Compartment tightness testing (airtightness/watertightness) is a critical milestone prior to vessel delivery. While traditional "water filling/hose" tests are intuitive, they impose additional loads on the hull structure and present significant challenges in wastewater disposal and treatment. This is particularly problematic in machinery spaces where precision equipment has already been installed, and in accommodation areas where insulation work is complete—in such cases, water testing is nearly destructive in nature.
Jiangsu Haizhongzhou Shipping Industry Co., Ltd. is actively promoting a "Dry Tightness Testing" technical package to address these challenges.
Method 1: Vacuum Box Testing
This method is primarily employed for short weld seams such as block butt joints and insert plate welds. We utilize a portable vacuum box equipped with sealing gaskets and a transparent viewing window. The procedure is as follows: first, a soap solution is applied to the weld seam. The vacuum box is then placed over the seam, and a vacuum pump evacuates the air to create negative pressure. Should any through-thickness defects exist in the weld, external air will be drawn into the box, producing distinct and visible bubbles in the soap film. This method enables pinpoint accuracy in locating pinhole-level leaks, with a single inspection taking merely 20–30 seconds.
Method 2: Ultrasonic Leak Detection
This technique is utilized for the overall airtightness inspection of large compartments. An ultrasonic transmitter is placed inside the sealed compartment, emitting sound waves at a specific frequency. An inspector then slowly scans the exterior weld seams with a handheld ultrasonic receiver probe. If a microscopic leak path exists, the ultrasonic waves will escape through the channel, causing the receiver's readings to spike and producing a distinct "hissing" sound in the inspector's headset. This method offers exceptional sensitivity, capable of detecting minute leaks that even hydrostatic pressure tests might fail to reveal.
Method 3: Tracer Gas Detection
For the tightness testing of cargo tanks on LNG/LEG carriers, the more stringent Helium Leak Detection method is mandatory. In this process, we fill the tank with nitrogen mixed with trace amounts of helium gas. A technician then scans the exterior weld seams using a sniffer probe connected to a Helium Mass Spectrometer Leak Detector. Given the extremely small molecular size of helium, no crack or fissure can escape detection.
Through this combined approach, Jiangsu Haizhongzhou achieves green, non-destructive, and highly efficient quality control while ensuring absolute safety and structural integrity.