Heat exchanger inspection

Heat Exchanger Inspection – Performance and Integrity Assessment for Australian Industrial Systems

In Australia’s oil and gas, power generation, mining, and chemical processing industries, regular heat exchanger inspection is essential to maintain thermal efficiency, prevent unplanned downtime, and ensure compliance with AS 1210 (pressure vessels) and AS 3920 (boiler and pressure vessel code). Heat exchangers are critical for heat recovery, process cooling, and HVAC systems. Our ISO/IEC 17025 accredited laboratory provides comprehensive inspection services – including visual examination, non‑destructive testing (NDT), pressure testing, corrosion analysis, and thermal performance verification – to detect tube thinning, fouling, weld defects, and leakage before they cause costly failures.

Types of Heat Exchanger Samples We Inspect

Our laboratory and field inspection services cover a wide range of heat exchanger types used across Australian industries:

• Shell and tube heat exchangers (oil refineries, power stations, chemical plants)
• Plate heat exchangers (dairy, food processing, HVAC, hydronic systems)
• Air‑cooled heat exchangers (fin‑fan coolers in mining and gas processing)
• Double‑pipe (hairpin) heat exchangers (small‑scale chemical plants)
• Spiral heat exchangers (pulp and paper, wastewater treatment)
• Brazed plate heat exchangers (refrigeration and heat pumps)
• Welded plate heat exchangers (high‑temperature and high‑pressure applications)
• Tube bundles removed from service (for internal fouling and corrosion assessment)
• Heat exchanger gaskets and sealing elements (condition verification)
• Witness coupons (tube or plate samples cut from exchangers)

Key Inspection Parameters and Test Methods

We evaluate multiple critical aspects to guarantee the reliability and efficiency of heat exchangers in Australian harsh environments – from tropical humidity (Queensland) to arid dust (Western Australia).

1. Visual and Dimensional Inspection (Shell, Tubes, Plates)

Under bright lighting (500–1000 lux), we visually examine internal and external surfaces for pitting, scaling, fouling, erosion, cracks, and weld irregularities. For shell and tube exchangers, we measure tube diameter (using a go/no‑go gauge), tube wall thickness (ultrasonic), and baffle alignment. We also check gasket seating surfaces for corrosion or damage.

2. Tube Wall Thickness Measurement – Ultrasonic Testing (UT)

Using a digital ultrasonic thickness gauge (calibrated on a reference block), we measure tube wall thickness at predetermined grid points (e.g., 10 points per tube, 5% of tubes per bundle). Minimum acceptable thickness is calculated from original thickness minus corrosion allowance. Areas of localized thinning (< 70% of original) are flagged for repair or tube plugging.

3. Eddy Current Testing (ECT) – for Non‑Ferromagnetic Tubes (e.g., Copper, Brass, Stainless Steel)

We insert a probe into each tube and scan for pits, cracks, erosion, and wall loss. Calibration is done using a reference tube with known defects. ECT can detect corrosion under deposits and support plate intersections. Results are recorded as a phase‑amplitude plot; any signal exceeding the reference defect depth (e.g., 20% wall loss) is rejected.

4. Internal Rotary Inspection (IRI) – for Ferromagnetic Tubes (Carbon Steel)

Using a rotating ultrasonic or eddy current probe, we scan the internal surface of carbon steel tubes for pitting and wall loss. This method is slower than ECT but effective for magnetic materials. We report the maximum pit depth (mm) and area affected (%).

5. Hydrostatic Pressure Test – AS 1210 Appendix J

We fill the heat exchanger’s shell side and tube side with clean water, vent air, and raise pressure to 1.3× the design pressure (minimum). The pressure is held for 30 minutes while inspecting for leaks at gaskets, tube sheets, and welded joints. Any pressure drop > 2% or visible weeping causes rejection. For plate exchangers, we test both channels.

6. Leak Testing – Shell‑and‑Tube Exchangers (Gas)

For gas‑side leak detection, we pressurize the tube side with nitrogen (5 bar) and immerse the shell side in water (or apply soap solution). Bubbles indicate leakage at tube‑to‑tube sheet joints or tube perforations. Alternatively, we use a helium leak detector (sensitivity 10⁻⁶ mbar·L/s) for critical applications (e.g., hydrogen service).

7. Thermal Performance Measurement – AS 2355 (Heat Exchanger Testing)

We measure inlet and outlet temperatures, flow rates, and pressure drops for both fluid streams under stable operating conditions (or using a test rig). From these data, we calculate the overall heat transfer coefficient (U) and compare it to the design value. A U value < 70% of design indicates fouling or flow maldistribution.

8. Fouling and Deposit Analysis (Weight and Composition)

We weigh a clean tube/plate sample, then scrape or brush off deposits and reweigh. Fouling mass (g/m²) is calculated. Deposits are analysed by X‑ray fluorescence (XRF) or FTIR to identify scaling compounds (calcium carbonate, silica, iron oxide, biofouling). We provide recommendations for chemical cleaning based on composition.

9. Tube‑to‑Tube Sheet Weld Inspection – Dye Penetrant (PT) or Magnetic Particle (MT)

All tube‑to‑tube sheet welds are cleaned and examined using dye penetrant (for stainless steel) or magnetic particle (for carbon steel). Any crack or porosity indication exceeding 1 mm in length is cause for repair. For critical welds, we perform radiography (RT) of representative samples.

10. Gasket and Sealing Element Inspection

We visually inspect gaskets for compression set, cuts, swelling, or chemical attack. Using a durometer (Shore A), we measure hardness (acceptable range within ±10 units of new gasket). Gaskets that are hardened (> 10% increase) or cracked are replaced.

11. Corrosion Under Insulation (CUI) Assessment – Shell Side

For insulated heat exchangers, we remove insulation panels at representative locations and inspect the shell surface for pitting, cracking, or chloride stress corrosion cracking (CSCC). We use an ultrasonic thickness gauge to measure remaining wall thickness. Areas with > 10% thickness loss require repair or re‑insulation with moisture‑resistant materials.

12. Vibration and Flow‑Induced Fatigue Analysis – Optional (Tube Bundles)

For exchangers with history of tube vibration, we install accelerometers on selected tubes and measure vibration amplitude during operation. CFD modelling is used to predict natural frequencies. If vibration exceeds 100 µm (peak‑to‑peak), we recommend installation of anti‑vibration baffles or tube support inserts.

Quality Grading and Acceptance Criteria

Based on our heat exchanger inspection, we classify equipment into three grades (clients provide specific acceptance criteria referencing AS 1210 or API 510):

• Grade A (Serviceable – 5 years to next inspection) – No tube leaks, wall loss < 10% of original, fouling < 5% of original U value, pressure test passes, NDT shows no cracks.
• Grade B (Monitor – 2‑year inspection interval) – Wall loss 10–20%, fouling reduces U by 5–15%, minor pitting (< 1 mm deep), some weld porosity but non‑leaking.
• Grade C (Repair or Replace) – Wall loss > 20%, through‑wall pits, leaking tubes, failed pressure test, cracked tube‑to‑sheet welds – immediate shutdown required.

Reporting and Deliverables

Our heat exchanger inspection report includes: asset identification (manufacturer, model, serial number, design pressure/temperature, service fluid), visual and dimensional findings (photographs), thickness measurement logs (grid map), ECT/UT scan data, pressure test charts, leakage rate (if applicable), thermal performance calculation (U actual vs. design), fouling weight and composition analysis, weld inspection results, gasket condition, and a clear pass/fail recommendation with recommended next inspection date. Raw data (scan files, test curves) are archived for 10 years.

In summary, systematic heat exchanger inspection ensures energy efficiency, safety, and reliability for Australian process industries – from LNG plants in Darwin to alumina refineries in Queensland. Contact our laboratory to schedule on‑site or in‑shop inspection for your heat exchanger fleet.

Applications in the Australian Industry

• Oil and gas (LNG plants in Karratha, Gladstone; gas processing in Moomba): Condenser and reboiler inspection.
• Power generation (coal‑fired stations in NSW, Victoria; gas turbines in South Australia): Feedwater heaters and cooling water exchangers.
• Mining (iron ore in WA, copper/gold in SA, coal in QLD): Hydrometallurgy heat exchangers and slurry coolers.
• Food and dairy processing (Victoria, NSW): Plate heat exchangers for pasteurisation and CIP testing.
• HVAC and refrigeration (commercial buildings, data centres): Chiller and condenser bundle inspection.