Monday, July 20, 2015

Ten Things to Know Before Purchasing an Overhead Crane

There are many things to know and understand prior to purchasing an overhead crane. Your purchase is typically to improve productivity and safety within your facility. Therefore you really need to take several things into account prior to your purchase. Lowest bid does not work in the crane industry. There are too many crane variations, safety requirements, and technological features available today that you will miss the boat on if you go with lowest bid. Not only that but you may get a crane that is not even suitable for your application. In the end you will spend too much money on a crane with specifications that are not required for your application. I have seen way too many times bids on overhead cranes that have specs way over what the application requires. This causes them to spend sometimes double the amount for a crane and it does not even fit their application. Before you invest your money into a new overhead crane, take into account these ten items that will not only save you money but you will invest in the best crane for your application.




This is the most important thing to know over anything else. Depending on the application could change many of the deciding factors on what kind of crane you will need. For example certain chemicals can make plastic brittle or accelerate metal corrosion. Cutting oils can make neoprene and PVC brittle. Heat and moisture can cause your motors to overheat. You will not pick the right crane without the crane company knowing what the application is.  Your crane will need to come with certain components depending on its application. To know your application you will need to know what you’re picking up, and the environment in which the crane will be used. Added components will be required for areas with heavy dust, humid, high or low temperatures, outdoor, indoor, chemical exposure, Light, and even altitude can affect the crane. Outside of the standard range, additional components will be required.
Look out for these items on your application.

·         Standard Altitude is Below 3280ft (Altitude can affect cooling of electronic components and not allow heat dissipation)
·         Standard Temperature Range is 32˚F to 104˚F
·         Standard Humidity is below 90%
·         Outdoor Applications will require features to prevent damage during rain, snow, ice, heat, wind, and ultraviolet radiation.
·         Corrosive  or Explosive Chemicals/ Fumes will require added features
·         Heavy dust environments from cutting will require protective added features
·         Heat can liquefy lubricants, and affect motors, and electrical components
·         Cold can freeze lubricants, crack plastic components, and electrical parts
·         Drastic temperature changes can cause condensation and short out electrical components and cause corrosion


2.      Duty Cycle
The crane’s duty cycle is going to depend partly on the application. If the crane is a production crane it will probably need a heavy duty cycle. If it is a maintenance crane or a crane used for shipping then the cycle may be shorter. You will need to ask yourself how often will this crane will get used every hour and how often will it be lifting near full capacity? Depending on this, different components will be used to make your crane. Electric motors have duty cycles and you want to make sure that your crane has the right motor for the job. Picking a severe duty motor for a light duty application will just cause you to spend well over what is required for the application.  
There are two standards crane manufacturers go by when picking out the right duty cycle. FEM and CMAA. CMAA is the Crane Manufacturers Association of America and FEM is Federal European De La Manutention. This is the standards for design and manufacturing internationally of overhead traveling cranes. Both specifications are written based on the input from the larger crane companies. The difference is that FEM is worldwide while CMAA is the United States only.  FEM will also separate each main part of the crane (hoist, trolley, and bridge) while CMAA specs classify the crane as a whole. To understand these classifications you will also need to understand what a lift or work cycle is. A work cycle is lifting the load, having a rest period where the trolley or bridge is moving, lowering the load, having a rest period again where the trolley or bridge may be moving, and then returning the hook to the starting position.

FEM Class Definitions
        
1Bm 
·         Light Loads less than two hours per day (Occasional full loads, Usually light load, Small fixed load)
·         Medium loads less than one hour per day ( Occasional full loads, usually light load, Average fixed load)
1Am 
·         Light Loads less than four hours per day (Occasional full loads, Usually light load, Small fixed load)
·         Medium loads less than two hours per day (Occasional full loads, usually light load, Average fixed load)
·         Heavy loads less than one hour per day (Repetitive full loads, Usually average load, Heavy fixed load)
2m 
·         Light loads less than eight hours per day (Occasional full loads, Usually light load, Small fixed load)
·         Medium Loads less than four hours per day (Occasional full loads, usually light load, Average fixed load)
·         Heavy loads less than two hours per day (Repetitive full loads, Usually average load, Heavy fixed load)
·         Very heavy loads less than one hour per day (usually almost full loads, Very heavy fixed load)
3m 
·         Light loads less than sixteen hours per day (Occasional full loads, Usually light load, Small fixed load)
·         Medium Loads less than eight hours per day (Occasional full loads, usually light load, Average fixed load)
·         Heavy loads less than four hours per day (Repetitive full loads, Usually average load, Heavy fixed load)
·         Very heavy loads less than two hours per day (usually almost full loads, Very heavy fixed load)
4m 
·         Medium Loads less than sixteen hours per day (Occasional full loads, usually light load, Average fixed load)
·         Heavy loads less than eight hours per day (Repetitive full loads, Usually average load, Heavy fixed load)
·         Very heavy loads less than four hours per day (usually almost full loads, Very heavy fixed load)
   5m
·         Heavy loads continuous use per day (Repetitive full loads, Usually average load, Heavy fixed load)
·         Very heavy loads continuous use per day (usually almost full loads, Very heavy fixed load)

CMAA  Class Definitions
This service class covers cranes which may be used in installations such as power houses, public utilities, turbine rooms, motor rooms and transformer stations where precise handling of equipment at slow speeds with long, idle periods between lifts are required. Capacity loads may be handled for initial installation of equipment and for infrequent maintenance.
This service covers cranes which may be used in repair shops, light assembly operations, service buildings, light warehousing, etc. where service requirements are light and the speed is slow. Loads may vary from no load to occasional full rated loads with two to five lifts per hour, averaging ten feet per lift.
This service covers cranes which may be used in machine shops or paper mill machine rooms, etc., where service requirements are moderate. In this type of service the crane will handle loads which average 50 percent of the rated capacity with 5 to 10 lifts per hour, averaging 15 feet, not over 50 percent of the lift at rated capacity.
This service covers cranes which may be used in heavy machine shops, foundries, fabricating plants, steel warehouses, container yards, lumber mills, etc., and standard duty bucket and magnet operations where heavy duty production is required. In this type of service, loads approaching 50 percent of the rated capacity will be handled constantly during the working period. High speeds are desirable for this type of service with 10 to 20 lifts per hour averaging 15 feet, not over 65 percent of the lifts at rated capacity.
This type of service requires a crane capable of handling loads approaching a rated capacity throughout its life. Applications may include magnet, bucket, magnet/bucket combination cranes for scrap yards, cement mills, lumber mills, fertilizer plants, container handling, etc., with twenty or more lifts per hour at or near the rated capacity.
This type of service requires a crane capable of handling loads approaching rated capacity continuously under severe service conditions throughout its life. Applications may include custom designed specialty cranes essential to performing the critical work tasks affecting the total production facility. These cranes must provide the highest reliability with special attention to ease of maintenance features.



3.      Capacity
Picking the right capacity is very important to not only picking the right duty cycle but also extending the life of your crane.  For example you may have a product that weighs 10 tons. However, do you have other product that the crane will be picking up that weighs less than 10 tons? It may be more ideal to increase the capacity of the crane to 15 tons and keeps a Class C rating instead of increasing the rating to Class D.  A ten ton crane may be your best option as well if most of what you are picking up on weighs five tons. It all depends on the loads and they need to be taken into consideration not just the largest weight requirements. You should also think about any below the hook requirements that may be needed to pick up your product. Sometimes the below the hook device can weight several tons. This will have a great impact on the crane requirements.



I would say that out of these ten things to consider, speeds is what gets missed the most. Typically the standard speeds will work for most applications, there still are some applications where you will need faster or slower speeds. Depending on the capacity the hoist speed will vary but your bridge and trolley speeds are fairly close regardless of speeds. A typical bridge speed is around 100 fpm, a trolley speed is around 70 fpm, and the hoist is between 30-60 fpm depending on capacity. Depending on the application you may need higher speeds. If you have a crane that is feeding your facility with raw material or loading the finished product such as rebar you may need a high speed crane that would not come with the standard features. The last thing you want is to purchase a crane to increase production and find out that the crane operates too slowly. You may also have an application where you need to utilize the crane for assembling a product. This often requires precise lifting and very slow speeds. If you purchase a standard crane the speeds will be too fast for this application making the load jerky and you will not be able to assemble your product using the crane. Take the time to discuss the required speeds with your crane company.
 



You will also need to know any safety issues for the application that may exist for the crane operator. Perhaps radio control will be required, or a cab, perhaps even automation. Depending on what the operator is exposed to you may need something other than pendant control.  Lighting may also be something you need to think about. If your crane is large it may cover much of the overhead lighting. Often lights will be provided on the crane to help the operator and workers see when it is blocking the overhead lights. You may also need a cab control if you have chosen high speeds for your crane.  Can the operator keep up with the trolley and bridge speeds safely by walking? If not then you should add cab control to the crane.

When considering your crane control, think about..
·         Chemical Exposure
·         High or Cold Temperatures
·         Explosive Fumes
·         Lighting
·         Walking Hazards
·         Crane Speeds


6.      Area Coverage
Another factor to consider is where in the crane area do you need to reach with the load hook? This is called your hook approach. The hook approach end is the minimum horizontal distance that is parallel to the runway and goes from the centerline of the hook to the centerline of the runway.  The hook approach side is the minimum horizontal distance, perpendicular to the runway between the centerline of a hook and the centerline of the runway rail. You will need to know how much coverage your process or application will require prior to getting crane pricing. A crane consultant or crane provider can help with acquiring this information.
a.      Building Clearances for hook approach
·   Center of runway rail to face of building column or side obstruction
·   Approximate length of runway
·   Number of Cranes on runway
·   Runway conductor location
·   Below the hook dimensions



Depending on whether you are installing a new system or a new crane on an existing system you will need different information.  Your lifting requirements will be restricted based on the height and design of your existing building. If you have an existing runway you will have even greater restrictions. To get crane pricing you will need some preliminary information.

a.      Building Clearances for existing runway
·   Floor to Top of Runway Rail
·   Top of runway rail to lowest overhead obstruction
·   Runway rail size
·   Below the hook dimensions

b.      Building Clearances for new system
·   Available dimension from floor to nearest ceiling obstruction
·   Height of product being lifted
·   Below the hook equipment dimensions




8.      Technology Features
Another item to look at when getting crane pricing is the features that your crane will come with. Many people overlook these and look at price alone. However, these features can greatly increase your production and is well worth the investment. Unlike the automotive industry or any other for that matter, you can still purchase cranes today with decade old technology. This would be the worst investment you could do for your company. With the latest technology available you can increase your production and at the same time make your facility safer for your employees. Certain technology you should never purchase a crane without. Always ensure your crane comes with variable frequency drive for the crane and trolley motions. This will ensure safe operation of your crane and will help in reducing load swings. Radio controls also help keep your operators away from the load. This is typically an option and is never quoted unless requested. However this allows your operators to stand away from the load. The cost to add this on a new crane is minimal and well worth the extra cost. Another important considerations to think about when you are reviewing your crane’s technology is real time analysis of your crane’s operation. This is currently limited in the crane industry but is readily available with certain manufacturers. Find a manufacturer that will provide at least 6 month monitoring service for free so you can see how this will benefit your facility. There are many other features that can be added to your crane today. All are designed to improve your productivity or make your crane safer to operate. Features such as sway control, inching, microspeed, slack rope prevention, load floating, hook centering, follow me, hoist synchronization, extended and adaptive speed ranges, and shock load prevention, are available and may greatly benefit your application. Talk to a consultant or your crane provider for these options.


9.      Warranty



When reviewing your quotes you want to take into consideration your warranty. Not all warranties are created equal. Key things to look for with your crane’s warranty is the following..

·   How long is your warranty?
·   Does it include labor?
·   What doesn’t it cover?
·   Is there a local service group that can deal with warranty issues?




10.  Service
Your crane purchase does not end with the crane installation. During the life of the crane it will require servicing and sometimes warranty issues. There will also be a need for crane inspections to meet local regulations and ensure your crane is operating safely and efficiently.  You will also be in the need of training your operators on your new equipment.  When reviewing crane proposals ask about their service to ensure they have someone local to meet your needs.
                Make you ask yourself these questions  
  • Ensure that whoever you’re purchasing your crane from they are a turn key supplier. They will provide everything needed to get your crane installed and up and running, including crane commissioning by the manufacturer, and even shipping of the crane.
  • Is your quote all inclusive? With the exception of local taxes and certain instances with local permitting it should cover everything.
  • Are you purchasing from the manufacturer or a distributer?
  • Who will be handling any warranty issues? The manufacturer or distributor?  Are they local?
  • Is there a local manufacturer representative that can provide training on my new equipment?
  • Can the manufacturer of my crane provide periodic inspections on their equipment? 






If you review these 10 items prior to purchasing or getting a quote for your next overhead crane you will be one step ahead and on the right track to making the best decision for your company. You can always send me an email or give me a call and I would be happy to consult with you on your next overhead crane project. 


               



Works Cited
CMAA Specification 70



11 comments:

  1. Replies
    1. Solid questions that one need to know prior to purchasing an overhead crane.

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