Transport Equipment (ll) - Cranes

The next handling equipment that facilitates transportation we are going to touch on is Cranes.

What is cranes?

In definition, Crane is a machine for hoisting and moving heavy objects by means of cables attached to a movable boom.

Jib crane, bridge crane, gantry cane, stacker crane are the different types of cranes available in the industry and they all have different uses. It is very important to understand the types of lifting systems available and how they differ from each other when deciding on what types of cranes to use.

Therefore we need to ask questions like:

• What am I actually doing with the system? For example, will it be used to move expensive tools into/out of a molding machine or to load/unload steel from trucks?


• How can a crane increase the safety of the loads being lifted?


• How can a crane improve my workers' safety in handling the loads?


• How frequently will it be used each shift?


• How will the load need to be moved and located?
  
• How easy is it to move the system to a new location in my factory?


• Do I really need three axes of hook movement (e.g., up/down, left/right, and forward/back) or will only two be sufficient?


• How heavy are the loads to be lifted?


• How much money should I invest in a system?
  

Crane Safety

Construction crane safety is also a very important issue to take into consideration. The Division of Occupational Safety and Health (DOSH) held a share holder meetings on October 29th through November 5th to gather feedback on the Construction Crane Certification and Operator Qualifications and Experience drafts.

The following article is on new crane safety law in US:

Last updated October 19, 2007 9:33 p.m. PT
L&I looks to public on new crane safety law
Comments can help agency work out the detail
By ANDREA JAMESP-I REPORTER

A tough new law passed earlier this year is designed to give some peace of mind to people who live and work near the looming construction tower cranes dotting Western Washington's skylines.

But the specifics -- just how the safety law will be carried out -- are still being written by the state Department of Labor and Industries.

By the end of this month, L&I plans to have completed its first draft of the rule, spokeswoman Elaine Fischer said. The department will gather comments on the draft in a series of meetings statewide from Oct. 29 through Nov. 5.

The construction industry already voiced its concerns and opinions in a round of meetings in July.

"The biggest issue for discussion was probably the number of operator hours that should be required for operator certification on different types of cranes," Fischer said.

To be considered qualified, according to the law, a crane operator must have up to 2,000 hours of experience -- a maximum that has been challenged by many in the industry as unworkable.

Legislators enacted the law in the wake of several alarming crane incidents late last year. After a 210-foot-high crane collapsed in downtown Bellevue, killing a man in his nearby apartment and severely damaging three buildings, structural problems were found in several more cranes operating in the Seattle area.

A six-month L&I investigation found that the collapsed crane's steel base was to blame. Tower cranes, which are used for construction on skyscrapers, are normally installed in concrete. The Seattle engineering firm that designed the foundation, Magnusson Klemencic Associates, was fined $5,600.

Lease Crutcher Lewis, the general contractor at the Tower 333 site, where the crane fell, was fined $9,200. Both firms are named in a lawsuit filed by the family of the deceased.
Under the new law, which takes effect Jan. 1, 2010, the state will play a much bigger role in ensuring that tower cranes are being operated properly and are secure in their foundations. Under the old rules -- criticized for being lax -- responsibility for safety fell mostly to construction companies.

In the upcoming meetings, L&I will take suggestions in two areas: how crane inspectors should be certified, and what qualifications should be needed to become a crane operator.

"There's a lot of different kinds of cranes and a lot of people that want to weigh in on that," Fischer said. "We're starting from scratch here in our state developing rules in this industry. We have to involve people in the industry that know how things operate."

Developers will have to contract with a certified crane inspector to certify their cranes. That means that the cranes, its inspectors and its operators must all be certified.

The crane inspector rule will likely operate similar to sister rules regarding amusement ride inspectors and maritime crane inspectors, she said.

The law also requires that an independent professional engineer stamp approval on any "non-standard" tower crane base.

P-I reporter Andrea James can be reached at 206-448-8124 or andreajames@seattlepi.com.


Therefore, we can see that general safety rules is also taken into serious considerations. Some of the rules operators shall comply when operating cranes and even hoist are:

• Do not engage in any practice that will divert your attention while operating the crane.
• Respond to signals only from the person who is directing the lift, or any appointed signal person. Obey a stop signal at all times, no matter who gives it.
• Do not move a load over people. People shall not be placed in jeopardy by being under a suspended load. Also, do not work under a suspended load unless the load is supported by blocks, jacks, or a solid footing that will safely support the entire weight. Have a crane or hoist operator remain at the controls or lock open and tag the main electrical disconnect switch.
• Ensure that the rated load capacity of a crane's bridge, individual hoist, or any sling or fitting is not exceeded. Know the weight of the object being lifted or use a dynamometer or load cell to determine the weight.
• Check that all controls are in the OFF position before closing the main-line disconnect switch.
• If spring-loaded reels are provided to lift pendants clear off the work area, ease the pendant up into the stop to prevent damaging the wire.
• Avoid side pulls. These can cause the hoist rope to slip out of the drum groove, damaging the rope or destabilizing the crane.
• To prevent shock loading, avoid sudden stops or starts. Shock loading can occur when a suspended load is accelerated or decelerated, and can overload the crane or hoist. When completing an upward or downward motion, ease the load slowly to a stop.

Jib crane, Bridge crane, Gantry crane, Stacker crane are some of the different types of crane available.

Jib Cranes

Jib crane is a crane having an arm guyed at a fixed angle to the head of a rotating mast and it consists of a pivoting head and boom assembly which carries a hoist and trolley unit. The pivoting head is supported either by a floor-mounted mast providing 360 degree boom rotation or by an existing building column which provides 180 degrees of boom rotation.

Advantages of Jib cranes :

The advantage is the strength, stability and flexibility of the device. It is ideal for lifting a product to or from one material handling system to a work station or machine. It should be a repetitive process.

Another advantage is that jib crane is commonly used for workstation and simple loading / unloading operations where it is not necessary to spot a load precisely. Also, Jib cranes most often handle lighter loads at lower duty cycles than their bridge and gantry crane counterparts.

Disadvantages of Jib crane :

The major disadvantage is that it is stationary and cannot be moved easily from one work area to another. It is designed for positioning a work piece or tool, rather than for moving a product along in the work flow like an overhead crane.

It is also unsuitable to use when there is a need for precise locating of heavy loads, a large area of hook coverage, or frequent use for heavy loads. Another disadvantage is that the hook coverage is limited to the boom length (typically a maximum of 20 ft). The hook operates along a boom which rotates about a fixed point.

Bridge Crane

A bridge crane runs on an elevated runway system along the length of a factory and provides three axis of hook motion (X, Y, and Z). The hoist moves the load up and down, the trolley moves the load right and left, and the bridge of the crane moves the load forward and backward. Both single and double girder overhead traveling bridge crane designs allow very precise hook positioning and gentle load placement.

Advantages of bridge crane :

• greatest flexibility for hook coverage and control over the load fewest number of physical obstructions on your factory floor
• no interference with the work on the floor
• reduced aisle space requirements, easy access to most areas within the lifting bay
• extension to areas outside the building.

Disadvantages of bridge crane :

Problems encountered like:

• Crane travelling too far before stopping.

It is likely that it uses electric motor brakes and that, like most cranes, the brake pads haven't been replaced (they require replacing or adjusting every 3 months).

• Bearings wearing out too soon.
• Contactor problems.
• Broken push button pendant or cable.
• Parts availability problems.
• Brakes wearing out or not working properly.

Please enjoy the following video from North American Industries

http://www.naicranes.com/gallery/vidgallery.htm