Increase coupling performance while reducing time, money and enviromental waste

The paper industry continues to be a large, lucrative industry in the world today, rolling out hundreds of thousands of tons of paper each year from individual plants.  The industry incorporates quite a few technologies in the production of paper.  Each of these areas is critical to maintaining a clean and smooth paper production process.

The pain

One pain area for many pulp and paper companies has always been the paper mill pump house.   A pump house is a centralized location where the electrical motors and pumps are located. Most of the fluids used in paper production are pumped through this central location.

Generally, for of ease of maintenance, the motors and pumps are spaced apart to allow easier access to pump seals, pumps and motor bearings, etc.  It is a common practice for the paper mill to shut down for a few days each year for annual inspections of all the equipment, including connecting couplings.  If needed, the equipment or couplings are serviced and/or replaced during this shutdown. For many years, the couplings used to connect the motors and pumps have been floating shaft gear couplings.

Some of the concerns voiced by the maintenance teams at these paper mills when servicing gear couplings are: 

The messiness and waste: When the couplings are disassembled for maintenance reasons, there is usually a large amount of grease to contend with, sometimes gallons.  This grease in not easy to handle and there is always the eventual issue of how to dispose of the used grease. 

Difficulties with hubs and sleeves inspection: The hubs and sleeves need to be cleaned to inspect the gear teeth.  If the lubrication has started to breakdown, it can be difficult to get residue out from between the gear teeth in the coupling, especially the sleeve where access can be difficult.  Depending on wear, the seals may need to be replaced.  It is common for the hubs and sleeves to be replaced if the amount of wear exceeds normal levels. 

Downtime to re-install couplings: When the coupling is reinstalled, new grease needs to be loaded into the coupling(s) and alignment checked.  This process has been known to take anywhere from an hour to as long as a day to complete.  If components need to be replaced, this service could run into days (plural). 

Moist environment: Another important is that these pump houses are usually very wet environments and rust is often a serious issue that can lead to premature failures when using the floating shaft gear couplings.

A versatile solution

To assist the paper industry with resolving this maintenance concern, a versatile disc coupling (such as the Lovejoy DIR Coupling) is used nowadays to replace the floating shaft assemblies in the existing gear couplings.  This versatile disc coupling can have a fixed floating shaft length, or when used with an external shaft locking device, it can vary in length (up to a couple of inches). These couplings can be designed to accommodate the high torque capacities of the gear couplings.

Unique features – easy access, easy inspection and quick replacement

These versatile disc couplings are popular because of the ease of access to the flexible member of the coupling, or the stainless steel disc packs, and the ability to inspect the disc packs without disassembly of the coupling.  The disc packs are clearly visible in disc couplings and can be inspected for wear, misalignment issues, or breakage with the coupling either stationary, or in operation. 

With the use of a safety shield and strobe light, you can inspect the coupling without shutting down the equipment.  If one of the disc packs show signs of wear or breakage, it can be easily removed by undoing the bolts that hold the disc pack in place, slide in a new disc pack, and replace the bolts.  Since the disc coupling does not require grease, there is no issue with disposal and replacement of grease when performing inspections.  For concerns with buildups of rust in humid or wet environments, Electroless Nickel plating is an available to mitigate this rust problems with the couplings.

Lasting benefits

Essentially, the time (hours or days) it took to inspect and service a coupling is decreased to a fraction of that time.  This huge saving makes up for the difference in the cost of the technology.
How about lasting effects to the environment?  Since the disc coupling does not require grease, there is no issue with grease waste; hence, there is not any need for disposal or replacement. This action in itself will help cut down environmental contamination footprint. 

A good case to demonstrate both benefits is a naval project completed not too long ago: maintaining 15,000 surface ship pump applications. Sailors spent 29 Sailor-days per year per pump repairing and replacing mechanical seals, couplings, and bearings.  Also, the yearly grease waste output was about 3 pounds per pump.   Let’s do some math: 3x15,000 = 45,000 pounds of waste or about 22 tons a year … that is a lot of oozing grease.  Once these versatile couplings were installed, time was cut down to a savings of 1700 sailor years and waste footprint was reduce considerably.

Reduce Operator and Machine Fatigue on Farm Equipment

Vibration and noise levels (among many others) are some of the reasons for operator fatigue.  Reducing any decibels of noise in any way can be of great help for a combine operator.

No too long ago, we were involved in a particular farm equipment engineering challenge – improve reliability, decrease downtime and increase the performance of a combine harvester.

Across the United States (and many parts of the world), farmers battle time and weather conditions to harvest their crops at their peak maturity and moisture. With more than 70 million acres to harvest in the U.S., a reliable and continuous harvesting operation makes a big difference in both yield and profit.

In the case of vine or bean crops, harvesting or combining is the most costly operation of crop production. Any adjustment to the harvesting equipment literally can make or break a farmer’s bank account because of the fluctuation of dollars per bushel harvested at its peak efficiency (or not).

Actual Install

Improving one of the key components of a combine harvester, the mechanical reel, was the focus of the engineering challenge. The traditional U-Joint attachment that connected the drive to the gear box was a constant problem for the wind reel. A broken wind reel meant downtime for the combine harvester, which in turn translated to the loss of crop and loss of money. The ingenuity happened here when a SU132-6 hub and SU132-6 Disc Pack from Lovejoy, was mounted to a flange plate then bolted to an existing gear box sheave.

The metal disk coupling properties, zero backlash and powerful hold, allow instant reaction to turn the shaft and instant stream flow.  In other words, this disc coupling is practically maintenance free, reducing downtime. In addition, the secure hold provided by this metal coupling reduces both vibration and noise levels in the cab, to help reduce operator fatigue.

Best Way to Install Your Coupling

In this particular case, the picture really is worth a thousand words. Obviously what is depicted in the picture on the left would be something extreme that most reputable business will not do -  at least we hope is not the case in your own situation.

For proper coupling installation procedures that will look more like the picture on the right, Lovejoy recommends you follow your manufacturer's installation instructions. The installation procedure usually comes in a detailed step-by-step guideline (generally in PDF or print form). For warranty related aspects and to avoid any major problems related to improper coupling installation, you must follow your manufacturer's guidelines.

However, if you need some further knowledge or additional tips on coupling installation, you may consider watching Lovejoy's installation videos on couplings.com. Lovejoy has an excellent library of over 20 installation videos, where you can see the step-by-step details of proper ways to install your coupling. Our coupling videos will visually show you all the needed parts and tools for a successful installation. Additionally, all the coupling installation steps are clearly explained, in an easy to follow format, with visual aids and voice narration.

While these videos are specific to Lovejoy products (jaw, curved jaw, grid, disc, etc.), many of the concepts and principles pictured are broadly applicable to coupling installations in general, and could prove as a worthwhile reference relative to the coupling you are looking to install.

Again, our videos are a great aid to help you get some additional pointers on installing your flexible coupling (be it a jaw, gear, grid, disc... whatever). But Lovejoy certainly does not warranty or formally endorse using Lovejoy installation videos for non-Lovejoy couplings as the basis of your installation... use the manufacturer's provided guidelines.

Our videos are widely watched by people in different job functions such as engineering, maintenance, etc., servicing a variety of equipment like steam turbines, gensets, pumps, crushers, fans, blowers, exhausters, conveyors, injection molding, shredder, bailers, etc. Also, our users come from a variety of industries including power generation, fluid power, food and beverage, aggregates, pulp and paper, steel, mining, etc.

Top 5 Ways to Trash Your Pump

One critical component in your pump is the coupling that might be connecting your motor to the pump.  In the case of fire pump for example, it would be a grid coupling.  Like other coupling types, grid couplings often have "signature failures" modes that can completely make your pump fail.

In the case of fire pumps, where a flex or grid coupling is recommended (as per NFPA standards), here are 5 reasons that may cause grid coupling failures:

1) Reversing or highly fluctuating loads

Figure 1 - Fatigue Wear

Fatigue failures are typically due to high start-up or impact loads and/or in combination with reversing or highly fluctuating loads.  Signature fatigue wear, which can generally be viewed as normal grid coupling wear, shows up as cracks in the grid spring element approximately in the center of the grid spring element legs (see Figure 1 – Fatigue Wear).

With a few grid spring element legs broken in the center, a grid coupling will likely still be operational and transmitting torque through the remaining unbroken legs. However, once such a condition occurs, the coupling is operating in a compromised state and the grid spring element should be replaced as soon as possible.

2) Undersized Coupling 

A bad combination of undersized coupling and peak torque load(s) in excess of the calculated coupling sizing torque can cause a torque overload.  In this situation, the cracks in the grid spring element legs are not centered but rather further up or down the center 

3) Lack of Lubrication

Not lubricating the coupling properly can lead to failures.   In this case, the cracks are often localized to one side of a grid spring (where lubrication was lacking) and may resemble or look like a fatigue failure. The grid coupling is a metal-on-metal coupling, and a lack of lubrication will lead to premature wear (or fatigue) of the grid spring element. (How should you pack the grease in a Grid Coupling?).

4) Misalignment

Figure 2 - Misalignment Failure

A grid coupling is an excellent vibration dampening high power density coupling.  They are unfortunately not very good at accommodating misalignment. Grid couplings are not designed to handle parallel shaft misalignment, they are only designed to handle about a quarter degree of angular misalignment (see How sensitive are Grid Couplings to misalignment?).

Figure 2 is an example of a grid coupling element misalignment failure.  In such a failure, the grid spring break on the outer bends of the grid spring legs. Similar to fatigue failures, a grid coupling may have broken legs due to misalignment and still transmitting torque through the unbroken legs. This is not a desirable long term state and the grid spring should be replaced as soon as possible.  To prevent such failures (or to correct from such a failure from re-occurring), it is critical that the coupling shafts be realigned and within the misalignment tolerance of the given grid coupling. 

5) Excessive temperature and/or chemical exposure

Environmental conditions include excessive temperature and/or chemical exposure. Operational temperatures above or below the temperature range of the grid coupling seals will lead to seal damage or failure. Similarly, grease can also break down given extreme temperature exposure. Chemicals can also lead to seal damage and failure. In addition to visible damage to seals and lubrication breakdown, environmental failures may appear similar to an overload condition.  

To learn more about Grid Couplings, please read Why a Grid Coupling - Features & Benefits, Design Basics, and Element Options. 

Evolution of Gear Couplings

To discuss the evolution of gear coupling, we first need to discuss the history of general couplings. The first type of coupling used was a flexible coupling.  It’s said that the used of this coupling came with the invention of the wheel. The invention of the wheel itself, according to many historians, has its roots with the Sumerians more than 5000 years ago (Tigris and Euphrates rivers region). Earliest history known today tells us that flexible couplings and universal joints were used by Greeks around dates 300 B.C., and the Chinese around A.D. 25.

The Flexible coupling was invented by Jerome Carden in 16th century. It was a simple device consisting of two yokes, a cross and four bearings. This joint is still being used with modern modifications and known as the ancestor of all flexible couplings. In 1650 Robert Hooke developed the application of Hooke or Carden Joint. During the period between 1700 and 1800, there were no major advancements recorded in history until the industrial and automobile revolution.

In 1886 Roots developed a theory that if the flange of rigid coupling thin down then it would flex and prevent the equipment and shaft from falling down. This idea is still used in modern diaphragm couplings. In the period 1900-1930 many coupling manufacturers were established. The rapid advancement and expansion in couplings was direct result of the invention of the automobile in 1920s.

In the period 1930-1945 gear couplings were introduced into the industrial market. In the 1940s and 1950s technology was advanced rapidly. Rotating equipment was introduced in this period. By time larger and higher horsepower equipment came into use which brought the need of more power dense flexible coupling with great misalignment to be accommodated in systems. Around this time fully crowned gear spindle was developed and introduced into the steel industry.  

In the period of 1945-1960 gas turbines, generators and compressors were introduced and they were becoming more and more popular by the day. This brought out the requirement of higher speed couplings. So gear couplings were upgraded to handle more power and higher speeds. But with rotating equipment and higher operating speeds brought a lot of systems problems regarding gear coupling failure due to torsion or weight of the couplings. So lighter weight coupling were introduced which were also able to absorb (dampen) anticipated load peaks and help tune the system called resilient couplings.

In 1960-1985 period the advancement in the systems were continued with more and more horsepower and higher speeds. As it is seen in 1960s many new types of gear couplings were introduced. Around this time standard line of tooth gear coupling was developed. In this period need of non-lubricant gear couplings grew rapidly. So gear couplings upgraded to meet new change of speed and torsional characteristics of power transmitting shafts.

From 1985 to present time, a lot of advancements have happened in the gear coupling industry. These new advancements were the result of the use of new materials, finite element analysis (FEA) techniques, advanced manufacturing systems e.g.; computer numerical control (CNC) and electron welding etc. A great example of these technological advancements is HercuFlex.

Overhead Crane (or Bridge Crane) Gear Couplings

Guest Post: Ron Haynes, Lovejoy Field Sales Representative

Whether it is called an “Overhead Crane” or a “Bridge Crane”, it can be found in a multitude of industrial environments, ranging from steel, automotive, power generation, pulp and paper to name just a few. The typical overhead crane consists of parallel runways with a traveling bridge spanning or straddling the gap. A hoist, mounted on the bridge is the lifting component of the crane.

Unlike mobile or construction cranes, overhead cranes are typically used for manufacturing or maintenance applications, where efficiency and downtime are critical factors.
The origin of today’s industrial crane can be traced to the Ancient Greeks, who in the 6th Century BC, developed a winch and pulley-hoist system to replace a series of ramps as the main means of vertical lift.

Today, cranes exist in a variety of forms, each tailored to a specific use, and although the style and function may vary, they all maintain many of the same basic design requirements. First and foremost is the inherent need to connect multiple shafts, drums and brakes to the prime and auxiliary movers powering the drive, travel and hoist function of the crane.  Over the years the “coupling of choice” for crane and hoist builders has been the Gear Coupling. With the highest power density, ability to adapt to multiple design and misalignment variations, along with a wider size torque and bore capacity then other style of couplings, it is easy to see why this series of coupling has become an industry standard.

Although considered a mature product, the Gear Coupling not unlike the cranes they are used on, are being asked to do more while remaining true to the industry standards necessary for form fit and function. With the launch of the HercuFlex™ gear coupling product line in late 2014, Lovejoy has redefined and reinvented the gear coupling. Crane and hoist designers can look to Lovejoy for a new “Industry Standard” that offers increased torque and bore capacities combined with a design that increases service life while still retaining interchangeability within existing gear coupling sleeve flanges per AGMA standard dimensions. Simply put, the increased capacities will allow designers to maximize their system design or downsize the coupling to gain cost reductions without sacrificing performance.

 
To learn more about the HercuFlex gear coupling, please visit the Lovejoy product page to review technical specifications, review a whitepaper on the product, or download a catalog. To learn more about gear couplings in general, please check out the five part series on this blog starting with: Gear Coupling Tutorial - Part 1: Overview.

To find a Lovejoy distributor for either the HercuFlex or tradition Lovejoy/Sier-Bath gear coupling, please check out Lovejoy's Find a Distributor tool.

About the Author: Ron Haynes is a seasoned mechanical power transmission and coupling expert with over four decades in the field. To find a highly qualified Lovejoy representative in your corner of the world, please use the Find a Sales Representative Tool.