GRAPHALLOY® Solves Power Plant Damper Failure

Pre-heated secondary air makes the inlet-air section of a utility boiler hot...hotter, in fact, than most steel bearings can handle.

A power plant had difficulty operating the dampers that control the flow of preheated air into the combustors. The hot air quickly dried out the lubricant in the steel damper bearings, causing the dampers to seize.

The problem was solved by replacing the steel bearings with self-lubricating GRAPHALLOY^® bearings. These new bearings have been in operation for years without a single failure.

Failing Dampers Hurt Productivity
Secondary air accounts for 85% of the total combustion airflow to the cyclone burners. This air is heated to 650°F - 750° F (350° C - 400° C) by flue gas through a large heat exchanger. It then flows through a windbox duct to the cyclone burners where it is mixed with powdered coal. Airflow to each burner is determined by an 8’ by 6” by 2’ control damper. The dampers are not moved often and the grease quickly carbonized, locking the bearings.

The utility did not want to bring the unit offline for a bearing problem so it tried to make do. The plant was often forced to alter its firing methods.Frequently, the cyclone burners worked inefficiently due to the inability to control the combustion air. In some cases, it was necessary to fabricate a device to forcefully move a damper manually because operators could not budge them.

The Solution

The power plant solved the problem by replacing the lubricated steel bearings with self-lubricating GRAPHALLOY bearings. Of the 40 bearings used in the plant, 30 consist of three sizes of pillow block bearings while the other 10 are four-bolt flange block bearings.

The upgrade was accomplished during a planned outage. Initially, all of the bearings in one boiler unit were replaced. The GRAPHALLOY bearings ran without any problems and, one year later, the plant replaced the bearings in the other boiler.

The Benefits
The power plant experienced the following benefits by switching to GRAPHALLOY

• The cyclone burners now operate more efficiently because the plant can precisely control the flow.
• Operators are now freed from the time-consuming and distracting task of manually 
• The plant has also had a substantial savings in costs for replacement bearings and labor.

Are you experiencing similar problems with heat and bearing failure? If so, the engineers at GRAPHALLOY will work with you to develop the right solution and help you beat the heat.

GRAPHALLOY® Electrical Solutions

GRAPHALLOY® Brushes, Slip Rings and Contacts solve signal applications where low noise is a requirement. They are available in various sizes and grades including copper, bronze and silver.

Brushes

GRAPHALLOY Brushes are common in rotating equipment to conduct currents ranging from minute instrument or signal values to power ratings. Brush materials include Silver Graphalloy and Copper Graphalloy. Special high altitude grades are available as well.

These brushes can be used in:
•Microwave equipment
•Servo systems
•Synchros
•Inverters
•Thermocouple and strain gauge circuits
•Pulse systems
•Computer grounding contacts
•Torque indicators
•Medical equipment
•Packaging machinery

Contacts

GRAPHALLOY Contacts are particularly valuable for interrupting highly inductive or heavy overloaded currents in circuit breakers, controllers, contactors and relays.

Possible Applications:
•Alarms
•Circut breakers
•Furnace Controls
•Medical apparatus
•Oven controls
•Switches
•Welding Machines

GRAPHALLOY® Solves a Proton Beam Problem

The Fermi National Accelerator Laboratory (Fermilab) is a Department of Energy atomic particle research lab in Batavia, IL. Fermilab specializes in high energy physics research and devotes much of their efforts toward understanding the basic properties of fundamental particles including neutrinos and other subatomic particles.

Fermilab turned to GRAPHALLOY® bearings from Graphite Metallizing Corporation to solve a problem in a critical "neutrino target adjustment" mechanism when previous solutions had failed.

Fermilab's MINOS (Main Injector Neutrino Oscillation Search) is designed to observe neutrino beam composition and energy distribution as it travels underground from Fermilab in Illinois to the Soudan Iron Mine in Minnesota. Neutrinos produced by the particle accelerator at Fermilab are "beamed" 450 miles through the earth.

To produce this beam of neutrinos, a proton beam starts at the Main Injector accelerator. The protons are magnetically focused onto a target. Once the protons strike the target, secondary particles are produced, focused by a pair of magnetic focusing "horns". The particles of interest then decay into neutrinos. It is the mechanical adjustment of these focusing horns that requires GRAPHALLOY bearings.

This operation runs in a particularly hostile environment. It is radioactive and corrosive and is exposed to nitric acid and ionized air. Metallic bushings cannot be used. In addition, polymers, organics, plastics and oil cannot be used in the operation. Finally, the bearings must run dry.

The unique properties of GRAPHALLOY provided the solution to this application. GRAPHALLOY bushings were used to target and position the horns because other materials would corrode and freeze up...and continue to outlast the other materials in this target assembly.

(Image courtesy of Fermilab Visual Media Services)

GRAPHALLOY for Bakery Applications

High temperature GRAPHALLOY® bushings have been the choice of oven manufacturers for many years. GRAPHALLOY bushings extend bearing life and reduce maintenance costs for bakeries in temperatures reaching 1000° F (535° C). GRAPHALLOY may be the answer to the most difficult operating problems.

The Food and Drug Administration (FDA) has accepted GRAPHALLOY for "repeat use in food contact equipment" in bakery ovens, pumps, mixers and conveyors. Ovens and conveyors, in particular, undergo high heat and continuous operation that challenge the life and durability of critical components. Self lubricating GRAPHALLOY bushings and bearings perform in temperature extremes...when conventional materials fail.

GRAPHALLOY, a graphite/metal alloy, prevents unnecessary downtime and lost production. It also survives wash down conditions common in many food applications. With its low coefficient of friction and high strength, GRAPHALLOY bearings deliver long life and are not subject to seizures binding or sudden failure. In addition, the high temperature, self lubricating capabilities of GRAPHALLOY bushings reduce maintenance costs

GRAPHALLOY® Provides Help With Bearing Maintenance Problems

Need help with your bearing maintenance problems?
GRAPHALLOY® - a unique graphite/metal alloy commonly used as a bearing material - may be the solution. Self-lubricating GRAPHALLOY has provided solutions in pumps, dampers, turbines, valves and other process equipment.

What can GRAPHALLOY bushings do for you?
Deliver simple solutions for your design and maintenance problems;

◦Self-lubricating; requires no grease or oil
◦Low maintenance: install & forget
◦Non-galling; no metal to metal seizure
◦Stable; does not melt or cold flow or swell when submerged
◦Operates in temperature extremes: -450° F to +1000° F (-240° F to +535° F)
◦Low, constant coefficient of friction
◦Dry; does not collect dust or contaminants
◦FDA accepted grades available

GRAPHALLOY® Turns Lead-Free Into Problem-Free

In an effort to address environmental concerns, a manufacturer of fluorescent lighting tubes initiated a program to remove lead from the glass. When this move to lead-free glass caused manufacturing problems,GRAPHALLOY® came to the rescue.

Lead was beneficial to the production process. The move to lead-free glass caused a problem with the bushings in the machine that flared the end of the tube and prepared it to attach and seal to the end plugs.

The lead in the glass had provided additional lubrication and kept the units from “gumming up” and sticking. With lead-free glass, the maintenance crew went from rebuilding the units once a year to once every three months.

The plant engineer contacted GRAPHALLOY engineers who then designed copper-grade self-lubricating GRAPHALLOY bushings to test in the machine. The GRAPHALLOY bushings were installed and the machine ran for three months with no problems. At that time, the plant placed a production order for an additional 200 pieces.

The machine fitted with GRAPHALLOY bushings has been operating for over one year without failure...four times the life of the original bushings.

The success of these GRAPHALLOY high temperature bushings provided this plant with better performance and significant cost savings. It demonstrates the potential for GRAPHALLOY upgrades in other manufacturing applications.

GRAPHALLOY® Attending International Exhibition in 2012

SEPEM Industries
Practical solutions on operation, maintenance and development to energy, chemicals, wood and furniture, metallurgy, plastics, rubber and various other sectors. For more information about this conference, please click here.

January 31, 2012 - February 2, 2012
Avignon Sud Parc des expositions
Avignon, France