PNL QUALITY EXAMINER

PNL has outgrown its home in Phoenix, and currently is undergoing a vastly upgraded move to a newly purchased 38,000 square foot facility in Tempe, Arizona. The move will be completed by July 31st, 2023. Among its latest enhancements are increased laboratory space on 2.5 acres, ten welding booths, plus welding store, additional office space, conference rooms, training rooms, technician stations, and needed additional parking spaces. A forklift accessible walk-in radiography vault allows for inspection of larger components in-house. Multiple high volume cabinet X-ray systems will also increase our overall RT resources.

The new location offers a 2350 square feet state-of-the-art training center for speaker engagements, seminars, conferences, training groups, and multi-purpose availability for leasing to the public. The training center provides space for at least 60 people, furnished with a podium, audio visual equipment, a wall-sized white board, a 4K projector displaying images onto a 150" screen, 12-foot ceilings with embedded speakers, wireless internet, and ample power supply for attendees.

Our new location at 941 South Park Lane, Tempe, Arizona features 5500 square feet of office space, 80+ parking spaces to accommodate our fleet, visitors and employees, two grade loading doors, truck well, and proximity to I-10, Loop 202 and AZ-143 freeways. It is located two miles from Sky Harbor International Airport and is situated within two miles of downtown Tempe amenities.

One of the frustrating things about being a technician is having to examine parts and materials that are dirty.  We’ve been asked to examine materials in service through peeling paint and or other coatings, grime, scale, rust, chemical deposits, even caked on dirt.  Examination through these conditions will be limited at best, if not make it impossible to find in-service defects.  For heat exchanger tubes we have seen dirt, sand, rocks, scale and chemical deposits limit our examinations.

Below is an example of eddy current test data from a tube before and after cleaning.  Obviously, you can see the amount of noise generated from the dirty tube condition.

Eddy currents were first discovered by the French scientist Jean Foucault in 1855. Foucault noticed that when he tried to rotate a copper disc between two magnetic poles, it became increasingly difficult to rotate, the faster it moved. Michael Faraday was the English chemist who in 1831, discovered electromagnetic induction, electromagnetic rotations, the magneto-optical effect, and diamagnetism. In 1879, another English scientist named David Edward Hughes recorded changes in the properties of a coil when placed in contact with metals of different conductivity and permeability. The development of Eddy Current Testing is the result of the confluence of the scientific observations of the three men. These properties were not applied to practical use until the 1940’s for testing materials. In the 1950’s and 1960’s Eddy current testing began in the aircraft and nuclear industries.

Eddy currents are currents which circulate in conductors like swirling eddies in a stream. They are induced by changing magnetic fields and flow in closed loops, perpendicular to the plane of the magnetic field. They can be created when a conductor is moving through a magnetic field, or when the magnetic field surrounding a stationary conductor is varying i.e., anything which results in the conductor experiencing a change in the intensity or direction of a magnetic field can produce eddy currents. The size of the eddy current is proportional to the size of the magnetic field, the area of the loop and the rate of change of magnetic flux, and inversely proportional to the resistivity of the conductor.

Eddy current testing is a non-destructive testing method widely used to examine tubing in heat exchangers, steam generators, condensers, air coolers and feedwater heaters. Magnetism, the underlying principle behind electric motors and generators, relays, and stereo speakers, is also the force that enables an important category of NDT tools called eddy current testing instruments. Eddy current (ET) testing is a no-contact method for the inspection of metallic parts.

Eddy currents are fields of alternating magnetic current that are created when an alternating electric current is passed through one or more coils in a probe assembly. When the probe is placed close to the part under inspection, the alternating magnetic field induces eddy currents in the test part. Discontinuities or property variations in the test part change the flow of the eddy current and are detected by the inspection probe, enabling material thickness measurements or the detection of defects such as cracks and corrosion.Eddy current testing of tubes is an effective way of assessing the condition and lifespan of tubes, particularly in the power generation, petrochemical, chemical, fertilizer and air conditioning industries. The technique is applied to detect corrosion, pitting, cracks, erosion and other changes to both the tube’s interior and exterior surfaces. There are several other applications for ET, like weld inspection, crack sizing, defect detection, corrosion detection and sizing. It is used in the aerospace, mining, manufacturing and power generation industries. 

At PNL, Eddy current is utilized primarily for tube examinations in heat exchangers or coolers. We use Core Star Eddy Current equipment which is state of the art and renown in the industry. Our equipment utilizes a mechanical probe driver to easily track the location of the probe within a tube to accurately identify the location of defects. We analyze test data using CoreStarr Eddyvision software which is available to our clients so they can view our test data.

Phoenix is undertaking a huge construction boom with multiple semiconductor plants currently being erected alongside associated support plants and businesses. Due to the ever-present cranes in the Phoenix metropolitan area, we deemed it fitting to discuss crane safety in this issue of the Quality Examiner. Additionally, PNL will be using cranes to move and situate several of our large tension/compression and other testing machines to our new facility. There are stringent skill sets, OSHA safety requirements and guidelines necessary to successfully transport, rig, and assemble heavy construction materials, equipment, and machinery from one place to another. PNL has procured the remarkable services of Southwest Industrial Rigging to help orchestrate our move.

Cranes are generally equipped with a hoist rope, wire ropes or chains, and pulleys, that can be used both to lift and lower materials and to move them horizontally. Cranes use one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human.

Slings are used to carry loads. They are made of chain, wire rope, synthetic fabric, or metal mesh. Slings that surround the load affix to hitches which attach to the crane. There are three methods to hitch a load: vertical hitch, basket hitch (the most common), and choker hitches, which hook the sling carrying the load to the crane, which moves the load. Riggers follow OSHA industry hand signals to communicate with the crane operator to hoist up, down, sideways, stop and emergency stopping. OSHA also requires that a suspended load’s height equals the radius that workers should keep their distance i.e., 20 feet up corresponds to 20 feet radius distance on the ground.

Among the required protocol for rigging is certifying that the load being handled can be done without exceeding the crane’s limitation, inspecting the gear, ascertaining the capacity of the hardware of slings being used, choosing the correct hitch sling, utilizing original OEM (original equipment manufacturer) parts, always using covered slings, maintaining load control, understanding the structural integrity of the load and consulting rigging charts that enumerate lift angle, hitch, sling size and sling type for the required WLL (working load limit).

It is imperative that rig and crane operators and support personnel wear PPE (personal protective equipment) including hard hat, safety glasses, heavy leather gloves, steel toe shoes, shirts with sleeves and shirt tails that they tuck inside.

We ask everyone to be aware when cranes are operating, especially on construction sites, to always keep a safe distance, as crane accidents have been known to happen. Loads can break away from the rigging and fall to the ground or crane components can fail if conditions are abruptly changed, such as gusts of wind or inclement weather.  Additionally, unstable ground conditions can lead to cranes tipping over.

Approximately 80 crane workers are killed annually in the United States; many others sustain severe, debilitating injuries. Fifty-four percent of crane accidents result from swinging the boom or making a lift without the outriggers fully extended. Fifty percent of all crane accidents across the country in any given year result in fatalities. Forty-five percent of crane accidents involve electrocution from power lines or lightning.

Please be aware of the crane conditions while working on your jobsite! 

When required by a referencing code or if no referencing code is provided, examinations are conducted in accordance with ASME Section V, Article 8, Appendix II for Eddy Current Examination of Nonferromagnetic Heat Exchanger Tubing and Article 17 for Remote Field Testing (RFT) Examination of Ferromagnetic Heat Exchanger Tubes.

Eddy Current Testing (ECT) and RFT are techniques within the Electromagnetic Testing Method as defined by ASNT SNT-TC-1A.  ECT and RFT are often used interchangeably in industry, but are very different test methods with different detectability limits. ECT is a high frequency method and can detect much smaller defects as compared to RFT, which is a low frequency system.  ECT is very good for detecting smaller defects including isolated pitting as well as ID and OD corrosion.  Both axial and circumferential cracking can be detected using ECT, but is limited.  RFT is able to detect changes in metal volume caused by corrosion rather than discrete small indications.  While ECT can distinguish between ID and OD indications, RFT cannot differentiate between ID and OD sources.  

Typical tube materials tested using ECT include stainless steel, copper, copper/nickel, titanium and other nonferromagnetic materials.  ECT is not effective on carbon steel tubes which must be tested using RFT.

With either test method, it is important that tubes which have been in service be properly cleaned as debris in the tubes can cause false indications or mask defects.  

Equipment and probes for both methods are generally provided by the same equipment manufacturer. PNL utilizes Corestar equipment and probes to perform both methods.  For each method, the test system is set up using artificial flaws fabricated in a reference tube of the same material as the tubes to be inspected.  Indications are recorded with location along the tube and through wall depths indicated. For in-service inspections, which is the majority of testing applications, tubes with 80% wall loss are recommended for plugging. Typically, up to 10% of tubes in a heat exchanger can be plugged without adverse effects in efficiency.  Tube support wear is a common problem and is easily detectable using ECT.