Measures of vibration exposure for a high-speed craft crew

Abstract

The paper compares measurement-based measures for human vibration exposure. Data were collected during sea trials on a 10 m, 50 kn coastguard craft equipped with a three-axial accelerometer at the coxswain seat and with vertically mounted gauges measuring the acceleration of the cockpit floor. The ISO 2631-1:1997 measures of vibration (namely the root-mean-square (r.m.s.) value of the whole-body vibration (determined from the frequency-weighted acceleration signal), the maximum transient vibration value (MTVV), and the vibration dose value), the ISO 2631-5:2004 measure (namely the daily equivalent static compression dose Sed), and also statistically based measures to evaluate the acceleration magnitude are compared and discussed with respect to their ability to identify the mitigating effect of the suspension seat and how the different measures rank the severity of the high-speed craft (HSC) ride. The paper concludes that the r.m.s. value and the MTVV are unsuitable for evaluation of the conditions aboard while the other investigated measures show potential in this respect. Further the approach of ISO 2631-5:2004 taking both the short-term and the long-term perspectives on the human exposure to vibration is concluded to be the most mature method well suited to evaluation of HSC conditions.

Prediction and evaluation of working conditions on high-speed craft using suspension seat modelling

“…1 The experiment data consist of 12 sets of vertical accelerations of the seat base, € z b, exp , and the human-seat interface, € z 1, exp . Using the seat base acceleration € z b, exp as model input, the seat acceleration € z 1 is determined and then compared to the corresponding measured signal € z 1, exp .…”

“…Back pains, headache and tiredness in connection to duty are common health problems among HSC operators. 1 Other reported problems are acute injuries to the back, knees, neck and shoulders. 2 The motions of HSC can also reduce the crew’s physical ability and cause muscle damage and fatigue, 3 which adversely affect the crew’s decision-making capacity and ability to perform their task.…”

“…Vibration mitigation techniques such as suspension seats, which are widely used on board HSC, can be an effective means of reducing the levels of vibration and shock transmitted to the human body. 1,3,4 Although the configuration varies, such seats typically consist of a suspension mechanism including springs and dampers, whose characteristics are critical for the mitigation and need to be designed carefully along with other factors such as the seat’s motion stroke, position in the craft and the craft’s operational profile.…”

Rough water performance of lightweight high-speed craft

“…6 According to a survey conducted by the US Naval Health Research Centre, 95% of the reported injuries that required hospitalization were attributed to the motions of the craft. 7 Furthermore, Garme et al 6 and Allen et al 8 show that daily exposure limits, set by the European Union directive 9 of whole body vibrations (WBVs), may be exceeded in a matter of minutes on a high-speed craft in rough conditions. This article investigates the consequences of the selection of material concept on the rough water performance and the effect of different ballast configurations for a high-speed patrol vessel.…”

Development and validation of a web-based questionnaire for surveying the health and working conditions of high-performance marine craft populations

“…Studies by KTH Royal Institute of Technology and Umeå University in collaboration with the Swedish Coast Guard show that the statutory vibration exposure action and limit values 11–13 are exceeded after a short time of exposure. 14 This indicates that severe conditions are common and the fact that the exemption of statutory laws for seaborne and airborne occupations seems contradictory. 11 Consequentially, the measures to assess the working conditions aboard marine vehicles related to risk for health impairments and performance deteriorations are in debate, 14–20 together with the question on how to interpret the measures.…”