Explosions in Electrical Control Boxes as a Potential “Nested Bang-Box” Mechanism for Severe Vapour Cloud Explosions

The ignition source for Buncefield, the United Kingdom’s most severe recent vapour cloud explosion (VCE) was potentially electrical control boxes situated inside a pump house immersed in the vapour cloud. There are other reports of confined or bang box ignition sources for other VCEs, such as Port Hudson and Jaipur where it is proposed these ignition sources were responsible for transition to detonation (DDT). There has, however, been relatively little previous research into this type of ignition mechanism and its effect on the explosion severity. Commercially available electrical control boxes measuring 600 mm high, 400 mm wide and 250 mm deep were used to explore the pressure development, venting processes and flame characteristics of stoichiometric propane/air explosions using cling film, aluminium foil and the supplied doors as vent coverings. In this work the boxes were empty of their usual contents in order to establish a baseline for the effect of the internal congestion of the boxes. It was found that, in these empty-box tests the overpressure was dominated by the bursting pressure of the ventcovering and the external explosion, although clearly presenting significant ignition source to a potential surrounding flammable cloud, it produced no significant overpressure. The door produced a flat petal shaped flame that differed drastically from the rolling vortex bubble flame shape traditionally associated with vented explosions

Experimental investigation of potential confined ignition sources for vapour cloud explosions

Electrical control boxes are prolific on high vapour cloud hazard sites, and in the case of the Buncefield explosion the ignition source was inside such a box that was sited in an emergency pump house building. There has, however, been relatively little previous research into this type of ignition mechanism and its effect on the explosion severity. Commercially available electrical control boxes measuring 600 mm high, 400 mm wide and 250 mm deep were used to explore the pressure development, venting processes and flame characteristics of stoichiometric propane/air explosions using aluminium foil and the supplied doors as vent coverings. In this work, the boxes were empty of their usual contents in order to establish a baseline for the effect of the internal congestion of the boxes. It was found that, in these empty-box tests, the door produced a flat petal shaped flame, which differed drastically from the mushroom flame shape, associated rolling vortex bubble venting traditionally observed with large orifice vented explosions

Management of orthodontic emergencies in primary care – self-reported confidence of general dental practitioners

Objective: To determine general dental practitioners’ (GDPs) confidence in managing orthodontic emergencies. Design: Cross-sectional study. Setting: Primary dental care. Subjects and methods: An online survey was distributed to dentists practicing in Wales. The survey collected basic demographic information and included descriptions of ten common orthodontic emergency scenarios. Main outcome measure Respondents’ self-reported confidence in managing the orthodontic emergency scenarios on a 5‑point Likert scale. Differences between the Likert responses and the demographic variables were investigated using chi-squared tests. Results: The median number of orthodontic emergencies encountered by respondents over the previous six months was 1. Overall, the self-reported confidence of respondents was high with 7 of the 10 scenarios presented scoring a median of 4 indicating that GDPs were ‘confident’ in their management. Statistical analysis revealed that GDPs who saw more orthodontic emergencies in the previous six months were more confident when managing the presented scenarios. Other variables such as age, gender, geographic location of practice and number of years practising dentistry were not associated with self reported confidence. Conclusions: Despite GDPs encountering very few orthodontic emergencies in primary care, they appear to be confident in dealing with commonly arising orthodontic emergency situations

General dental practices with and without a dental therapist: a survey of appointment activities and patient satisfaction with their care.

Introduction Policy changes regarding the role of Dental Hygienist-Therapists (DTs) have been implemented in recent years with a view to promoting delivery of oral health-care through a more preventive-focused, team work approach. Aims To explore i) treatments led by dentists and DTs, and ii) patients' satisfaction with the care they received. Materials and methods Six case-studies of general dental practices in Wales, UK: three with, and three without a DT. For each participant, a patient-satisfaction questionnaire and a staff-member-completed appointment record form were completed. We sought to recruit 150 patients seeing a dentist and 100 patients seeing a DT, per case-study practice. Results 1,224 patients were recruited in total (314 DT and 910 dentist appointments). Preventive work accounted for nearly half of all treatments. Dentists, in practices with a DT, undertook significantly less preventive and restorative work, and significantly more extractions and advanced treatment (p <0.005, χ² = 15.352). Patient satisfaction and confidence in dentists' or DTs' ability was uniformly high (97% and 99% each group respectively). Conclusion Practices with DTs provided a more preventive-focused approach to oral health-care delivery; dentists in these practices performed more complex work. Positive patient satisfaction and confidence in practitioners' ability suggest patient acceptability of a preventive model