On the construction site of a large logistics park, the Sany Heavy Industry STC250C4 crane has always been a trusted "tough guy". But recently, this "tough guy" seems to be sick, always "panting" when working. When starting, the engine idles unsteadily, accompanied by strange jitters, and the roar becomes weak. During a container lifting operation, its power suddenly dropped sharply, and the container hanging in the air almost slipped, making the operator's palms sweat. The construction team leader looked at this crane "working with illness" and was full of anxiety. If this equipment breaks down, the construction progress of the logistics park will be greatly reduced. Everyone is looking forward to making this "tough guy" recover as soon as possible and show its prowess on the construction site again.
Solution:
Solution
1. Check cylinder compression pressure: Use a cylinder pressure gauge to measure the compression pressure of each cylinder. Before measurement, ensure the engine is at normal operating temperature, remove all spark plugs or fuel injectors, fully open the throttle and choke, then tightly connect the connector of the cylinder pressure gauge to the spark plug or fuel injector hole on the cylinder head. Start the engine, let the crankshaft rotate for 3 - 5 seconds, record the reading of the pressure gauge. Each cylinder should be measured 2 - 3 times, and the average value should be taken. If the compression pressure is lower than the specified value, further inspection is needed to find the cause.
2. Deal with piston ring wear: If it is determined that insufficient compression pressure is caused by piston ring wear, the engine needs to be disassembled. First, drain the engine oil, remove the external components of the engine, such as the intake manifold, exhaust manifold, timing chain cover, etc., then remove the cylinder head, take out the piston - connecting rod group, use special tools to remove the old piston rings, and clean the carbon deposits and oil stains in the piston ring grooves. Select new piston rings matching the engine model. When installing, pay attention to the opening direction of the piston rings. The openings of each ring should be staggered by 120° - 180°, and must not be aligned with the piston pin hole and the weak part of the piston skirt. At the same time, adjust the end gap, side gap and back gap of the piston rings to meet the specified standards to ensure the sealing performance of the piston rings. After installation, assemble the engine components in the reverse order.
3. Replace the cylinder head gasket: If the cylinder head gasket is found to be damaged, it needs to be replaced in time. First, remove the cylinder head bolts, take off the cylinder head, remove the residues of the old cylinder head gasket, and check the flatness of the cylinder head and cylinder block. A straightedge and feeler gauge can be used for measurement. If the flatness error exceeds the specified value, the cylinder head and cylinder block need to be repaired or replaced. When replacing with a new cylinder head gasket, pay attention to the installation direction, ensure the positioning pins are aligned with the holes, then tighten the cylinder head bolts according to the specified torque and sequence.
4. Repair valve sealing: Check the valve sealing. If there is a problem of poor sealing, first clean the sealing surfaces of the valve and valve seat. For slight poor sealing, apply an appropriate amount of sealant; if the sealing surface is worn or has scratches, a valve grinder should be used for grinding. During grinding, apply grinding paste on the valve sealing surface, install the valve on the valve seat, and rotate the valve back and forth with a grinding tool until a continuous and uniform halo appears on the sealing surface. After grinding, clean the remaining grinding paste and check the sealing condition.
5. Secondary inspection: After the repair is completed, use the cylinder pressure gauge again to check the compression pressure of each cylinder to ensure that the pressure reaches the specified value, so as to verify the maintenance effect.
1. Engine performance restored: After maintenance, the cylinder compression pressure of Sany Heavy Industry STC250C4 engine has returned to the specified value, the idle speed is stable, the jitter phenomenon has disappeared, and the power output is strong. It can meet the operation needs of the crane under various working conditions, and the working efficiency of the equipment has been greatly improved.
2. Fault root causes eliminated: The engine faults caused by piston ring wear, cylinder head gasket damage, poor valve sealing and other problems have been completely solved, reducing the frequency of equipment failures and lowering the subsequent maintenance costs and downtime.
3. Operation safety improved: The stable operation of the engine ensures the safety and reliability of the crane in lifting operations, avoids safety accidents caused by engine faults, and provides a solid guarantee for the life safety of construction personnel and the smooth progress of the project.
4. Equipment service life extended: The mechanical components of the repaired engine work well together, reducing abnormal wear between components, effectively extending the overall service life of Sany Heavy Industry STC250C4 crane, and improving the cost - performance ratio of the equipment.
