The Portascanner® WATERTIGHT is a world-leading water and weather-tight integrity testing device for hatch covers, watertight doors, multi-cable transit (MCT) areas across bulkheads in marine structures. Ideal for detecting leaking hatch covers, hatch coamings and any hatch cover gasket.
Our ultrasonic testing systems are powerful, portable tools to aid you in your watertight integrity testing procedures. Results can be displayed in decibels, linear or numerical code, or as an open hatch value. In this blog we will explain the meaning and utility of decibel readings.
Decibel Measurements
Portascanner® WATERTIGHT is an ABS Approved & RINA Accepted method for check any critical watertight or airtight seal for leak sites, with results in decibel and mathematical linear. DNV GL states that anything under 10% of the open hatch cover reading is considered weathertight. This reading must be reported in decibel (dB) to comply with regulations.
Below is a table demonstrating the meaning of the reading provided by the Portascanner® in accordance with DNVGL regulations for ultrasonic tightness testing of closing appliances such as hatches and doors:
DNV GL – Service Suppliers Performing Tightness Testing of Hatches With Ultrasonic Equipment on Ships, High Speed and Light Craft and Mobile Offshore Units .
Converting this into a simple pass and fail:
2.9 Operational procedures Fail/pass criterion:
- from 1 dB to 10% of OHV shall mean that the hatch cover is considered weathertight, subject to verifying the design and the condition of the hatch cover, the coaming and the drainage arrangements
- above 10% of the OHV shall mean that the hatch cover is considered not to be weather tight and that corrective action to gaskets and drains is required.”
Why Provide Linear Scale Readings?
Calculating 10% of the decibel scale can be complex. To counteract this problem, the Portascanner® WATERTIGHT can test for leak sites in both decibel and in the linear scale.
The graphs below demonstrate both the decibel and linear scale. As you can see, the linear scale increases at a constant rate, unlike the decibel scale. It is easier to work out 10% in the liner scale because of this. Therefore, we suggest testing in the linear scale and then converting to dB as this is easier for the crew. The converted linear reading can then be used to comply with regulations, as per the above. The Portascanner® WATERTIGHT has a “MODE” button which instantly converts linear readings into dB readings, which is designed so that the crew can really easily comply with regulations.

Ultrasonic Hatch Cover Testing
Ultrasonic hatch cover testing is the only recognised method endorsed by P&I Clubs worldwide for determining the weathertightness of hatch covers, as marine safety regulations dictate.
Unlike traditional methods such as the chalk test or hose test, which are labour-intensive and processes that require multiple operators, the Portascanner® provides quick and seamless testing. The system automatically calculates the %OHV, ensuring compliance with standards such as DNVGL-CP-0484 and IACS URZ17. It suits all bulk carriers, offshore structures, and marine vessels.
The operating principles are simple:
- An ultrasonic pulse is emitted from the device’s transducer.
- The signal is reflected from any solid structure and will transmit through any air gaps, so any signal detected indicates a leak. In contrast, no readings are recorded for an intact structure.
- The operator moves the sensor along the tested area to locate the exact point of the leak. The test provides a decibel reading and an Open Hatch Value (%OHV), helping to quantify the leak’s severity.
A moderately experienced operator can complete this entire process in minutes

For more information, contact the team at Coltraco Ultrasonics and we would be delighted to help.
Keywords: Shipping,Fire Safety, Fire And Sea, Ultrasonic Liquid Level Indicators