Safety remains paramount when undertaking potentially hazardous bulk handling and confined space entry operations
Improvements in the offshore oil and gas market have led to growing activity and increased demand for offshore vessel charters.
To meet this demand, owners are reactivating vessels such as PSVs and AHTS that transport essential supplies like drilling fluids, mud, cement and methanol in their tanks, and equipment such as casings, drill pipes, skips and containers on their decks.
As charter demand increases and vessels return to service, owners and crews must remain alert to safety issues that stem from these vessels’ lack of recent use, for example cleaning drilling mud from tanks.
The last decade or so has seen significant improvements in efficiency and safety when it comes to such operations, including decreased cleaning times and less confined space entry operations.
Traditional methods of manual mud tank cleaning involve personnel entering contaminated tanks. The process is costly and time consuming, not to mention tiring, dirty and potentially dangerous.
This was illustrated in April of this year by a safety alert issued by the US Coast Guard (USCG). The alert was issued in the wake of an incident – the investigation into which is still ongoing – into the deaths of three crew by asphyxiation while working aboard a laid up mobile drilling unit.
A key element of the incident involved the Captain and two other crew members descending into a confined space without safety equipment to assist another crew member who had already been overcome by fumes.
“50% of deaths in enclosed and confined spaces occur when attempting to rescue co-workers”
The alert notes that the crew members who entered the leg may have lost situational awareness, adding that studies illustrate that obvious cues can often be missed while under stress and when crew are focused on another effort or action.
Investigators were particularly concerned by the Captain’s decision to enter the space with two other persons without personal protective gear and an SCBA. The alert notes that sources indicate more than 50% of worker deaths in enclosed and confined spaces occur when attempting to rescue co-workers.
An IMCA safety flash released in January this year further emphasises the need for proper procedures, equipment and training. A worker felt dizzy and weak while cleaning a mud tank. The tank watchman, noticing this, initiated emergency rescue procedures to recover the worker from the confined space. The worker received first aid and a further diagnosis of increased blood pressure but returned to their duties several hours later following rest.
Analysis of factors affecting the incident identified several issues; these included a failure to safely control the work process, unsuitable rescue equipment – certificates evidencing inspection of pieces of kit were absent – and the absence of a confined-space rescue plan. It also noted that the mud previously loaded into the tank did not have a safety datasheet, meaning the hazardous nature of the situation was unable to be identified.
Confined space entry - USCG recommendations
The USCG strongly encourages all who work or may be employed onboard vessels in any role, whether they be senior shipboard officers or crew, riding crew, shore side managers, owners/operators, and other personnel to:
Importance of PPE
IMCA’s safety statistics also highlight the importance of safe working practices and proper personal protective equipment (PPE) in other areas of bulk cargo handling on OSVs.
In one incident, a crew member injured his leg while moving a mud agitator with unprotected blades while the vessel was en route to port. First aid was administered immediately on-board, followed by further examination and treatment of the wound at a clinic onshore. The injured person returned to the vessel on the same day.
IMCA’s safety flash says there was inadequate risk awareness – risks could have been reduced by protecting the blades before lifting/handling the agitator; waiting until the vessel reached port could also have reduced manual handling risks. Furthermore, manual handling practice could have been improved; while the agitator was suspended by chain blocks during the work, whilst gripping the blades using pieces of rag (rather than wearing gloves), the load slipped from the operator’s hands and hit the crew member’s leg. A rope or another hands-off approach could have been used to turn/move/stabilise the load.
The lessons learned focused on better risk awareness when moving objects with blades or sharp edges:
IMCA also detailed two incidents, which were reported in 2013, of crew members working on PSVs receiving injuries to their hands from sharp blades on mud-mixing equipment.
The first incident occurred during tank cleaning of a mud tank when a crewman lost his footing and, on putting his hand out to steady himself, sliced his finger through his gloves on the mud-mixer blade.
In the second incident, a crewman removed the protective cover fitted on the mud mixer in order to clean it. During this process he managed to rotate the blade into his own leg, causing a cut that required six stitches.
OSVs are often used to aid in the disposal of drill cuttings from offshore platforms. When water-based drilling fluids are used, these can generally be safely dumped overboard; however, if oil-based drilling fluids are used the cuttings require specialist processing before they can be safely disposed of.
“You only need one lift to have an accident, and when you’re doing a skip-and-ship operation you’re looking at maybe 5,000 lifts per well”
The efficient transfer of drill cuttings away from platforms is essential to avoid causing bottlenecks in drilling operations. A commonly used method of disposal is known as ‘skip-and-ship’. In this method, cuttings are collected from the shaker house on board the platform via a simple mechanical conveyance, such as a screw conveyor, that transfers the cuttings into a skip or storage box. These typically range in size between four and 11 tonnes and are lifted onto an OSV’s deck via crane operations before being transported to shore-based processing facilities.
Drilling waste disposal specialist TWMA’s technical sales manager Andrew Morris outlined the pluses and minuses of this method of transfer. “We all know we only need one lift to have an accident, and when you’re doing a skip-and-ship operation you’re looking at maybe 5,000 lifts per well to contain all the drilling waste,” he says, adding: “If you can eliminate lifts you’re eliminating a high-risk operation.”
Bulk transfer offers an alternative to skip-and-ship operations if vessel-based transfer is required. In this method, cuttings are first transferred from shale shakers to a specially designed cuttings storage tank (CST) on the rig, and then pumped into CST units carried on the deck of an OSV. TWMA’s CST units have a 70-tonne capacity and are fitted with integrated positive displacement pumps. Each bulk storage tank can hold the equivalent of 12 or 13 skips’ worth of cuttings in a smaller footprint, making better use of space on the vessel’s deck. This allows more efficient use of vessels, Mr Morris says, noting that the space saved can be used for other supplies needed for the rig. “It can potentially lower costs because you don’t need as many vessels, but it also maximises the potential of a vessel on a rig site with these tanks,” he adds.
Storing the drill cuttings in CST units, rather than in a vessel’s integrated tanks, offers further benefits to vessel owners and operators. Mr Morris explains: “If you put [drilling waste] into the vessel’s tanks, it could settle while transferring onshore, which makes it more difficult to discharge when it gets there. Costly cleaning methods also need to be taken into account.”
Using CSTs designed to handle drilling waste means tank cleaning is not required, saving on costs and also avoiding the need for confined space access by the vessel’s crew. It also speeds up operations at the quayside, making for a quicker turnaround, and provides better visibility on stored material.
However, deck storage of bulk cargo can bring its own challenges, as evidenced when reviewing safety alerts from recent years.
To give just one example from IMCA, which concerns an intermediate bulk container (IBC). The IBC, which held a tonne of monoethylene glycol, was being transferred using a vessel crane when it started to rotate, owing to the liquid inside sloshing around. This resulted in the lift rigging device being unable to support the load and the IBC falling 3.5 m to the vessel’s deck and bursting open, spilling its contents. No injuries were reported, and the spill was contained on board, avoiding damage to the environment. However, it was found adequate risk assessment had not been carried out and that the lifting rig used was unsuitable for the task.
In another example from the Marine Safety Forum, a cargo carrying unit (CCU) containing an IBC came unlatched during lifting operations. On investigation, it was found that the IBC was not secured within the CCU, and that the CCU design did not include features such as internal securing points to allow the IBC to be secured, or external buffers to prevent snagging of the door handle.
Guidance from OCIMF is designed to improve the safety of deck cargo operations on OSVs
The Oil Companies International Marine Forum (OCIMF) has identified deck cargo operations on OSVs as posing a high safety risk and released an information paper, titled Deck Cargo Management Onboard Offshore Vessels, comprising guidance and best practices on how to make deck cargo operations safer. The guidance is targeted at offshore industry personnel, vessel crews and others. It covers topics including accountability of key personnel, best practices, routine lifting operations, manifests and stowage plans, and methods for cargo securing and lashing.