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.

Scalloped Disc Pack Couplings - Ideal for Paper Mill Applications

Today's paper mills have been targeted with aggressive up-time requirements to keeping them running as efficiently and profitably for their shareholders as possible. Once such technology that has quickly crept into paper mills over the past few years has been the flexible disc coupling. 

Whereas gear couplings have long been used, and require system shutdown for coupling inspection and re-lubrication, disc couplings (paired with a steel mesh coupling cover and strobe light) can be inspected while running. Furthermore, they require no lubrication and have a theoretical infinite life. 

A stumbling block that Lovejoy has seen with disc coupling installations at various mills is that they have selected a disc coupling with misalignment limitations far below what the given system actually sees. Under such circumstances, the disc coupling will quickly fail and the operator will question why they even bothered trying to switch. 

One of Lovejoy's veteran sales personnel documented the case of a specific east coast US paper mill going through a disc coupling every ~90 days in the dryer section of the machine. The failures caused production stops of an entire shift, with economic consequences that were certainly being felt by upper management. 

Broadly speaking, paper machines are comprised of two main areas (a wet area and a drying area), and can have somewhere in the range of 100 to 125 processing pumps supporting a single machine. 

The Right Solution

Advanced scalloped disc pack coupling designs (such as Lovejoy's offering) offer considerably more misalignment capability relative to traditional early iterations of the disc coupling, and are generally well suited for many paper mill applications. 

Even when utilizing scalloped disc pack designs, it remains critical that installers understand and work actively to mitigate the inherent misalignment in a given system. Disc couplings are beautiful, in that, when well aligned, they have a theoretical infinite life (no wearing parts) and can last 10 years or more. 

And regarding the competitor disc coupling that had been failing rapidly above, the Lovejoy sales rep reported back to Lovejoy that, after 3 years, the new Lovejoy disc coupling was still running well. That's certainly dollar signs and peace of mind to the supervisors of the plant in question! 

To learn more about flexible scalloped disc pack couplings, please visit Lovejoy's product page and/or download their PDF product catalog.