Brazing And Leak Inspection For One Closed Flat End Tubes

Meta: Brazing and leak inspection for one closed flat end tubes, covering pre-weld cleaning, joint grinding, inflation test and refrigerant circuit integrity check.

1. Core Industry Pain Points

Brazing is a high-risk station for one closed flat end tubes capillary assembly. Common pain points include insufficient pre-weld cleaning: oil and oxide on the joint form welding slag that falls into the lumen and causes internal blockage. Some workers skip proper joint grinding, leaving an uneven face that causes poor solder fusion and micro-leaks. During brazing, molten solder easily flows inward and blocks the capillary throat. The most dangerous hidden trouble is skipping post-weld inflation inspection, so weld closure or slag blockage is found only after refrigerant filling, causing rework and project delay. The one closed end reduces one leak point, but the welded open-end joint still needs careful integrity verification.

2. Fundamental Working Principle

Brazing connects one closed flat end tubes capillary to the filter dryer and evaporator, forming a complete refrigerant throttle circuit. Clean joint surface ensures full fusion of solder and stainless steel base metal, creating an airtight weld without slag inclusion. Proper end grinding improves solder flow and joint strength. Post-weld inflation test uses dry gas flow to judge whether the channel is through, detecting closed weld and foreign body blockage. During pressure tuning, air is drawn through the repair valve at the process port and ejected from the open end; if the weld is sound and the lumen clean, the high-pressure gauge reaches the 1–1.2MPa window, confirming circuit integrity.

3. Equipment and Category Classification

Material: SUS304 for general systems; SUS316 for corrosive environments. Brazing equipment includes TIG welding machine, laser welder, brazing torch, end grinding fixture and inflation test bench. Supporting machining equipment: cutting, grinding, bending, flaring and swaging machines for forming. Surface treatment: polishing the joint area to remove oxide before brazing. Tube shapes customizable to round, square, oval and rectangular. All raw materials and finished goods covered by ISO9001:2015 and SGS. Packaging: standard clean carton or customer scheme.

4. Standard Operation Guide

Pre-weld preparation: complete tube cleaning and drying by three-stage flow, seal before transfer, remove rubber plug only immediately before welding. Clean the capillary tip and matching nozzle joint thoroughly, and grind the end face to a proper angle. Align the capillary and nozzle accurately and control welding heat input to prevent solder from flowing into the lumen. After brazing fully cools, connect the inflation tool and blow dry gas into the channel. Judge pass status: smooth gas flow means no blockage; no gas passing indicates weld closure or slag jam. Then perform pressure tuning by the repair valve at the process port, verifying the high-pressure gauge within 1–1.2MPa.

5. On-Site Practical Experience

New operators often think joint grinding is optional and skip it for speed; unchamfered capillary joints have markedly higher weld failure. The heat affected zone of stainless steel brazing is easy to oxidize, so local nitrogen protection is recommended. Do not blow strong air to cool the weld rapidly; thermal stress cracks may occur. Inflation test pressure should be fixed; too low pressure cannot detect tiny slag blockage. Separate qualified and unqualified welded parts clearly, and prohibit reworking welding without re-cleaning. Record the tuning gauge readings for each unit.

6. Conclusion and Value

Standardized brazing and leak inspection guarantee airtight connection and smooth capillary channel for one closed flat end tubes. Pre-cleaning, proper grinding and post-weld inflation test form three defense lines against blockage and weld closure. Pressure tuning within the 1–1.2MPa window confirms system integrity and improves refrigeration reliability.

7. Industry Outlook and Suggestions

Automated laser brazing with visual positioning will gradually replace manual flame brazing. Factories should make color-coded operation cards for grinding and inflation test. Customers should mark chamfer and inflation test clauses on drawings. For long-life equipment, select SUS316 tube and laser welding for better corrosion resistance.