Friday, March 27, 2015

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.

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