucial steps in achieving long-term reliability. The frequency of inspections, tests, and monitoring shall be consistent with applicable manufacturer’s recommendations and good engineering practices, and more frequently if determined necessary as dictated by operating history. Inspections and tests should be performed using documented procedures and qualified industry-certified technicians and inspectors. All inspections, tests, and monitoring should also be documented.
Written maintenance procedures are not very effective if personnel are not properly trained in how to carry out the instructions contained within the procedures. Mechanical integrity tasks should be performed by personnel qualified to do those tasks. Training is how personnel become qualified. Inspection tasks require trained and qualified inspectors and examiners. There are industry standards and qualification/certification programs to aid operators.
An example of a very effective industry training and certification for a critical skill is for Advanced Ultrasonic Thickness Examiners. The availability of high-quality and accurate ultrasonic testing data is often the cornerstone for engineering and inspection planning decisions, and it is becoming increasingly important for those applications. Therefore, in the industry’s best interest, API (US) implemented a Qualification of Ultrasonic Testing Examiners certification program to assist in defining criteria for assessing the performance of UT technicians. API certifications are offered as follows:
QUTE certification verifies examiner competency in the detection and characterization of defects. QUTE certification utilizes the hands-on, performance demonstration testing method. To qualify, applicants must currently possess a current or previous certification in ASNT UT Level II, Level III, or equivalent.
QUSE certification is the next level up and verifies examiner competency for crack height sizing. In certification testing, applicants will be expected to detect flaws, position them with respect to the weld, and identify and sketch the flaw position within the weld using conventional UT methods (not phased array).
QUPA and QUSE-PA certifications also exist which parallel the certifications described above for phased array UT technicians.
Another critical component of a mechanical integrity program is deficiency handling. The operator in any case must effectively identify and correct deficiencies of concern in equipment and piping that are outside acceptable engineering established limits before further use, or in a safe and timely manner provided means are taken to ensure safe operation. In many cases, operators have some time after finding any deficiencies to continue operation if necessary with appropriate engineering analysis, additional operator controls, safeguards, and so on.
Quality assurance (QA) in mechanical integrity programming is a broad topic. Through QA efforts, operators ensure that new plants and new, modified, or repaired equipment are suitable for the process application for which they will be used. Appropriate checks and inspections shall be performed as necessary to ensure that equipment is installed properly and is consistent with design specifications and manufacturer’s instructions. Operators shall ensure that maintenance materials and spare parts and equipment meet design specifications and applicable codes. Operators necessarily should “stay current” with design specifications and applicable codes for existing equipment, and consider the need to upgrade parts or the whole when improved reliability may be achieved.
Material verification is an essential QA effort to maintain mechanical integrity in critical assets. Industry reported data suggests a probability that as much as 3% of rogue material will make its way into the field as part of a final fabricated assembly, piping circuit, pressure vessel, or other critical process equipment1. Causes include incorrect material stamps on finished components; fabricators using unmarked, unknown material during the fabrication; material traceability not maintained during fabrication; welders using incorrect filler metals; potentially compromised integrity of the original mill test report (MTR); and improper tagging or marking of materials during temporary removal of components and lack of verification prior to re-installation. At least part of the remedy is inclusion of positive materials identification (PMI) testing in both fabrication and field testing prior to installation and in installed critical assets where the materials of construction have not been verified (and documented!). A facility-owned versatile PMI testing instrument is a great investment in mechanical integrity!
Mechanical Integrity Assessments
An assessment of a comprehensive mechanical integrity program should focus on all the following areas as a minimum:
- Organizational support
- Mechanical integrity management documents
- QA and quality control (QC)
- Degradation management
- Inspections, testing, and condition monitoring practices
- Pressure relief systems
- Repairs and replacement
- Lessons learned/continuous improvement
Assessment of organizational support for mechanical integrity programming may consider the following:
- An all-encompassing mechanical integrity champion identified at the facility and corporate level with resourcing capability
- Inspection and other mechanical integrity functions often independent from operations and maintenance departments
- Good working relationships with inspection, operations and maintenance
- Necessary staffing and competencies within staff supporting mechanical integrity
- Ready access and training of facility process safety information and procedures
Assessment of mechanical integrity management documents in a mechanical integrity program may consider the following:
- The existence of a current, comprehensive set of mechanical integrity program documents covering topics such as:
- Safety in design
- Organization and reporting structure for inspection personnel
- Documenting and maintaining facility inspection and QA/QC procedures
- Documenting and reporting inspection and test results
- Developing and documenting inspection plans
- Establishing and documenting appropriate inspection intervals
- Controls necessary so that only qualified NDE and testing personnel are utilized
- Corrective action management for inspection and test results
- Bad actor identification
- Review and approval of drawings, design calculations, engineering assessments, and specifications for repairs, alterations, and reratings
- Internal auditing requirements
- Reporting to the inspection department function any process changes or other conditions that could affect mechanical integrity (IOWs)
- Initial acceptance and periodic re-review of mechanical integrity program documents
- Regular training on mechanical integrity program documents
- A written and enforced standard for comprehensive and organized retention of inspection and test records:
- Organized at the asset level (equipment, loop, or piping circuit level typically)
- Design information along with PMI records and all inspection reports included
- Inspection isometrics, loop sheets, wiring diagrams, etc., prepared as applicable
Assessment of personnel competencies for mechanical integrity programming may consider the following:
- Established competency levels for all mechanical integrity personnel (supervisors, engineers, inspectors, technicians), supported with initial educational and experience background requirements, training, and company/industry certifications
- Complete and current training/certification records for all mechanical integrity personnel
- Contractor competencies established and routinely monitored by company personnel by way of a rigorous formal process
Assessment of QA/QC for mechanical integrity programming may consider the following:
- Management systems, procedures, practices, and controls to ensure that QA program requirements are continually met
- Comprehensive QA/QC program that is in compliance with applicable company and industry codes and standards and routinely updated as appropriate when standards change
- Well-documented facility QC program for fabrication and receipt of new equipment (including PMI and receipt inspections)
- Mechanical integrity personnel access to applicable company and industry design codes and standards
- Material selections for critical components made by personnel with appropriate expertise
- New, repaired, and replacement equipment procured from a list of company-approved suppliers (including subcontractors of the primary fabricator or supplier)
- Appropriate welding controls for fabrication
- An effective material control, marking, and PMI program to ensure that new project and maintenance alloy and non-alloy materials are being installed as specified
- Procedures for safe and effective pressure testing within facilities
Assessment of design and installation practices for mechanical integrity programming may consider the following:
- Front-end engineering design that considers HSE hazard identification, process availability, production capacity, and turnaround frequency
- Preliminary risk assessment and corrosion control
- Assessment for supplementary protective measures (e.g., relief valves, control valves, lubrication, alarms, etc.)
- Design failure mode and effects analysis and mitigation of output risks
- Installation, commissioning, and management of change
Assessment of degradation management for mechanical integrity programming may consider the following:
- Determination of likely degradation mechanisms and expected degradation rates for all critical components, updated with any design and process changes
- Degradation mechanism reviews conducted by experts to determine likely degradation mechanisms
- Necessary process controls when determining degradation mechanisms
- Communications and ready access to current degradation mechanism reviews and associated recommended process controls
Assessment of inspection and testing practices for mechanical integrity programming may consider the following:
- List of all critical equipment and piping for inspection and testing planning considerations, with clear responsibilities as to the mechanical integrity personnel responsible to address each item (e.g., thermowells, auxiliary piping on pumps, third-party equipment)
- Regular testing of all safety instrumented systems
- Effective procedures for establishing comprehensive inspection and test plans based in part on damage mechanisms
- An Inspection Data Management System (IDMS) to store data, calculate corrosion rates (if applicable), store inspection plans, and monitor compliance to support inspection programs
- Structures, idle equipment, spares, and cooling towers, as applicable
- Review of inspection and testing techniques for applicability by inspectors, technicians or appropriate company SMEs; in addition to the review of qualifications of technicians applying these procedures, with test procedures demonstrated to be appropriate for the expected flaws/degradation
Assessment of pressure relief systems for mechanical integrity programming may consider the following:
- Effective management system in place to ensure that the design and design basis for all pressure relief devices (PRDs) are developed and documented
- Procedure to ensure all PRDs are scheduled for service at appropriate frequencies in accordance with site-specific procedures, industry codes, and regulations
- Consistent and critical review of initial “pop tests,” and follow-up analysis conducted and mitigations taken when tests demonstrate lack of proper PRD function
- Tank pressure and vacuum vents
- Procedure(s) for certain necessary on-stream PRD inspections such as pre-start-up installation inspections and periodic on-stream monitoring
- Procedures to ensure flare systems are periodically inspected for significant fouling and corrosion
Assessment of instrumentation and controls with regard to mechanical integrity may consider the following:
- All instrumentation listed with criticality specified
- Documented testing schedule and recorded results
- Bad actor identification and elimination program
Assessment of repairs and replacement with regard to mechanical integrity programming may consider the following:
- Appropriate mechanical integrity personnel (inspectors, engineering, and supervision) involved to specify and review the repair and testing procedures needed to restore equipment to serviceable condition
- Procedures and responsive resources to effectively conduct engineering analysis to determine fitness for service when defects and thinning are found during inspection and testing, often to avoid unnecessary “knee jerk” conservative reactions
- Work process for the review and approval of temporary repairs, along with tracking to ensure monitoring and timely removal
- Hot tap procedures to ensure appropriate and safe application
Assessment of handling “lessons learned” with regard to mechanical integrity programming may consider the following:
- Tracking and trending leak histories for lessons learned and inspection planning updating
- Failure analysis on all failures that impact reliability or safety
- Root cause analyses used for all substantial failures that result in significant reliability and/or safety impacts
- Key performance indicator (KPI) monitoring of mechanical integrity program performance
Assessment of continuous improvement with regard to mechanical integrity programming may consider the following:
- Protocols and procedures for facility mechanical integrity supervisors to routinely monitor inspection activity compliance to procedures and codes
- Periodic third-party comprehensive mechanical integrity program audits to bring more expertise and outside perspective to the process
- Welder performance routinely monitored for defect rate, rework, etc.
- Equipment and piping component suppliers and contractor NDE providers currently approved for facility support routinely monitored for performance, in addition to routine review of other sources for outside support of facilities
Summary
In conclusion, there is a lot to PSM mechanical integrity, and everyone in facilities with hazardous materials has a role to play to make the program successful and achieve reliable and safe operations. With so many elements, mechanical integrity programming is best driven from the top-down and effectively implemented from the bottom-up, and will be the most effective with maximum engagement.
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1 Gas Processing News, "Mitigate pipeline corrosion by prioritizing positive material identification", December 2020
