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Inland Navigation: Locks, Dams, and Channels (ASCE MANUAL AND REPORTS ON ENGINEERING PRACTICE)

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Inland Navigation: Locks, Dams, and Channels (ASCE MANUAL AND REPORTS ON ENGINEERING PRACTICE)

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From (http://gen.lib.rus.ec)

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Many companies spend a good amount of money and time making sure shaft couplings are aligned correctly. But the actual coupling assembly and maintenance is just as important. If coupling design, assembly, alignment, and maintenance is done properly, a coupling should last for a long time. If done improperly, the machine may not even get up to speed before it fails.

In industrial machinery, the flexible coupling is common. Within that category are many different designs. But most flexible couplings require similar assembly methods.
DESIGN
Just because a coupling will fit on a shaft does not mean it is the right type of coupling. Couplings serve many purposes. They should transmit power from the driver to the driven. They should be rated for the correct horsepower, torque, starting load, and so on. They should also be the weak link between the driver and driven, meaning the coupling element should fail before causing damage to the driving or driven machines. Make sure your coupling is correct for your application. If you don't know, check with the coupling manufacturer or your engineering department.
HUB TO SHAFT FIT
Follow the manufacturers and machine designers recommendations. Some couplings have a slip fit. Others have an interference fit. But generally speaking, the coupling hub bore should only be slightly larger than the shaft (0.0005-0.0015″ for a slip fit), or slightly smaller than the shaft (0.0005-0.002″ for an interference fit). This fit should not be assumed, but should be measured with micrometers BEFORE attempting to install the hub onto the shaft.

Resist the temptation to drive a coupling on that seems too tight. This often ends in poor axial spacing, or even worse, a broken coupling hub. On the other end of the spectrum, a hub with a fit that is too loose can damage the shaft, overload the key, and if severe enough, can cause the coupling hub to run eccentric to the shaft, increasing vibration and coupling element wear.
SETTING KEYWAYS 180 DEGREES APART
This recommendation has been around for many years. The thought was that if there was any unbalance caused by the key stock, or by machining part of the shaft or hub away for the key seat, that setting the keys 180 degrees out would allow the slight unbalances to counteract each other. If machines are properly balanced, and keys and key seats are cut to proper lengths, then this should not be required. But generally speaking, setting the keys 180 degrees apart doesn't hurt anything, and it is normally good practice.
AXIAL SPACING
While some coupling types are more sensitive to this than others, axial spacing of the coupling hubs is another important component of coupling assembly. If the hubs are too close, it can cause axial (thrust)loading of the bearings, and a decreased capacity for coupling flexibility. If they are too far apart, it tends to minimize contact between the hub and element, causing increased wear, and the chance of element failure on startup.

Some coupling types, such as disc packs, are especially sensitive to axial spacing. Read and follow the coupling manufacturers recommendations to make sure the spacing is within tolerance.

The shafts of motors with sleeve bearings can move axially during operation, as the rotor finds its magnetic center. Be sure the motor shaft is positioned on its magnetic center before setting the axial spacing.
REPLACING COUPLING ELEMENTS
Whenever possible, replace the coupling element with an element from the hub manufacturer. In addition, make sure to replace the element with one designed for the same horsepower and temperature ranges. Elastomeric elements are different colors for different applications, not just different manufacturers. Just because the elastomer will "fit", doesn't mean that it is the right application.
LUBRICATION
There are many good coupling designs which require lubrication. If your couplings are the lubricated type, be sure to follow the coupling manufacturer's recommendations for the right type of lube. You may need a different lubricant for the coupling than what is used for the bearings.
INSPECTION
Coupling inspection should be an integral part of a machine's preventive maintenance task. Look for proper lubrication, signs of wear or misalignment, properly tightened set screws, properly seated keys, and so on. If the coupling grease shows signs of hardening, clean the old grease out, and re-lubricate.

Proper design, application, assembly, and maintenance of a coupling is just as critical as any other machine component.

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Many companies spend a good amount of money and time making sure shaft couplings are aligned correctly. But the actual coupling assembly and maintenance is just as important. If coupling design, assembly, alignment, and maintenance is done properly, a coupling should last for a long time.

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Electrical Construction & Maintenance (EC&M) Magazine

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Today's electrical grid delivers reliable electricity to millions of homes and businesses. However, electrical failures that affect large geographic areas do happen on a recurring basis due to hurricanes, floods, or major equipment failures. Local outages that affect smaller numbers of people happen much more often. In fact, in 2012, there were more than 2,800 unplanned power outages in the United States that lasted an average of 2.5 hr. Combined, these affected more than 25 million people, according to Eaton Corp.'s "Blackout Training Annual Report 2012."

For individual households, such power outages are often just an inconvenience. For hospitals and other health-care facilities, however, they can be life-threatening. For businesses like data centers, these outages can be extremely costly. A recent study by the Department of Energy found that financial losses from power outages at data centers ranged from $20,000 to $2 million per occurrence. Other mission-critical facilities at risk include government offices, police, fire, airports, and water/sewage treatment plants.

Having a well-designed and well-maintained standby power system is the best protection against utility power outages. According to the industry group Diesel Technology Forum, diesel-powered generators provide the most reliable form of emergency backup power, and can start/assume full-rated load in less than 10 sec. While backup generators typically can go 30,000 hr or more between major overhauls, even the best system needs to be exercised and maintained on a regular basis to make sure it operates properly when needed. When standby generators fail to start or perform as designed, it is usually due to faulty maintenance procedures or neglect. In fact, the top three reasons standby generators fail to automatically start or run are:

* The generator START switch was left in the OFF position instead of AUTO.

* Starting batteries were dead or insufficiently charged.

* The fuel filter was clogged due to old or contaminated fuel.

All of these common issues can be eliminated with a regular generator maintenance routine performed by properly trained personnel. Facilities with qualified in-house technical
personnel often can perform required preventive maintenance on diesel generators. Other facility managers prefer to contract with a local service provider or power system distributor for regular maintenance service, especially if they have generators in multiple locations.

Following is a list of maintenance procedures that need to be performed on a regular basis. In addition to these checks, exercising the power system under load on a weekly or monthly basis ensures that the generator set and its system of controls and transfer switches is operating as designed.

Preventive maintenance

Because of the durability of diesel engines, most maintenance is preventive in nature and consists of the following operations:

* General inspection

* Lubrication service

* Cooling system service

* Fuel system service

* Servicing and testing starting batteries

* Regular engine exercise

It is generally a good idea to establish and adhere to a schedule of maintenance /service based on the specific power application and the severity of the environment. For example, if the generator set will be used frequently or subjected to extreme operating conditions, the recommended service intervals should be shortened accordingly. Some of the factors that can require more frequent maintenance include:

* Using the diesel generator set for continuous duty (prime power)

* Extreme ambient temperatures

* Exposure to weather

* Exposure to salt water

* Exposure to dust, sand, or other airborne contaminates

If the generator set will be subjected to some or all of these extreme operating conditions, it is best to consult with the engine manufacturer to develop an appropriate maintenance schedule. The best way to keep track of maintenance intervals is to use the running-time meter on the generator set to keep an accurate log of all services performed. This log also will be important for warranty support. The Table shows a typical diesel engine maintenance schedule for generator sets.

General inspection

When the generator set is running, operators need to be alert for mechanical problems that could create unsafe or hazardous conditions. Following are several areas that should be inspected frequently to maintain safe and reliable operation.

* Exhaust system: With the generator set operating, inspect the entire exhaust system, including the exhaust manifold, muffler, and exhaust pipe. Check for leaks at all connections, welds, gaskets, and joints - and make sure that the exhaust pipes are not heating surrounding areas excessively. Repair any leaks immediately. Check for excessive smoke upon starting: It can indicate possible performance and air quality issues that may require immediate attention.

* Fuel system: With the generator set operating, inspect the fuel supply lines, return lines, filters, and fittings for cracks or abrasions. Make sure the lines are not rubbing against anything that could cause an eventual failure. Repair any leaks or alter line routing to eliminate wear immediately.

* DC electrical system: Check the terminals on the starting batteries to make sure the connections are clean and tight. Loose or corroded connections create resistance, which can hinder starting.

* Engine: Monitor fluid levels, oil pressure, and coolant temperatures frequently. Most engine problems give an early warning. Look and listen for changes in engine performance, sound, or appearance that will indicate that service or repair is needed. Be alert for misfires, vibration, excessive exhaust smoke, decreases in power, or increases in oil or fuel consumption.

* Control system: Inspect the control system regularly, and make sure it is logging data properly during engine exercise. Be sure to return the control system back to normal automatic standby (AUTO) when testing and maintenance are completed.

Lubrication service

Check the engine oil level when the engine is shut down at the interval specified in the Table. For accurate readings on the engine's dipstick, shut off the engine and wait approximately 10 min. to allow the oil in the upper portions of the engine to drain back into the crankcase. Follow the engine manufacturer's recommendations for API oil classification and oil viscosity. Keep the oil level as near as possible to the "full" mark on the dipstick by adding the same quality and brand of oil.

Change the oil and filter at the intervals recommended in the Table. Check with the engine manufacturer for procedures for draining the oil and replacing the oil filter. Used oil and filters must be disposed of properly to avoid environmental damage or liability.

Cooling system service

Check the coolant level during shutdown periods at the interval specified in the Table. Remove the radiator cap after allowing the engine to cool, and, if necessary, add coolant until the level is about 3/4 in. below the radiator cap's lower sealing surface. Heavy-duty diesel engines require a balanced coolant mixture of water, antifreeze, and coolant additives. Use the coolant solution recommended by the engine manufacturer.

Inspect the exterior of the radiator for obstructions, and remove all dirt or foreign material with a soft brush or cloth. Use care to avoid damaging the fins. If available, use low-pressure compressed air or a stream of water in the opposite direction of normal air flow to clean the radiator. Check the operation of the coolant heater by verifying that hot coolant is being discharged from the outlet hose.

Fuel system service

Diesel is subject to contamination and deterioration over time, and one reason for regular generator set exercise is to use up stored fuel before it degrades. In addition to other fuel system service recommended by the engine manufacturer, the fuel filters should be drained at the interval indicated in the Table. Water vapor accumulates and condenses in the fuel tank - and also must be periodically drained from the tank along with any sediment present. Bacterial growth in diesel fuel can be an issue in warm climates. Consult the generator set manufacturer or dealer for recommendations on treating stored fuel with a biocide. Regular testing and fuel polishing may be required if the fuel is not used and replenished in three to six months.

The charge-air cooler piping and hoses should be inspected regularly for leaks, holes, cracks, or loose connections. Tighten the hose clamps as necessary. In addition, inspect the charge-air cooler for dirt and debris that may be blocking the fins. Check for cracks, holes, or other damage.

The engine air intake components should be checked at the interval indicated in the Table. The frequency of cleaning or replacing air cleaner filter elements is primarily determined by the conditions under which the generator set operates. Air cleaners typically contain a paper cartridge filter element that can be cleaned and reused if not damaged.

Starting batteries

Weak or undercharged starting batteries are a common cause of standby power system failures. Even when kept fully charged and maintained, lead-acid starting batteries are subject to deterioration over time and should be replaced approximately every 24 to 36 months - or when they no longer hold a proper charge. NiCad starting batteries require less maintenance than lead-acid and are often used in mission-critical applications. However, they are also subject to deterioration and need to be regularly tested under load. See the Table for the recommended inspection interval for lead-acid batteries and the charging system.

* Testing batteries: Merely checking the output voltage of the batteries is not indicative of their ability to deliver adequate starting power. As batteries age, their internal resistance to current flow goes up, and the only accurate measure of terminal voltage must be done under load. On some generators, this diagnostic test is performed automatically each time the generator is started. On other generator sets, use a manual battery load tester to verify the condition of each starting battery.

* Cleaning batteries: Keep the batteries clean by wiping them with a damp cloth whenever dirt appears excessive. If corrosion is present around the terminals, remove the battery cables and wash the terminals with a solution of baking soda and water (¼ lb baking soda to 1 quart of water). Be careful to prevent the solution from entering the battery cells, and flush the batteries with clean water when finished. After replacing the connections, coat the terminals with a light application of petroleum jelly.

* Checking specific gravity: In open-cell lead-acid batteries, use a battery hydrometer to check the specific gravity of the electrolyte in each battery cell. A fully charged battery will have a specific gravity of 1.260. Charge the battery if the specific gravity reading is below 1.215.

* Checking electrolyte level: In open-cell lead-acid batteries, check the level of the electrolyte at least every 200 hr of operation. If low, fill the battery cells to the bottom of the filler neck with distilled water.

Generator set exercise

Generator sets on continuous standby must be able to go from a cold start to being fully operational in a matter of seconds. This can impose a severe burden on engine parts. However, regular exercising keeps engine parts lubricated, prevents oxidation of electrical contacts, uses up fuel before it deteriorates, and, in general, helps provide reliable engine starting. Exercise the generator set at least once a month for a minimum of 30 min. loaded to no less than one-third of the nameplate rating. Periods of no-load operation should be held to a minimum because unburned fuel tends to accumulate in the exhaust system. Whenever possible, test the system with actual building loads in order to exercise the automatic transfer switches and verify performance under real-world conditions. If connecting to the normal load is not convenient for test purposes, the best engine performance and longevity will be obtained by connecting it to a load bank of at least one-third the nameplate rating. Be sure to return the generator control to AUTO at the conclusion of any maintenance.

The backup plan

Although the United States enjoys high levels of reliable electrical service, utility outages happen often enough to require mission-critical facilities to have standby power systems. Preventive maintenance for diesel engine generators plays a critical role in maximizing the reliability of these standby systems and reducing the severe financial and life-safety risks associated with the loss of power. Financial losses from just a single data center outage can cost upward of $2 million in lost revenue. Preventive maintenance also minimizes the need for repairs and reduces equipment life cycle costs. By following generally recognized diesel maintenance procedures and application-specific manufacturer recommendations, facilities can be assured that their standby power systems will start and run when needed.

Kovach is operations manager for Cummins Power Generation's PowerCare maintenance program, Minneapolis. He can be reached at [email protected] .

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Implementing a Standby Generator Maintenance Program for Diesel Engines

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Today's electrical grid delivers reliable electricity to millions of homes and businesses. However, electrical failures that affect large geographic areas do happen on a recurring basis due to hurricanes, floods, or major equipment failures. Local outages that affect smaller numbers of people happen much more often.

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At Coastal Power & Equipment we specialize in new and used generator sales, engines and generator ends. We are based in Houston, Texas.

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Setting up a planned maintenance schedule, and performing all associated testing will insure generator availability upon demand. Possibilities of generator failure increase when service and maintenance checks are not performed.

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Home Plumbing Maintenance Checklist: What You Should Be Doing Daily, Weekly, and Seasonally

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Regular maintenance is essential to the health of your home's plumbing. This checklist from the experts at Mr. Rooter has everything you need to know.

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In order for water pumps to run properly they need regular maintenance. Developing a water pump maintenance checklist will not only reduce your expenditure but it will ensure optimum performance.