As a core equipment in many industrial fields such as chemical industry, energy, metallurgy, etc., heat exchanger acceptance is a key link to ensure the long-term safe, stable and efficient operation of the device. A rigorous and comprehensive set of acceptance standards should run through the entire process of equipment manufacturing, delivery, installation and performance testing. The following will elaborate on the core points of heat exchanger acceptance in stages.
1. Pre-factory acceptance (manufacturing process supervision and document review)
This stage is the basis of quality control and focuses on prevention.
1. Design documents and qualification review:
Design documents: Check whether the general drawing, component drawings, nozzle orientation drawings, strength calculation sheets, etc. are complete and accurate, and comply with relevant national standards (such as GB/T 151 "Heat Exchanger") and industry specifications.
Material quality certification documents: Review the quality certificate (MTC) of all pressure components (shells, tube sheets, heat exchange tubes, etc.) and main pressure component materials to ensure that their grades, specifications, mechanical properties, chemical composition and heat treatment status meet the design requirements. Retest if necessary.
Manufacturing process documents: Review the welding process qualification report (PQR), welding process specification (WPS), non-destructive testing process card, etc. to ensure the compliance and traceability of the manufacturing process.
Manufacturer qualifications: Confirm whether the manufacturer has the corresponding special equipment manufacturing license (such as a pressure vessel manufacturing license).
2. Supervisory inspection of key points in the manufacturing process:
Material marking and identification: Check whether the material has traceable marking transplantation.
Forming and size: Check the forming quality (such as roundness, straightness) and main dimensional deviations of the head and cylinder.
Welding quality: This is the core of the core. Check the appearance and shape of the weld to ensure that there are no surface defects such as cracks, undercuts, and incomplete welding. Oversee the non-destructive testing (NDT) process, including:
Radiographic testing (RT) or ultrasonic testing (UT): 100% testing of the main butt welds, and the assessment standards must meet the specifications.
Penetrant testing (PT) or magnetic particle testing (MT): Test the surface of all pressure-bearing welds to detect surface and near-surface defects.
Tube bundle assembly: Check the expansion or welding quality of the heat exchange tubes (such as expansion ratio, welding leg height) to ensure there is no over-expansion or under-expansion. For the connection between the tube sheet and the pipe, an air tightness test (such as ammonia leakage test) needs to be carried out to check its tightness.
Cleanliness: After manufacturing is completed, the interior must be thoroughly cleaned to remove scale, welding slag, oil and other debris.
3. Pressure test and factory documents:
Pressure test (mainly hydraulic test): This is a mandatory test before leaving the factory. The test pressure is generally 1.25-1.5 times the design pressure (according to the standard). During the pressure maintenance period, check all welds, sealing surfaces and connection parts for leaks, visible deformation and abnormal noise. The chloride ion content of test water needs to be strictly controlled (especially for stainless steel equipment).
Document package: Receive complete factory information, which should include: as-built drawings, product quality certificates (including material certificates, welding records, non-destructive testing reports, heat treatment reports, pressure test reports, etc.), product certificates, installation instructions, etc.
2. Unpacking and acceptance of the goods upon arrival (preliminary inspection on site)
After the equipment arrives at the site, it must be unpacked and inspected immediately.
1. Appearance and packaging inspection: Check whether the outer packaging of the equipment is intact and whether there is any collision damage, deformation or rust caused by transportation.
2. Verify the physical objects and documents: According to the packing list and drawings, check whether the quantity and specifications of all components (main body, accessories, anchor bolts, gaskets, etc.) are complete and correct.
3. Macroscopic inspection: Check whether the equipment nameplate information (design pressure, temperature, medium, category, etc.) is consistent with the design. Check whether there is any obvious damage to the main structure, whether there are any bumps or scratches on the sealing surface of the nozzle flange, and whether the lifting lug supports are intact.
4. Dimensional review: Key installation dimensions, such as the distance between the support bolt holes, the elevation and orientation of the pipe mouth center, etc., need to be reviewed on site to ensure that they match the foundation.
3. Acceptance after installation
The quality of the installation process directly affects equipment performance.
1. Installation inspection: Check whether the level and verticality of the equipment meet the requirements, whether the supports are in firm contact, and whether the sliding supports can move freely.
2. Pipe connection inspection: When connecting pipes, it is strictly prohibited to apply excessive additional external force to the heat exchanger nozzle to avoid abnormal stress on the equipment. Check mating flanges for parallelism and coaxiality.
3. Fastening and sealing: Use the correct fastening tools and sequence (diagonal tightening) to install gaskets and bolts to ensure reliable sealing.
4. Performance acceptance (test run and assessment)
This is the link to verify whether the heat exchanger meets the process requirements.
1. System pressure test: As part of the process pipeline system, the equipment needs to participate in the pressure test (water pressure or air pressure) of the entire system to re-confirm its pressure-bearing capacity and the sealing of the connection with the pipeline.
2. Leak test: For occasions where the mixing of tube side and shell side media is strictly prohibited (such as flammable and toxic media), after the pressure test, a more sensitive leak test may be required, such as air tightness test or halogen leak detection.
3. Thermal performance assessment (key acceptance link):
Assessment conditions: Conducted when the device reaches stable working conditions (assessment conditions specified in the design or contract).
Measuring parameters: Accurately measure and record the inlet and outlet temperature, pressure, and flow of the tube side and shell side.
Performance calculation and comparison:
Heat transfer capacity (heat load): The actual heat transfer capacity is calculated based on measured data, and should reach or exceed 95%-105% of the design value (the specific range is subject to contract agreement).
Heat transfer coefficient (K value): Calculate the actual total heat transfer coefficient, compare it with the design value, and evaluate the heat transfer efficiency.
Pressure drop (resistance drop): Measure the actual pressure drop on the tube side and shell side, which must not exceed 110% of the design value (or the value agreed in the contract). Excessive pressure drop means increased energy consumption or blockage.
Long-term operation stability: During the assessment period and the subsequent period, monitor the equipment for abnormal vibration, leakage (especially at the pipe head), uneven temperature distribution, etc.
5. General and special requirements
Anti-corrosion and thermal insulation: Check the integrity of the anti-corrosion coating (paint, lining) and whether the insulation layer construction meets the requirements.
Special type of heat exchanger: For plate heat exchangers, it is necessary to focus on checking the sealing gasket and compression size of the plates; for air coolers, it is necessary to check the fan vibration, speed and noise.
Contracts and specifications: All acceptance activities must be carried out strictly in accordance with the technical attachments, data sheets and technical standards recognized by both parties (such as ASME, TEMA, GB, etc.) in the procurement contract.
In summary, a complete set of heat exchanger acceptance standards is a multi-dimensional and hierarchical system engineering. It is not just a stress test, but a full-chain, documented and data-based management and control process from "paper design" to "actual operation". Only by closely combining factory quality, installation accuracy and operating performance and strictly controlling them can we ensure that the key component in the "industrial heart" of the heat exchanger can serve the production device efficiently, reliably and for a long time.
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