A hatch cover can look fully closed while worn seals, poor alignment or small gaps leave the cargo hold exposed to water ingress. A chalk test gives crews a quick way to check whether the rubber packing contacts the compression bar, but it cannot confirm full weathertightness.
This guide explains the chalk test procedure, how to interpret the result and when ultrasonic testing provides clearer evidence of leakage.
What Is a Chalk Test?
A chalk test is a visual contact test used on hatch covers and watertight doors. Chalk is applied to the compression bar or sealing edge before the closure is secured and reopened. The rubber gasket is then checked for a continuous chalk mark.
Missing or broken marks show where the gasket did not make contact. The test does not measure compression or prove that the closure is fully weathertight.
Why Does Hatch Cover Weathertightness Matter?
Hatch covers protect the cargo hold against rain, spray and seawater. On bulk carriers and other cargo vessels, damaged rubber packing or uneven compression can allow water to reach grain, steel and other sensitive cargo.
The consequences may include contamination, corrosion, rejected goods, cargo claims and delays at the discharge port. The higher the cargo value, the greater the financial risk associated with an undetected leak.
Crews should therefore inspect more than the visible hatch panels. Rubber gaskets, compression bars, hatch coamings, landing pads, hydraulic components and securing arrangements all affect weathertight integrity.
The practical point is simple: a cover being fully closed does not mean that uniform compression has been achieved around every hatch joint.
What Is the Chalk Test Procedure on a Ship?
When crews refer to a chalk test in ship maintenance, they usually mean a contact check carried out between the rubber packing and compression bar.
A typical chalk test procedure involves five steps:
- Open the hatch and clean the rubber packing, compression bar and surrounding contact surfaces.
- Apply a clear, even line of chalk along the compression bar or relevant sealing edge.
- Close the hatch panels fully and secure them using the vessel’s normal operating procedure.
- Reopen the hatch carefully without wiping or disturbing the contact surfaces.
- Inspect the rubber packing for a continuous chalk mark and record any missing sections.
The test should be completed under safe working conditions, with personnel kept clear of moving hatch panels and hydraulic equipment.
Crews should also look for damaged hinges, hydraulic oil leaks, worn landing pads and panel misalignment. These faults may prevent the correct compression even where the hatch appears secure.
How Should You Read the Chalk Mark?
A continuous chalk line suggests that the rubber packing contacted the compression bar. A broken or missing section points to a contact gap, damaged gasket, uneven surface or alignment problem.
The strength of the chalk mark is only a visual clue. Results can be affected by the amount of chalk applied, dirt on the contact surfaces and how the hatch was closed.
Where a mark is missing, inspect the rubber packing, compression bar, landing pads and panel alignment. Clean the surfaces, correct any obvious defect and repeat the test.
If the cause remains unclear, ultrasonic testing can determine whether leakage is still present at that point.
What Can Chalk Testing Show and What Can’t It Prove?
Chalk testing answers one narrow question: did the sealing surfaces make contact when the hatch was closed?
This makes a chalk test for hatch covers useful during routine maintenance, after replacement of rubber gaskets or as an initial check before loading. It can reveal obvious gaps around hatch joints, corners and coaming sections.
A chalk test hatch cover result should not, however, be treated as proof of weathertightness. A gasket may leave a continuous mark while still lacking enough compression to resist water during heavy weather.
Chalk testing also cannot:
- Measure the amount of compression applied to the gasket
- Detect every small hole or crack
- Show the relative size of a leak
- Replicate movement and pressure at sea
- Produce a measurable leakage record
How Does Chalk Testing Compare With Other Testing Methods?
Ship owners and crews commonly compare chalk testing with hose testing and ultrasonic testing. Each method provides different information.
Testing method | What it shows | Main limitation |
Chalk test | Contact between rubber packing and the compression bar | Does not measure compression or leakage |
Hose test | Whether water enters when a directed jet reaches the hatch joint | Uses water and depends heavily on operator technique |
Ultrasonic test | The position and relative scale of sound leakage | Requires suitable equipment and trained interpretation |
What Are the Limits of Hose Testing?
During hose testing, a powerful jet of water is directed at hatch joints while someone inside the cargo hold looks for water ingress. Industry guidance commonly refers to hose pressure of around 2–3 kg/cm².
The test can reveal leaks, but it may not be suitable when cargo is loaded, temperatures are below freezing or contamination must be avoided. Results also depend on the operator directing the hose across every section at the right distance and pressure.
Hose testing shows that water can enter, but it does not produce a measured leakage value. It may also create an unnecessary risk around moisture-sensitive bulk cargo.
Why Is Ultrasonic Testing More Informative?
Ultrasonic hatch cover testing places a transmitter inside the cargo hold. The transmitter runs continuously while the hatch is fully closed.
An operator then moves an external receiver around the hatch joint, compression bar and other possible leakage points. Ultrasound escaping through gaps, cracks or holes is detected from outside the hold.
This method keeps the cargo space dry and allows small leaks to be located directly. It can also provide measurable readings rather than relying on a visual chalk mark.
The Portascanner® WATERTIGHT PLUS displays results in decibels and as a percentage of the Open Hatch Value.
The Open Hatch Value is a reference reading taken while the hatch is open. Readings collected after closure are compared with that baseline to assess leakage.
Industry guidance commonly uses 10% of the Open Hatch Value as an important leakage threshold. Users should still follow the equipment instructions and any applicable survey or regulatory requirements.
How Does a Chalk Test Work on Watertight Doors?
A chalk test for watertight doors follows the same contact principle used for hatch covers.
Chalk is applied to the knife edge, frame or compression surface before the door is closed and secured. When the door is reopened, the rubber gasket is inspected for a continuous transferred line.
Missing chalk may indicate debris, worn rubber, misalignment or uneven closing pressure. As with hatch cover testing, the result does not confirm that the door will prevent leakage through small openings under water pressure.
Ultrasonic testing can inspect watertight doors without flooding the compartment or applying a hose. It can also be used on hatches and multi-cable transit seals.
When Should Ship Owners Use Ultrasonic Testing?
Ultrasonic testing is useful when crews, surveyors or ship owners need to locate and measure leakage rather than check contact alone.
It may be appropriate:
- Before loading moisture-sensitive cargo
- After hatch cover repairs or gasket replacement
- Before a survey or planned voyage
- Following suspected water damage
- When hose testing cannot be carried out safely
The method also helps direct maintenance. Once leakage has been located, the affected seal, compression bar or hatch component can be repaired and tested again.
In a Belships Management hatch testing case study, Portascanner® equipment was used to inspect vessel hatches and support repairs before departure. The example shows how measured results can turn a general inspection into targeted maintenance.
How Does Coltraco Support Hatch Cover Testing?
Coltraco Ultrasonics develops handheld equipment for inspecting the weathertight and watertight integrity of marine closures.
Portascanner® WATERTIGHT PLUS is designed for hatch covers, watertight doors and multi-cable transit seals. The transmitter generates ultrasound inside the enclosed space, while the receiver detects sound escaping through the external seal.
Coltraco’s guide to the progression from chalk to ultrasonic hatch cover testing explains how traditional and modern methods fit into vessel inspection and maintenance.
The wider ultrasonic hatch cover testing range supports leak detection, measurement and reporting for crews responsible for cargo protection, vessel safety and regulatory compliance.
Choose the Test That Matches the Risk
A chalk test can show whether rubber packing contacted the compression bar, but it cannot prove that a hatch cover or watertight door will resist water ingress. It works best as a preliminary maintenance check rather than a complete assessment of weathertight integrity.
Where vessel safety, cargo value or survey requirements call for clearer evidence, ultrasonic testing helps crews detect small leaks without wetting the hold. Measurable results allow maintenance teams to target repairs, test again and reduce the risk of preventable cargo damage.
