BW crane

Shield machine cutterhead function description

The cutterhead is a cutting disk with multiple feed slots. It is located at the front of the shield machine and is used for cutting soil. The opening rate of the cutterhead is about 28%. The diameter of the cutterhead is 6.28m. It is also a shield machine. The largest diameter part of the machine, a flange plate with four support strips is used to connect the cutterhead and the cutterhead driving part. The cutterhead can be equipped with hard rock cutters or soft soil cutters according to the softness and hardness of the soil to be cut. There is also an over-excavating cutter installed on the outside of the disc. When the shield machine turns to tunnel, the over-excavating cutter cylinder can be operated to make the over-excavating cutter extend outward along the radial direction of the cutter disc, thereby expanding the excavation diameter, which is easy to achieve. Steering of TBM. The stroke of the super digging cutter cylinder rod is 50mm. All types of cutters mounted on the cutterhead are bolted together and can be replaced from the dirt bin behind the cutterhead.

There is a rotary joint installed at the rear of the flange plate, which is used to input foam or bentonite to the cutterhead panel and to deliver hydraulic oil to the super-excavating cutter hydraulic cylinder.

2 years ago | [YT] | 0

BW crane

Introduction to concrete shot blasting machine equipment and description of working principle

The concrete shot blasting machine mainly solves the defects in the treatment of concrete surface. It can clean the floating slurry and impurities on the concrete surface at one time, and can roughen the surface of the concrete to make the surface uniform and rough, which greatly improves the waterproof layer. The adhesion strength to the concrete base layer allows for better integration between the waterproof layer and the bridge deck. It can also fully expose the cracks in the concrete and prevent problems before they occur. Centrifugal shot blasting machine is an efficient, clean and dust-free method for treating bridge decks with hard surface impurities. This method is most commonly used. The interior of the shot blasting equipment is an impeller that can rotate at high speed. Abrasives, dust and impurities are cleaned to the debris recovery machine, and the cleaned steel shots can be recycled again. The surface of shot blasted concrete is clean and hard, with a relatively uniform texture. This works especially well on unobstructed, level surfaces.

2 years ago | [YT] | 0

BW crane

Cause analysis and troubleshooting methods for "sliding arm" failure of crawler cranes

During an operation of the 7250 crawler crane (tower working condition, lifting 14t weight), when the marching jib was lowering at low speed, the heavy object suddenly appeared and the heavy object fell directly to the ground. Fortunately, the man and machine were safe. After stopping the machine for inspection and doing a load test, this phenomenon did not occur again. However, an incident occurred in which the jib slid down a certain distance, and the heavy object did not slide down to the ground. The two identical failures were both accidental and highly concealed.

1. Cause analysis

The braking system and free-fall hook function normally, and the focus of analysis should be the working principle of the jib (see Figure 1). By operating the different positions of the handle, the hydraulic motor moves oil in and out in different directions, and the arm can be raised or lowered. The key component of the jib operating system is the combined balancing valve. The valve model is RF1M32J10B1A-965-0, with a rated pressure of 32MPa, a working pressure of 28MPa, a working flow of 420L/min, and a control pressure (opening) of 1.2~1.8MPa. The working process is as follows:

(1) Promotion

The control valve is in the loading and lifting position at the right end, the hydraulic oil from the pump outlet enters port A of the combined balance valve, the one-way valve opens, and the oil enters port A' of the hydraulic motor. The return oil returns from the port B' of the hydraulic horse to the port B of the combined balancing valve. In the lifting state, the combined balance valve does not have any control effect.

(2) Decline

The control valve is in the lowered position at the left end, and the hydraulic oil at the pump outlet enters the hydraulic motor from the B-B′ oil line. At this time, the hydraulic motor cannot return oil due to the closure of the one-way valve and the hydraulic control valve spool, so the hydraulic oil pressure output by the pump continues to rise. High, when the oil pressure exceeds the spring force of the control valve spool to close, the hydraulic control valve opens, the A′-A oil circuit returns oil, and the hydraulic motor operates to reduce the load.

2 years ago | [YT] | 0

BW crane

A brief discussion on the safety and protection of elevator brakes

An escalator accident on Beijing's Line 4 subway resulted in the death of a 13-year-old boy, serious injuries to three people, and minor injuries to 27 others. It is reported that the culprit of the accident may have been a faulty elevator brake.

Elevator brakes are generally composed of coils, iron cores, brake push rods, brake arms, brake bands, brake wheels, brake springs, brake bases, etc. All brake machinery involved in applying braking force to the brake wheel or disc should Divide the equipment into two groups to prevent the failure of one group of components from causing failure of the other group and thus causing an accident. Of course, the brake must have sufficient braking torque to ensure that when the car carries 125% of the rated load and moves downward at the rated speed, operating the brake should be able to stop the traction machine.

In the control of the brake, GB7588-200312.4.2.3.1 stipulates that cutting off the brake current should be achieved by at least two independent electrical devices, regardless of whether these devices are integrated with the electrical device used to cut off the current of the elevator drive host. When the elevator is stopped, if the main contact of one of the contactors is not opened, the elevator should be prevented from running again until the next change of running direction at the latest. These two independent electrical devices refer to the devices that control the brake coil. They do not refer to devices that have the same necessary conditions for elevator operation, such as door lock circuits and safety circuits. Instead, they should refer to devices that meet the necessary and sufficient conditions for elevator operation. Like the device that operates the contactor, the behavior of two independent devices should be logically ANDed rather than ORed.

2 years ago | [YT] | 1

BW crane

What issues should be paid attention to when connecting metal structures and pin shafts of tower cranes?

1. Tower crane metal structure connection

There are generally two ways to connect the metal structure of a tower crane. That is, high-strength bolt connections and pin connections. The high-strength bolt connection of tower crane relies on friction to transmit the internal force of the structure, which requires the connection surface to be clean and have a high friction coefficient. Tightening torque values are very important, especially pretightening torque. The purpose of preloading is to enhance the reliability and tightness of the connection to prevent gaps or relative slippage in the connection parts after loading, so as to ensure the final installation quality. The following points should be paid attention to when installing high-strength bolts:

(1) The pre-tightening torque of high-strength bolts is specified during tower crane design. In order to meet the design requirements, the pre-tightening torque value of high-strength bolts must be determined and a special torque wrench must be used before the tower crane is installed.

(2) Before installation, dirt and rust should be removed from washers, bolts, nuts and threads, and a small amount of grease should be evenly applied on the nut threads. Bolts whose stems are not straight and gaskets, bolts, and nuts with rust damage and screw thread damage cannot be used.

(3) Before the bolts are penetrated into the fastened structure, all connecting parts should be cleaned, and the bolts cannot be struck and forced to penetrate. Take effective measures to prevent moist air, water, etc. from entering the joints to ensure dry friction and no rust on the joints.

(4) When tightening bolts, nuts should be tightened. Bolts are only allowed to be tightened as a last resort: high-strength bolts of the same specification should be used in the same part and cannot be mixed with bolts of other specifications; ordinary bolts and nuts cannot be used instead of high-strength bolts. Bolts and nuts are used for connecting pairs; in my country's construction machinery and equipment industry standard "Technical Conditions for High-Strength Fasteners", it is required to regularly check the pre-tightening torque to prevent loosening, and the tightening should be checked universally and evenly after 100 hours of use after the first installation. , it should be checked every 500 hours of work in the future. In particular, high-strength bolts and nuts that have been removed after use are generally not allowed to be reused.

2 years ago | [YT] | 0

BW crane

How to prevent impeller coal feeder failure?

1. Strengthen dust control on gap coal troughs



The reliable SMZ comprehensive dust removal technology (i.e. water spray + seal + LZZ type flat bag dust collector) is used at the gap coal trough. In order to completely eliminate the dust generated when coal is pulled and dropped, while strengthening the sealing of the guide trough of the impeller coal feeder, the dust collector and water pump are installed on the impeller coal feeder, on the beam at the lower part of the gap coal trough. The water tank, dust collector and water pump are installed to move with the movement of the impeller coal feeder, thus realizing dust removal and water spraying in the entire section of the gap coal tank, greatly reducing the dust concentration and improving the working environment.



2. Change slip speed regulation to variable frequency speed regulation



Since the slip motor has shortcomings such as large starting current during operation, it cannot run at low speed for a long time, the slip clutch and the tachometer generator are easily damaged and affect the reliability of speed regulation. Moreover, the slip motor has a complex structure and large volume, making it difficult to repair. It is more difficult, so variable frequency speed regulation with wide speed range, stable operation and easy maintenance is used instead of slip speed regulation. Our factory uses the FR-A500 variable frequency speed regulator produced by Mitsubishi Electric Co., Ltd. of Japan. Its frequency range is 11 to 50 Hz.



3. The power supply method is changed from sliding conductor to tow cable



In order to improve the reliability of power supply, the power supply from the trolley wire is changed to the power supply from the drag cable. The power supply is directly sent from the drag cable to the motor, which reduces the intermediate link (current collector) and fundamentally eliminates the problem of poor contact between the collector and the trolley wire. As well as the burnout accident of the drag motor caused by the power supply phase loss and phase failure caused by the collector falling off.



After the above improvements, the operational reliability of the impeller coal feeder has been greatly improved, the failure rate has been greatly reduced, the maintenance workload has been reduced accordingly, and the operation has become relatively simple.

2 years ago | [YT] | 0

BW crane

Introduction to crane hook group types and their characteristics

The crane hook group is the combination of the sliding pulley hooked to the pulley block. There are two types of hook sets: long type and segment type.



The long hook group uses ordinary short hooks with shorter hook handles, which are supported on the hook beam, and the pulley is supported on a separate pulley shaft. Its height is larger, which reduces the effective lifting height.



Segment-type hook sets used to use long hooks. The pulleys of this hook set are directly mounted on the hook beam, and the height is reduced, but they can only be used for double-rate pulley sets. Because the balancing wheel of the magnification pulley set is at the bottom, this balancing pulley can only be installed with a long hook set. The short hook group currently produced is similar in structure to the long hook group, but has the characteristics of the short type. Short hook sets can only be used with smaller pulley block magnifications. When the magnification is large, the number of pulley blocks increases, and the hook beam is too long, so the bending moment is too large, making the hook too heavy. Therefore short hook sets are only suitable for smaller cranes.



In order to facilitate lifting, the hook should be able to rotate around the vertical axis and the horizontal axis. Therefore, the hook is supported on the hook beam with a thrust bearing, and the nut at the tail of the hook is pressed against this thrust bearing. The nut should have a reliable anti-loosening device, and the thrust bearing should have a dust-proof device. In order to allow the hook to rotate around the horizontal axis, the shaft end of the long hook beam is made into an annular groove where it matches the fixed axis baffle, allowing the beam to rotate; on the contrary, the shaft end of the upper pulley shaft is a flat notch, which does not allow slippage. The axle turns.

2 years ago | [YT] | 0

BW crane

Several measures to reduce resonance damage of engineering machinery parts

Resonance means that when an object is in forced vibration, when the frequency of the change in driving force is equal to the natural frequency of the object, resonance occurs. At this time, the amplitude of the forced vibration of the object is the largest. When a motor vehicle or parts reach a certain rotational speed (or resonance frequency), resonance will occur and the parts will be damaged. The speed at which parts are damaged is called "dangerous speed". The size of the dangerous speed is related to the length, cross-sectional shape and mass distribution of the parts.

In order to reduce the resonance of parts, it is necessary to increase the value of its "dangerous speed". To this end, many technical measures have been taken on motor vehicles, such as:

1. Design the long part into two sections. Since the transmission of the car is far away from the rear axle, a long universal transmission device is designed to connect the two. In order to reduce resonance, the drive shaft of most cars is designed into two sections, and a universal joint and an intermediate bearing are installed at the connection between the two sections, thereby effectively reducing the length of the drive shaft and reducing the harm of resonance damage to the drive shaft. . In addition, if the oil radiator pipe of some models often cracks and causes oil leakage, you can saw off the corner of the radiator pipe, then find a piece of scrapped hydraulic hose about 25cm long (with a braided steel mesh inside), and cut it out. The sawed parts are connected together and then clamped with clamps, which can effectively reduce resonance damage.

2 years ago | [YT] | 0

BW crane

Solution to the problem that XCMG QY16C crane cannot rotate

XCMG QY16C crane failed to rotate during hoisting. After inspection and repair, I started the engine and continuously stepped on the foot valve while operating the rotary valve. I found that sometimes it could still rotate and move. It was suspected that the foot valve was faulty. Start with the following inspection. After turning off the engine, remove the thin tube on the rotary motor. This thin tube is used to deliver hydraulic oil to the brake chamber of the rotary motor and is used to open the return spring to release the brake. Start the engine, operate the rotary valve back and forth, and when you step on the foot valve to brake, there should be no oil flowing out; when you release the foot valve, oil should come out quickly from the thin tube. The result is that no matter whether the foot valve is stepped on or not, there is no oil flowing out of the thin tube. It is suspected that the valve stem does not return to its position.



Troubleshooting: After removing the foot valve assembly and disassembling it, it was found that there was embroidery and a lot of impurities inside. It was analyzed that the spring was stuck or the impurities blocked the oil hole of the foot valve. After rust removal and impurities were removed, the car was installed and the rotation returned to normal. .

2 years ago | [YT] | 0

BW crane

Introduction to the safe use of W2000 milling machine

The W2000 milling machine is a highly automated special equipment produced in Germany for milling asphalt, asphalt-cement concrete and cement concrete pavements. Here are some issues that should be paid attention to during its use:

Since the overall size of the milling machine is large (14.8m in length and more than 5m in height), the machine will be damaged if care is not taken during operation, transfer, and transportation.

1. When shipping, if the trailer is short (about 9 meters), the conveyor frame can extend above the trailer cab. At this time, the conveyor frame must be supported by a bracket to prevent the frame from falling or vibration during walking to damage the hydraulic cylinder of the frame. and its connections. If the middle part of the frame is supported when supporting, it is best not to support the lower end on the tractor frame but on the trailer to prevent the conveyor frame from swinging at an angle of more than 45° when the tractor turns and damage the machine. On the contrary, when the trailer is longer (more than 12 meters), the frame head can be supported, and it can be supported on the tractor. When loading, pay attention to the climbing angle to be less than 12 to prevent the milling drum from hitting the trailer.

2 years ago | [YT] | 0