A Guide To Hatch Cover Testing
Back in the olden days, sailing vessels would have cargo hatches as small as possible to preserve the hull’s integrity. During ocean crossings, the decks would be awash with seawater so the smaller the openings, the drier the holds. Small hatch, not much thought for a hatch cover.
Nowadays, anything that slows down loading and discharge speeds is money, so the bigger the hatch the better. You’re still looking at the same problems though in keeping the hold dry, but now it’s amidst a framework of moving parts such as steel covers and closing devices designed to provide the crucial access and sealing of the hold.
These are strong and tight when they are brand new of course, but the hatch covers suffer from wear and tear, so thorough testing of hatch covers and good maintenance are essential.
Damaged cargo caused by water ingress from hatch covers make up the vast majority of P&I claims – even the smallest leak can do extensive damage to cargos like steel and paper that are sensitive to seawater.
But let’s not forget that besides the potential loss to your cargo, it’s a statutory requirement that your ship is watertight and weathertight. Leaky hatches are the most common cause of vessels being selected for unscheduled condition surveys, so besides the potential for damage to your cargo, you could be looking at lost time in dock if you don’t stay on top of your hatch maintenance.
Regulations on Hatch Covers
Hatch covers and locking devices are the responsibility of the ship’s owners and operators and the 1966 International Convention on Load Lines dictates the position of hatchways, height of coamings, strength of covers and the need for securing devices.
Their focus is primarily around the safety of the ship, defining how deep vessels can be loaded for a safe voyage and how to construct and equip vessels to avoid ingress of seawater through various openings. You’ll need to meet all of their criteria for the issuance of your International Load Line Certificate.
Whilst hatch cover and locking device compliance is down to owners and operators, class and flag state are responsible for ensuring certain classification and load line rules are met for their Classification Certificates to be issued. In addition, SOLAS regulations stipulate that ‘openings on deck have the means to be watertight’ in order to receive an International Cargo Ship Safety Construction Certificate.
Types of Hatch Testing Methods
Various methods can be used to test a vessel’s hatch covers such as light test, chalk test, air test, putty tests, moulding tests, hose tests and ultrasonic tests (UST). UST tests are now the most reliable and widely accepted method, but hose tests are still used extensively – partly because shipowners claim that UST tests find too many leaks but that’s another story!
Hose tests have been extensively used for a while, but there are limitations to using this method:
- Cargo holds need to be free of cargo
- The test can’t be conducted in sub-zero temperatures
- Leakages can’t be pinpointed accurately
- Results can be affected by water pressure variance and the distance of the jet from the vessel
- Excess water on deck can lead to pollution so many port authorities won’t permit this method
- At least two crew members are required for this method
- This test can only be conducted in static conditions
The main issue with the hose test is that the results are only applicable to the static vessel as the flex needed by the hatch and coaming structures while the ship is at sea isn’t allowed for. The contact between the rubber packing and the compression bars when the ship is in motion and subjected to the forces of wind and waves isn’t tested.
Your issue here is that you can’t gauge the compression being achieved by the steel to rubber contact, so you’re clueless on the watertight integrity when the ship is moving – until you’re looking at a compromised hold full of wet paper or steel!
Why Use Ultrasonic Testing For Hatches?
The benefits of UST testing are extensive which explains why it is by far the most popular hatch testing choice. The ease of testing is one of the core benefits – when you’re fighting tight loading and dispatch turnarounds in dock, time is critical, so having to remember to fit in a hose test when the hold is empty is a challenge you could do without – and then you have to make a significant amount of time to do the hose test.
Not only are you saving crucial time, but there are also other factors which make UST a much easier solution;
- UST tests can be done with full cargo – the cargo levels don’t impact the test
- The test can be conducted and trusted in sub-zero temperatures
- The test takes minutes to conduct so the time saved vs other methods is significant and tangible
- Leakages can be accurately pinpointed immediately
- Results from successful tests are reliable and accurate – immediate feedback from the equipment will alert you to a failed test so you simply do it again within minutes
- No pollution or impact on other parties so you won’t have limitations such as port authority restrictions placed on you – the test can be conducted anywhere
- Only one person needed to conduct the test
- This test can be conducted in all states of transit – meaning no time is lost from other operations to do the UST tests – ie could be conducted at sea during a crossing already in operation
- The test results are widely accepted (and often requested) by insurers and authorities
Ultrasonic testing enables the location of leaks to be pinpointed quickly and accurately. After the test, it is imperative to conduct a visual inspection to determine the reason for leakage and thereby determine the appropriate remedial action.
Trusted UST Testing
Whether you have an empty or full load, are in transit or in dock, ultrasonic testing is by far the most accurate way of ensuring your hatches are functioning correctly. Many major steel exporters request ultrasonic tests to be carried out on all ships and UST (where the necessary equipment is available) is also P&I‘s preferred hatch testing method.
P&I insurers accept UST records as they are the only method of testing which provides measurable and reliable results of the degree of hatch cover leakage. They dictate that the leakage range needs to be less than 10% of the open hatch value (OHV).
If you breach this, the club can insert a certificate of entry warranty so any claims you may have for leaking hatch covers won’t be reimbursed by the club until the warranty is lifted. The hatch covers will need to be repaired and the club arrange a follow-up UST before the warranty is lifted.
How Do Ultrasonic Hatch Cover Tests Work?
UST tests use ultrasonic equipment to check for leakages in hatch covers and hatch coamings. By placing devices in the cargo hold to emit sounds with a frequency above 20 kHz, UST operators can activate them and measure how much of the sound leaks outside the hatch covers. These results can be used as records for their ultrasonic hatch test reports.
Hose and chalk tests can show if there is contact between the compression bar and rubber packing, but ultrasonic testing indicates whether you actually have the required levels of compression to create the seals needed to keep cargo dry when the vessel is in motion.
Because of its unique dome configuration, our Hatchtite device goes even further than standard UST devices as the effectiveness of an ultrasonic tester is determined by the amount of sound energy reaching the hatch cover and most transmitters emit in an upward direction. By using 13 transmitters, the Hatchtite device gives complete cover in even the largest of holds making it 1,000 times more powerful than any other devices currently available.
How To Do An Ultrasonic Hatch Cover Test
Depending on which method and equipment you are using, there will be various practices you’ll need to implement as part of your hatch test, but here’s a walkthrough of a Hatchtite™ hatch test…
Every time a Hatchtite™ check is conducted, you’ll need to verify that the unit is working within the limits of calibration set by the manufacturer. The Emitter, Microphone and Extension Arm (E.M.EA) Tester are used to confirm compliance so each of these will need checking.
- Emitter test – ensure the batteries are new or fully charged and turn the transmitter unit on. It should be emitting a continuous tone.
- The E.M.EA Tester – hold this over each emitter in turn. If the emitters are fully functional the green LED will be lit on the tester.
- The Microphone – plug the E.M.EA Tester into the microphone using the emergency microphone lead and hold the microphone over any one of the emitters on the transmitter unit. If the microphone is fully functional, the green LED will light on the tester. Repeat for both microphones.
Positioning The Transmitters
If the hold is virtually square the transmitter can be placed in the centre. If the hold is rectangular then the transmitter needs to be placed roughly a quarter of the way along the length of the hold to survey the first half of the hatch cover. Once complete, you can reposition the transmitter three-quarters of the way along the hold and survey the latter half of the hatch cover.
Open Hatch Value Test
Before starting, you’ll need to obtain a reading for the level of ultrasound reaching the underside of the cargo hatches. This can be done using an access hatch, or by opening the hatches on deck. This value is known as the Open Hatch Value or OHV. The microphone should be lowered down the access hatch so that it can “see” the transmitter.
Once the OHV has been obtained, the hatch cover survey can be conducted with the receiver unit in either decibel mode or OHV% mode. A value of 10% of the OHV depicts an area of potential water ingress. In decibel mode, an OHV of 74db would mean any reading over 7.4db (10% of the OHV) indicates an area for potential water ingress. In OHV% mode, the knob on the receiver is turned so that 100 is obtained when taking the OHV reading. A value of 10 or above recorded during the survey indicates an area for potential water ingress.
The exterior of the ship is then inspected using the receiver unit. The microphone is used to identify any ultrasonic sound and registers this as a value on the display and as an audible noise through the headphones.
Tightness Test Survey Form
Your tests will need recording sand a Tightness Test Survey Form is completed with every hatch cover survey. Photographs are often taken to support the reported findings too. The form shows Section 1 completed after the pre-survey checks have been carried out.
The Hatchtite™ can be used if the cargo hold is either empty or full as the flexible microphone allows for pin-point accuracy when identifying areas of potential water ingress.
Mark these areas with chalk, so that when the hatches are opened the cause of the hole can be identified.
The Tightness Test Survey Form is completed during the inspection and photographs are taken to support any conclusions drawn.
If no ultrasonic sound has leaked through the cargo hatch, the display will register a zero and no noise will be detected by the headphones. This indicates a perfect seal.
If ultrasound has escaped at this point on the hatch cover a reading of 3 will have been recorded in OHV% mode. When OHV% mode is used, any reading above 10 indicates an area of potential water ingress showing the hatch cover is not watertight.
This diagram from the North of England P&I Club’s January 2005 publication “Hatch Cover Supplement” shows the most common defects found in hatch covers.
Why Use Hatchtite™ For Your Hatch Tests?
As you can now see, this method of testing saves valuable time in both execution and scheduling as it can be conducted around other operations going on.
Within minutes you have a reliable result which in real terms is the difference between maintaining compliance and meeting tight turnarounds and being ground to a halt for unscheduled condition surveys.
Hatchtite™ devices take all of this into account…
- Rated as IP66 and measured in dBs to meet P&I clubs and DNV regulations,
- Designed to be cheap to maintain and operate with a run time of 40 hours instead of 10,
- It only needs calibrating after 5 years,
- Can even be lowered into the hold regardless of whether the ship is empty or loaded so no disruption to operations.
If you’d like more information on using one of the most trusted and cost-effective ways of keeping your cargo free from water damage, get in touch here.