The Heat Exchanger Inspection article provides you with information about the inspection of the heat exchanger and heat exchanger testing during the manufacturing phase, as well as in-service inspection in operating units. You may want to review shell and tube heat exchanger inspection procedure and related inspection and test plan.
Shell and Tube Heat Exchanger Inspection in Manufacturing Shop
The construction code for shell and tube heat exchangers is ASME Code Section VIII, and it covers the minimum requirements for design, materials, fabrication, inspection, testing, and preparation for initial delivery.
After the 2003 addenda of ASME Code Section VIII Div. 1, the design of the shell and tube heat exchanger needs to be done based on Subsection C, in UHX part. The design based on TEMA, or any similar code might be accepted which meeting the requirements of UHX part.
The heat exchanger still is a pressure vessel and all requirements for ASME pressure vessel does apply for heat exchanger as well. We are going to avoid to repeat those requirements for the heat exchanger. You may review pressure vessel inspection article for those requirements.
There are several inspection requirements that only apply to the heat exchanger and not regular pressure vessel:
Tube Inspection – The tube outside diameter, inside diameter, thickness, and ovality shall be checked before the building of the tube bundle. You need to refer to ASME Section II to get the acceptance tolerances.
For example, if your tube material is SA 179, you have to refer to the SA 179 and that will refer you to the SA 450 ( Specification for General Requirements for Carbon, Ferritic Alloy, and Austenitic Alloy Steel Tubes) for acceptance tolerance. You have to use your caliper, machinist ruler, etc. to make these measurements and make sure the values fall within acceptance range.
Tube Bundle Inspection – The bundle dimension shall be checked based on the approved drawing. The baffle diameter and distance between them shall be controlled and meet the acceptance tolerances in the drawing.
The tightness of stay bolts and spacers must be controlled. The shell cleanliness needs to be verified and make sure the inside welds are complete and are ground as per drawing requirements.
Tubesheet Inspection – The Tubesheet shall be inspected before welding to the shell. The hole diameter, grooves dimensions, drilling pattern, the thickness of the tubesheet and surface finish shall be measured and checked aginst acceptance tolerances in the approved drawing.
Tube Rolling Inspection – The tube rolling shall be checked based on customer specification. The wall reduction (after rolling) and depth of roll shall be measured and shall meet the customer specification. The wall reduction should not be less than 5% and should not be more than 8% of the tube wall thickness.
Leak Testing of Seal Weld (Tube to Tubesheet) – if seal welding considered, then the leak test will be a mandatory requirement. The shell side will be subjected to the air pressure, and water and soap solution will be sprayed to the tubesheet to make sure all seal welds are defect free. The bubble will be developed if there was any welding defect such as crack, pinhole, etc.
Shell side Hydrostatic Testing – After manufacturing completion, the heat exchange shell side will be subjected to the hydrostatic testing. The test pressure amount shall be consistent with the value indicated in the approved drawing. The holding time shall be based on the supplier approved test procedure.
The pressure gages calibration and range shall be controlled. The pressure gage range shall be within 1.5 thru 4 times of test pressure. The shell body and welding seams shall be inspected. The tubesheet also shall be checked. No leakage is allowed.
The test pump hose shall be disconnected, and no pressure drop is allowed. The test result will be satisfactory if no leakage being observed and no pressure being dropped while the shell side was under pressure.
Tubeside Hydrostatic Testing – After successful completion of shell side hydrostatic testing, the bonnets are assembled, and tube side is subjected to hydrostatic testing. Similarly, the amount of test pressure shall be as the one indicated in the approved drawing. Other requirement is similar to the shell test. No leakage and pressure drop shall be observed while the tube side is under pressure.
Third Party Inspection for Shell and Tube Heat Exchanger article provides you a procedural content for heat exchanger inspection. Review following standard Inspection and Test Plan for Shell and Tube Heat Exchanger.
You might be interested in reviewing following related articles:
Fin Tube Heat Exchanger Inspection
Third Party Inspection for Fin Tube Heat Exchanger
Inspection and Test Plan for Fin Tube Heat Exchanger
Shell and Tube Heat Exchanger Application
Shell and Tube heat exchangers are the most popular type in the industry. This type is made from 3 components as listed below:
- Two heads (one rear head, and the other one stationary head)
- Shell
- Tube
One fluid is in the tube side and the other one in the shell side. The heat transfer is done through the tube wall.
So your heat exchanger with more tubes will have more heat transfer surfaces, and at the same time will have a higher heat exchanger diameter.
There are different kinds of shell and tube heat exchangers with different applications.The reason for the high amount of applications is that they are easy to maintain.
Besides, the shell and tube heat exchanger is the only type that can be designed and operated at a temperature greater than 360 degrees centigrade, as well as in pressure higher than 30 bar.
In-Service Inspection of Shell and Tube Heat Exchanger
The In-Service Inspection code for shell and tube heat exchangers is API STD 510. The other API recommended practices and codes also have to be used in with this Code.
Some of these Recommended Practices are API RP 572, API RP 577, and API RP 571, and also construction code sections might be used, such as ASME Code Section VIII and ASME Code Section IX.
For repair, the requirement of API STD 510 or ASME-PCC-2 needs to be met. The title of ASME-PCC-2, which was first published in 2006, is: “Repair of Pressure Equipment and Piping.”
Please note: if your shell and tube heat exchanger is “U” stamped and you need to do the repair, you have to use a Repair Organization holding an “R” Stamp from the National Board Inspection Code.
The API 510 Pressure Vessel Inspectors are qualified persons to perform shell and tube heat Exchanger inspection. You may also review the Industrial Plant Inspection article.
What are the Important Items in the Shell and Tube Heat Exchanger Inspection in Overhaul?
Shell and Tube Heat Exchanger Inspections are categorized in the following way:
Shell and Structure in Heat Exchanger Inspection:
- Neutralization of Austenitic Stainless Steel shell, clads, liner or weld overlay, which contains H2S service. The process needs to be done based on approved procedures by a corrosion engineer.
- Neutralization is also required for shell material with admiralty brass to reduce the risk of SCC.
- Neutralization of thermocouples, if necessary, and doing dye penetration test
- Sampling from shell fouling and corrosion products and making lab analysis and making interpretation by corrosion engineer (if necessary)
- Cutting small area of insulation sheet and removing the insulation and doing visual inspection for any sign of corrosion under insulation
- Thickness measurement of different parts of shell and shell nozzles and making corrosion rate and remaining life calculation
- Inspection of shell cleaning and approval i.e. water jetting etc.
- Checking inside surface for any cladding, liner failure or separation
- Inspection of Shell flange gasket seating area for any erosion, damage and cracking
- Inspection of longitudinal and circumferential weld joints, inlet and outlet nozzles, reinforcement pads and small bore connections for any crack, corrosion and mechanical damage and deformation
- Dye penetration test on weld joints that are susceptible to cracking, austenitic flange face, weld overlay and cladding surface and exchangers exposed to amine and caustic
- Hydrogen blistering inspection in hydrogen services (hand lamp procedure)
- Heat exchanger support, steel structure, foundation, bolt and nut inspection
Bonnet in Heat Exchanger Inspection
- Thickness measurement and making corrosion rate and remaining life calculation
- Girth flange inspection for corrosion and erosion
- Internal surface inspection for corrosion and fouling
- Painting inspection of external surface
- Dye penetration or magnetic particle examination of weld joints susceptible to cracking
Tube Bundle in Heat Exchanger Inspection
- Taking care in the pulling out of tube bundle to avoid any mechanical damage
- Sampling from tube side fouling and corrosion products and making lab analysis and making interpretation by corrosion engineer (if necessary)
- Controlling of water jetting or lancing cleaning process
- Controlling wire brushing process of inner tube edge and rolling area (preparation for ID measurement)
- Inside diameter measurement in tubes and tubes rolling areas
- Rate off and accordingly plugging the tubes when their OD reaches to the ID plus one thickness
- Retubing of tube bundle if more than 10% of tubes reach the above rejection limit
- Inspection from tube bundle components such as tubesheet, tube, tie rods and spacers, transfer baffles or support plate, impingement baffle, floating head flange and floating head backing device
- Inspection from internal surface of tubes for corrosion and fouling
- Pulling out a sample tube for sectioning and corrosion anlaysis if necessary
- Retubing when sectioning result proves the thickness is half of the nominal value
- Visual inspection and dye penetration test from tube to tubesheet seal or strength weld
- Eddy current testing if it is necessary
Channel in Heat Exchanger Inspection
- Thickness measurement and making corrosion rate and remaining life calculation
- Inspection of gasket seating area, pass partition and nubbing for corrosion and deformation
- Inspection of internal surface for fouling, corrosion and soundness of linings (if any)
- Balance hole inspection for corrosion and erosion
- Welding joints inspection for any possible cracks
- Reinforcement pad inspection and doing soap test if necessary
- Cathodic protection anodes inspection and replacement if necessary
- Diaphragm and division box visual inspection and dye penetration test of diaphragm for any possible cracks (for high pressure exchangers)
Channel Cover in Heat Exchanger Inspection
- Thickness measurement and making corrosion rate and remaining life calculation
- Inspection of gasket seating area for corrosion and deformation
- Inspection for internal surface for fouling, liner, cladding and coating soundness
- Soap test in channel cover with liner
- Lifting lug weld joint inspection for any possible crack
Floating Head Inspection:
- Thickness measurement and making corrosion rate and remaining life calculation
- Inspection of gasket seating area, pass partition and nubbing for any possible corrosion and deformation
- Girth flange weld joint inspection for any possible crack and corrosion
- Internal surface inspection for corrosion and fouling and soundness of liner, coating and cladding (if any)
Expansion Joint Inspection
- The heat exchangers with expansion joints need to be inspected for:
- Flange inspections for corrosion and erosion
- Inspection from internal surface for corrosion and erosion
- Air test
- The tube and shell hydrostatic test need to be done after the above stated inspection activities.
Executive Summary & Industrial Inspection Scope
In demanding industrial environments across Oil, Gas, Petrochemical, Offshore, and Heavy Process Infrastructure, rigorous compliance with ISO 9001 / ASME / API is essential to ensure operational integrity, personnel safety, and compliance with statutory regulatory frameworks. This technical specification provides QA/QC managers, procurement engineers, welding inspectors, and third-party inspection (TPI) agencies with an authoritative, field-tested guideline for “Heat Exchanger Inspection”.
Ensuring compliance regarding heat exchanger inspection minimizes the risk of catastrophic asset failures, costly unscheduled shutdowns, and supplier non-conformances. The following technical sections delineate the scope of inspection, mandatory verification protocols, acceptance criteria, documentation deliverables, and root cause mitigation strategies.
Governing International Engineering Codes & Specifications
Verification and validation of Heat Exchanger Inspection must strictly conform to the latest editions of the following international engineering codes and project specifications:
• **Primary Standard Reference:** ISO 9001 / ASME / API
• **Quality Management & Inspection Systems:** ISO 9001:2015 & ISO/IEC 17020 (Requirements for the operation of various types of bodies performing inspection)
• **Material Compliance & Traceability:** EN 10204 Type 3.1 / 3.2 Inspection Certificates for metallic and non-metallic pressure-retaining components
• **Personnel Qualification:** ASNT SNT-TC-1A / ISO 9712 for NDT personnel, CSWIP 3.1 / AWS CWI for welding inspection, and NACE / AMPP Level 2/3 for coating and corrosion personnel
• **Statutory & Health Safety Directives:** ASME Boiler & Pressure Vessel Code (BPVC), API Standards, OSHA, and regional local authority regulations.
Step-by-Step Quality Control & Inspection Procedure
The execution of quality surveillance for Heat Exchanger Inspection is structured across four progressive QA/QC intervention phases:
Stage 1: Pre-Inspection & Engineering Document Review (Review Point – R)
Prior to commencement of any physical activities or manufacturing operations related to Heat Exchanger Inspection, the contractor or vendor must submit all technical submittals to the Owner or TPI agency for formal review and approval.
- Verification of approved Inspection and Test Plan (ITP) identifying all Hold (H), Witness (W), Review (R), and Surveillance (S) intervention points.
- Cross-examination of Material Test Reports (MTR / Mill Certificates) against standard design specifications (ISO 9001 / ASME / API).
- Review and approval of specific Procedure Qualification Records (PQR), Welding Procedure Specifications (WPS), or calibration certificates.
- Verification that all measurement instruments, gauges, and NDT equipment hold valid calibration certificates from ISO/IEC 17025 accredited calibration laboratories (within 6 to 12 months validity).
Stage 2: In-Process Witnessing & Fabrication Control (Witness / Hold Point – W/H)
During the active execution phase, the certified inspector performs physical surveillance to ensure strict adherence to certified drawings, manufacturing procedures, and code tolerances.
- Verification of material traceability (heat number, heat treatment lot, plate number) transferred accurately onto fabricated components.
- Dimensional verification and visual inspection using calibrated gauges, micrometer depth dials, or laser alignment systems.
- Monitoring ambient environmental parameters (relative humidity, dew point, substrate temperature) when applying surface treatments, welding preheat, or pressure testing.
- Witnessing non-destructive examination (RT, UT, MT, PT, PMI) at specified percentages according to project critical rating and code requirements.
Stage 3: Final Acceptance, Pressure/Performance Testing & Marking (Hold Point – H)
The culminating milestone where the fully assembled or completed item is subjected to definitive acceptance tests in the presence of the Owner’s Third-Party Inspector (TPI).
- Execution of pressure proof tests (Hydrostatic at 1.3x to 1.5x MAWP or Pneumatic test) with dual calibrated pressure gauges and temperature recorders.
- Full visual inspection of completed surfaces, welds, protective coatings, and flange contact faces for absence of mechanical damage or code defects.
- Validation of permanent stamping, low-stress die markings, nameplate data verification, and barcoding in strict conformity with project specs.
- Clearing all open punch-list items, non-conformance reports (NCRs), and concession requests prior to issuance of the release note.
Stage 4: Packing, Preservation & Inspection Release (Inspection Release Certificate – IRC)
Ensuring the inspected equipment is adequately protected against atmospheric corrosion, mechanical shock, and marine transit degradation.
- Inspection of rust preventative coatings, desiccant bags, flange face blind protectors, and vapor corrosion inhibitor (VCI) packaging.
- Verification of heavy-lift sea fastening lugs, center-of-gravity markings, and export crating compliance (ISPM 15 wooden crating).
- Compilation and signing of the final Inspection Release Certificate (IRC / Shipping Release) and manufacturer data dossier (MDR).
Technical Acceptance Criteria & Tolerances Matrix
All measurements and physical characteristics must comply with the engineering tolerances and acceptance thresholds tabulated below:
| Inspection Parameter / Test Item | Applicable Standard & Clause | Permissible Tolerance / Acceptance Limit | Verification Method | Intervention Type |
|---|---|---|---|---|
| Material Chemical & Mechanical Verification | ISO 9001 / ASME / API / EN 10204 3.1 | 100% compliance with minimum tensile, yield, elongation, and impact values (Charpy V-Notch at design temp) | Optical Emission Spectrometry (OES) / MTR Verification | Review (R) |
| Visual & Dimensional Tolerances | ISO 9001 / ASME / API / Project Specs | Zero cracks, lack of fusion, severe pitting; dimensional tolerances within ±1.0mm to ±3.0mm per code drawings | Calibrated Vernier, Bridge Cam, Depth Micrometer | Witness (W) |
| Non-Destructive Examination (NDT) | ASME Sec V / ASNT SNT-TC-1A | 100% compliant with code acceptance criteria; zero planar defects or unpermitted volumetric indications | Radiographic (RT) / Ultrasonic (UT) / Magnetic Particle (MT) | Hold (H) |
| Pressure / Proof Testing (Hydrostatic) | ISO 9001 / ASME / API / ASME Sec VIII | Test pressure maintained for minimum 30 to 60 mins; zero pressure drop, zero leakage or visible sweating | Dual calibrated Bourdon pressure gauges + Chart Recorder | Hold (H) |
| Surface Prep & Protective Coating Quality | SSPC-SP / NACE / ISO 8501 | Surface profile 50 – 75 µm; Dry Film Thickness (DFT) within 80/20 rule of specified nominal thickness | Replica Tape (ASTM D4417) & Magnetic Gauge (SSPC-PA 2) | Witness (W) |
| Nameplate & Final Preservation Verification | API / ASME / Client Specs | 316L SS nameplate securely affixed with correct design code, MAWP, design temp, and national board stamping | Physical visual check & VCI preservation verification | Hold (H) |
Mandatory QA/QC Dossier & Inspection Deliverables
Prior to the final issuance of the Inspection Release Certificate (IRC), the contractor and vendor must compile and submit the verified manufacturer data record containing:
- Approved Inspection & Test Plan (ITP) with sign-off stamps by Contractor, Client, and TPI.
- Material Test Reports (MTR / Mill Test Certificates EN 10204 Type 3.1 or 3.2).
- Certified Welding Procedure Specifications (WPS), Procedure Qualification Records (PQR), and Welder Performance Qualifications (WPQ).
- Calibration Certificates for all test instruments and measuring equipment (NABL / ISO 17025 accredited).
- Non-Destructive Examination Reports (RT, UT, MT, PT, PMI, Ferrite Content) evaluated by Level II/III inspectors.
- Heat Treatment & PWHT Time-Temperature Recorder Charts with thermocouple layout drawings.
- Hydrostatic / Pneumatic Pressure Proof Test Certificate with calibrated chart recorder logs.
- Surface Preparation and Protective Coating Inspection Reports (Daily environmental log, blast profile, DFT summary).
- Non-Conformance Report (NCR) and Concession Disposition Closeout Log.
- Official Inspection Release Certificate (IRC / Shipping Release Note) permitting packing and dispatch.
Common Non-Conformances & Field Mitigation Strategies
Based on extensive third-party inspection field records in oil & gas projects, the following deviations require heightened surveillance:
Defect / Hazard: Material Grade Substitution & Lack of Heat Traceability
Root Cause: Uncontrolled workshop storage, missing color coding, or unverified supplier sub-tier procurement without EN 10204 3.1 documentation.
Preventative Action: Enforce strict 100% Positive Material Identification (PMI) prior to cutting, and mandatory material receiving inspection with physical stamping cross-referenced to original mill test certificates.
Defect / Hazard: Out-of-Tolerance Fit-Up & Alignment Mismatch
Root Cause: Poor thermal cutting, thermal distortion from excessive preheat, or inadequate jigging and tacking arrangements.
Preventative Action: Establish a mandatory Witness/Hold point at joint fit-up before root pass deposition. Use calibrated Hi-Lo gauges to verify bevel angle, root face, and root gap according to the qualified WPS.
Defect / Hazard: Premature Coating Delamination & Blistering Under Film
Root Cause: Excessive soluble salt contamination (>20 mg/m²) left on the substrate, blast cleaning below dew point (<3°C above dew point), or oil/moisture in the blasting compressor air line.
Preventative Action: Perform Blotter Test (ASTM D4285) daily on compressed air, enforce Bresle patch chloride testing, and apply primer within 4 hours of abrasive blasting before rust blooming initiates.
Defect / Hazard: Pressure Drop During Final Hydrostatic Proof Testing
Root Cause: Micro-leakage through temporary test flange gaskets, entrapped air pockets inside vessel high points, or inadequate temperature stabilization.
Preventative Action: Ensure thorough venting at all high-point vents until bubble-free fluid emerges, allow minimum 15-minute temperature stabilization between filling medium and ambient metal, and torque all blind flanges with calibrated torque wrenches.
Frequently Asked Questions (FAQ)
Q: What are the mandatory qualifications for inspectors verifying Heat Exchanger Inspection?
A: Inspectors must hold recognized international certifications applicable to the discipline. For welding and fabrication: CSWIP 3.1/3.2, AWS CWI, or API 510/570 Source Inspector. For NDT: ISO 9712 or ASNT SNT-TC-1A Level II minimum. For coatings: NACE / AMPP Level 2 or FROSIO Level III. Additionally, the inspection agency must operate under an ISO/IEC 17020 accredited quality management system.
Q: How does PtroTek resolve non-conformances (NCRs) encountered during vendor surveillance?
A: When a deviation from certified drawings or ISO 9001 / ASME / API is detected, the inspector issues a formal Non-Conformance Report (NCR) within 24 hours. The vendor must submit a Root Cause Analysis (RCA) and proposed disposition (Rework, Repair, or Concession). Work on the affected component is halted (Hold Point) until the Owner’s engineering authority approves the disposition and a re-inspection confirms full compliance.
Q: What is the difference between Witness (W) and Hold (H) points in an Inspection & Test Plan (ITP)?
A: A Hold Point (H) is a mandatory milestone where fabrication or testing CANNOT proceed without the physical presence of the designated client or third-party inspector. Written clearance or stamping is strictly required. A Witness Point (W) requires prior notification (typically 24 to 48 hours) to the inspector; however, if the inspector fails to attend at the scheduled time, fabrication or testing may proceed with subsequent review of the test records.
Q: Can international clients review inspection reports and photos in real time?
A: Yes. PtroTek provides comprehensive Flash Reports issued within 24 hours of inspection completion, followed by detailed formal inspection reports accompanied by high-resolution calibrated photographic evidence, dimension logs, and signed vendor test records for complete global transparency.
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