Construction crews continue working on a piping project in the Glennis McCrarry Music Building parking lot after a damaged power line was repaired Thursday.

The Moody Memorial Library, Jesse H. Jones Library and Poage Legislative Library were closed early Thursday morning after a construction crew damaged a power line on Wednesday afternoon.

The construction crew damaged the power line to the library while in the process of replacing piping from the Baylor Energy Complex to the Glennis McCrary Music Building, explained Carl Flynn, director of marketing and communication for information technology and university libraries.

While the libraries experienced no power loss, the entire electrical system for the libraries was shut down in order to repair the damage. The part being repaired was the underground conduit raceway, a casing that houses the power line.

“Because of the fire safety issues we can not have anyone in the building,” said Sheron Cook, facilities coordinator for Baylor University libraries. The libraries were closed from 1 a.m. until 6 a.m., when they resumed their normal schedule.

The project that damaged the power line has also gotten in the way of student parking for the libraries.

Parking has always been a hot button issue for students, and with this project limiting parking near the library, students are finding it that much harder to park on campus.

“I always study in Moody, and I always try to park in that parking lot because it’s so close,” Georgetown junior Matt Covey said.

The parking lot is designated as the McCrary Music Building parking lot, according the Baylor Parking and Transportation Services campus map, but its proximity to the library makes it a prime parking lot for students going into Moody and Jones libraries. Parking is still available near the libraries in the Sid Richardson Science Building and Jones Library parking lots.

The state government had also sanctioned a number of power projects for generating electricity through renewable energy sources. A detailed project report for setting up of five biomass power projects of 39 Mw capacities had been approved by the state government and action had been initiated by the developers to set up these projects. The electricity generated from these projects would be purchased by the power utilities on the rates decided by the regulatory commission.

PM NEWS BUREAU , Thursday, August 26, 2010, 12:35 Hrs  [IST]

Who’s Blogging» Links to this article

By Steven Mufson
Washington Post Staff Writer
Friday, January 1, 2010

BEIJING — China condemned on Thursday a U.S. agency ruling that clears the way for tariffs on imports of steel pipe from China and asserted that the global economic slowdown was the real reason for lower demand for U.S.-made steel pipe.

China’s Ministry of Commerce said that China was “strongly dissatisfied” with the U.S. International Trade Commission’s Wednesday ruling that Chinese subsidized imports had harmed or threaten to harm U.S. steel pipe manufacturers.

The ITC ruling involved one of the largest U.S.-China trade cases ever. It focused on the quadrupling of U.S. imports of steel pipe from China between 2006 and 2008 from $681 million to $2.8 billion. U.S. companies alleged that their Chinese rivals received discounts on raw materials and loans from government-owned firms.

The Commerce Ministry said that the ITC ruling was “wrong” and “ignored the fundamental reason” for the drop in demand for U.S.-made pipe. The ministry also blamed the collapse in oil prices in early 2009 for hurting U.S. manufacturers; steel pipe is largely used in the oil and gas industry.

“The export of oil well pipes from China won’t damage or threaten the U.S. industry,” the ministry said on its Web site.

Chinese companies said the tariffs would hurt business, but also noted that exports had already fallen in 2009. A report by the Shanghai Customs Office said that from January to November 2009, the export of oil well pipes in the Shanghai area plunged 85.5 percent compared with the year before.

But U.S. companies said that Chinese firms were still gaining market share in the first nine months of 2009 and that they had contributed to a drop in U.S jobs from 5,800 workers in 2008 to 3,400 workers.

WSP Holding Limited, a seamless pipe producer based in Wuxi, said that even though Chinese demand for steel pipe had dropped in 2009, it was down less than exports, which still account for 27 percent of total sales.

Han Fei, a salesman from Shengli Oilfield Highland Petroleum Equipment responsible for the South American and North American markets, said that the financial crisis had led to cancellations of orders during 2009. Before then, half of Shengli’s output was sold to the United States.

Han said the company now has more than 10,000 tons of steel pipes stockpiled after customers opted to pay the penalty for breaking sales agreements in 2009. Some shipments were en route to the United States when customers backed out, and some workers were laid off.

Nonetheless, some firms said that the tariffs would still matter. Li Lianchang, head of the export intelligence department of Tianjin Pipe Group, called the tariffs “frost on the top of snow,” an expression that means one disaster follows another. The snow, he said, is the economic crisis and the frost is the tariff.

Tianjin Pipe Group, the world’s largest maker of steel pipe, would remain competitive in the United Sates with a 10 to 16 percent anti-subsidy tariff, said Li. But, he added, if the total amount is more than 20 percent, “it’s totally impossible for us to export to the U.S.”

Exports to the United States accounted for just 5 percent of the output of Tianjin Pipe Group, a state-owned enterprise.

The United States and Europe have been pressing China to let its currency appreciate so that its exports wouldn’t have an unfair advantage. But President Hu Jintao recently brushed aside such a plan. And on Thursday the State Administration of Foreign Exchange, a unit of the central bank, said in a report that it “should decide on the method, content and timing of yuan exchange rate reform according to our own needs and development.”

Artificial heart valves consist of an orifice, through which blood flows, and a mechanism that closes and opens the orifice. There are two types of artificial heart valves: mechanical devices made from synthetic materials; and biological or tissue valves made from animal or human tissue. In general, biological valves are used for patients who are over 65 or cannot take anticoagulants. Mechanical valves are used for patients that have a mechanical valve in another position, have had a stroke, require double valve replacement, and usually are recommended for those under 40. These type of valves require the patient to take anti-coagulating drugs.

Mechanical valves can be further broken down into three types based on the opening and closing mechanism. These mechanisms are: a reciprocating ball, a tilting disk, or two semicircular hinged leaflets. The first type is based on a ball-in-cage design, which uses a rubber ball that oscillates in a metal cage made from a cobalt-chromium alloy. When the valve opens, blood flows through a primary orifice and a secondary orifice between the ball and housing. About 200,000 of these have been implanted.

The tilting disk valve uses a circular disk retained by wire-like arms that project into the orifice. When the disk opens, the primary orifice is separated into two unequal orifices. About 360,000 of these valves have been implanted. The current design consists of two semicircular leaflets connected to the orifice housing by a hinge mechanism. The leaflets separate during opening, producing three flow areas in the center and on the sides. Over 600,000 bileaflet valves have been implanted.

History
The first recorded surgical operation on a heart valve took place in 1913. Replacement of diseased valves did not take place until 1962, when the first successful biological valves were invented using human tissue from a donor. Ball valves were the first type of mechanical valves and were developed around the same time. Miles Edwards, an electrical engineer who founded a medical device company called American Edwards Laboratories in the 1950s, is credited with co-inventing the first commercially available artificial heart valve. Disk valves became popular in the 1970s after the first successful design was introduced in 1969. The reduced height improved clinical performance. The bileaflet design was first introduced in 1977 and became more popular during the 1980s.

Advances in materials also helped spur the development of mechanical valves. In 1965,

 
Artificial heart valves consist of an orifice, through which blood flows, and a mechanism that closes and opens the orifice.
scientist Dr. J. C. Bokros from the General Atomic Company was investigating pyrolytic carbon materials for nuclear fuel applications. Because the material’s properties were suitable for biomedical applications (durability, blood compatibility), he looked at it for making artificial heart valves. Today, about 90% of all mechanical heart valves implanted have at least one pyrolytic carbon part.

In 1976, medical devices (including prosthetic heart valves) came under the jurisdiction of the Food and Drug Adminstration (FDA). FDA then issued guidelines for Premarket Approval (PMA) applications for heart valves. In 1993, FDA issued a guidance document based on objective performance criteria. This set the minimum amount of follow-up required for a PMA study at 800 valve-years.

The performance of mechanical valves has been noteworthy. The ball valve, in use for over 30 years, has had only a dozen structural problems that caused no major harm to the patient. The tilt valve had fewer than 1% of failures after 15 years of experience. The most popular type of bileaflet valve only reported several dozen failures to the FDA. However, in early 2000, one valve manufacturer recalled silver-coated valves because of a leaking problem in 2% of patients. In all, there have only been about 50 failures out of the approximately one million valves in service.

Approximately 265,000 prosthetic valves are now implanted worldwide each year, valued at over $700 million. About 60% of these are mechanical valves, with a market value of around $400 million. Over two million mechanical valves have been implanted in patients around the world during the last several decades.

Raw Materials
Most artificial valves are made of titanium, graphite, pyrolytic carbon, and polyester. The titanium is used for the housing or outer ring, graphite coated with pyrolytic carbon is used for the bileaflets, and 100% pyrolytic carbon is used for the inner ring. The pyrolytic carbon is sometimes impregnated with tungsten so that the valve can easily be seen following implantation). The sewing cuff, used to attach the valve to the heart, is made out of double velour polyester.

Titanium is used for its strength and biocompatibility. The outer rings come already fabricated from an outside manufacturer and are made from machined bar stock. Lock rings and wire, used to hold the cuff in place, are also made from titanium. The polyester comes in the form of tubes. All plastic components are deburred by the supplier, which involves removing any bumps from the surface. Occasionally the valve manufacturer may have to deburr some parts.

The pyrolytic carbon coating is produced by depositing gaseous hydrocarbons (usually methane) onto a heated graphite substrate at temperatures of 3,272-4,172°F (1,800-2,300°C) in a chamber. These gases break down into carbon. The inner rings are made from 100% pyrolytic carbon using a fluidized bed process at another manufacturer. This material’s atomic microstructure helps resist cracking, making it ductile. However, the processing method can still introduce microcracks that must be detected.

The Manufacturing Process
1 The majority of components are made by a third party, except for the polyester cuffs. These are made by a sewing process that includes various looping, folding, and stitching steps. The manufacturing process therefore consists mainly of various assembly and inspection steps.
Assembly
2 Assembly takes place in a clean room to avoid contamination. The leaflets are attached to the inner rings, which are then placed in the housing or outer ring.
3 While this is being down, the sewing cuffs are being made. A special pressurized heating process is then used to form the cuffs around the valve, which takes place at several hundred degrees. The valves are then mounted into a rotator assembly, which the surgeon uses for implanting.
Sterilization and packaging
4 After the valves are assembled and tested, they are sterilized in a double plastic container. Steam sterilization is used, which involves temperatures up to 270°F (132°C) and times of 15 minutes or more. To make sure the sterilization process has worked, a biological indicator is placed inside. If the indicator shows no growth of bacteria or other viable organisms, the valves and its packaging have been properly sterilized. Each plastic-encased valve is then packaged in a box for shipping.
Quality Control
All components are inspected visually, dimensionally and functionally prior to assembly to make sure they meet specifications. The diameter of each ring is measured and assigned a size, which is then matched to the appropriate bileaflet to make sure they will fit together. Microscopic analysis using high power magnification is used to check components for scratches. In total, up to 50 inspections are made during the assembly process.

Proof testing is used to determine the structural quality of potentially flawed heart valves. In this method, a valve is loaded to a certain stress level using a special pressurization fixture to see if it will fail at this stress. During the stress test, acoustic emission technology is used to detect minute cracks that might go undetected so that these valves can be rejected. Once the valves are sterilized and packaged, they are inspected to make sure the labels are accurate.

Byproducts/Waste
Due to the stringent quality control procedures, there is little or no waste produced during the assembly process. Any scrap material is recycled if it is feasible. Defective components are returned to the manufacturer. Some chemicals used for cleaning must be disposed of properly following safety regulations.

The Future
Blood clotting is still a problem with mechanical valves and manufacturers continue to improve designs, sometimes using super-computing modeling tools, as well as surgical procedures. The shape of the orifice is being improved to reduce pressure losses, turbulence and shear stresses. Flow area is maximized by using stronger materials, which minimizes wall thickness. Tapering the sides of the valve pumps blood more efficiently. Operations are also being developed that only require a 3-4 in (8-10 cm) incision instead of 12 in (30 cm). Manufacturing efficiencies will continue to improve.

Researchers are looking at making heart valves out of plastic material that are flexible enough to simulate the opening and closing action. This approach may not require anticoagulation drugs. Others are working on developing artificial heart valves made from a patient’s own cells. Experiments have been successful using sheep. Both developments may take decades before they are put in practical use.

Where to Learn More
Periodicals
“Baxter Announces Name of Cardiovascular Spin-Off.” PR Newswire (January 14,2000).

Dolven, Ben. “Take Heart.” Far Eastern Economic Review (November 4,1999).

Lankford, James. “Assuring Heart Valve Reliability.” Technology Today (Summer 1999).

“Maker Recalls Heart Valves.” Newsday (January 25, 2000): A49.

“Medical Carbon Research Institute Announces On-X Prosthetic Heart Valve CE Mark Approval.” Business Wire (July 24, 1998).

Reed, Stephen. “Sarasota Doctors Trying Out a Better Artificial Heart Valve.” Sarasota Herald Tribune (June 5, 1998): IA.

“Researchers Grow Artificial Heart Valves in Sheep.” Reuters Ltd (November 7, 1999).

Stemnberg, Steve. “In Medicine, a Shortage Prevented.” USA Today (August 3, 1998): 06D.

Other
“Medtronic Announces First Implant.” Medtronic, Inc. http://www.medtronic.com (December 29, 2000).

“St. Jude Medical Announces One-Millionth Mechanical Heart Valve Implant.” St. Jude Medical, Inc. (April 6, 2000). http://www.pmewswire.com (May 2000).

— Laurel M. Sheppard
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Read more: How artificial heart valve is made - material, making, history, used, processing, parts, components, steps, History, Raw Materials, The Manufacturing Process of artificial heart valve, Quality Control http://www.madehow.com/Volume-6/Artificial-Heart-Valve.html#ixzz0wHUnqIKb

Have you ever looked at a valve, sluice or similar rotating equipment and wondered how to operate it?

In these days of limited maintenance coupled with reduced staffing levels, it is becoming increasingly difficult to find personnel with sufficient time to operate large multi-turn or difficult-to-turn valves and equipment in a timely manner. Some large valves are typically operated only once or twice a year during a plant shutdown situation, and often require the use of cheater bars (valve wrenches) with extension arms and a work crew to complete the task.

This manual operating procedure can take many hours and cost more in labor. Because of the high installation costs, the use of permanently installed actuators (actuator, control system and any associated power supplies) on these valves is often not an economic alternative for infrequently operated items.

Portable Valve Operating Technology Specifications
A possible answer to this problem is to use a one-man operated portable valve operating system (or valve exerciser), which can typically consist of a handheld continuous torque output driver, not an impact wrench. Commonly referred to as the “gun,” this driver can be powered by either plant air (90- to 100-psi at 25- to 30-cfm), main electricity (120 to 220 VAC), battery electric (18 VDC) or a hydraulic power source (2000-psi, 4.75-gpm). With any of these power sources, it is possible to obtain guns that will produce  in excess of 8,500-ft-lbs of torque that can then be utilized to turn valves or equipment when supplied complete with a mounting kit.

The mounting kit can be designed for permanent attachment to a valve in place of the operating handwheel / lever or alternatively can be supplied as a “clamp-on” type. The clamp can be attached to the existing valve handwheel/lever using bolts or U-bolts, allowing removal and relocation to another valve if required. Included in a well-designed mounting assembly is a safety “reaction arm,” which attaches the gun to the valve body/adjacent equipment or steelwork.

This feature ensures that the gun does not spin should the valve stall or the valve stem stop turning during operation for any reason, minimizing the possibility of operator injury. Some handheld valve operators or exercisers currently require the operator(s) to become the reaction device with all the inherent dangers and injury possibilities involved (see Figure 1 for a typical operational situation).

By selecting a gun based on valve torque requirements and operating conditions, it is possible to operate almost any item with a rotating stem with speeds varying from a few RPM up to 65- to 70-rpm dependent on the torque output required from the gun. Speeds in excess of 65- to 70-rpm should be avoided, as most valves and gearboxes used with valves and manually operated equipment are not designed for high-speed operation.

The torque output from a gun is variable and controlled by different methods depending on the power source, usually a stepping clutch control system for electric units or raising/lowering the air pressure for pneumatic units. Each gun is supplied with a calibration graph or chart of power source against torque to assist with selection of the correct operating torque for an individual application.

As the gun-type units are light weight (a common maximum weight is in the range of 28- to 30-lbs), they can easily be moved, attached to another valve and connected to an adjacent power source to operate. This portability can be extended further with truck-mounted or transportable compressors for pneumatic versions or cab-mounted inverters for electric or battery units. With this flexibility, it is possible to operate equipment in remote locations, including along pipelines, within dams, at pumping stations, etc.

If the location involves operation in a hazardous or explosive area, only air-driven units can be used, as no other power source unit is approved for use within these areas. If other operational restrictive parameters require the operator to position himself away from the valve (with or without hazardous area considerations), remote control operation versions are available for operation up to 50-ft away from the equipment. These versions use either pendant-type pneumatic controls or an electrical control module.

Operation
Using pneumatic versions as an example, the method of operating a valve for the first time is to:

1) Securely attach the required mounting kit to the valve if it is not already installed.

2) Connect the pneumatic torque driver to the valve adaption using any supplied adaptors and location pins, ensuring that the reaction arm is correctly aligned and attached to the gun body.

3) Check that the supplied filter, regulator and lubricator unit (FRL) is filled with oil to lubricate the air motor and that an adequate air supply is available.

4) Set the air supply to the gun using the FRL to zero. If the operating torque required to turn a valve is known, proceed as A). If the torque is unknown, proceed as B).

A) Use the FRL regulator to set the required air pressure to produce this torque using the calibration chart supplied with     the unit. Select the required rotation setting on the gun-forward or reverse-operate the control trigger to turn the gun on and rotate your valve.

B) Slowly increase the supply air pressure using the FRL regulator from zero during operation of the gun until the valve turns freely in a continuous manner. Once continuous operation is achieved, record this operational pressure for future reference, either on the valve body or in the maintenance record for the particular valve.

In addition to mounting directly onto the handwheel, gearbox or valve stem, extension arms, stem adaptors (AWWA or similar), offset gearboxes, indirect reaction arms, revolution counters and other system modifications can be supplied to suit different individual applications. In cases where a valve is inaccessible for direct operation, the use of a flexible, cable-driven drive system together with a torque driver can also be considered.

Martin West is sales manager (USA) for Smith Flow Control and has worked in the fields of valve locking for safety and valve drive systems for more than 20 years

Tags: September 2008 Issue , Valves

The person with the best answer receives a ticket to an upcoming Pump School.

Pumps & Systems, November 2009

Dr. Nelik (aka “Dr. Pump”) is president of Pumping Machinery, LLC, an Atlanta-based firm specializing in pump consulting, training, equipment troubleshooting and pump repairs. Dr. Nelik has 30 years experience in pumps and pumping equipment. He has published more than 50 documents. He can be contacted by visitingwww.PumpingMachinery.com.

This article will introduce the basics of stresses and anchor loads induced by thermal expansion. To stick to the basics, a straight piece of restrained pipe will serve as the example. We will also look at some available options to reduce the pipe stresses and anchor loads.

Stresses Induced by Thermal Expansion-The Basics
We will start with some definitions of commonly used flexibility terms. Stress is defined as force per unit area in a material:

S = F/A (Equation 1)

S = Stress (psi-can be negative or positive)

F = Force (lbf-can be negative or positive)

A = Area (square inches)

Strain is defined as a percentage or ratio of a change of length divided by the original length:

ε = ΔL/Lo (Equation 2)

ε = Strain (inch/inch-can be negative or positive)

ΔL = Change in length (inches-can be negative or positive)

Lo = Starting length (inches)

Stress and strain are related by Hooke’s Law:

S = Eε  (Equation 3)

S = Stress (psi)

E = Young’s Modulus (psi)

ε = Strain (in/in)

Piping materials exhibit nearly linear expansion and contraction with temperature. The rate of thermal expansion and contraction is characterized by the coefficient of thermal expansion, a, and has units of in/in-°F, or strain per degree Fahrenheit. The change in dimensions of an object is then:

ε = a (T2-T1) (Equation 4)

ε = strain (in/in)

a = Coefficient of thermal expansion (in/in-°F)

T2 = End temperature (°F)

T1 = Starting temperature (°F)

If the object is a straight bar or pipe, the more familiar form of this equation is:

ΔL = aLo(T2-T1) (Equation 5)

ΔL = Change in length (in)

Lo = Initial length of pipe (in)

Consider a 6 in diameter steel (ASTM A53) pipe, 100 ft long, anchored at one end. The pipe is empty, and the inside is at atmospheric pressure. The temperature is increased to 200 deg F above ambient. The expansion of the pipe from equation (2) is:

a = 6.33 x 10-6 in/in-°F

Lo = 1,200 in

T2 = 270 deg F

T1 = 70 deg F

ΔL = (6.33 x1 0-6 in/in-°F)(1,200 in)(270°F-70°F)

= 1.52 in

In these days of limited maintenance coupled with reduced staffing levels, it is becoming increasingly difficult to find personnel with sufficient time to operate large multi-turn or difficult-to-turn valves and equipment in a timely manner. Some large valves are typically operated only once or twice a year during a plant shutdown situation, and often require the use of cheater bars (valve wrenches) with extension arms and a work crew to complete the task.

This manual operating procedure can take many hours and cost more in labor. Because of the high installation costs, the use of permanently installed actuators (actuator, control system and any associated power supplies) on these valves is often not an economic alternative for infrequently operated items.

Portable Valve Operating Technology Specifications
A possible answer to this problem is to use a one-man operated portable valve operating system (or valve exerciser), which can typically consist of a handheld continuous torque output driver, not an impact wrench. Commonly referred to as the “gun,” this driver can be powered by either plant air (90- to 100-psi at 25- to 30-cfm), main electricity (120 to 220 VAC), battery electric (18 VDC) or a hydraulic power source (2000-psi, 4.75-gpm). With any of these power sources, it is possible to obtain guns that will produce  in excess of 8,500-ft-lbs of torque that can then be utilized to turn valves or equipment when supplied complete with a mounting kit.

The mounting kit can be designed for permanent attachment to a valve in place of the operating handwheel / lever or alternatively can be supplied as a “clamp-on” type. The clamp can be attached to the existing valve handwheel/lever using bolts or U-bolts, allowing removal and relocation to another valve if required. Included in a well-designed mounting assembly is a safety “reaction arm,” which attaches the gun to the valve body/adjacent equipment or steelwork.

This feature ensures that the gun does not spin should the valve stall or the valve stem stop turning during operation for any reason, minimizing the possibility of operator injury. Some handheld valve operators or exercisers currently require the operator(s) to become the reaction device with all the inherent dangers and injury possibilities involved (see Figure 1 for a typical operational situation).

By selecting a gun based on valve torque requirements and operating conditions, it is possible to operate almost any item with a rotating stem with speeds varying from a few RPM up to 65- to 70-rpm dependent on the torque output required from the gun. Speeds in excess of 65- to 70-rpm should be avoided, as most valves and gearboxes used with valves and manually operated equipment are not designed for high-speed operation.

The torque output from a gun is variable and controlled by different methods depending on the power source, usually a stepping clutch control system for electric units or raising/lowering the air pressure for pneumatic units. Each gun is supplied with a calibration graph or chart of power source against torque to assist with selection of the correct operating torque for an individual application.

As the gun-type units are light weight (a common maximum weight is in the range of 28- to 30-lbs), they can easily be moved, attached to another valve and connected to an adjacent power source to operate. This portability can be extended further with truck-mounted or transportable compressors for pneumatic versions or cab-mounted inverters for electric or battery units. With this flexibility, it is possible to operate equipment in remote locations, including along pipelines, within dams, at pumping stations, etc.

If the location involves operation in a hazardous or explosive area, only air-driven units can be used, as no other power source unit is approved for use within these areas. If other operational restrictive parameters require the operator to position himself away from the valve (with or without hazardous area considerations), remote control operation versions are available for operation up to 50-ft away from the equipment. These versions use either pendant-type pneumatic controls or an electrical control module.

Operation
Using pneumatic versions as an example, the method of operating a valve for the first time is to:

1) Securely attach the required mounting kit to the valve if it is not already installed.

2) Connect the pneumatic torque driver to the valve adaption using any supplied adaptors and location pins, ensuring that the reaction arm is correctly aligned and attached to the gun body.

3) Check that the supplied filter, regulator and lubricator unit (FRL) is filled with oil to lubricate the air motor and that an adequate air supply is available.

4) Set the air supply to the gun using the FRL to zero. If the operating torque required to turn a valve is known, proceed as A). If the torque is unknown, proceed as B).

A) Use the FRL regulator to set the required air pressure to produce this torque using the calibration chart supplied with     the unit. Select the required rotation setting on the gun-forward or reverse-operate the control trigger to turn the gun on and rotate your valve.

B) Slowly increase the supply air pressure using the FRL regulator from zero during operation of the gun until the valve turns freely in a continuous manner. Once continuous operation is achieved, record this operational pressure for future reference, either on the valve body or in the maintenance record for the particular valve.

In addition to mounting directly onto the handwheel, gearbox or valve stem, extension arms, stem adaptors (AWWA or similar), offset gearboxes, indirect reaction arms, revolution counters and other system modifications can be supplied to suit different individual applications. In cases where a valve is inaccessible for direct operation, the use of a flexible, cable-driven drive system together with a torque driver can also be considered.

Martin West is sales manager (USA) for Smith Flow Control and has worked in the fields of valve locking for safety and valve drive systems for more than 20 years

Tags: September 2008 Issue , Valves
Written by Martin West, Smith Flow Control
Pumps & Systems, September 2008

Power Plant Emissions
Sulfur emissions are one of the most environmentally harmful air emissions from coal fired power plants. Sulfur creates an unpleasant haze in the atmosphere and causes human respiratory problems. It returns to the earth in rain, commonly known as acid rain, which destroys plants in streams and lakes. The water may look clean, but fish die from the lack of a food source.

To combat these environmental problems, power plants worldwide use technology to filter out harmful ash, sulfur, heavy metals and carbon. Significant progress has been made to filter emissions through flue gas desulfurization (FGD). Modern FGD systems help the environment by scrubbing flue gases to create cleaner air emissions. Many companies have implemented FGD systems to negate the harmful effects of emissions from coal fired power plants.

Implementing an FGD System
Dayton Power & Light (DP&L) is leading the way in protecting the environment from sulfur emissions by using a wet limestone flue gas desulfurization (WFGD) process at their Stuart and Killen power stations. The WFGD process went into initial operation in May 2007 at the DP&L Killen Unit 2 plant, an existing, nominal 650-MW (gross output) coal-fired unit located on the Ohio River about two hours east of Cincinnati, Ohio. About 15 miles down the Ohio River, DP&L’s Stuart station [af1] began operating its fourth WFGD system in late spring 2008.

The WFGD process includes a Jet Bubbling Reactor (JBR) where absorption, oxidation, neutralization and crystallization happen at the same time particles are removed. The process typically guarantees 98 percent removal of Sulfur Dioxide (SO2) and consumes less power than standard methods.

The WFGD process works differently than a spray tower (countercurrent system) typically used in power plants. First, cooling sprays reduce the flue gas’ saturation temperature. In the JBR, the flue gas contacts the reagent (limestone slurry). The plant’s induced draft fans draw the flue gas through the reagent slurry, causing the flue gas to be cleaned within the reagent tank.

In the reagent tank, a continuous layer of bubbling froth on the slurry surface called the “jet bubbling zone” dissolves SO2 and captures multi-pollutants from the flue gas. The clean flue gas bubbles out the reagent tank (hence, “jet bubbling reactor”) to the mist eliminator and then out the stack. Users can automatically control pollutant removal by adjusting the liquid level. Although the JBR and spray tower processes are different, there are similar applications in both processes. The common applications are limestone slurry, gypsum slurry, centrifuge isolation, equipment drain lines and flush water systems.

The WFGD process uses an aqueous solution of limestone sprayed countercurrent to the exhausting flue gas, which effectively wet scrubs the majority of harmful sulfur from the air. Sulfur drops into the aqueous limestone slurry mixture. Unfortunately, scrubbing sulfur into the aqueous solution creates sulfuric acid, a corrosive and abrasive solution. Therefore, pumps and valves need to be extremely corrosion and abrasion resistant to be used in the WFGD process and many other similar FGD processes.

Corrosion-Resistant Valves for FGD Systems
During the early stages of the WFGD installation at DP&L, its consultant, Black & Veatch, sought a tough valve that could handle the corrosive and abrasive limestone slurry in the JBR. During the search, one valve manufacturer explained how a urethane-lined knife gate valve would work in the WFGD process.

First, the replaceable urethane liners in the knife gate valve protect the valve body from the abrasive and corrosive limestone slurry. The liners also protect the perimeter seal from direct abrasive flow. Since the liners are not used for sealing, the liner material remains hard for superior abrasion resistance.

A triple scraper incorporated into the liners cleans the gate and prevents media build-up in the chest area. The triple scraper works during operation so the process does not need to be shut down for routine maintenance. A taper is added to the liner’s internal diameter to eliminate the possibility of material collecting at the bottom of the port and preventing proper closure. The taper ensures automatic clean-out and flushing.

Second, the perimeter seal of the valve provides bi-directional, drip-tight shutoff without discharging limestone slurry into the environment. The perimeter seal has shoulders, which mechanically retain (lock) the seal in the seal groove located in the liners. The seal groove is specially designed to prevent seal pull-out but also allows the seal to move and prevent over-compression.

Moreover, the one-piece perimeter and chest seal design eliminates leakage paths because the chest seal wraps around the entire gate. The chest seal also completely encloses injectable packing, which eliminates contamination of the limestone slurry by “loose” packing. Additionally, even at low pressures, shutoff performance is unaffected by differential pressure, and bi-directional shutoff is excellent.

Finally, injectable packing allows easy packing adjustments under line pressure without valve disassembly or removal of the valve from the pipeline. These valve features provide a reduced total cost of ownership, easy maintenance and solution for the conditions present in the WFGD process.

DP&L accepted the proposal and installed 200 ITT Fabri-Valve® urethane-lined knife gate valves in their power plants. The valves have performed well with no maintenance issues. The improvements made at the five DP&L power plants will eliminate 97 percent of SO2 and a large portion of the fine particulate matter and mercury oxide emissions.

Conclusion
Ultimately, projects like this one will advance FGD technology in the utility marketplace and provide flexibility in fuel choices, regulatory compliance, reducing acid rain-causing emissions and a cleaner environment for local communities.

Heather Sandoe is marketing communications manager and David Peschell is global marketing manager-power industry for ITT.

The WFGD process in this article is a Chiyoda Corporation proprietary process under exclusive license to Black & Veatch for North America.

United Utilities is to construct a new sewer overflow chamber on Lostock Road, and to lay new connecting sewers on nearby streets. Work will start this autumn.

The overflow chamber acts like a safety valve for the sewer system when there is very heavy rain - by releasing excess stormwater into the nearby watercourse.

The new chamber will use latest screening technology to ensure that the stormwater released back into the environment is of a higher quality, and is free from rubbish and debris.

The local watercourse - Bents Lane Brook - is set to benefit.

A public exhibition will be held on Wednesday, July 14) at the 3rd Davyhulme Scout Hut, located off Conway Road, to explain the proposal to residents.

Residents requiring more information can phone United Utilities on 0845 746 2200, quoting project number NCA/80018801.

http://www.messengernewspapers.co.uk/news/8267676.A_better_environment__Lostock_and_barrel/