NAUTICAL INSTITUTE, CYPRUS BRANCH | Nautical Institute Cyprus

NAUTICAL INSTITUTE, CYPRUS BRANCH

NAUTICAL INSTITUTE, CYPRUS BRANCH

‘Hatchcovers – an inconvenient truth’ by Walter Vervloesem (FNI) Chairman IMCS Group of Companies Ltd (UK) 

The Branch was delighted to welcome Walter to speak at their evening presentation in Oct 2018.

Walter began by stating that according to IMCS data, 75% of ships inspected have hatch cover problems, ranging from maintenance issues to serious and unacceptable problems. 42% of the ships inspected have serious issues that may cause significant damage to steel (and other) cargoes. Regardless, all the ships were classed and had P&I covered at time of inspection. With current designs, hatch covers can weigh up to 100MT, but their proper operation depends on tolerances and clearances in the range of mm!

So, whatever type of hatch covers/closing appliances we are dealing with, they all have one thing in common – When not well designed, properly maintained and operated by trained personnel, they can cause very serious safety and commercial accidents such as injuries, cargo claims and pollution.

After looking at the history of hatch cover design and development, Walter pointed out that current hatch covers are bigger, heavier and more technically complex than ever before and withstanding the powers of the oceans is becoming a real challenge. Walter also explained how the design has been improving through strength, tightness, security as well as Classification Society rules (IACS UR IACS UR S 26-27-28-30).

He then went on to explain the various movements that take place on a hatch cover in a seaway and then explained the various design features such as the hatch cover steel plating, the rubbers and the drains, which prevent water ingress. After reviewing the key maintenance needs, he then showed us a short video on ultrasonic testing (UST)

He also explained why UST (which is a piezzo electric crystal based transmitter and a receiver arrangement) cannot really be compared with hose testing.

 A hose test measures ‘contact’ while UST measures ‘compression’. And contact is not the same thing as compression, so the results cannot be compared. He then showed some real test results and asked the audience whether they could determine if the hatchcovers were weathertight. Herein lies the issue of interpreting results and deciding which UST leak areas are ‘critical’ and what magnitude of leakage should give cause for concern.

Let’s consider an open hatch value (OHV) of 50dBμV as reference for an UST test. We then set a fail/pass level of 5dBμV and consider a “leak” of 35dBμV in a spot, and a “leak” of  8 dBμV over a long length (a cross joint for example).

The problem is that many people will focus on the value of the readings (the higher the more problematic) rather than the consequences of these readings.

So in many cases people will consider a value of 35dBµV on a small spot to be more important than a reading of 8 dBµV (slightly above the fail/pass criteria) over a long length. However, what is often overlooked is that ultrasonic tightness testing gives an idea of the compression in a sealing arrangement. This means that a “slight” leak indicates that the compression and compensating capacity of the rubber is already compromised and that the seal may open up prematurely in “normal” heavy weather because its capacity to compensate for relative movements between the panels and coaming whilst the ship is at sea is affected. In case of a spot leak, there is a fair chance that the incoming water will be contained in the drain channel and drained out on deck without a risk of contaminating the cargo. However, and in case of a linear leak over a long length a considerable amount of water may pass through the sealing arrangement and overflow the drain channel and as such the risk of cargo damage is more significant.

It is therefore important to understand the information obtained from a UST and then to assess the risk rather than considering the values alone.

Walter questioned why Class was happy with a hose test but then the vessel still got water in the holds and still got claims.

If, in normal heavy weather (say force 8, i.e. hatch covers should not leak in such condition!) water infiltrates through  the sealing arrangements and is collected in the drain channel, most of the water will be drained away and as such the vessel’s safety as a result from incoming water is not affected. However, it is possible that, due to rolling and pitching, a small amount of water drips on the cargo and damages it. The Master will blame the heavy weather but Cargo interests will rather blame the damage on poor maintenance and lack of due diligence in preparing the ship for going to sea, basing their argument on the fact that hatch covers should be weathertight and able to withstand the rigours of an ocean voyage.

Is there a paradox here? Owners are earning money by transporting and delivering cargo in good condition. Class is checking statutory requirements and the ship passes her class and statutory surveys (Safety equipment, safety Construction and Loadline) and necessary tests (hose test), which show that no water entered the hold.

It is possible that, at the first loading (after the renewal survey), a UST is done by the Charterers and leaky spots are found but Class & cargo interests have different requirements because:

  • No water in hold that can jeopardise the safety of the ship (seaworthiness).
  • There is no water damage to the cargo (cargo worthiness)
  • Cargo insurance is based on class certificates.

Then confusion, arguments and claims might arise. There still seems to be work to be done in this area.

Visual inspection of hatch covers is absolutely essential with the main problem areas being rubber packing, bearing pads, coaming drain valves, drain channels and perimeter cleats.

The main challenges facing Owners were considered to be:

  • Improper/temporary repairs made by crew.
  • Superintendents overestimating the capability of the ship’s crews for repairs.
  • Lack of knowledge about hatch cover basics.
  • Missing manual/drawings (spares, maintenance, inspection)
  • No on-board instructions for maintenance.
  • No maintenance and test files on board.
  • No understanding of the due diligence principle/issues.

Common mistakes to achieve weather tightness include:

  • Replacing the rubber seals but not fixing the resting pads.
  • Installing backstrip rubber everywhere.
  • Mixing new and old rubber seals.
  • Using small pieces to fill in gaps.
  • Not painting the rubber channel leading to rust and corrosion.

The event was well attended by both members and friends of the NI Cyprus Branch. A networking and social hour was held afterwards generously sponsored by SDT International (Belgium).

Contribution by Graham Cowling, NI Cyprus Branch