HYDRAULIC HOSE TYPES IN MINING MACHINES
HYDRAULIC HOSE TYPES IN MINING MACHINES
HYDRAULIC HOSE TYPES IN MINING MACHINES, HOSE SELECTION, HYDRAULIC HOSE COST ANALYSIS AND SAFE WORKING TECHNIQUES IN HYDRAULIC SYSTEM
TYPES OF MINERAL HYDRAULIC HOSE, HOSE SELECTION, ANALYSIS AND HYDRAULIC SYSTEM HYDRAULIC HOSE COST-SAFE WORKING TECHNIQUES
Author: Ahmet İPEK
ABSTRACT
In this study, types of hydraulic hoses, hose according to operating conditions and usage according to their calculation methods that are required for the selection of the correct hose selection with the selection of the wrong hose, hydraulic hose fitting that may arise from the hydraulic system with cost analysis stemming from the illicit practices that may endanger job security into applications to switch to safe working methods of the hydraulic system is presented.
1. INTRODUCTION
Hydraulic systems are used mainly in mining machines, agricultural machinery, road cleaning vehicles, cranes, work machines, scissor lifts, presses, ships and yachts, iron and steel factories, aircraft, military vehicles and even amusement vehicles in amusement parks. For this reason, the place and importance of hydraulics in industry is great. Hydraulic systems are known and applied in many countries of the world. Since this sector is newly developing in our country, it is important that we have information on these issues.
Although the necessary calculations are made for equipment such as pumps, valves, filters, cylinders, hydromotors used for the hydraulic system in the world, product selection and cost analysis are made, the necessary sensitivity is not shown for hydraulic hoses and fittings, which have an important place in the hydraulic system.
Hydraulic hoses are generally made of rubber and thermoplastic materials. Since the raw material of hydraulic hoses is rubber, the product has a shelf life even if it is not used at all. The hose must be used within 8 years from the date of manufacture. Otherwise, the hose will lose its feature and will lose its pressure resistance.
Hydraulic hose should be used in different diameters for each system. A hydraulic system has suction, pressure and return lines. The diameter of the hydraulic hoses should be respectively suction> return> pressure, the hose diameter decreases in direct proportion to the fluid velocity in the hydraulic system. Along with the selection of the hose diameter, the hydraulic system pressure, the type of fluid to be passed through the hose, the bending radius of the hydraulic hose and the external environment conditions that the hydraulic hose will be exposed to are among the factors that should be taken into account in the selection of hydraulic hose. If even one of these criteria that I have stated is not taken into account, unfortunately the life of the hydraulic hose will be shortened and all the necessary conditions should be examined.
2.VISUALLY DESCRIPTION OF HYDRAULIC HOSE
Hose identification can be made from the hose label on the hose. Manufacturer brand, hose standard (International norm compliance), hose working pressure, hose's internal diameter size and production date and lot number can be determined on the hose. (Figure 1)
Figure 1. Definitions on the hose.
Hoses must be used within 8 years from the date of manufacture. The hose is scrapped after 8 years. (Chart 1) It has been noted that storage conditions potentially reduce the service life of hose fittings. Pressure elements are transferred, which could potentially reduce the service life of the coupled hose. It also includes the 6-year storage period, which is the maximum usage capacity. As a result, each storage period consumes the service life of the coupled hose in equal parts.
Table 1. Hose service lives.
3. HYDRAULIC HOSE STORAGE CONDITIONS
General storage conditions and placement policies are provided in all standards. Suggestions are presented by listing them with the following parameters.
HEAT DEGREE
Usually 0-35 degrees (Preferably 15 degrees)
MOISTURE
Very humid or dry conditions should be avoided. Recommended average humidity should not be higher than 65%.
LIGHT
Hoses should be protected from sunlight or strong artificial light. It is generally recommended that the warehouse's windows be painted red or orange, hoses should be stored in sealed boxes.
OXYGEN AND OZONE
Due to the harmful effects of ozone on rubber products, hoses should be stored in ventilated closed boxes, and their proximity with mercury vapor lamps or tubes, high-voltage electronic materials should be avoided.
OILS, SOLVENTS, GRESS OILS
Stored hoses should be protected from possible contact with risky objects.
HEAT SOURCES
Hoses should be stored away from hidden (indirect) heat sources.
ELECTRIC AND MAGNETIC FIELD
The proximity of materials in storage areas should be avoided as it may create electrical and magnetic fields. Storage areas should not be close to materials that may cause current and heating in magnetic parts and create electric and magnetic fields.
STORAGE CONDITIONS
Hoses should always be stored in comfortable conditions and should be stored without any damage or stress.
The minimum recommended bending circumference should be as large as possible.
The hose should be stored in such a way that its outer coating avoids abrasion caused by accidental contact with the environment.
MANUAL PROCESSING METHODS
When touching the hoses, they should be protected against shocks and hose coating abrasion as much as possible.
4. HYDRAULIC HOSE TYPES
Hydraulic hoses are produced according to internationally valid standards. For this reason, hydraulic hoses are defined according to ISO and EN norms. (Chart 2)
Table 2. International definitions of hoses.
Inner and outer layers of hydraulic hoses are made of rubber and thermoplastic materials. The pressure resistance of the hoses is increased by wrapping cloth, wire and fabric braids on the inner layers of the hoses. The pressure resistance of a single wire braided hose and two wire braided hoses of the same diameter is not the same. (Picture 1) The pressure strength of the hoses varies according to the manufacturers and the norms specified in Table 2. For more detailed information, you can look at SAE and EN standards.
Picture 1. Single layer and two layers of wire braided hose internal structures.
5. DETERMINING THE RIGHT HOSE DIAMETER AND SELECTING THE HOSE
Choosing the wrong diameter of hose in a hydraulic system will damage not only the hose but also many equipment in the hydraulic system. For this reason, the pump suction line should be larger than the pipe in the discharge line. The pipeline from the tank to the pump should be kept as short as possible. Elbows or similar elements should be avoided at the entrance to the pump. Otherwise, overheating will occur in the pump, which may damage the pump and other components. When calculating the suction line, V suction = 0.8-1 m / sec Flow Rate value is taken. Pump pressure line should be selected with a smaller diameter than the suction and return line. Otherwise, we cannot get the desired pressure from the pump. While calculating the discharge line, the flow rate value between V pressure = 5-6 m / sec is taken. The pump return line should be chosen larger than the pressure line, just like the suction line. Otherwise, the restricted passages in the return lines cause the pressure to rise and the power to be wasted unnecessarily. While calculating the return line, the value of V rotation = 2-4 m / sec flow velocity is taken. Hydraulic hose diameter calculation can be done by two methods, the first method is the practical selection table (Table 3) and the second method is to choose the appropriate hose using the formula below.
Table 3. Choosing the appropriate hose diameter according to the hydraulic system flow rate.
Many details should be reviewed in the selection of hydraulic hoses. First of all, it is necessary to determine the electrical conductivity in the environment where the hydraulic hose will be used. In some applications, it is desired that hydraulic hoses do not conduct electricity, and in some applications, it is desired to conduct static electricity on the hose. Since this choice directly affects human life, it should never be forgotten and its determination should be made without any question marks. While determining the hydraulic hose, it should definitely be determined whether the maximum working pressure of the system is suitable for the working pressure of the selected hose. It should not be forgotten that this criterion directly affects human life. As the structure of the suction line hoses and pressure line hoses are different, as stated in the product description, it should be determined whether the selected hydraulic hose will be used in the pressure line or in the suction line. It should not be forgotten that the wrong choice to be made here causes serious malfunctions in the system elements. It should be determined that the working temperature of the selected hydraulic hose is suitable for the fluid temperature and ambient temperature. A mistake made here could cost a fire in the facility or human life. If necessary, heat protectors such as Glass Fiber should be placed on the hose.
If the selected Hydraulic Hoses are used in gas systems, the outer surfaces of the hoses must be perforated, because gas passes through the layers more easily than the liquid. Therefore, bubbles form on the hose, if the gas used is explosive, human life is endangered due to the risk of explosion. The diameter of the selected Hydraulic Hose should be determined very well, otherwise the equipment used in the system will be damaged by excess flow or insufficiency or operate with low efficiency. The route of the hose should be determined very well in order not to cause complexity in the system. . Mechanical loads in the system directly affect the life of the hose. Therefore, while selecting the hose, it should be also applied to the point as well as other criteria. The hose should always be protected against cutting effects and friction effects. The hose length should be determined carefully. The long hose causes friction, buckling and complexity. A short hose shortens the life of the hose. The installation of the hydraulic hose is at least as important as choosing the hydraulic hose. Details of hydraulic hose assembly should be considered. (Figure 2)
Figure 2. Things to be considered in the assembly of hydraulic hoses.
Different pipe diameters should not be used in hydraulic systems, sudden reduction or increase in cross section should be avoided. Sharp corners should be avoided while turning on the lines used in hydraulic systems. Extremely long and unnecessary pipes and hose lines should be avoided. In order to prevent vibration and cavitation in the system, hoses should be fixed with clamps at regular intervals. The suction hose should be short. Return hose should be short. Hoses should be used in moving and vibrating places. Hose diameters should be sufficient to provide the desired flow and pressure. Hose connections must be tight. The innermost layer of the hose must be resistant to the fluid used in the system.
6. HOSE FITTINGS AND HOSE FITTING INSTALLATION
The dimensions of all selected materials (Hose, Socket and Fittings) should be checked before pressing. Hoses and Heads that are not suitable for each other should never be used together. Mold size and settings of the machine to be pressed should be checked. (Picture 2) Old materials should never be reused. (Removing and pressing the fittings again or pressing new fittings into the old hose) As the hose pressing process directly affects human life in many cases, the people who do the pressing should think about what kind of problems may arise from the most horizon error and should pay attention to the pressing process.
The mistakes that can be made in the pressing process are as follows;
Delivery of hydraulic hose with union without pressing the fittings into the hose
Incorrect calculation of the pressing size or pressing by reading incorrectly from the table
Pressing the pressing process with the correct size but with the wrong mold
Pressing is carried out without sufficiently inserting the fittings into the hose.
Distortions that may occur due to the pressing of elbows or bent special fittings due to the fittings hitting the jaws of the press.
Part of the socket is out of the mold during the pressing process.
Picture 2. Hydraulic hose fitting assembly machine.
Coating is of great importance in hose fittings, metal surface coatings increase the corrosion resistance of the hose coupling. If the hydraulic hose is working in an environment that is open to the atmosphere and in an environment exposed to water, it is absolutely important that the hose fitting is zinc-nickel plated. (Figure 3) Otherwise, the hose coupling will rust and its life will be shortened. (Picture 3)
Figure 3. Comparison of the coating structure of different surfaces after 120 hours of salt water test.
Picture 3. Corroded hose fittings.
7. HYDRAULIC HOSE COSTS IN WRONG APPLICATIONS
Choosing hydraulic hoses is an important factor affecting the cost. The biggest mistake made in this regard is that the hose used in a hydraulic system has the same properties as a result of the explosion of the hose. If a hydraulic hose bursts in a short time, the selection of the hose should be considered. With the wrong hose selection, we throw away thousands of liras a year without knowing it. A company's monthly hose consumption is 400, which makes 4800 hoses annually. If the unit price of the hose is calculated from 17 TL / piece, the annual usage is 81,600 TL. However, since the hose suitable for the job used is 21TL / piece, this hose is expensive at a unit price, and the cheap one is generally preferred. However, the monthly hose consumption of the company will decrease to 280 pieces in the use of hoses suitable for the job. This makes 3360 hoses per year. Annual usage amount is 70.560 TL. In addition, we did not even calculate the annual 1440 hose removal and installation costs for these products.
8. SAFE WORKING TECHNIQUES IN HYDRAULIC SYSTEM
Injuries caused by injecting hydraulic oil into the body Dangerous toxic effect of hydraulic oil Contact with hot hydraulic oil Explosions occurring in the hydraulic system, hoses and pipelines enter the body by piercing the fluid under pressure and reach the body tissues. This substance, which is injected into the body, quickly passes through the skin tissue and goes deep into the nerve cells and hand / body cavities. A pinhole leak in the hydraulic hose causes the toxic oil to eject at a speed of 180m / sec under high pressure. This is almost the speed of the bullet coming out of the gun. For this reason, before intervening in the hydraulic system, only experienced people trained in this field should intervene in the hydraulic system. The person who will intervene in the hydraulic system failure must wear all protective clothing. Valves in the hydraulic system should be taken to neutral position. It is checked whether the hydraulic cylinders are under load or not and the loaded cylinders are placed in neutral position. The hydraulic system is stopped and all switches are controlled. Checking the manometers in the hydraulic system, it is ensured that the pressure values are "0". Since hydraulic foggers are moving parts, necessary precautions should be taken to prevent the movement of the equipment connected to the cylinder before disconnecting the hoses connected to this line.
9. CONCLUSIONS
Hydraulic hoses are used at high operating pressures. Small mistakes that can be made in the selection, application or assembly of hydraulic hoses are important to a great extent as well as paying high costs, as well as damages to human health. It should not be forgotten that fatal accidents occur as a result of wrong practices. It is important that hydraulic hoses are selected and assembled by personnel who have been trained in this regard, and that they are always controlled and commissioned and applications are made.
10. REFERENCES
ISO 8331, Rubber and plastic hoses and hose fittings-Storage usage and containment selection standard.
BS 5244, Storage and expiry date application standard for hose fittings and hydraulic rubber hoses.
DIN20066, Hydraulic fluid strength hose Fittings service performance evaluation.
SAE J1273, Recommended practices standard for hydraulic hose assembly.