Inspection of Piping Systems

The inspection of piping systems is an engineering service in which the conformity of metallic piping systems carrying fluids under pressure, temperature or chemical loading is verified against the design and the applicable code during manufacturing, and their structural integrity is verified during operation, through independent third-party surveillance and inspection. The underlying principle of the method is that the safe operation of a piping system depends on the wall thickness remaining above a defined minimum value, the weld seams being free of discontinuities, and the system being able to carry the design pressure with a margin of safety. Over time, mechanisms such as corrosion, erosion, creep and fatigue progressively weaken this integrity; the inspection activity aims to detect this degradation with measurable data before it develops into a leak or a rupture.

The application is divided into two main branches according to the stage of the life cycle the line is in. During manufacturing and erection, the service covers the review of welding procedures (WPS/PQR) and welder qualifications, the traceability of material certificates (mill certificates), dimensional and installation checks, and witnessing of the non-destructive testing applied to weld seams (visual, penetrant, magnetic particle, radiographic or ultrasonic). For lines in service, the activity is based on periodic inspection and on the risk-based inspection (RBI) approach: wall thickness is measured at critical points, the corrosion rate is calculated and the remaining life is estimated.

Technically, the core of the service is quantitative measurement. Using ultrasonic thickness gauges, wall thickness is monitored with sub-millimetre accuracy at defined recording points (TML — Thickness Measurement Location); the measured value is compared with the minimum required thickness (t-min) calculated from the code. Radiography and phased array ultrasonic testing (PAUT) techniques are used to map weld and internal surface flaws; penetrant and magnetic particle methods are used for surface cracks. The pressure-retaining capability of the system is generally verified by a hydrostatic test, observing for leakage and permanent deformation at the test pressure and holding time required by the relevant code.

The depth of inspection specific to piping systems arises from the fact that damage is mostly concentrated at predictable locations. Corrosion under insulation (CUI), dead legs where the fluid stagnates, injection and mixing points, the outer radii of elbows and support contact areas are addressed as priorities in the inspection plan. The annual corrosion rate is derived from the measured thickness loss; using this rate together with the current thickness and the t-min value, the next inspection interval and the remaining life of the line are determined. In this way, the inspection is not merely a snapshot of a past condition but becomes an engineering input that also guides future maintenance decisions.

Acceptance criteria are always linked to the code applied and the design data: the discontinuity limits of the relevant manufacturing standard for weld flaws, the calculated t-min value for thickness, and the absence of leakage and permanent deformation for the pressure test. The inspection results are compiled in a traceable report covering the measurement points, the methods used and the calibration of the equipment, the findings identified and the accept/reject evaluation. Such a report enables the operator both to meet the statutory periodic inspection obligation and to prioritise the maintenance budget. TÜV AUSTRIA SILA KALİTE performs the inspection of piping systems as an accredited Type A inspection body under TS EN ISO/IEC 17020, in accordance with the principles of independence and impartiality, and documents the results with internationally recognised inspection reports.