Respiratory Flow Rates of Metal Welders Compared to a Population Not Exposed to Metal Welding Dust

Background: The welding trade includes many industrial activities in both the formal and informal sectors. Workers in this professional environment do not have access to individual and collective means of protection adapted to the activity, which exposes them to the dust emitted during their activity and therefore contributes to increasing the risk of developing respiratory disorders in this population. Objective: Our study aimed to evaluate the ventilatory function of metal welders in the city of Dakar. Method: This was a comparative study based on the analysis of the spirometric parameters of metal welders working in the city of Dakar (Senegal) with those of a control group of the same kind, selected from the general population. Measurements of forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF) and maximum mid expiratory flow (MMEF) were measured. Results: A total of 75 men between the ages of 19 and 61 were recruited and divided into two groups (43 controls and 32 welders). The welding population had more frequent distal and central obstructions and pulmonary restriction compared to the control group. The metals most commonly used by welders were aluminum for welders who had an obstruction, while for those who had a restriction, iron was the most used metal. Signs of metal fever were frequently found in welders, especially those with ventilatory disorders. Conclusion: The prevalence of respiratory disorders observed is close to that observed in industrial environments, where exposure levels are the highest. The lack of personal protective equipment could also be a significant risk factor in the development of these disorders.

Occupational Hearing Hazards among Informal Sector Welders in Lubumbashi, Democratic Republic of Congo

Introduction: Noise, an undesirable sound which is found in all areas of occupational activity, is still a matter of concern given the damage it causes. Various machines and tools, from simple to sophisticated ones, produce several types of noise in the workplace. The purpose of this study was to assess the current status of occupational hearing loss among informal sector welders in the city of Lubumbashi, in the Democratic Republic of Congo. Methods: This was a descriptive cross-sectional study which was conducted among 122 informal sector welders over a period of five months. The study used an anonymous questionnaire on noise exposure in the workplace and collected audio-metric data of welders. The survey collected data on welders who had a minimal three-year duration of employment without the morbidity associated with the Ear Nose Throat (ENT) region. Socio-professional data (age, duration of employment, sex, education), noise exposure, awareness of hazards and audiometric data were taken into account. Results: 122 questionnaires were completed by male subjects, or 100% (n = 122). The mean age of welders was 36.37 ± 11.91 years with extremes being 20 and 63 years. The mean duration of employment was 11.51 ± 9.6 years with extremes being 3 and 44 years. Audiometric data have shown 37.96% (n = 41) of occupational hearing loss. Three degrees of hearing loss were recorded, notably mild hearing loss standing at 80.49% (n = 33);moderate and severe hearing loss standing at 2.44% (n = 1). Ninety-six percent (n = 117) of welders reported not using personal protective equipment (PPE) and 1% (n = 111) were aware of the hazard associated with noise exposure in the workplace. A correlation was found between welders with an advanced age (p < 0.001;RP = 3.66 (2.16 - 6.22)) and hearing loss, and between the duration of employment and hearing loss (p < 0.001;RP = 6.48 (3.32 - 12.65)). Conclusion: In the study area, occupational hearing loss among welders is a relevant fact. Three degrees of hearing loss were identified. Most of those suffering from it have developed a mild type of hearing loss whose continued development can be stopped. Despite the fact that welders are aware of the hazards associated with noise exposure in the workplace, they hardly protect themselves. Lack of a culture of prevention and poor enforcement of the existing laws could account for such a situation. There seems to be a crucial need to put in place a program for protecting the welders’ auditory organs in the workplace.

Early diagnosis of health damage in arc welders based on their serum ferritin level

To develop a method for the early diagnosis of health damage due to arc welding, we measured serum ferritin in 96 general employees and 320 arc welders in Company A. A positive correlation was observed between age and the serum ferritin level in the young group (age, 20 - 44 years) among the general employees. The mean serum ferritin level in the general employees was 119 ± 56 ng/ml. When the mean ± 2.5 SD was used as the standard value, ferritin levels > 260 ng / ml could be regarded as high. Based on this standard value, high ferritin levels were observed in 7 (6.6%) of 106 young arc welders in Company A but none of the general employees. Chest X-ray films showed minimal abnormality in one of 7 young arc welders who showed high ferritin levels. These results suggest that the determination of the serum ferritin level is useful for the early diagnosis of health damage due to arc welding.

State of Eye Protection for Metal Welders in the Workshops of Conakry

Introduction: Welders are an occupational group at high risk for eye injuries. The aim of this study was to investigate the state of eye protection of metal welders in the workshops of Conakry. Material and Methods: The study was cross-sectional, descriptive, and included 180 welders from 45 welding workshops in the city of Conakry for a period of three months. It involved all welding professionals working in an informal unit selected by the study and who had agreed to participate in the study. Results: The average age of the participants was 33.9 ± 13.4 years, with extremes of 15 and 68 years. The study found that 99% of the welders owned glasses, 27% owned face shields, and 49% owned welding masks. Goggles were used regularly by 86% of the welders but were not suitable for welding (98%). All welders had reported having had an eye injury at least once. Foreign bodies were cited in 81%, arc strike in 65%;eye burns in 61%. However, approximately 81% of welders did not have first aid kits at their work sites. Conclusion: The use of protective equipment during welding remains very low in the workshops of Conakry, which is the cause of great ocular morbidity among welders.

聚丙烯中空纤维人工肺纠治呼吸衰竭的实验研究

聚丙烯中空纤维人工肺纠治呼吸衰竭的实验研究天津市肺科医院人工肺研究室丁伟，张向，马景良，叶宏琛聚丙烯中空纤维是七十年代发展起来的一种新型材料。由于其疏水性和良好的血液相容性被广泛应用于人工肺制作。八十年代末，美国将聚丙烯中空纤维置入腔静脉进行血气交换...

Digital Twin for Human-Robot Interactive Welding and Welder Behavior Analysis

This paper presents an innovative investigation on prototyping a digital twin(DT)as the platform for human-robot interactive welding and welder behavior analysis.This humanrobot interaction(HRI)working style helps to enhance human users'operational productivity and comfort;while data-driven welder behavior analysis benefits to further novice welder training.This HRI system includes three modules:1)a human user who demonstrates the welding operations offsite with her/his operations recorded by the motion-tracked handles;2)a robot that executes the demonstrated welding operations to complete the physical welding tasks onsite;3)a DT system that is developed based on virtual reality(VR)as a digital replica of the physical human-robot interactive welding environment.The DT system bridges a human user and robot through a bi-directional information flow:a)transmitting demonstrated welding operations in VR to the robot in the physical environment;b)displaying the physical welding scenes to human users in VR.Compared to existing DT systems reported in the literatures,the developed one provides better capability in engaging human users in interacting with welding scenes,through an augmented VR.To verify the effectiveness,six welders,skilled with certain manual welding training and unskilled without any training,tested the system by completing the same welding job;three skilled welders produce satisfied welded workpieces,while the other three unskilled do not.A data-driven approach as a combination of fast Fourier transform(FFT),principal component analysis(PCA),and support vector machine(SVM)is developed to analyze their behaviors.Given an operation sequence,i.e.,motion speed sequence of the welding torch,frequency features are firstly extracted by FFT and then reduced in dimension through PCA,which are finally routed into SVM for classification.The trained model demonstrates a 94.44%classification accuracy in the testing dataset.The successful pattern recognition in skilled welder operations should benefit to accelerate novice welder training.

Potential Oxidative Stress in the Bodies of Electric Arc Welding Operators: Effect of Photochemical Smog

Objective To investigate whether photochemical smog emitted during the process of electric arc welding might cause oxidative stress and potential oxidative damage in the bodies of welding operators. Methods Seventy electric arc welding operators (WOs) and 70 healthy volunteers (HVs) were enrolled in a randomized controlled study design, in which the levels of vitamin C (VC) and vitamin E (VE) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and the level of lipoperoxide (LPO) in erythrocytes were determined by spectrophotometry. Results Compared with the average values of the above experimental parameters in the HVs group, the average values of VC and VE in plasma as well as those of SOD, CAT and GPX in erythrocytes in the WOs group were significantly decreased (P<0.005-0.0001), while the average value of LPO in erythrocytes in the WOs group was significantly increased (P<0.0001). The findings from the partial correlation analysis on the controlling of age suggested that with a prolonged duration of exposure to photochemical smog the values of VC, VE, SOD, and GPX, except for CAT, in the WOs were decreased gradually (P<0.05-0.005), the value of LPO in the WOs was increased gradually (P<0.001), and that with the ozone dose increased in the air in each worksite VC, VE, SOD, CAT and GPX decreased (P<0.005-0.001), but LPO increased (P<0.001). The findings from the reliability analysis for the VC, VE, SOD, CAT, GPX, and LPO values which were used to reflect oxidative stress and potential oxidative damage in the WOs showed that the reliability coefficients?alpha (6 items) was 0.8021, P<0.0001, and that the standardized item alpha was 0.9577, P<0.0001. Conclusion Findings in the present study suggest that there exists an oxidative stress induced by long-term exposure to photochemical smog in the bodies of WOs, thereby causing potential oxidative and lipoperoxidative damages in their bodies.

Development of Full Automatic Flash Butt Welding with Digital Control

The hardware and software design of two digital control systems based on 80C196KB MCU for flash butt welder is introduced in this paper.The welding power supply is made of six-phase half-wave rectifier.The welding outer characteristic of welding machine is realized by digital PI algorithm with the voltage close-loop feedback.The flashing curve is finished by elec- tric-hydraulic servo valve.The process control system transfers datum with power supply system by a serial communication inter- face.The parameters of the control systems are collected by photoelectrical seclusion to avoid the disturbing of the electromagnetism in welding process.

A study on frequency domain mathematics model of arc welding reverse converter

Arc welding converter (AWC) power source is a nonlinear and discrete abnormal system. It is difficult to get the accurate analytic solution in theory. In this paper, an average state equation of the system is established by means of state space analysis method. The mathematics model of the reverse converter is gotten after the average equation of the system is linearized. The model is a two ranks oscillation link. With the parameters of the AWC, when the condition of (1/RC) 2 >>4/LC is available, the mathematics model may be simplified to a serial structure which includes a integral link and a one rank inertia link. On the basis of this, it can be analyzed and rectified in frequency domain, then some groups of reality rectification parameters are gotten around the theory rectification parameters. These groups of parameters are taken to do the resistance load experiment and welding technology experiment. The result of experiment accords with the theory analysis result. This paper also provides some practical analysis of the model under the large signal process such as the sudden opening of the load, short circuit, turning on and turning off the machine. The result of the research shows that the power source system of AWC can be analyzed and rectified by the frequency domain analysis method in the engineering. The deduced mathematics model of small signal average frequency domain shows the basic characteristics of the system, and the structure parameters of the system is formed by R, L, C and switching ratio D. The model is very simple and clear, and it can be used to analyze and design the power source system of AWC and it can also be used to direct the regulation for dynamic characteristics of the system.

A high precision electron beam welder power supply based on buck-boost converter using fuzzy PID control

A novel electron beam welder （ EBW） power supply was developed. Compared with the traditional 3-phase contrail 12-pulse rectifying supplies, it requires a much lower step-up ratio transformer, but a much less output ripple voltage can be obtained. The design of the main circuit of this new power supply is based on PWM buck-boost converter topology. In developing the system a fuzzy PID control method is adopted because of the strong non-linearity and big signal working conditions of the circuit system. The SABER-MATLAB models and fuzzy algorithm were used in developing the fuzzy PID controller. The co-simulation and experimental results displayed that the unit introduced herein has the characteristics of high control precision and antinterference capability.

能砂磨的粘接剂

美国马萨诸塞州Danvers的Devcon公司开发出能砂磨打光(SD)的粘接剂Plastitc Welder SD，能粘接聚苯醚、PVC、聚酯、聚碳酸酯、苯乙烯系列树脂和要求表面填料必须被磨去得到平滑、无孔的优良外观的复合材料。该粘接剂为低温升配方，

Situation on welder training in China

The state of welders training in China is introduced in this paper.There are different specifications because of variable examining organizations,as the deeping of reform and openning in China, welders are trained according to variable specification to fit specific requirement.

镀锌线电阻缝焊机研究及应用

简要介绍电阻缝焊机的焊接原理及在镀锌线上的应用和维护。

Structure Design and Finite Element Analysis of a Connection Assembly Program

The new connection assembly program contains four cone-shapes of fixed welders and four bolts.It is used for connecting the cover assembly of a Down-The-Hole( DTH) drill rig and its chassis.The design feasibility and reliability are evaluated according to the mechanical calculation and finite element method.