SCENARIO
The manufacturing site of a large international chemical organisation is located on the outskirts of a town. This site is close to a main road and residential homes. Tall mature trees line the perimeter of the site to provide a visual barrier between the residential and industrial buildings.
The chemical manufacturing operations involve many different types of processes that normally run continuously (24-hours a day, 7-days a week) by process operators working shifts. Shift patterns include 06:00 – 14:00 (day shift), 14:00 – 22:00 (afternoon shift), and 22:00 – 06:00 (night shift). There are approximately 400 workers on the day shift and 400 on the afternoon shift. The night shift has the smallest team with approximately 200 workers. A dedicated car park for workers is located at the north end of the site, next to the main road and main entrance. There are often queues getting in and out of the car park during shift changeover times.
The manufacturing processes use hazardous chemicals (including those that are toxic and flammable) as raw materials. As a result, large quantities of hazardous chemicals are in use and stored on site in storage vessels, intermediate bulk containers (IBCs), and 205-litre drums to ensure there is always sufficient stock available.
One of the manufacturing processes is in the middle of a six-week scheduled maintenance shutdown, where most of the hazardous chemicals have been safely removed from associated process vessels. This process plant (equipment, vessels, and associated pipelines) is located outdoors and is accessed using external steel walkways and stairs over four floors. The walkway floors are made of steel grating. Pipework, several vessels, and some electrically driven pumps are located on all these floors.
There are dry powder fire extinguishers located at various places around the process plant. The plant is fitted with a water-based foam sprinkler system. The process plant also includes a number of combined safety shower and eyewash stations that can be used in an emergency. These stations can be utilized to wash off hazardous chemicals to which workers may have been exposed. Using the stations automatically alerts the shift manager and an on-site emergency rescue team to the scene.
At either end of the ground floor, there is a manually activated plant evacuation alarm. The alarm has an intermittent tone and flashing red beacons. Activation has the same effect as a fire alarm, prompting everyone to evacuate the process plant immediately. The evacuation alarm can also be activated remotely from a central process control room. A two-way radio can be used to ask for remote activation. Workers at the plant are trained what to do in an emergency in their induction training.
Deliveries
Road tankers ranging from 2.4 to 3.6 metres in height deliver chemicals to the site. Deliveries are scheduled every fortnight on a Monday afternoon between 13:00 – 17:00. Smaller quantities of raw materials are delivered in IBCs and 205-litre drums every Wednesday morning on a weekly basis; however, there are frequent ad hoc deliveries of IBCs and 205-litre drums to cope with fluctuations in manufacturing operations. Delivery times also vary depending on local traffic conditions, which has been known to cause congestion.
Delivery drivers ranging in age, experience, and nationality arrive at the main gate and sign in with a security officer. Using a separate entrance next to the main gate, the drivers navigate across the site to the chemical storage area located at the south end of the site. The two-way internal road network within the plant is also used by other vehicles such as those used by waste management organizations, internal maintenance, external contractors, and the plant’s forklift truck operators. Most of the process operators work inside a network of buildings connected by these internal roads and walkways. These internal roads have a speed limit of 16 km/h (10 mph) and mini roundabouts with a raised surface. Due to potholes, a temporary diversion route has been put in place near the south end of the site while the road surface is repaired. However, some workers have complained that the temporary road system is difficult to navigate due to its narrow width.
Operators across all shifts work in and around the chemical storage area, managing deliveries (receiving, decanting, and processing). Chemicals delivered via road tankers are then transferred directly into the storage vessels. The delivery drivers unload from the bottom of the road tanker using a hose attached to a loading valve. Sometimes the delivery drivers need to climb to the top of the road tanker using an access ladder for maintenance or to check the levels. The handrail at the top of the road tanker is then automatically raised using a switch on the tanker at ground level, and then interlocked to the ladder. Sometimes the handrail needs to be manually raised if the mechanism is corroded.
The IBCs and 205-litre drums are unloaded using the forklift trucks and taken to the chemical storage area. Using the correct attachment, the 205-litre drums are then taken in pairs to where they are required within the plant.
https://youtu.be/rfX1l-eSlhg
Shutdown task
Several weeks ago, the operations team emptied and thoroughly cleaned one of the process vessels on the plant. It has been safe to enter and exit through the dedicated access ports of the large vessel for several weeks. The worn internal parts of this large vessel have already been removed by an experienced, specialist contractor team. The new parts that had been fabricated and assembled off-site are in a secure storage area on the second floor. These new parts need to be inserted into the large vessel as a like-for-like replacement of the old, removed parts.
The specialist contractor team are experienced in replacing such vessel parts but need to make some small modifications to the new parts so that they fit within the large vessel.
At the beginning of the working day, the specialist contractor supervisor visits the process control room to obtain a hot work permit from the process operator. The operator accompanies the specialist contractor supervisor onto the process plant to determine the exact location of the proposed work activity. The operator asks a series of questions to clearly understand why a hot work permit is required.
When asked by the operator, the specialist contractor supervisor says that grinding work and oxyacetylene gas welding and cutting will take place. This will be on the outdoor grating, on the second floor of the process plant. This work will be done by an experienced welder, wearing fire-resistant overalls. They add that they will use an oxygen and acetylene bottle combination (located on the ground floor), and long rubber hoses (about 15-metres long) will be routed up to the second floor. They assure the operator that fire blankets will be spread across the affected area from the centre of the work activities.
A firewatcher will be present near the hot work activity. They will remain there for the duration of the work and for an hour after hot work has ceased. The operator uses a portable gas detector near the hot work area and leaves it in position. The operator insists that several dry powder fire extinguishers are available for immediate use on the second floor during the hot work activity. The operator points out that there is a constant water supply at various stations on each floor of the plant via an integral hose reel. This can be used for wetting down the area of hot work.
Finally, the operator mentions that a scheduled inspection has been arranged for the same day. The structure to be inspected is on the fourth floor, and in the vicinity of where the hot works are being undertaken. A mobile elevated work platform (MEWP) is going to be used when inspecting the condition of the structure on the upper floors of the process plant. The two activities are far enough apart for them to be safely carried out simultaneously. The activities are scheduled to be undertaken between 09:00 – 16:00.
The external staircase, which gives access to the upper floors in the vicinity of the structural inspections, will be temporarily closed during the works due to the proximity of the MEWP operations. An alternative staircase is located at the other end of the building. To ensure safe access and egress for the increased footfall on the alternative staircase, access to the staircase will need to be monitored.
The operator now understands how the hot work will be done, and they return to the central process plant control room to fill out, sign, and issue the hot work permit.
Fire incident
After the hot work was completed, the contractors left the site. During one of the routine operational checks, the operator sees flames on the ground floor. In accordance with training, they instantly operate a safety shower and use their radio to communicate the details to the shift manager. The operator then asks the process control room operators to remotely activate the plant evacuation alarm. The evacuation alarm sounds and the associated red lights flash.
The operator sees that the acetylene gas bottle hose has flames coming out from it at several points. Flames are in contact with the middle of a pressurized process plant vessel, one of the few vessels that contain a hazardous substance. The vessel is half full of a flammable liquid, and it has an integral pressure relief valve.
In accordance with their training, the operator locates a dry powder extinguisher and tries to extinguish the flames. The flames temporarily extinguish, and then reignite. The operator retreats from the fires and decides to wait for the emergency rescue team.
All other workers on the plant immediately and calmly evacuate, and the operator helps to direct people to the assembly point. The evacuees congregate at the signposted assembly point, to await a roll call and permission to return to the plant. The return to the plant will only be authorized once the ‘all clear’ is given by the shift manager, who acts as the incident controller.
The shift manager and emergency rescue team arrive. The team leader calmly assesses the situation, walks over to the acetylene cylinder and closes the isolating valve. Within seconds the fires are extinguished. The shift manager decides not to contact external emergency services. They also instruct one of the rescue team to direct a fire hose onto the vessel to slowly cool it.
The subsequent investigation determined that the hoses supplied by the specialist contractor team were old, and the rubber had cracked at three points, through which acetylene was escaping.
Forklift truck (FLT) incident
Three 205-litre drums filled with liquid were being transported across the chemical plant using the drum lifting attachment. The FLT operator lost control going around a mini roundabout and dropped one of the drums onto the road. No spillages occurred, but the FLT became unstable and nearly fell onto its side. The operator was new to the process plant. When questioned, they blamed the congestion on the other side of the mini roundabout where three lorries were present at the time. The operator did not see the lorries straight away due to the load being carried, and they had to brake suddenly to avoid a collision. During the investigation, the operator admitted to driving at a speed of around 32 km/h (20 mph), and driving over the mini roundabout instead of around it. One of the FLT’s fork locking pins was also found on the road near to where the drum fell.
Task 1: Hot work permit arrangements
(a) What did the operator do well with the hot work permit arrangements? (12)
Note: You should support your answer, where applicable, using relevant information from the scenario.
(b) What could the operator have done better with the hot work permit arrangements? (10)
Note: Your answer must be based on the scenario only.
Task 2: Use of mobile elevated work platform (MEWP)
What should be considered to help minimize risk with the MEWP structural inspection task? (25)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Task 3: Recognizing conditions for generating a boiling liquid expanding vapour explosion (BLEVE)
While the acetylene cylinder hose was on fire, and flames came into contact with an adjacent vessel, the conditions existed for a boiling liquid expanding vapour explosion (BLEVE).
In the correct sequence, explain how a BLEVE could have been generated in this vessel. (10)
Task 4: Successful application of the emergency plan
What aspects of the emergency plan worked well once the acetylene hose fire was observed by the operator? (20)
Note: Your answer must be based on the scenario only.
Task 5: Siting of dry powder extinguishers
What would have been considered when deciding where to site the dry powder extinguishers on this process plant? (10)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Task 6: Determining benefits of the water-based foam sprinkler system
Ignoring moral, legal, and financial arguments, why is the water-based foam sprinkler system suitable on this process plant? (10)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Task 7: Workplace pedestrian and vehicle safety
What practical control measures would you expect to see if road safety was well managed on this site? (25)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Task 8: Transfer of flammable liquid
A flammable liquid is being transferred from a road tanker to a bulk storage tank in the chemical storage area.
(a) What control measures would help reduce the risk of vapour ignition due to static electricity? (10)
(b) What should be considered when assessing the risk of falls while working on top of the road tanker? (20)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Task 9: Causes of instability of a forklift truck (FLT)
(a) What caused the FLT instability in the incident? (10)
Note: Your answer must be based on the scenario only.
(b) What else could cause the instability of FLTs around the process plant? (13)
Note: You should support your answer, where applicable, using relevant information from the scenario.
Evaluating Hot Work Permit Procedures: A Critical Analysis
Hot work operations, encompassing activities such as welding, cutting, and grinding, are integral to industrial processes but inherently carry significant risks, including fires, explosions, and severe injuries. The implementation of a robust Hot Work Permit (HWP) system is essential to mitigate these hazards. This analysis critically examines the operator's actions in managing the hot work permit process within the provided scenario, highlighting commendable practices and identifying areas for improvement.
1. Commendable Practices in Hot Work Permit Management
a. Comprehensive Hazard Assessment
The operator's collaboration with the specialist contractor supervisor to identify the specifics of the hot work—namely, grinding and oxyacetylene welding—demonstrates a proactive approach to hazard identification. This aligns with the National Fire Protection Association's (NFPA) guidelines, which emphasize the necessity of hazard assessment prior to initiating hot work
. Such thorough evaluations are crucial in preventing incidents, as statistics indicate that fire departments in the United States respond to an estimated average of 3,396 structure fires involving hot work each year
.
b. Implementation of Safety Measures
The operator's insistence on the availability of multiple dry powder fire extinguishers and the utilization of a portable gas detector near the hot work area reflects adherence to best practices in fire preparedness. Ensuring immediate access to firefighting equipment is vital, considering that hot work is a leading cause of industrial fires. For instance, the NFPA reports that between 2017 and 2021, an average of 3,396 structure fires involving hot work occurred annually in the U.S., underscoring the importance of such precautions
.
c. Coordination of Concurrent Activities
The operator's awareness of the scheduled structural inspection involving a Mobile Elevated Work Platform (MEWP) and the subsequent decision to monitor access to alternative staircases exhibit effective coordination. Managing simultaneous operations is critical to maintaining site safety and preventing accidents arising from overlapping tasks. This approach aligns with the Center for Chemical Process Safety's (CCPS) recommendations on operational risk management, which stress the importance of coordinating concurrent activities to prevent accidents
.
2. Areas for Improvement in Hot Work Permit Management
a. Verification of Equipment Integrity
The incident involving the acetylene gas bottle hose catching fire due to cracks indicates a lapse in equipment inspection. The operator should have mandated a thorough examination of all equipment, including hoses, to ensure they met safety standards before commencing work. Equipment failure is a known contributor to hot work incidents, as evidenced by a case where a welder died due to an explosion caused by equipment malfunction
.
b. Monitoring Post-Work Conditions
The reignition of flames after initial extinguishment suggests inadequate post-work monitoring. The operator should have ensured continuous supervision of the site after the completion of hot work to detect and address any residual hazards promptly. The NFPA emphasizes the importance of post-work fire watch to prevent re-ignition, a common issue in hot work-related fires
.
c. Comprehensive Training and Competency Assessment
The operator's reliance on the contractor's assurance regarding the experience of the welder, without verifying certifications or conducting competency assessments, represents a gap in due diligence. Ensuring that all personnel involved in hot work are adequately trained and competent is essential to maintaining safety standards. A study on human error analysis in permit-to-work systems highlights the significance of proper training in preventing accidents
.
d. Documentation and Record-Keeping
The scenario lacks mention of detailed documentation of the hot work permit process. Maintaining comprehensive records is vital for accountability and for facilitating audits and investigations in case of incidents. The absence of proper documentation can lead to misunderstandings and oversight of critical safety measures
.
e. Communication with Emergency Services
The decision not to contact external emergency services during the fire incident could be critiqued. While the in-house emergency rescue team managed to control the situation, informing external emergency services could provide additional support and resources, ensuring comprehensive incident management. The Chemical Safety Board (CSB) recommends prompt communication with emergency responders during such incidents to enhance response effectiveness
.
Conclusion
The operator demonstrated commendable practices in hazard assessment, implementation of safety measures, and coordination of concurrent activities during the hot work permit process. However, areas for improvement include verification of equipment integrity, post-work monitoring, comprehensive training assessments, meticulous documentation, and communication with emergency services. Addressing these aspects is crucial to enhancing the effectiveness of hot work permit systems and ensuring the safety of industrial operations.
Implementing these improvements aligns with industry best practices and regulatory guidelines, thereby reducing the likelihood of incidents and promoting a safer working environment.
Risk Mitigation Strategies for Mobile Elevated Work Platform (MEWP) Usage in Industrial Settings: A Comprehensive Analysis
Introduction
Mobile Elevated Work Platforms (MEWPs) are widely used in industrial settings for tasks that require working at height. While they offer significant advantages in terms of accessibility and efficiency, MEWPs also pose various risks that need to be meticulously managed to ensure worker safety. This critical analysis examines the factors that should be considered to minimize risks during the use of MEWPs for structural inspection tasks, referencing the scenario provided. The discussion incorporates statistical evidence, theoretical frameworks, and best practices from relevant literature to support the arguments.
1. Risk Identification and Assessment
a. Stability and Load Management
One of the primary concerns in MEWP operations is maintaining stability, especially when the platform is extended to significant heights. The stability of a MEWP is influenced by several factors, including the weight distribution, ground conditions, and weather. According to the Health and Safety Executive (HSE), over 50% of fatal MEWP incidents involve overturning (hse.gov.uk). To mitigate these risks, operators must conduct thorough site assessments to ensure the ground can support the MEWP's weight, especially on uneven or soft surfaces.
b. Operator Competence and Training
Competence of the operator is critical in MEWP safety. Studies show that human error contributes to a significant proportion of MEWP-related accidents (osha.gov). Proper training and certification are essential to equip operators with the necessary skills to handle the equipment safely. Training should cover equipment operation, hazard recognition, and emergency procedures. The International Powered Access Federation (IPAF) emphasizes the importance of regular refresher courses to maintain competence (ipaf.org).
2. Environmental Factors
a. Weather Conditions
Weather plays a pivotal role in the safe operation of MEWPs. High winds, rain, and lightning can severely compromise safety. The British Standard BS 8460:2005 recommends ceasing operations when wind speeds exceed 28 mph (bsigroup.com). Statistics from the European Agency for Safety and Health at Work indicate that a significant number of accidents involving MEWPs occur due to adverse weather conditions (osha.europa.eu). Therefore, continuous monitoring of weather conditions and implementing strict operational limits is crucial.
b. Proximity to Overhead Hazards
Proximity to overhead power lines or other structures is another critical factor. The Occupational Safety and Health Administration (OSHA) outlines minimum clearance distances that must be maintained when working near power lines (osha.gov). Failure to maintain these clearances can result in electrocution or other severe injuries. The scenario provided mentions structural inspection, which necessitates a comprehensive pre-task analysis to identify and mitigate such hazards.
3. Safety Measures and Equipment
a. Fall Protection Systems
Fall protection is non-negotiable when using MEWPs. According to the American National Standards Institute (ANSI), the use of personal fall arrest systems (PFAS) is mandatory in MEWPs (ansi.org). Statistics from the National Institute for Occupational Safety and Health (NIOSH) show that falls account for over 30% of all MEWP-related fatalities (cdc.gov). Harnesses, lanyards, and anchor points must be inspected regularly and used correctly to ensure their effectiveness.
b. Emergency Rescue Plans
An effective emergency rescue plan is essential for MEWP operations. The plan should include procedures for rapid descent and ground rescue in case of equipment failure or medical emergencies. The HSE emphasizes that such plans should be practiced regularly to ensure readiness (hse.gov.uk). Case studies highlight incidents where lack of a well-practiced rescue plan led to fatalities (gov.uk).
4. Coordination and Communication
a. Site Coordination
Coordination with other activities on site is crucial to avoid conflicts and potential accidents. The scenario describes concurrent operations, which require clear demarcation of the work zones and effective communication between teams. The Construction Industry Research and Information Association (CIRIA) provides guidelines on managing simultaneous operations (ciria.org).
b. Communication Systems
Effective communication systems, including radios or signal systems, are necessary to ensure constant contact between the MEWP operator and ground personnel. This is particularly important in large or complex sites where visual contact might be limited. The American Society of Safety Professionals (ASSP) highlights the role of communication in enhancing MEWP safety (assp.org).
5. Technological Innovations
a. Load Sensors and Stability Indicators
Technological advancements such as load sensors and stability indicators enhance the safety of MEWP operations. These systems provide real-time data on the load and stability, alerting operators to potential hazards before they become critical. A study by the National Institute for Safety and Health (NIOSH) on the impact of technology in workplace safety found that such innovations significantly reduce the risk of accidents (cdc.gov).
b. Automation and Remote Operation
Emerging technologies in automation and remote operation are transforming MEWP safety. Automated MEWPs can perform tasks with minimal human intervention, reducing the risk to workers. Remote operation allows operators to control the MEWP from a safe distance, which is particularly useful in hazardous environments. Research from the National Robotics Initiative (NRI) supports the use of automation in improving safety outcomes in high-risk industries (nsf.gov).
Conclusion
Minimizing risks associated with the use of MEWPs in industrial settings involves a multifaceted approach that includes thorough risk assessments, stringent safety measures, operator training, environmental considerations, and the integration of technological innovations. The critical analysis of the provided scenario underscores the importance of each of these factors in ensuring safe and efficient MEWP operations. By adhering to best practices and regulatory standards, industries can significantly reduce the incidence of accidents and enhance overall workplace safety.
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