Source: https://www.youtube.com/watch?v=GcjDquUg8zs
Explosions are dramatic events often resulting in significant impact and intrigue. Characterized by their sudden release of energy, resulting in a rapid increase in volume and release of gases, explosions can range from simple combustion to complex chemical reactions. Their investigation requires a deep understanding of physics, chemistry, and environmental factors.
In this article, we will discuss two fascinating case studies. The first examines an unusual travel trailer explosion, while the second investigates a fire in a cannabis facility’s desiccant dehydrator. Both cases showcase the complexities and challenges faced in explosion investigations, emphasizing the critical role of detailed analysis and expert insight in solving these perplexing incidents.
Case Study 1: Travel Trailer Explosion
Travel trailers are typically somewhat leaky and don’t usually hold propane in, which would increase the likelihood of reaching an explosive limit. Despite this, the explosion that occurred was quite substantial.
It was minus 30 degrees out when this incident happened; understandably, it was cold.
Remarkably, the person involved in the explosion managed to survive with relatively minor injuries. The event was identified as a 2001 travel trailer explosion.
The incident initially pointed towards a propane supply issue. The trailer was linked to multiple propane sources, including an adjoining barn with heaters involving several cylinders. Investigations revealed that the propane stove and heater in the trailer were in use. The individual struggled to start the heater, and the explosion occurred while attempting to light the stove.
The investigation was delayed as the fire and explosion investigator arrived eight days later. The remote location in Northern Alberta and the absence of scene security complicated the preservation of evidence.
The examination of the scene revealed a setup involving multiple propane cylinders. A notable aspect was the use of hay bales placed around the trailer for extra insulation, intended for winter use, possibly as a bunkhouse. The propane equipment in the trailer included a refrigerator, a range, a furnace, and a water heater, all connected to a power supply through the trailer’s electrical cord.
Outside the trailer, additional equipment included two barn heaters installed inside an adjacent barn, which housed hay and other items. The explosion resulted in a debris field extending approximately 180 meters at its furthest point.
The incident began with the insured individual having trouble igniting the furnace. They tried lighting the range for heat to compensate, which led to the explosion. Although injured, the insured survived. Preliminary findings by a propane supplier investigator pointed to a furnace explosion, a conclusion supported by the fire department investigator.
Propane Supply:
The propane supply at the scene consisted of a trailer cylinder and a 100-pound cylinder feeding the barn heaters. This is the state in which the propane cylinders were found. The setup included a 40 PB cylinder directly connected to the trailer near the furnace and range and 100 PB cylinders attached to the barn heaters. The propane for the barn heaters utilized a CER CSA-certified propane hose, typically used for portable or mobile appliances but not approved for this specific use.
Though this setup did not contribute to the explosion, it’s crucial to understand that not all hoses are suitable for every connection. Propane for the travel trailer was connected using a CSA-certified propane hose with a QCC1 connector, a quick connect type often found on barbecue cylinders and utilized for various applications, including travel trailers and portable appliances.
The system also included a regulator, ensuring controlled pressure from the cylinders. Additionally, various hoses with sheared brass connections were found at the scene, indicating the diverse types of connections in the setup. This arrangement of propane cylinders and connections provides insight into the infrastructure during the incident.
A regulator was noted on the right in examining the propane system, a vital setup component. This regulator and two hoses feeding into the system significantly affected the overall arrangement.
The investigation also focused on determining the extent of the debris field. Debris from the explosion was found approximately 108 meters from where the trailer initially stood. This measurement of the debris field provides a stark illustration of the explosion’s impact and spread.
These trailers are not made robustly, so a blast from this trailer could scatter debris far. Considering this, significant debris was found about 188 meters from where the explosion occurred, like a window frame or similar substantial parts, not just insulation. This indicates that parts of the trailer’s framing were blown out.
Near the explosion site, the hay barn collapsed due to the blast. In the area where the furnace, refrigerator, and range were located, these items mainly stayed the same from their original positions within the trailer. However, the water heater was a different story. After about half an hour of searching, it still couldn’t be found, highlighting the force with which the explosion dispersed the trailer’s components.
The insured was in the hospital, but their partner confirmed that the water heater had been removed, explaining its absence from the debris field. A copper line with no shear marks was identified as an open line, indicating it had been disconnected rather than sheared off. This aligned with the information that the water heater had been removed.
Water Heater Connection:
The partner from the hospital mentioned that the water heater was removed a few months before being replaced. They did not cap the line but turned off the electrical switch to the water heater, mistakenly believing this would also shut off the propane supply.
This misconception is common among laypeople, who may assume that cutting off an electrical switch also stops the propane supply. Additionally, the propane supply to the trailer had been modified from its original setup to accommodate the hay bales, involving some makeshift adjustments.
The Explosion:
While these modifications didn’t significantly exacerbate the situation, they did contribute to the case’s complexity. Removing the water heater and leaving an open line posed a potential problem. The supply line for the water was still connected to the primary regulator of the trailer, and when the propane supply was turned on, this open propane line remained active.
The open line from the removed water heater prevented other appliances from remaining lit, as the propane pressure could not be maintained. The propane, taking the path of least resistance, primarily escaped through the open line. This caused the propane to accumulate inside the trailer, reaching a lower explosive level of 2.5% propane to air. The concentration found an ignition source in the range spark igniter when the range was lit due to the cold inside the trailer. This was the cause of the explosion.
Lesson Learned:
Key lessons learned from this incident include having a certified explosion investigator attend the scene immediately. This is crucial for maintaining scene security and gathering accurate information. If an immediate investigation isn’t possible, the scene should be secured until all interested parties can attend and conduct a joint examination. Interviewing the insured and all witnesses before concluding the cause is essential, along with documenting all appliances and supply containers to assess their original locations and involvement in the incident.
Upon initial assessment of the situation, it was clear there was an explosion, and information indicated that the furnace and range were not operating correctly. Focusing on these areas seemed ideal, as less information before arriving at the scene often leads to a more unbiased investigation. The fact that the water heater had been removed wasn’t initially considered, but this detail came to light after it couldn’t be found and further inquiry with the insured.
The scene presented the explosion originating from the right side of the trailer, where the water heater was located, not near the back corner where the barn and propane supply were. In the initial assessment, there was noticeable damage on this particular side. Once it was discovered that the water heater was removed, leaving an open line, it explained the extensive damage on that side.
Another important lesson from this investigation is to avoid tunnel vision and preconceived notions about the cause. What might seem like the probable cause can be different upon thoroughly examining the scene. This case highlights the need for open-mindedness and thoroughness in investigations.
Case Study 2: Desiccant Dehydrator Fire
The second case study involves a desiccant dehydrator fire. This particular dehydrator was installed in a cannabis drying facility. Its primary function is to keep the air as dry as possible to facilitate cannabis drying. For simplicity, the terms ‘weed’ and ‘cannabis’ will be used interchangeably.
The device is a desiccant wheel installed inside a modified makeup air unit. These units have recently gained popularity; this was only the second instance of encountering such a device. The desiccant wheel’s primary purpose is to extract moisture from the air, and it rotates slowly to achieve this.
The desiccant dehydrator operates slowly, and its airflow mechanism will be shown shortly. The unit closely resembles a typical makeup air unit often found on the roofs or exteriors of buildings. These units are primarily used for heating and replacing air within a building. The provided picture showcases the similarities of this dehydrator to standard makeup air units commonly seen in such applications.
Background
The desiccant dehydrator had inlet and outlet air supplies that passed through the unit, situated just outside the building on one side. This equipment, a specialized piece for the wholesale cannabis production industry, was a natural gas direct-fire make-up air dehydrator with a maximum BTU rating of 745,000. The central damage was to the appliance, and some product was lost.
The investigation was conducted by the service company working on the equipment at the time of the incident and was also the installer two years prior. The equipment’s primary function was humidity removal from the process rooms. Unlike the previous case, the scene was secured and could only be accessed with a key card through a fence gate.
The scene was initially examined by investigators representing the equipment owner before other investigators got involved. Five investigators were assigned from various parties, including the installation company, the service company, the cannabis company, the manufacturer, and a shared liability insurer. Engineered Air specially built the gas dehydrator equipment and could be modified per the client’s requirements, such as adding extra switches or equipment.
The main dehydration wheel inside the equipment had direct contact fire damage, with no external heat source involved. Other components within the equipment, including electrical and gas components, sustained smoke and heat damage but were largely intact, with only minor damage to some electrical switches. The entire equipment was boxed with wood walls and a plastic tarp ceiling to preserve it.
The Scene as Found at the Time of Investigation:
During the investigation, a structure built around the equipment protected it from snow and ice, facilitating examination. The equipment’s process involved air passing through the desiccant wheel and filters, which are not typically used in winter due to freezing risks. These filters were in place during an examination, possibly contributing to the equipment’s issues. This setup allowed for a detailed analysis of the equipment and its operating conditions.
Natural Gas Supply:
The central appliance regulator used on the equipment had an inlet supply pressure of five pounds, with the regulator designed to supply 7 inches of water column, approximately 4 ounces. This pressure level is standard, though some equipment requires higher pressure. A different service company replaced the regulator before the current one started working on the unit. The natural gas supply was adjusted by cannabis company personnel when the unit malfunctioned, but this adjustment was not done correctly.
Service History:
The unit was installed around July 2019 by the company represented in this case. The installation company stopped servicing the unit in 2020 due to outstanding payments. Consequently, another service company took over but ceased their service for the same reason. During a period, cannabis company personnel serviced the equipment to keep it operational. The equipment often needed resetting when it failed to fire, which is not ideal. Resetting without proper training or understanding the root cause can lead to recurring problems. Employees frequently resetting the unit indicates a lack of adequate training and understanding of the equipment.
The cannabis company’s employees who serviced the equipment lacked certification or sufficient knowledge for proper assessment and repair. Despite denial by the cannabis company, it was evident they serviced the equipment. This was confirmed when the representing company’s personnel asked on-site employees about their actions and were told they were servicing the equipment.
During multiple service calls, the installing company noted incorrect pressures supplied to the equipment. Each time they visited, the pressures had been adjusted, which only happens with manual intervention or a regulator problem. The regulator had been replaced, suggesting manual adjustments by someone not knowledgeable.
Although not the primary concern, these pressure adjustments were significant. The hypothesis formed about the cause differed from other investigators. On the day of the incident, the installation company’s technician received directions from the manufacturer to fire the unit. This involved bypassing the high-fire switch to start the unit, contrary to the usual procedure of starting on low fire and then cycling up.
For some reason, the technicians were instructed to bypass the high-fire switch. Typically, this switch delays the unit’s transition to high fire for safety reasons. Bypassing enables a quicker analysis of the problem, a typical old service technique used to diagnose issues by removing all switches to get the unit to fire. However, this approach is not generally recommended.
The bypassing of the switch allowed the unit to start up faster, but almost immediately after firing, a fire occurred. Smoke and desiccant material were seen coming out of the vent, leading to an immediate shutdown of the unit. This incident highlights the risks of modifying standard operating procedures, especially when dealing with complex machinery.
Conditions of the Unit Before Servicing by the Insured:
The unit experienced increased pressures on both the inlet and manifold sides. Non-certified personnel had worked on it before the insured’s servicing. This was confirmed by directly asking the personnel about their actions to get the unit running, indicating it was not operated per manufacturer-certified instructions.
One of the personnel mentioned having to kick the damper motor to start the damper, and the filters were still in during minus 30° weather, which is not recommended for these units. X-rays of downstream components in the burner manifold, later performed, revealed the damage caused by the repairs initiated by the cannabis company’s personnel. However, the extent of this damage was unclear and required further testing.
Removal and Testing of Components:
The desiccant wheel and the supply regulator were removed and x-rayed. However, the results were inconclusive and pointed towards the need for additional testing to understand the failure mechanism fully. Although further testing would have been beneficial, the focus remained on the actions of the insured service personnel and the directions provided by the manufacturer.
The cannabis company’s investigators concluded that the actions of the insured personnel caused the incident, but this conclusion was reached without extensive testing. It’s essential to exhaust all options before drawing definitive conclusions. Despite disagreement, no further testing was conducted, and the cannabis company investigators remained firm in their determination.
The findings indicated that additional testing and disassembly were needed to determine the failure mechanism of the remaining equipment. Requests for interviews with cannabis company personnel were denied, and the company insisted that any further testing should be performed by the service company under their observation, essentially reversing the onus of proof.
Lesson Learned:
Key lessons include having a knowledgeable person involved in the investigation, gathering technical information about the equipment, involving the manufacturer early, and interviewing all service personnel for comprehensive statements. Obtaining the service history from previous service companies or owner-service personnel is also crucial.
Wrap-Up:
Exhausting all testing and examination procedures before determining the failure mechanism and cause of the fire is essential, and this is where Origin and Cause come in. If the failure mechanism cannot be conclusively resolved, the cause should be labelled as undetermined. Recommendations for additional testing or examination should always be made, even if not always followed, to ensure that every possible cause has been thoroughly investigated.