International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 7, Issue 3, May June 2016, pp. 77 86, Article ID: IJARET_07_03_007 Available online at http://www.iaeme.com/ijaret/issues.asp?jtype=ijaret&vtype=7&itype=3 ISSN Print: 0976-6480 and ISSN Online: 0976-6499 IAEME Publication BEHAVIOUR OF THE ROPES CONSTITUENTS UNDER THE ACTION OF RISK FACTORS THAT EXIST IN THE WORK ENVIRONMENT Nicoleta Crăciun Head of PPE Certification: Certification Body The National Research and Development Institute of Occupational Safety (INCDPM) "Alexandru Darabont", Bucharest, Romania ABSTRACT The ropes used as primary elements of the various components of individual systems for protection against falls from height, have an important role in maintaining the safety of workers. Even if they are used in systems limitation, positioning, rope access, fall arrest or rescue, maintaining the characteristics of their protection throughout the period of use is mandatory. Knowing that workplace hazards not only act on the worker but also on personal protective equipment, through this study I intended to find out the sliding behavior of the sheath from the core (the main charge carrier) under the action of the possibly risk factors that exist for the workstation. Key words: Working at Height, Danger, Ropes, Sliding Sheath Cite this article: Nicoleta Crăciun, Behaviour of the Ropes Constituents under the Action of Risk Factors that Exist in the Work Environment. International Journal of Advanced Research in Engineering and Technology, 7(3), 2016, pp 77 86. http://www.iaeme.com/ijaret/issues.asp?jtype=ijaret&vtype=7&itype=3 1. INTRODUCTION Present in the most workplaces, activities at height requires ensuring the adequate protection for workers. Depending on your workplace, the personal protective equipments against falls from height may be selected and mounted differently, so making various systems whose function is to limit the movement, for prevention of falls from height, for rope access, to stop the pit fall or as a rescue goal. Depending on the specific activities carried out at height, workers are not only in danger due to falling from height but also to the actions of other physical hazards, mechanical and chemical present in the environment. http://www.iaeme.com/ijaret/index.asp 77 editor@iaeme.com
Nicoleta Crăciun The presence of hazards in the work environment has a negative impact not only on the worker but also to personal protective equipment against falls from height (abbreviated as PPE for working at heights). Designed to link an anchor and the holding device of body, the ropes used in individual systems of protection against falls from height, must be made such that under the action of other hazards (physical, chemical, etc.) existing in the working environment, to maintain the protection features throughout the entire period of use. The harm action of dangerous factors to the string behavior it cannot be estimated by a single characteristic, for example following the appearance or change in mass, but it must be considered how they may influence the defining characteristic of that type of protection. If not considered the action of physical or chemical dangers [1] to the components of PPE made of rope it is possible that over time they lose the protection features and does not perform its function when the leading factor exercise its action, which can lead to accidents at work or serious occupational disease [2]. Because of the large number of accidents at work [3] registered each year as a result of breaking the ropes especially in the access activities through a rope, and the fact that at the national and international level there are not addressed such problems, the study conducted analyze the risk factors of chemical action of the movement towards the core mantle to support decision makers in selecting appropriate ropes used in personal protection systems against falls from height. 2. STUDY AND RESULTS Since in the last few decades in manufacturing technology ropes have not been fundamental changes in the market prevails one material used to make ropes - polyamide. Other materials such as polyester, aramid coated polyamide or polyester, steel may be used in special circumstances but only with special protection because of their lack of elasticity, premature failure or reduced capacity to absorb the energy produced when fall. In general, the manufacturers carry out two different types of ropes: with a low coefficient of elongation (hereinafter referred to as static) and dynamic. The static ropes do not stretch to absorb the impact energy. Used in most industrial sectors in rope access systems, as well as for positioning systems and limiting movement in the workplace, the static ropes (4) are used for rappel and lifting, but never to climb. Dynamic ropes stretch enough to absorb impacts in a fall, and are manufactured specifically for climbing. Structurally the ropes are made of two independent components: The SHEATH (the outer shell) is the component that serves both to keep strands core close in the established contexture and to protect against damage caused by the action of various factors. This protective sleeve is an elastic yarn braided grouped into strands The CORE - the main charge carrier - made of many parallel elements (strands). The strands are formed from yarn braided and twisted together in the same direction. http://www.iaeme.com/ijaret/index.asp 78 editor@iaeme.com
Behaviour of the Ropes Constituents under the Action of Risk Factors that Exist in the Work Environment Strands Yarn The Sheath The Core Figure 1 The components of the rope Different technologies to achieve the two components of the rope, lead those two elements to have various elongations. For this reason, when ropes are used with different specific devices friction forces arise which causes additional movement of the sheath from the core. As the lengthening string is higher, the possibility of slipping the sheath from the core increases. If, during work, there is a large shift of the sheath to the core may experience the following situations: There may be areas where the rope contains only sheath and user's weight is supported only by this element, which does not have sufficient mechanical strength to ensure the necessary protection (core is component-carrying) There may be portions of the sheath is crowded, which can have an adverse impact on the functioning of other devices, blocking them. As a result the previous studies have been established by standards (SR EN 1891: 2003 and SR EN 892: 2005) [4], [5] limits considered by specialists as admissible on the slip value for sheath against the core in a positive or negative test under standardized conditions. However, depending on the type of string, these values differ. Thus, the relative movement of the sheath from the core to: The static ropes type A with the diameter less than 12 mm should not exceed the value obtained by applying the formula: 20 mm + 10x (D-9) mm, where D is the diameter of the rope to try expressed in millimeters; The static ropes type B should not exceed 15 mm; The dynamic ropes must not exceed 20 mm. However, many producers claim in briefing documents that their products for sheath elongation have a value virtually zero. The length measurement for sheath displacement from the core is performed according to the test method given in section. 5.5 of SR EN 1891: 2003, respectively 5.4 of SR EN 892: 2005 and consists of: Exposing at least 24 hours in an atmosphere with a temperature of (50 ± 5) C and a relative humidity of less than 10%, followed by cooling them for 2 hours in an atmosphere having a temperature of (20 ± 2) C and a relative humidity of not more than 65% The exposure of at least 72 hours in an atmosphere having a temperature of (20 ± 2) C and a relative humidity of (65 ± 2) %. http://www.iaeme.com/ijaret/index.asp 79 editor@iaeme.com
Nicoleta Crăciun Figure 2 shows the equipment used and the principle of the test method. Figure 2 The Presentation of the Equipment used and Test Principle Most often, however, working conditions differ from those in the laboratory, not only in terms of temperature, but also the presence of certain factors such as water (rain, immersion), the presence of acidic and basic solutions, as well as repeated exposure to the caloric radiation. All these factors can strongly influence the sliding feature of the sheath. Knowing the influence of risk factors present in the work environment on different types of ropes can be an important factor in selecting the type of chord. To obtain more comprehensive information the choice of ropes needed to the study was based on the variety and the configuration of jobs and the wide range of diameters posed by the ropes. Thus the series of tests were performed on samples of rope made from polyamide, both dynamic (simple with 10.5 mm diameter and double with 9.5 mm diameter used primarily mountaineering) and static (type A and B, with diameters between 10 mm and 11 mm). Samples of ropes acquired to carry out series of tests are shown in Table 1. http://www.iaeme.com/ijaret/index.asp 80 editor@iaeme.com
Behaviour of the Ropes Constituents under the Action of Risk Factors that Exist in the Work Environment Table 1 Acquired string samples Rope number The Rope Type Diameter, mm Structure Encoding 1. 10.5 the sheath structure has colored yarn woven in 48 (12 threads orange and 36 black yarn) A Dynamic - Single Rope the core is made up of 13 strands twisted with the diameter 1.9 mm 2. 10.5 the braided sheath structure has 48 colored wires (4 wire red, green 4- wire, 4-wire blue 12 yellow and 24 black yarn threads) B Dynamic - Single Rope the core consists of 162 twisted strands with a diameter of 0.46 mm 3. 9.5 the sheath structure has colored yarn woven in 48 (30 red yarn, 4 wires green, 10 blue yarn, 4 yellow yarn) C Dynamics - Half Rope the core it consists of 10 twisted strands with a diameter of 1.96 mm 4. 10 the sheath structure has 32 colored wires twisted (2 red, 2 blue, 28 white) D Static Rope Type B the core is made up of 11 strands twisted diameter of 2.08 mm 5. 10.5 the sheath structure has 16 colored wires twisted (2 wires blue, one red wire, one wire yellow, gray 12 threads) E Static Rope Type A the core is made up of 40 strands twisted diameter of 0.63 mm 6. Static Rope Type A 10.5 the sheath structure has 64 wires twisted black the core is made up of 16 strands twisted with a diameter of 2.03 mm F http://www.iaeme.com/ijaret/index.asp 81 editor@iaeme.com
Nicoleta Crăciun 7. Static Rope Type A 10 the sheath structure has 40 colored wires twisted (4 wires black and blue wires 36) the core is made up of 16 twisted strands of 1.86 mm diameter G 8. 11 the sheath structure has twisted 48 colored wires (6 wires black and blue wires 42) the core is made up of 16 twisted strands of 1.68 mm diameter H Static Rope Type A 9. Static Rope Type A 10.5 the sheath structure has 54 colored wires interlaced (6 wires khaki and 48 black wire) the core is made up of 16 strands of 1.82 mm diameter twisted In order to have a clear picture of the behavior of the sheath slippage relative to the core to the different types of chord, attempts were made both in standard conditions and in conditions simulating actual use, when the ropes may come into contact with water with acidic or basic chemical substances or they can be exposed to sources of radiant heat. The results obtained after performing the series of tests the sliding core to the sheath, under standard conditions, are shown in Table 2 and plotted in Figure 3. Table 2 The sheath slippage relative to the core under conditions imposed by standards method I No. The code of the test sample Rope Type Diameter, mm The sheath slippage relative to the core, mm The sheath slippage, S s, % 1. A Dynamic Single Rope 10.5 3-2. B Dynamic Single Rope 10.5 25-3. C Dynamic Half Rope 9.5 0-4. D Static Rope Type B 10 0 0 5 G Static Rope Type A 10 1 0.052 6. E Static Rope Type A 10.5 0 0 7 F Static Rope Type A 10.5 0 0 8. I Static Rope Type A 10.5 1 0.052 9 H Static Rope Type A 11 0 0 http://www.iaeme.com/ijaret/index.asp 82 editor@iaeme.com
Behaviour of the Ropes Constituents under the Action of Risk Factors that Exist in the Work Environment The sheath slippage, Ss, % is calculated using the formula: Vx100 S s 1930 Where: - V is the sheath slippage relative to the core, in mm; - 1930 is length tested. (1) Figure 3 Sliding Core from Sheath under Standardized Conditions Analyzing the distribution of values for slipping of sheath to core obtained for different types of ropes it is noted that all the ropes are tested in relation to the movement of the sheath to the core, significantly lower than the maximum levels specified in the reference standards, with one exception (rope encoded B). Comparing the results we can say that the relative value of sliding for sheath is not influenced by the type of rope or diameter. Comparative analysis of the first two ropes dynamic (A and B), having the same diameter and which were made different amounts of displacement of the mantle, it can be said that discrepancies are due to both the structural characteristics of the sheath and the core. This conclusion was determined after analyzing the embodiment of the components of both types of chord, in which it is found that, the encoded string: A The sheath has a structure of 48 colored wires twisted and the core consists of 13 twisted strands, each strand with diameter of 1.9 mm; B - The sheath has a woven structure of 48 colored threads and the core is formed by 162 twisted strands, each strand having a diameter of 0.46 mm. Since the sheath is made by weaving the same number of strands, and has a structure similar in both cases, the conclusion would be that the sheath slippage relative to the core is influenced in this case only the core structure, this is the greater as the number of strands increases or decreases the diameter of each strand. In addition to static ropes, ropes with low coefficient of elongation, it is found that the relative value for lengthening the sheath from the core vary slightly depending on the diameter of the rope. http://www.iaeme.com/ijaret/index.asp 83 editor@iaeme.com
Nicoleta Crăciun Since the ropes are made of polymers, there is in principle a risk that under the action of existing hazards in the workplace, such as chemicals, humidity and heat, to lose its protective characteristics. Since moving sheath from the core represents one of the characteristics of protection to be achieved for marketing such a product, in the study was aimed specifically the influence of excess moisture, basic solutions, acidic and radiation caloric on this feature. Being used in most industrial areas, the influence of degradation above was followed on static ropes of different diameters. Thus, samples taken in the ropes of the encoded G, I, H were immersed for 4 hours in a solution of sulfuric acid concentration of 30% solution of sodium hydroxide with a concentration of 10% and water at a temperature of 24 0 C. The results obtained after carrying out series of tests on sliding sheath from the core are shown in Figure 4. Figure 4 Slipping Core from the Sheath in Real Conditions of use for Static Ropes Analyzing the distribution of values obtained is observed that all this have a movement of the mantle relative to the core, significantly lower than the maximum levels specified in the reference standards. However, high values are obtained for all the ropes when exposed to radiant heat; phenomenon that occurs after stiffening the mantle relative to the core, the latter slipping as through a channel. Regarding the distribution of values obtained for the four types of degradation, as seen in the figure 4 for rope whose diameter is 10 mm (codified G) is an increase. To understand the phenomenon that emerged after the damages that were exposed to three types of chord structures were analyzed both components of the chord (mantle and core). Thus it has been found that the encoded string: G with a diameter of 10 mm, whose mantle has 40 colored wires twisted structure (4 wires black and blue wires 36) weaving density is 4 threads/unit length; I diameter of 10.5 mm, whose mantle has 54 colored wires twisted structure (6 wires khaki and black yarn 48) weaving density is approx. 5.2 threads/unit length; H with a diameter of 11 mm, whose mantle has 48 colored wires twisted structure (6 wires black and blue wires 42) weaving density is approx. 4.4 threads/unit lengths. http://www.iaeme.com/ijaret/index.asp 84 editor@iaeme.com
Behaviour of the Ropes Constituents under the Action of Risk Factors that Exist in the Work Environment Corroborating the results of degradation with the results from the analysis of the sheath, it can be said that the only factor that increases the sheath from slipping core is its weaving way. Thus, one can say that if the ropes whose sheathing (outer fabric) have a low density favors penetration of chemicals or radiation calorific thereby internal structural changes that can lead to loss of protection features. 3. CONCLUSIONS Used to obtain various individual systems to protect against falling from height, either as a means of connection or anchoring support flexible the ropes have an important role in maintaining the safety of users. It is neglected that the elements being made of textile, the ropes, are exposed to action of hazards present in the work environment, being able to lose protection features. The loss of protection features determines in its turn the obstruction of the individual protection against falls from height to fulfill its function when the main factor exercising the action, which often leads to accidents at work or occupational diseases serious. The displacement of the sheath from the core being one of the protective characteristics of the ropes, was studied to see its behavior under the action of potential hazards existing at various jobs. Thus, in the study, different types of ropes were exposed to a series of degradation. After conducting series of tests it was found that the relative slip of sheath: It is not influenced by the diameter when the test is conducted under standardized conditions Depends on the achievement of core (thickness and number of strands); the ropes with stranded thicker they slip less; Is influenced significantly by exposure to radiant heat, in particular in the case of the ropes of small diameter, which is increase a rise of between 5 and 8 times greater than that obtained under standard conditions, while the hardening and contracting rope approx. 4.3%, Is influenced by the manner of the sheath (weaving density), and treatments applied to it, Is influenced by the damage caused by chemical agents (sulfuric acid solution with concentration 30%, respectively hydroxide solution sodium concentration of 10%), particularly ropes of small diameter. The study results can be used as a reference in a ropes selection processes used in various protection systems for working at height, after identifying existing hazards from risk assessment to workstations. http://www.iaeme.com/ijaret/index.asp 85 editor@iaeme.com
Nicoleta Crăciun REFERENCES [1] ROL.ro, Stirile. Climber died after falling from the fifth floor. http://webcache.googleusercontent.com/search?q=cache:fhwsraelucaj:stirile.ro l.ro/alpinist-utilitar-mort-dupa-ce-a-cazut-de-la-etajul-cinci- 617028.html%3FPageSpeed%3Dnoscript+&cd=11&hl=en&ct=clnk&gl=ro. [Interactiv] 8 mai 2010. [2] Someseanul. http://someseanul.ro/un-alpinist-utilitar-a-murit-la-cluj-dupa-ce-acazut-de-la-etajul-6/. [Interactiv] 8 martie 2013. [3] Click.ro. http://m.click.ro/news/national/video-un-alpinist-utilitar-murit-dupa-cecazut-de-la-etajul-sase-al-unui-camin. [Interactiv] [4] EN 1891:1998 Personal protective equipment for the prevention of falls from a height Low stretch kernmantel ropes [5] Saleh Alawi Ahmad, Usama H. Issa, Moataz Awad Farag And Laila M. Abdelhafez, Evaluation of Risk Factors Affecting Time and Cost of Construction Projects In Yemen. International Journal of Advanced Research in Engineering and Technology, 4(5), 2013, pp 168 178. [6] EN 892:2012 Mountaineering Equipment - Dynamic Mountaineering Ropes - Safety Requirements and Test Methods http://www.iaeme.com/ijaret/index.asp 86 editor@iaeme.com