Watertight offshore lifting2 October 2003
A new code of practice can help safeguard lifting on oil rigs and in other types of adverse conditions, says Derrick Bailes
In terms of safety, offshore and sub-sea environments present a particular challenge to those responsible for the management of lifting operations. Unfortunately, recent accident statistics suggest that a significant number of companies are failing to provide sufficient safeguards against the increased risks involved. Between January 2000 and January 2002, four of the six accidental deaths reported in the UK offshore sector were directly related to the use of lifting equipment. As a result, the Offshore Division of the UK agency responsible for workplace health and safety, the Health and Safety Executive (HSE), has made lifting operations a key priority.
Part of the new initiative has focused on the use of hand chain blocks and lever hoists. This follows several incidents involving these types of device and subsequent research into the causes of mechanical failures. The HSE Offshore Division has produced technical guidance on the safe use of lifting equipment offshore (available at www.hsebooks.co.uk) and, in line with the recommendations of a report it commissioned into this issue, invited the Lifting Equipment Engineers Association (LEEA) to produce a code of practice to help companies manage the risks involved in the use of hand chain blocks and lever hoists.
The need to take into account prevailing conditions has been something of a recurrent theme of this series of articles. In the case of the offshore and sub-sea sectors, the additional risk factors are wide ranging and not always immediately obvious. The combination of salt water and air that is present in locations such as splash zones can clearly lead to accelerated corrosion of the component parts of lifting equipment, but this is far from the whole story. Proximity to inflammable materials, flare stacks or hot condensate lines, temperatures outside the 0° to 25°C range, exposure to chemicals and acidic environments (such as drilling muds in the rig floor area), restricted working space and the additional dynamic loads imposed on lifting equipment by the movement of vessels and/or installations can all have a detrimental effect on the integrity of lifting devices used offshore. In terms of safety, another key characteristic of hand chain blocks and lever hoists is the fact that at least one person is inevitably in close proximity to the load throughout the lifting operation. The action needed to address such risk factors is equally wide ranging, and encompasses specification, thorough examination, transportation, storage and control, and maintenance.
Selection of appropriate equipment is clearly a sound starting point for any robust safe lifting procedure. The use of general-purpose lifting devices rather than equipment designed specifically for offshore conditions has emerged as a common theme in the incidents reported to the HSE. Hand chain blocks and lever hoists both contain components which will corrode in a marine environment and, as a result, can seize or suffer seriously impaired functionality. Lack of lubrication, or contamination of brake components with lubricants, is another risk common to both, along with the danger posed by lifting loads that are too light for the device in question. Hand chain blocks and lever hoists have a brake mechanism that relies on sufficient torque being generated by the load lifted. If the load is too light, the brake will not work. Consequently, to operate satisfactorily, a minimum safe load must be adhered to. It is generally accepted that hand chain blocks and lever hoists should be tested at no more than 5% of the SWL; British Standards specify this figure. However, it is undoubtedly good practice to allow an additional safety margin, particularly with equipment that is exposed to a marine environment. The LEEA therefore recommends that the minimum safe load should be no less than 10% of the SWL.
When specifying hand chain blocks, a number of issues should be taken into account. Modern chain blocks typically use alloy chain of either grade T(8) or V(10). Both are susceptible to hydrogen embrittlement if exposed to acidic conditions. It is also important to consider how best to deal with slack chain. Left loose, it can present an obstruction and/or hazard. However, if collection boxes are used, they must be designed to cope with all the potential slack chain both in terms of weight and volume. Once slack chain starts spilling from a collection box the tendency is for it all to fall out, representing a real danger to staff. In addition, where moisture or condensation is likely, a suitable drainage hole should be included, and corrosion-resistant materials employed for the construction and attachment of the chain collecting box.
As far as lever hoists are concerned, due to potential problems with corrosion, roller chain should not be used. In addition, lever hoists should be fitted with an automatic brake capable of arresting and sustaining the load, subject to the minimum safe load guidelines already outlined.
Alternatives to hand chain blocks and lever hoists should also be considered at the specification stage, particularly for underwater and splash zone applications. For example, jaw winches, which physically grip/pull the rope, offer some degree of corrosion resistance, along with the additional benefits that they cannot be over-lubricated and feature no components that can be compromised by contamination with lubricants.
In all cases, the buyer should provide a comprehensive specification for the supplier. If the application requires a load to be sustained for a long period between lifting and lowering, consideration needs to be given to the consequences of corrosion in critical components. Additional equipment may be needed to sustain the load, or fresh equipment employed before releasing it from the device it has been suspended from.
Although robust specification is essential, the procurement of appropriate equipment is not in itself sufficient protection against the increased risks of the offshore environment. In the UK at least, the Lifting Operations & Lifting Equipment Regulations (LOLER) provide an exemption from thorough examination for new, unused equipment for which the employer has received an EC declaration of conformity made out no more than 12 months before the equipment is taken into service. However, because of the exceptional conditions to which the equipment may be exposed, the LEEA believes that every block or hoist destined for an offshore or sub-sea application should be thoroughly examined before first use, including a light load test (2-5% of SWL) and a proof load test. Furthermore, although LOLER allows for a maximum 12 month interval between in-service thorough examinations, the LEEA believes that in offshore and sub-sea environments these should be conducted at intervals of no longer than six months. If this is not feasible, equipment should be placed in quarantine after six months and thoroughly examined before it is returned to service.
Transportation and storage
Transportation and storage also demand special attention. En route to installations, lifting equipment should not be exposed to water, extremes of temperature, solvents, corrosive chemicals or fumes and wind blown dust, grit or sand. Lifting equipment should then be transferred to a purpose-designed storage facility. This must be secure from unauthorised use and include a quarantine area.
The storage facility should be controlled by a nominated person (or persons). He or she should record the issue and return of equipment, ensuring that it is only released to authorised staff, with a clear indication of the length of time that the issue applies for. The nominated person should also take responsibility for inspection of equipment between thorough examinations. On return, they should question operators as to the condition of the equipment and quarantine it if necessary. To support this process, management should endeavour to create a 'no blame' culture, where staff feel free to report potential problems with equipment, rather than keep quiet out of fear of the repercussions.
Hand chain blocks and lever hoists should be cleaned and checked for contaminants. If subjected to salt water, hoists should be washed with fresh water. To avoid removing vital lubricants, or forcing such lubricant onto the brakes, pressure should not be used. Equipment should then be dried without using heat. The load chain may be lubricated, but hoists should only be dismantled for cleaning by an appropriately qualified, authorised person. A check should be made for correct operation by the nominated person each time an item of equipment is issued from storage.
Maintenance programmes should also be placed under the direct supervision of the nominated person. The efficiency and safety of hand chain blocks and chain lever hoists is dependent on them being suitably lubricated and free of contaminants and corrosion which could cause components to seize. Lubricant must be kept away from the brake. Furthermore, components liable to wear and deteriorate need to be replaced before their condition becomes dangerous. The nature of the environment is such that all these issues are of increased significance in the offshore and sub-sea sector. Maintenance will clearly need to be performed in line with the relevant manufacturer's instructions, but should include dismantling (without compromising the equipment's unique identification), cleaning and examination of components, treatment to resist corrosion, and careful lubrication. Only replacement parts of the same specification as the originals should be used, unless they have been superceded by improved versions that are more suitable for the offshore environment.
There can be little doubt that, at present, too many lifting operations undertaken offshore involve an unacceptably high degree of risk. The conditions involved present special challenges to those responsible for health and safety, and specific measures need to be taken to address them. The HSE Offshore Division is committed to reducing the incidence of lifting related accidents by 15% by 2004 and, as part of this initiative, is undertaking a test programme to collect data about the performance of typical hand chain blocks and lever hoists under the marine/saliferous conditions experienced offshore and sub-sea. In due course, this may well shed further light on the causes of mechanical failure and the best means of preventing them. For the moment, the LEEA's code of practice for hand chain blocks and lever hoists used offshore embodies the latest industry know-how and accepted best practice. Consistently applied it can undoubtedly make a significant impact on the number of lifting-related accidents experienced in the offshore sector. As a final point, however, it must be stressed that the new code (and the brief overview provided by this article) is very much a supplement to, rather than a replacement for, the more general advice and guidance offered by publications such as the Approved Code of Practice that accompanies LOLER and the LEEA's Code of Practice for the Safe Use of Lifting Equipment. Such documents remain the foundation of safe and efficient lifting, whatever the prevailing conditions.