(1) Use in cold seasons and low temperature areas
In the cold season, the lowest temperature in most parts of my country is below 0°C, the lowest temperature in the north is around -20°C, and the lowest temperature outside the Great Wall and plateau areas can reach -35°C. In principle, compaction should not be carried out in the cold season, because freezing will reduce the compaction quality of the soil or even make it impossible to compact. However, it is still possible to perform assault compaction operations in colder conditions. Working under low temperature conditions, the engine is difficult to start, the drive capacity of the road roller is reduced, the wear of the parts is increased, and even damage caused by freezing occurs.
①The influence of low temperature on the work of the roller
Low temperature makes it difficult to start the engine. The main reasons are the increase in the viscosity of the lubricating oil, the decrease in the working capacity of the battery and the poor fuel atomization.
The viscosity of engine oil increases as the temperature decreases, and the fluidity becomes worse, which makes the engine lubrication conditions worse and the rotation resistance of the crankshaft increases.
When the battery is at low temperature, the viscosity of the electrolyte also increases, the penetration ability decreases, and the increase in internal resistance makes the battery capacity and terminal voltage drop significantly, and even cannot discharge. The voltage drop makes the starter unable to obtain the required output power, and it is difficult to meet the requirements of the starting speed.
Due to the low temperature, the crankshaft speed for starting the engine is not high, the temperature of the intake pipe and the gas flow rate are low, and the quality of fuel atomization is poor, which further increases the difficulty of starting the engine.
Under low temperature conditions, various oils have high viscosity and poor fluidity, which brings difficulties to the operation of the roller and aggravates the wear of the parts.
The viscosity of the lubricating oil is large, and the oil stirring power loss during the operation of the mechanism increases, which reduces the engine power and the efficiency of the transmission system, thereby reducing the driving ability of the roller walking and the excitation mechanism.
The poor fluidity of lubricating oil adds difficulty to the lubrication of certain parts, reduces the lubrication effect, and intensifies the wear of the engine and transmission parts.
The high viscosity of the working fluid also increases the resistance of the pipeline, which makes the hydraulic steering difficult to manipulate, the efficiency of the hydraulically driven brakes deteriorates, and the difficulty of driving is increased, which has an adverse effect on safe driving.
There are widespread freezing hazards during construction in cold seasons. For example, the freezing of battery electrolyte will cause it to stop working; the freezing of water-cooled engine cooling water will freeze the radiator and cylinder block.
②Measures to be taken when the roller works at low temperature
In view of the difficulty of starting the engine, the reduction of the working capacity of the roller, the prone to wear of the parts and the prevention of freezing, the following technical measures can usually be taken:
A. The easiest way to warm up the engine is to inject water heated to 85°C into the cooling system and let the cooling system discharge water from the drain hole while adding water. When the temperature of the outflowing water reaches 30~40℃, close the drain plug and stay for 10~15min. When the water temperature in the engine water jacket and the cylinder block temperature are consistent, the engine can be started. The oil in the crankcase can also be discharged and injected after heating to enhance the lubrication effect and reduce the resistance of the crankshaft. When preheating the oil, be careful not to cause contamination of the new oil during operation.
b. Engine insulation: Install cotton insulation sleeves on the engine hood and radiator cover to reduce heat dissipation; install iron insulation covers on the intake and exhaust manifolds, and use the heat of the exhaust manifolds to preheat and mix gas. Thermal insulation measures can not only improve the low-temperature starting performance, but also improve the thermal poor state of the engine during operation.
C. Use low-freezing point diesel to replace the diesel in time with the change of seasons, and switch to low-freezing point light diesel in cold seasons, which can effectively improve the engine’s low-temperature starting performance and increase engine power. When there is a lack of low-freezing point diesel fuel, preheating measures can be used to improve the high-freezing point diesel fuel.
Diesel fuel preheating usually has the following two methods:
Exhaust gas preheating-connect a pipe from the engine exhaust pipe through the fuel tank, use the exhaust gas to preheat the diesel, but first start the engine with low-freezing point diesel, and then switch to high-temperature diesel after the heated fuel flows. Freezing point diesel, and switch back to low-freezing point diesel 10-20min before shutdown to avoid blockage of the oil circuit after shutdown.
Circulating water preheating-pipe the circulating water through the fuel tank, or make it into a sandwich fuel tank (with diesel oil in the inner layer and circulating water in the outer layer). Boiled water can be used to preheat before starting up (the diesel temperature should be controlled so that it does not exceed 60°C), but the preheating device should not leak water, oil, or gas.
In addition, 10% to 40% of kerosene can be mixed into the high freezing point diesel oil and mixed evenly, which can also reduce the freezing point of the fuel.
d. Strengthen the discharge capacity The battery should be fully charged and keep the electrolyte density at 1.28 (equivalent to full charge) to ensure the discharge capacity; adjust the generator regulator to appropriately increase the charging capacity of the generator so that the voltage of the charging circuit is higher than in summer 0.6V. In this way, the battery can be fully discharged and the difficulty of starting the engine when the engine is at low temperature is reduced.
E. Change to winter oil to change the oil, gear oil, hydraulic oil and brake oil used in the roller to winter oil, thereby improving the starting performance of the engine, overcoming the difficulty of running on the roller and reducing the wear of the parts.
F. Prevent freezing Water-cooled engines should always keep the water temperature around 80℃, and the temperature of the space under the engine hood at 30-40℃. Pay attention to the warmth of the water cooling system. Drain water or add antifreeze in time after shutdown. The roller with an air-cooled engine can completely avoid freezing. Generally do not use counterweight water and sprinkler during winter operations.
(2) Use in high temperature areas
In the hot season, the temperature is high, the rain is heavy and the air is humid, which brings many difficulties to the mechanical construction, such as: engine overheating and power drop; hydraulic transmission efficiency is low; friction pair wear is increased.
①The influence of high temperature on the work of roller
High temperature will make the cooling system difficult to dissipate heat, and the engine is prone to overheating. The high temperature of the engine is prone to deflagration, which makes the engine work rough and reduces the power.
The engine runs at high temperature, so that the lubricating oil that enters the top of the piston and the combustion chamber generates carbon deposits under the condition of high temperature and lack of oxygen, which accumulate on the piston crown, combustion chamber, valve top and fuel injection nozzles, and the carbon deposits form hot spots. . It can cause spontaneous combustion or deflagration in the engine.
The overheating and deflagration of the engine can cause thermal deformation of the cylinder block and cylinder head, even cracks or warping, and can also cause thermal burnout of the cylinder head, resulting in a decrease in the compression force of the cylinder and further reducing the power of the engine.
Tests have proved that, usually after the temperature exceeds 20°C, the power of the engine will drop by 4% for every 10°C increase in temperature. Road rollers sometimes have to work at an ambient temperature of 40~50°C, which may reduce the engine power by about 10%.
High temperature will make the lubricating oil thinner and reduce its viscosity, so it is not easy to form an oil film on the surface of the machine parts, thereby reducing the lubricating effect; under high temperature conditions, the oil’s anti-oxidation stability will deteriorate, which will easily cause the lubricating oil to deteriorate, making the glue and The deposit adheres to the surface of the piston assembly, cylinder wall and other parts, which deteriorates the thermal conductivity and aggravates the wear of the parts.
When the roller works under high temperature conditions, the thinning of the oil can cause extravasation and internal leakage, which reduces the efficiency of the hydraulic transmission system and makes the hydraulic drive weak.
In the high temperature season, the friction pair of the machine’s clutch and brake is extremely difficult to dissipate heat, which intensifies the wear of the friction element and even produces ablation.
Some high-temperature areas are often accompanied by humidity and rain. Humidity will also reduce engine power. At a temperature of 30℃, the efficiency of the engine when the humidity percentage is zero (desert climate) is about 3% higher than when the humidity is 60%; and when the humidity percentage is 100% (tropical climate), the efficiency of the engine is higher than the humidity When it is 60%, it drops by about 2%.
In addition, rain and damp weather can also cause corrosion of metal parts. After the water vapor is mixed into the oil, condensed water may be generated in the fuel tank and the hydraulic oil tank, which will adversely affect the work of the roller.
②Measures to be taken when the roller works at high temperature
The key to overheating the engine is to strengthen the maintenance and maintenance of the cooling system. Always check and tighten the fan tape, and clean the dust collection on the radiator in time to enhance the ventilation of the radiator. For water-cooled engines, you can also flush the radiator and water jacket with water from the opposite direction of the normal circulation of the cooling system to remove scale and deposits, thereby enhancing the heat dissipation effect.
In the hot season, the roller should be replaced with thicker oil, gear oil, hydraulic oil and grease with a higher dropping point when the roller is running.
At high temperatures, the power consumption when the engine starts is small. In order to prevent the electrolyte from evaporating further caused by the increase in battery temperature caused by high-current charging, the voltage regulator of the generator should be adjusted to reduce the charging current. In addition, the level of electrolyte should be checked frequently, and distilled water should be added in time.
(3) Used in plateau and mountainous areas
The characteristics of road roller construction in plateau and mountainous areas are: high terrain and thin air reduce the power of the engine, which will have some adverse effects on the steering and braking of the road roller. Therefore, certain technical measures must be taken to strengthen maintenance and maintenance.
①The influence of plateau and mountainous areas on the work of road rollers
As the altitude increases, the atmospheric pressure and air density decrease, which reduces the amount of charge of the engine and reduces the output power of the engine. Table 6 (with table) shows the relationship between the altitude measured when the temperature is 20°C and the humidity is 60% and the engine power drop.
Under special circumstances, the high temperature on the plateau may reduce the power of the engine by 40%~50%.
Because the air is thin, the normal oil-gas mixture ratio cannot be guaranteed. Due to the incomplete combustion, carbon deposits and glue appear too quickly in the cylinders, pistons and valves, which increases the wear of these parts.
The low air pressure on the plateau will lower the boiling point of water, and the boiling point of water at kilometers above sea level is only 86.8°C, thus increasing the consumption of engine cooling water.
Thin air will also cause the productivity of the air compressor to decrease, which will make the reliability of the pneumatic brake mechanism worse.
②Measures to be taken for road rollers working in plateau and mountainous areas
For machinery that is constructed in the plateau and mountainous areas, the performance parameters of the engine must first be checked to see if it can meet the requirements for use in this situation.
In order to adapt to the characteristics of thin air in the plateau and mountainous areas, the power of the roller is best to use an air-cooled diesel engine with a supercharger. For engines without a supercharger, the fuel supply should be appropriately reduced. When constructing in areas above 2500m above sea level, the advance angle of oil supply should be appropriately increased to overcome the shortcomings of carbon deposition and too fast gelling.
In order to reduce the adverse effects caused by coking and gelation, the decarbonization cleaning cycle for the combustion chamber, piston crown, valve top, etc. should be shortened, which can be shortened to 30%-50% of the usual.
For water-cooled engines, it is necessary to strengthen the sealing of the cooling water to reduce the evaporation and overflow of the cooling water. The cleaning cycle of the cooling system should also be shortened by half than usual to remove the fouling in a timely manner.
It is necessary to strengthen the maintenance and maintenance of control mechanisms such as braking and steering, and pay special attention to the pressure of the pneumatic braking system. Brake fluid must use mineral oil to avoid excessive evaporation and affect the transmission of braking force.
(4) Used in deserts and arid areas
In construction sites in deserts and arid areas, there will be a lot of dust and difficulties caused by the rapid evaporation of water.
If some dust particles enter the compressed air chamber through the engine valve, it will accelerate the wear of the piston and cylinder wall. In deserts and arid areas, there have been many examples of engines being worn out after using for less than 100 hours. Therefore, when the roller is working in dusty conditions, special attention must be paid to the selection and maintenance of the air filter. It is best to use the special-purpose desert area. air filter.
The sand particles will also stick to the open transmission mechanism, causing the external gear to wear out quickly. When designing the machine, the transmission components should be closed as far as possible to reduce wear and extend the service life of the transmission system.
When the climate is dry, the cooling water of the engine and the electrolyte of the battery evaporate quickly. Therefore, always pay attention to filling up the cooling water and filling the battery with distilled water during the operation. It is best to use road rollers equipped with air-cooled diesel engines to participate in construction in arid areas.
In addition, the construction of road rollers in desert areas will reduce the driving capacity due to the loose sandy soil, making it difficult to drive the road rollers or even get stuck. Therefore, the design should appropriately increase the distributed weight of the driving theory, or use all-wheel drive and use a low-voltage wide base. The tire is used as the driving wheel. The latest technology is to adopt anti-skid measures on the hydraulic system, and to provide the best traction conditions with the help of the adjustment of the system fluid flow, so as to make full use of the tire’s ground adhesion ability.