Overhead Cranes and Load Brakes... Why You Don't Need One!

 Since I have been selling and consulting with customers on overhead bridge cranes, I have received several quote request for hoist with load brakes. Mostly these are government or military specifications, but also a few private companies request the same. There are only three reasons why this would be listed in someone’s specifications today. One, it is the same spec they have used for decades so the easiest decision for those that know little about cranes to just continue with this decades old specification. Two, someone actually believes that is a requirement set by CMAA or other governing body. Or three, they honestly believe they are getting a safer more reliable crane with a load brake Well… all three are wrong and I will explain why.

First off you need to understand what the load brake is for. The mechanical load brake controls the speeds when lowering the load, and helps to hold the load when the motor is not running. The holding brake actually works together with the holding brake. The Weston Style brake only holds approximately 25 to 30% of the load while the holding brake does the rest.This is really what the load brake is for but I honestly don't feel that is why you see in many government specifications.  You can check out my more popular post Mechanical Load Brake Operation and Inspection. Here you will get a basic introduction to the load brake and learn about a few misconceptions about it.

Most hoist today do not have mechanical load braking technology in them. This is because it is outdated and does not fit the technology of our electric motors today.  A load brake does not make your crane safer. Many manufacturers who used to have load brakes in their equipment stopped decades ago. Yet, here we are still with new specifications requesting load brakes. The load brake was designed to control the load in it’s decent. In an emergency it should hold the load as well. This form of technology worked great back when all the hoist motors were wound rotor. A wound rotor motor cannot stop acceleration of the load from gravity. Therefore, load brakes were required for hoist and you certainly wouldn’t want to use a hoist without it. Today’s technology uses Squirrel Cage Motors. See video below for a two minute introduction. Squirrel cage motors are fully capable of regenerative braking. This technology meets all CMAA Spec 70 requirements. 

What about Variable Drives? Not only are load brakes not required with today’s technology, today’s technology does not work with load brake hoists.  If your hoist has a load brake you can forget about variable drives. You cannot get the speeds accuracy in a load brake hoist. Variable drives do not work with load brake hoist. You will have constant issues with your load brake and will become a safety and efficiency issue. If you need speed control on your hoist, and you have a load brake hoist, you will be out of luck.

So why do we need load brakes in all these government and military specs? If you ask me,.. I think it is a complete waste of money to invest in such outdated technology. It would be like going to Ford and asking them to remove power steering because you feel it would be more reliable without it. Just makes no sense. Don’t forget all the cost that is associated with your load brake hoist. That baby will need to be opened up at least every four years to verify the load brake is functioning properly, and re-adjust the air gap. The load brake is buried in your gear case; it is a very costly inspection. The brake works off of friction so it has pads or liners that wear causing it to need replacement periodically. Typically, it is best just to change them out during the inspection anyways. The labor to change them is more expensive than the liners so it is the perfect time. Your oil in the gear case will also be contaminated with the lining wear and dissipated heat from the load brake which will also affect your entire gearing in your gear box reducing the life of those gears.

Let’s also not forget that when you have high capacity cranes, or in process cranes you do not want a load brake. They create a lot of heat when stopping a load so it is very impractical for a process crane. This would also apply to any crane that would require a permanent below the hook device. If a below the hook device is connected to the load block permanently, the load brake is going to seize up causing costly downtime and repairs.

Today’s motor themselves are the secondary control braking function that is required by OSHA. Because people don’t really understand this process they disregard it altogether. The squirrel-cage motor functions using regenerative braking if the load tries to pull faster than the motors rated speed. Regenerative braking does not generate a lot of heat so it is a safer application for large capacity cranes and process cranes. 

Hopefully in the near future we will start to see the industry change to where there will be no more request for outdated technology.  It all starts with the best overhead crane companies training their customer's about the latest safety features available for their crane. You will get the safest cranes on the market using today's technology. 

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.

1.      Know 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

CLASS A (STANDBY OR INFREQUENT SERVICE)

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.

CLASS B (LIGHT SERVICE)

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.

CLASS C (MODERATE SERVICE)

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.

CLASS D (HEAVY SERVICE)

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.

CLASS E (SEVERE SERVICE)

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.

CLASS F (CONTINUOUS SEVERE SERVICE)

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.

4.      Speed

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.

 

5.      Safety Issues

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

7.      Lift Height Requirements

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

http://www.konecranesusa.com/resources/industrial-crane-terminology/girder-bridge-messenger-track

CMAA Specification 70

Do You Have Crane Tracking Problems?

Is your crane running straight? If it is not what are the consequences? Many people don’t realize the damage abnormal tracking can cause to your crane and your runway. Bad tracking can result in premature wear of your bridge crane wheels, bearings, runway rail,  and cause crane binding or racking, bridge drive breakage, or even causing broken couplings, gearing, and axles. I have seen time and time again where people will just fix these broken components instead of trying to find the cause of the breakage or excessive wear. People will change a bridge wheel and bearings just to find in a year or two later they have to invest in yet again another set of wheels and bearings. If you’re having excessive wear on your wheels or rail, or you are finding yourself replacing bridge couplings, and axles then this could be caused by abnormal tracking. There are several causes of abnormal tracking and finding these issues is becoming easier with new technology.

Crane Rail Alignment Requirements

In order to have correct tracking the runway and bridge system has to be within CMAA Spec 70 tolerances which requires the system to be square. The runway rail must be straight and parallel, and they must also be the same elevation the entire length of the runway. Depending on the span of the bridge the allowable tolerances will change.

•       The distance center to center of rails must be within +- 1/8”
•       The level of the runway rails should be within +- 1/8” of each other at all opposite points
•       The elevation of each rail along its length must be level within +- 1/8”    

Elevation

During the data collecting many crane companies fail to check the elevation of the runway and concentrate on the rail span. Although the rail span is vital for proper tracking elevation is just as important. Elevation problems can cause your tracking to be off center. One possible identifier in elevation issues is when one endtruck is centered straight on the rail and the opposite end truck is off center and against the wheel flange. If your elevation is off you will see premature wheel flange wear, and rail wear. 

Other Crane Tracking Issues

Just because you are having what appears to be tracking issues it is important to rule out certain crane problems prior to analyzing your runway. This could save you a whole lot of time and money if these issues are checked first. There are several crane issues that could cause abnormal tracking that is unrelated to your runway or bridge squareness including the following which should be verified before performing major runway alignment or repair.

•        Different diameter bridge wheels
•       Bent end trucks 
•       Bridge brakes not releasing simultaneously
•       Bad bridge bearings
•       Bad bridge couplings
•       Different RPMs on drive wheels
•       Different torque values on drive motors
•       Out of square bridge wheels

Crane Damage From Poor Alignment

Once these have been verified to not be the issue then we can focus on the runway. If the runway is the issue it is vital to correct the issue as soon as possible. Delaying repair can result in extensive crane issues that will not go away by just replacing the broken component. Your investment will be wasted in useless repairs that will only keep your crane running for a short period. Without the corrective action you will be causing your crane…

• Wheel Flange Wear
•  Railhead Wear
•  Bearing Damage
•  Coupling Damage
•   Axle Damage
•  Gearing Damage
•  Crane Racking and binding

10 Questions to Ask Your Crane Service Provider

There are several ways to fix runways that are out of alignment. However, to do the repair properly you really need to know exactly where the problem is and to what extent of repair is required. The solution of a cost effective repair is only going to be viable if you have an accurate reading of the dimensions of the entire length of runway including the runway area where no repair is required. This enables you to find the best solution for the runway repairs. This typically is a large investment so you want to make sure you have the right vendor finding out exactly where the runway and rail is off and how to correct it. When deciding on a vendor for your crane runway analysis you want to ask the following ten questions…

•         How will you be data collecting?
•        How accurate is your data collecting?
•         How long will my crane be down during the data collection?
•        What qualifies your team to collect the runway data?
•         How will I get my results?
•        Will I get any kind of report?
•        Who analyzes the data?
•         How do you decide what needs repair once the analysis is completed?
•        How long does this process take? 
•        How will you get to all the runway areas to take accurate measurements?
• 
  

     

     
 Once you have asked these questions and have asked more than one vendor, compare them and pick the one you are most comfortable with. Be sure one of the vendors you call is Konecranes. Konecranes has a state of the art runway survey called RailQ. This survey is the most accurate I have ever seen on the market. A robot called Roborail travels the length of your runway collecting data of the span and elevation throughout the length of the runway rail. It is a very fast way to collect all the required data reducing your downtime and no personnel has to walk the rail making it very safe to perform. The data is analyzed by engineers and the reports are in 3D giving you an easy understanding of your runway issues. The additional benefit is that this program will find the best solution to fix the runway reducing your overall repair cost. Find a nearest Konecranes and check out the newest technology on the market.