How to Mix Concrete in a Mixer

A portable concrete mixer provides an economical solution for do-it-yourself concrete projects. A mixer eliminates the need for backbreaking manual labor to mix up small batches of concrete. Both electric and gasoline-fueled mixers may be rented out by the hour or day. The equipment can be rolled right on site to build the slab for a garden shed or walkway.

Instructions

Roll the cement mixer onto level ground near the place the finished concrete will be spread. Lock the wheel brakes. Extend and lock the stabilizing legs (if the mixer has them) into place.Tip the barrel to the 45 degree up-angled position. Click the position lock into place.Dump bagged cement mix into the mixer barrel. Use one bag at a time unless otherwise permitted by the specific mixer instruction sheet. Add sand to the mixer barrel in the proportion listed on the cement bag.Plug the heavy-duty three-pronged electrical extension cord into the mixer plug receptacle. Plug the other end of the cord into a live electrical outlet. For gasoline-powered mixers, fill the mixer tank with gas and twist the gas cap tightly closed.Turn the mixer on to the lowest setting. Allow it to run until the sand and cement are well combined. Turn the mixer speed up to a medium setting. Pour in the volume of water indicated on the cement bag label. Use a bucket to add the water in a steady stream as the mixer continues turning.Switch the mixer off when all ingredients are completely combined. The mix should be slightly soupy without any dry clumps. Release the barrel lock and tip the concrete out into a wheelbarrow.Clean the mixer immediately before concrete machinery can harden on its surfaces. Unplug the equipment and then hose it off with a strong stream of water.

The Future of Cement Mixers

What the future holds for the concrete mixer is unclear. Like many industries, concrete is going "green." The manufacturers of volumetric concrete mixers say their products are more environmentally friendly because they save fuel by mixing materials at the construction site -- the trucks don't have to run their engines to keep the concrete from setting. In addition, truck operators can create only the amount of concrete needed to finish a job -- not only does this save materials, but this method also prevents dumping of excess concrete machinery.

Truck manufacturer Peterbilt is experimenting with compressed air "push" systems. The truck would be started using compressed air, and when it reached a certain speed, the diesel engine would kick in. Since an engine requires a larger amount of fuel to overcome inertia, getting it up to speed with relatively inexpensive compressed air would show fuel savings over time. This developing technology is now aimed at inner-city delivery trucks rather than larger trucks like mixers.
IVECO Trucks of Australia is working to perfect a compressed natural gas (CNG) engine for heavy truck use. The CNG trucks have comparable mileage, but release 40 percent less carbon dioxide than diesel and the natural gas is less expensive than diesel fuel. Like many of the new generation engine systems, CNG is paired with state-of-the-art electronics designed to get the most out of every tank of fuel.
For more on construction equipment and related technologies, get the concrete facts from the links on the next page.

Types of Cement Mixers

All mixers leverage power, torque and weight distribution to get the concrete to the site, but getting it out of the truck is where you'll see differences in truck designs.

Most of the mixer fleet, especially older batch model trucks, uses a simple tip-and-pour method to get the concrete out of the mixer. A chute attaches to a port and the concrete oozes (or pours, depending on its consistency) out of concrete mixer to the project. Usually, the driver of the truck operates the machinery and aims the chute. Many transit mixers are coupled to a hydraulic lift bed that can tip up the drum, similar to a dump truck, if needed.
Other trucks, many of them volumetric and the newer transit mixers, use a pump to move the concrete from the truck to the project. The pumps, usually reciprocating piston pumps, can be mounted on the front or the rear of the truck. Having the pump in front allows the driver to maneuver to a section of the work site and direct the concrete from inside the cab. The controls can be mechanical, electro-mechanical, hydraulic or purely electronic. Newer trucks are employing more on-board computers to monitor pumps and other components of the mixers.
Before the concrete is pumped or poured, a number of simpler machines act in concert to keep the concrete machinery from setting, and even mix the concrete at the site. Some of the older portions of the fleet, like early mixers, used paddles to stir the concrete and keep it from "settling out," or separating into its component pieces. This technology has been largely replaced by the use of augers and fins. Inside a traditional batch mixer is a concentric series of fins with a slight corkscrew pattern. The direction of the drum's spin squishes the wet concrete into the back of the mixer. When the mixer arrives at the site, the driver reverses the direction of the machine to push it out of the mixer to the chute. From there, gravity does the rest.
Volumetric mixers use augers to move concrete. These are similar to the blades in the batch mixer but smaller. Inside the mixer, an operator feeds data into the mixer and several augers feed aggregate and cement together. Water is added to the mix and larger augers blend the components.

How Cement Mixers Work

Most construction equipment is easy to understand. Cranes move things up and down. Dump trucks load up, move out and unload. Bulldozers push and graders grade. The one exception to this is the humble cement mixer, beloved by children, hated by in-a-hurry drivers, and misunderstood by most people outside the cab of the 30,000-pound (13,608-kilogram) behemoths.

While concrete has been around in one form or another since before the Romans built the Appian Way, the transit mixer is a child of the 20th century. But recent invention or not, the mixer is here to stay.

The misunderstanding begins with the name. What people refer to as a cement mixer is known in the construction industry as a concrete mixer and comes in a large number of types, sizes and configurations to handle the many tasks set before it each day. That need to fill so many roles means the machine is dynamic, changing shape and form as the needs of the people using concrete change as well.

In this article we'll examine some of the major types of mixers, from the traditional drum-shaped ready-mix transit mixer to the less-common but growing in popularity volumetric mixer, essentially a concrete plant on wheels. How cement mixers work and why they work the way they do is a fascinating combination of old and new technology. You'll never see a cement mixer the same way again.

But before we begin, let's clarify the difference between cement and concrete. In baking terms, the difference between concrete and cement is the difference between flour and a loaf of bread. Concrete is a generic term for a mix of aggregate -- usually stone or gravel, water and cement. Modern cement is a complex blend of finely ground minerals, and goes by the generic name of "portland." Concrete is made by combining the three ingredients in a mixer, whether that mixer is stationary or driving down the road, and the water is absorbed by the cement, which then binds the aggregate together, creating concrete.

Compulsory concrete mixer before starting aggregate screening mixing blade adjustment and routine maintenance of the whole machine

Forced concrete mixer before the repair work still needs to pay attention to power aggregate and a stirring blade after finishing

    Compulsory concrete mixer is often used in modern large-scale projects, do a variety of concrete mixing station mixing console, you can do stabilized soil mixing station mixing host. Compulsory mixer into a single horizontal axis compulsory concrete mixers and twin-shaft compulsory concrete mixer, high mixing efficiency, stir, good quality teaching version, discharge speed, small mixing blade speed, good wear resistance and less energy consumption. To ensure the normal operation of compulsory concrete mixer, power needs to pay attention to the following points after the inspection work is done:
(1) for concrete aggregate should be a rigorous screening, the maximum particle size must not exceed the allowable value, in case the card material. Join material mixing tube stirring each time, shall not exceed the capacity of the feed, in order to avoid power overload.
 (2) stirring and mixing tube gap bottom and side walls of the blade should always check compliance with requirements. When the gap exceeds the standard, it makes the cylinder wall and the cylinder bottom bonded residual material layer is too thick, increase cleaning difficult and reduce mixing efficiency, such as stirring blade wear, should adjust, repair or replacement.
Daily Care and Maintenance compulsory mixer
1, according to the mandatory use of concrete mixer periodic lubrication of the bearing components, gear box lubrication reference to its product description.
 2, regularly check the seals compulsory mixer found tainted slurry seals should be checked at the quality.
 3, always check the fastening shovel sheet, if loose should be tightened.
 4, always check the electrical control system is a good contact and dried.
 5, after long-term use mixer, shovel plate and the mixing tube to wear, adjust or replace wear.
 6, in the mixing process Never put your hands and the stick was inserted into the barrel to avoid danger.
    Above compulsory concrete mixer care and maintenance work can be understood as routine maintenance or a small seizure forced mixer, compulsory mixer of the inspection and general inspection work should be regularly quantitatively, and with professional inspection and maintenance teams!

Concrete Pump Tips

Concrete pump tips not only affect the efficiency of concrete pump, concrete pump, while more influence value, so workers can play a value of concrete pumps, to see whether the user can use reasonable skill of concrete pumps. So concrete pump tips contain what content?

1, the operator and associated equipment managers should read the instruction manual and grasp the structural principle, use and maintenance of the knowledge and pumping concrete; the use and operation of concrete pump, should be strictly in accordance with the instructions executed. Because the operator can fully grasp the mechanical properties of the need to have a process, it should be randomly alternate instruction manual. At the same time, should develop specific action points based on manual, to achieve effective control of pumping technology in some variables, such as the pump position, piping, etc.
2, the supporting concrete pumps ground should be flat, solid; machine required horizontal, not inclined during operation. Legs should be stably support machine, and securely locked or fixed. Position both easy to pump concrete mixer truck in and out of the hopper and feed, but also beneficial to consider pumping and piping to reduce the pumping pressure loss, and to ask from the pouring location near convenient power and water supply.
3, the pipe should be based on the characteristics of the construction site and concrete placement scheme, piping design to the level of checking whether the pipeline in terms of distance from the concrete pumps and pumping adapt. Piping should be as short as possible length of the pipeline, less elbow and hose. Delivery pipe laying pipelines should be easy to clean, troubleshooting, and disassembly and maintenance. When the new pipes and old pipe mix, should the new pipe installation in pumping pressure at large. Piping process should draw piping diagrams, lists a variety of pipe fittings, pipe card, elbow and hose size and number, and provide a list.
4, to be perpendicular to the pipe, increasing with increasing height that is potential, there is upward trend reflux concrete, and therefore should be laid horizontal pipe length between the concrete pump and vertical piping, in order to ensure sufficient resistance of concrete to prevent reflux . When pumping concrete high-rise buildings require vertical pipe up, at which time the ground level pipe length less than 1/4 the length of the vertical tube. When as a result of space limitations, can not be placed above the desired length of water pipe, can be bent pipe or hose instead.
I hope the above tips concrete pump can offer assistance in their work, often said that success depends on small details, for concrete pump, it is also applicable. We want to use to get closer to the actual work situation, to better serve the needs of the market in the future concrete pump.

Parts of a Tower Crane

The construction industry has the capabilities to build some impressive structures reaching ever-increasing heights. The work in building these utilizes a variety of construction equipment, with tower cranes typically providing the means to lift and move tools, materials and building parts around a site. The design of a tower crane includes a few different components.

Base

• The base of a tower crane typically has a steel unit, with this connected to a custom-built concrete pad. It provides the structure with stability, therefore needs to be well-designed and well-constructed.

Mast

• The mast provides a tower crane with its height, and comprises individual steel sections connected together. The number of sections determines the height of the crane, and a tower crane typically has a design which enables the mast to grow during construction by adding further sections. This ensures it has adequate height to safely and efficiently carry out the work required.

Slewing Unit/Top Climber

• A slewing unit sits at the top of the mas. This houses the motor and machinery which enables the crane to rotate. A top climber sits just below the slewing unit and this piece of equipment enables the mast to grow. The slewing unit disconnects from the mast, with hydraulic rams in the top climber raising it higher. On completion of this process, the crane can hoist and insert a new section of mast, with the slewing unit then reconnected.

Boom

• The boom is the working arm of a tower crane. Formed of individual steel sections connected together, it extends out from the top of the slewing unit parallel to the ground. A small trolley attached to the underside can run the length of the boom, and this holds the hoisting mechanism. The movement of the trolley, in combination with the rotation of the crane, enables accurate positioning for pick-up and set-down of loads.

Machinery Arm

• The machinery arm also extends out from the top of the slewing unit, in the opposite direction to the boom. Shorter in length and formed of steel sections, it houses machinery and electrics needed for the operation of the crane. Large counterweights on the machinery arm balance the weight of the boom and loads.

Chain and Hook

• The chain and hook sit below the small trolley on the boom. Raised and lowered by the hoisting mechanism, it picks up loads and places them in the required location.

Operating Cab

• The driver of a tower crane sits in the operating cab, which houses the controls needed to operate the equipment. Typically located on top of the slewing unit, it has enough space for one person to sit comfortably and use the controls. The cab has large windows fitted on front and sides to provide a good all-round view for safe operation.

How to Run a Concrete Mixer Truck

Cement mixers have completely changed the way cement is mixed. Long gone are the days of hand-mixing. Cementer mixers provide a quick, easy way to mix cement without the strain and hassle of hand-mixing.

Instructions

1. Get in the truck and start it up. Flip the switches on to begin the mixing process. Today's concrete mixer trucks have a drum in which the cement is mixed. The drum is rotated by a drive unit. There is a loading chute located at the top of the mixer. The ingredients will have to be added to the chute.
   
2. Pour the concrete into the chute and add the water using the same method. The ingredients to be mixed are funneled into the drum by way of the chute. In addition, there is a long chute that can be used to change the angle, depending on the position of the drum. There are also paddles located in the drum.
   
3. Get in the truck and set the drum of the truck to begin rotating. The drum contains blades that are set at an angle to the axis, located at the center of the drum. These blades run in a direction of longitude. There is a hydraulic gear that runs the main engine, thus rotating the drum. Because the drum is constantly rotating, the mixture of cement and water turns and rolls in the drum, coating the drum's surface.
   
4. Engage the truck's transmission to the drive position. Begin driving to your destination. The mixture will continue to turn and mix until the cement mixer reaches the desired destination. The paddles will then push the mixture toward the front of the drum so that the cement can be extracted when the time comes. When the mixer arrives at its intended location, the mixture will be ready to pour.
   
5. Park the truck next to the site where the concrete machinery will be poured.
   
6. Reverse the drum's rotation. Once this is done, the angle of the blades then push the cement toward the opening of the drum. It spills out of the drum and onto the chute. The chute can be pushed towards the intended site, and the concrete is then poured.

Become a Tower Crane Operator: Education and Career Roadmap

Do I Want to Be a Tower Crane Operator?

A tower crane is a piece of heavy-duty equipment that's used to transport large and oversized objects. As a tower crane operator, you'll maneuver these machines and check to make sure they function properly by moving levers and pushing pedals. You'll typically be working at construction sites, iron or steel mills or ports, which are hazardous by nature, and it's important to ensure that safety is maintained at all times. Full-time work is available, and sometimes you'll work long shifts and overtime hours in this field.

Job Requirements

Prospective tower crane operators need to complete a formal training program to gain experience in the field and prepare for employment. The National Commission for the Certification of Crane Operators (NCCCO) offers certification for tower crane operators. Additionally, a license may be required in some states and cities. The table below includes the requirements to become a tower crane operator.

Step 1: Complete a Heavy-Equipment Operator Program

Prospective tower crane operators can pursue either a heavy-equipment operator certificate, associate's degree or apprenticeship. These programs offer both academic coursework and field training. The goal is to teach students how to safely operate heavy equipment construction machines, read blue prints, identify machine parts and perform routine maintenance. Courses in a program will cover areas involving diesel engine systems, hydraulics for operators, operation of trenching equipment, construction safety management and powertrain and related systems.

Success Tips

• Focus on tower crane operation. While completing field training, focus on operating a tower crane. During a heavy-equipment operator training program, opportunities will be offered to work on a construction site and learn under an experienced tower crane operator. This is a chance to apply what was learned in the classroom to a real-world setting.
• Check the school's reputation. According to the U.S. Bureau of Labor Statistics (BLS), a vocational school program may help when job seeking. However, make sure the school has a good reputation among employers and find out if the school offers hands-on training on real machines.

Step 2: Earn Tower Crane Operator Certification

In order to earn certification, the NCCCO requires that candidates complete both written and practical exams. The written exam is 55 multiple-choice questions, and individuals have 60 minutes to complete the test. The practical exam ensures that operators are proficient in working with hammerhead, luffer and self-erecting cranes.

Step 3: Get Licensed

As of 2012, six cities and 18 states mandated that tower crane operators earn a license. In order to become licensed, a tower crane operator must meet the licensing requirements of the state in which they work. Requirements include an examination and a minimum amount of experience. However, it's important to note that NCCCO certification may fulfill the licensure requirement in some states.

How to operate after completion of compulsory concrete mixer

After the completion of compulsory concrete mixer should pay attention to what matters it?

conc

First, the work of staff in the use of the day after the forced mixer bulk cement tank should be completed using the gate closed, all shipped out within the cement spiral, not any residual cement in the tube. Wash thoroughly with mechanical and field.
Second, the concrete mixing drum compulsory concrete mixer Nene must be clean and clean. Maintenance of machinery maintenance, filling each smooth point lubricating oil, to the need to maintain some oiled rust.
Third, cleaning compulsory mixer various parts of slurry fouling. Stirred tank and machine cleaned surface dust, concrete and oil buildup to prevent concrete dry, keeping clean. After the production, to promptly stop the mixer thoroughly cleaned before the remnants of concrete, will stop all operations switch to the isolation position, and turn off all the power switch.
Some customers think that after the completion of compulsory concrete mixer just stop on the line, and had such a strong-minded is a mistake for the timely elimination of concrete mixers security risks, ensure mixer status intact, so after the suspension to an excellent maintenance, it will not often The emergence of some small problems.

Concrete boom pump strayed into "high zone" close to the mixer even burst two tires

Concrete boom pump in the air moving, accidentally close above the 220-kilovolt high-voltage wire, resulting in a concrete mixer and pump connected to two tires exploded near the ground by a shock of about 0.3 meters deep pit.

A physics teacher explained that due to a voltage of 220 kV high-voltage is very strong, when the conductor close to the wire, high-voltage arc release, the breakdown of air, the current conduction to the object. And when the object ground, they form a pathway. Air metal wheel between the hub and the tire rubber, because is energized, air is heated, the pressure increases, eventually causing a puncture.

Why lead electric pump, but it is a serious puncture mixer? In this regard, severalconstruction machinery workers at the scene of speculation, is being transferred between the two vehicles was concrete, the possibility of the presence of electricity.

Accident only individual wheel tire puncture or leak, and some of the tire has not been affected. Zeng wall ring analysis, water to flow, current is so easy to place a low flow resistance, blast resistance may occur several tire is slightly lower than the rest, so the flow of their current stronger. As for why their resistance will be relatively low, and the degree of wear, wet tire of these, whether glue metals and so on.

What are the working principle of the hydraulic piston type cement concrete pump

Piston pump foot concrete application of the first, most are also the most viable concrete conveying equipment. Press the Power TransmissionWay mechanical, hydraulic and a hydraulic three forms. Mechanical because the body is bulky, noisy, complex transmission toAnd can not pump anti-clogging when clear shortcomings, has basically been eliminated. Hydraulic type currently used not by much, but it has noPollution, water medium and low cost, with water as the working medium of the development and application of valve and other components, it will become the futureDirection of development. Now widely used is a hydraulic piston concrete pumps.Hydraulic piston pump is divided into single-casing concrete cylinder two. Cylinder type in a single-casing structure is far more complex, but because it is the work of two cylinders alternately, so work is relatively continuous smooth delivery, high productivity, the use of full engine power, so, medium and large concrete pumps-cylinder type a.Works (a) a hydraulic piston concrete pumpsHydraulic piston pump concrete through the pressure oil pushes the piston, the piston rod pushing through the concrete cylinders working piston pressure concrete. It works according to the different distribution valves and control methods are different, the main difference in reversing the realization of the action. The following S pipe valve concrete pump as an example how it works.

As shown in the picture above, concrete cylinder piston master cylinder, respectively, 7,8 l, 2 piston rod connected to the role of the master cylinder pressure oil reciprocates a cylinder advancing, the other cylinder back; concrete cylinders communicating with the hopper outlet, the dispensing valve 10 to one end of the discharge port, and the other end connected via a splined shaft and the swing arm 11, in the role of swing cylinders can swing around.
1,2 master cylinder tank 3- 4- commutation means 5,6 7,8 concrete concrete cylinder piston dispensing valve 11- 10- 9- hopper swing arm 12 and 13 cylinder 14- spoutPumping concrete under the influence of the master cylinder pressure oil. Concrete cylinder piston 7 advance, concrete cylinder piston 8 back, while in the role of swing cylinders, dispensing valve 10 communicates with the concrete cylinder 5. Concrete cylinder 6 communicates with the hopper 9.Back when concrete piston 8, 9 inside the concrete hopper suction concrete cylinder 6: concrete cylinder piston 7 advance concrete concrete cylinder 5 is fed to the dispensing valve 10 after discharge.When the concrete cylinder piston stroke back to the terminal, triggering tank 3 commutation device 4, the main liquid, cylinder l, 2 commutation, while the swing cylinder 12,1 3 commutation, the dispensing valve lO and concrete cylinder 6 Connectivity. Concrete cylinder 5 communicates with the hopper 9, then back concrete cylinder piston 7, 8 forward. This cycle, in order to achieve continuous pumping.When the concrete pump pipe blockage or downtime occurs, it must put the pipeline in concrete withdrawn. At this time anti-pump operation, so that in the suction stroke of concrete cylinder and a dispensing valve in communication with the hopper in the concrete cylinders communicating push stroke, thereby withdrawing the pipeline in concrete hopper, as shown in picture below.

Concrete Batching Plant summer maintenance three-Raiders

More rain this summer more frequently, but the dog days have already arrived, the hot and humid in the summer only to protect their own health, but also to maintain good concrete batching plant. Concrete batching plant next will accept a prolonged hot and wet Kaoshai tide, maintenance compared to the other seasons, concrete batching plant to get a better job, we have different ways to expand its maintenance methods, to want concrete equipment in the summer still affected the normal operation of'll have to do the following three steps Maintenance Guide:
Summer is the rainy season, so moisture is the first step: concrete batching plant and placed outdoors year round, so do the cleaning work mixing station, to ensure clean machinery around, no water produced in order to prevent the device surface of the concrete batching plant rust corrosion.

Summer is a hot season, so regular inspection is the second step: regular inspections of the various elements of concrete mixers and electrical overheating, whether they work in voice or instrument instruction anomaly is normal and so on, and if so, should be repaired immediately processed to prevent post-impact work.
Summer air while relatively dry, so the lubrication and maintenance is the third: To combat the hot, dry weather, extend the life of concrete equipment, must be the main lubricants used in the work, it needs to keep the oil level to the oil standard on-line, prohibit forced to work in a worry-free state.

Security control points tower crane

(1) Basic and concrete foundation must be designed tower crane track checking, before use of acceptance, built around the foundation should slope and drainage facilities, and maintain a safe distance from the pit.

(2) tower crane disassembly must be equipped with the following persons: holders of certificates of safety assessment project leader and head of security, mechanical management personnel; construction machinery of special operations have qualifications construction crane assembly and disassembly work, play heavy driver, lifting signal workers, rigging workers and other special operations operators.
(3) Working personnel should wear safety protection products, when high operating seatbelts, familiar and earnestly implement the dismantling process and procedures.
(4) Each member must check the hydraulic jacking system connections before lifting. Lifting prohibited swing arm and other job.
(5) After the tower crane installation, the overall technical inspection and adjustment, after a phased machine inspection and, before delivery. In the wireless load cases, vertical deviation of the tower and the ground shall not exceed 4/1000.
Reliable housing (6) metal structure tower crane, track and all electrical equipment should be reliable grounding device, grounding resistance should be greater than 4Ω, and the establishment of lightning protection devices.
(7) Before operation, the surrounding circumstances must work environment, with roads, overhead wires, buildings and component weight and distribution of the scene to conduct a comprehensive understanding. When the tower crane operation, shall be no obstruction in the tower crane boom pole landing and turning radius, and a safe distance from overhead transmission wires should be specified.
(8) tower crane commanding officers, the operator must be certified, the job should be strictly enforced signal commanding officers, such as confusion or error signal, the operator should be rejected.
(9) Before carrying tower crane slewing, luffing, walking and lifting hooks and other actions, the operator should check whether the power supply voltage 380V, the range of variation does not exceed + 20V / a lOV, before the power control switch should start at zero and shall indicate the song.
(10) The tower crane boom luffing limiter, walking limiter, torque limiter, height limiter hook and a variety of travel limit switches and other safety devices, must be safe complete, sensitive and reliable, can not be adjusted and dismantling . Non-limiting device instead of using the operating mechanism.
(11) shall not exceed the mechanical load tower crane and lifting objects of unknown quality. Must be used under special circumstances, it must go through checking, approved by the person in charge of enterprise technology, and to have someone on-site monitoring, but not more than 10% of limit load.
(12) when a sudden power failure, all controllers should immediately appropriated zero, disconnect the power switch, and take measures to secure the weight down to the ground, the air suspension after prolonged periods of heavy lifting.
(13) when lifting heavy banding smooth, firm, can not be hung or stacked objects scattered on the weight. Sporadic materials and articles must be secured in place by lashing back before lifting hoists or wire rope. Do not use tower crane were the oblique, oblique lifting and lifting an underground or heavy condensation on the ground.
(14) In case of 6 or higher winds or rain, snow, fog and other inclement weather, the outdoor tower crane operation should be stopped. When the job after the snow or rain or snow, take a test crane, rear brake operation can be carried out to confirm sensitive and reliable.
(15) reaches the rated lifting tower crane lifting loads of 90% or more by weight should be first lifted from the ground 20 ~ 50cm stop upgrading, check the following items: the crane's stability, reliability brakes, the weight smoothness, firmness banding.
(16) weight lifting and lowering speed to be uniform, non unsteadiness and sudden braking. Action to turn around smoothly, when the rotation is not completely stopped before the action shall not be repercussions. Non-gravity drop tower crane, non-load free fall.

How Are Cranes Removed From Sky Scrapers?

Crane Systems

• A crane is a pulley system used to move very heavy loads both vertically and horizontally. They are a vital part of skyscraper construction, because they are the only devices capable of moving up the heavy materials needed to construct machinery the upper stories. There are many different types of cranes, and different types may be involved in construction a skyscraper, from rotating jib cranes to pillar and gantry cranes. Sometimes the crane is placed on the top of the skyscraper and buildings underneath itself, but most often the crane is placed on top of a towering scaffold next to the building.
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Raising Cranes

• In either case, the question remains: how is the crane placed so that it can continually rise with the skyscraper, and how is the crane taken back down when the building is finished? The answers to both are deceivingly simple. Building the crane up is a relatively easy task accomplished mostly by the crane itself. The scaffolding or "mast" that the crane is supported on is built by the tower crane itself, level by level. Powerful hydraulic rams are then used to push the crane up another level (sometimes this is done first, and the new piece of mast is inserted underneath the crane. The crane then locks into place and does its work until it is ready to move up another level. Eventually, according to the type of crane and the weight and mass involved, workers will add stabilizers that connect the crane's scaffolding to the skyscraper itself, giving it needed support as it reaches the top of the building.

Removing Cranes

• When the skyscraper is done, the crane is quite literally dismantled, piece by piece. This happens several ways, depending on the type of crane, but most cranes are made to be easily taken apart. Usually the large crane will hoist up a smaller crane that is connected to the top of the skyscraper. This allows workers to detach pieces of the primary crane and slowly lower them back down to the ground. The mast itself and the base of the crane are lowered down by the same hydraulic rams that lifted them up, with each level of the mast being taken apart before the base is lowered.
  
  To remove the second crane, a third crane is often sent up, even smaller, to lower the pieces of the second crane down. This third crane is small enough to be taken apart by hand and removed through elevator shafts or other inner passageways, leaving the skyscraper intact and all the crane pieces disassembled on the ground. Sometimes cranes at the center of complicated skyscraper structures cannot be removed this way, and in those cases the pieces are taken away by powerful helicopters, although this is a much rarer method.