Pipe weld testing and pipe weld inspection with RT, UT and PAUT

• Radiography (RT) shoots through the weld wall with an X-ray tube or an iridium or selenium source. It records porosity, slag, lack of fusion and burn through as a permanent image, and it is the classic acceptance method for process piping. Digital radiography removes film processing and gives results in minutes.
• Phased array and TOFD ultrasonic testing (PAUT, TOFD) sweep sound through the weld and store the full scan. They find planar flaws such as lack of fusion and cracks better than RT, need no exclusion zone for radiation and are often used on thick wall piping. Our ultrasonic testing services page explains where UT beats RT and where it does not.
• Magnetic particle (MT) and liquid penetrant (PT) testing find flaws that open to the surface, for example on root and cap passes, socket welds and attachment welds. See magnetic particle inspection and liquid penetrant testing.
• Visual testing (VT) by a certified welding inspector comes first on every weld. It catches undercut, reinforcement, misalignment and arc strikes before money is spent on volumetric methods.
• Eddy current and borescope work cover small bore tubing and the inside of piping that cannot be reached from outside. See borescope inspection.

The method and the share of welds you test come from the construction code, not from the NDT company. ASME B31.3 for process piping sets examination by fluid service: normal fluid service commonly calls for visual examination of every weld and random radiography or ultrasonic examination of a percentage of girth welds, while severe cyclic conditions and high pressure categories raise that to 100 percent. ASME B31.1 for power piping ties volumetric examination to pipe size and wall thickness. Cross country pipelines are normally welded and tested to API 1104, which accepts RT or UT of girth welds and, for most lines, requires a high share of welds to be examined. Pressure vessel nozzles and shop spools follow ASME Section VIII and Section V for technique. Your piping class, line list or specification names the code, the examination percentage and the acceptance criteria, and the NDT company interprets the results against them. Always send those documents with the request, because a lab that guesses the acceptance table gives you a report your inspector will reject.

Ask for technicians qualified to ASNT SNT-TC-1A or CP-189 at Level II for each method, with a Level III on call for procedure approval. For visual acceptance, a certified welding inspector (AWS CWI) is the norm. Pipeline and nuclear work often add owner specific qualifications, and PAUT or TOFD needs operators who have passed a practical on weld samples with known flaws, not just a written exam. Radiography crews also need radiation safety certificates and a state or NRC license for gamma sources.

Mechanical contractors and pipe fabricators order RT or UT on spools to close out a turnover package. Plant owners buy it for shutdowns, tie ins and repair welds after a leak or a failed hydrotest. EPC project teams and owner inspectors hire third party NDT to sign off welder performance after a high reject rate. Facility managers add UT on high energy and steam piping at scheduled outages. Pipeline operators test girth welds on new construction and on integrity digs. Each of these buyers needs a firm price per weld or per crew day, a start date and a report format that matches the contract.

1. You send the line list or isometrics, pipe size and schedule, material, number of welds, the code and the examination percentage.
2. The NDT company selects a method and technique, often with a written procedure for your engineer to approve.
3. A crew arrives with the equipment, marks and identifies each weld, and tests in the agreed window. RT often runs at night or on weekends so other trades stay out of the controlled area.
4. A Level II reads the results and records every indication against the acceptance table.
5. You receive a report per weld with the technique, the result, and the images or scan data. Rejected welds go back for repair and a retest.

Small shop jobs usually turn in one to three business days. Field crews often deliver a daily summary and the final report in three to five.

These are typical US planning ranges, not quotes. Pipe size, wall thickness, access, shift work and report requirements set the real price.

Most companies set a minimum charge of about half a day, so grouping welds into a single visit is the main way to lower the price per weld. Our guide to NDT inspection cost shows how crews build quotes across methods, and the ultrasonic testing cost guide goes deeper on UT day rates.

Match capability to your piping class first. Ask whether the company holds the radiation license for the source type you need, whether it can run PAUT with encoded scans, and which procedures it already has approved on similar lines. Ask for a sample report per weld, not a summary sheet. Check that the Level III who signs procedures is on staff or on a retainer, and that the company can mobilize on short notice for shutdown work. Our page on NDT companies lists how to compare providers on scope instead of the lowest unit price alone. For buried and long distance lines also see pipeline inspection.