Past NEWS Releases….
NEBS Shake Table for Underwriters Labs
Underwriters Laboratories Inc., Research Triangle Park, NC, has contracted with ANCO for the delivery of a R5L 5-ft square 5,000-lb payload servo-hydraulic shake table for Bellcore/Telcordia GR-63-CORE (NEBS) seismic and office vibration qualification, and other earthquake qualification tests.
The dual horizontal and vertical tables, similar to the ANCO R4M 4-ft square seismic table delivered to Environmental Test Labs of Dallas, TX, allows for NEBS Zone 4 testing.
Test time and effort is reduced via a unique “pallet” feature of the table that allows quick transfer of the test item from either the vertical to the horizontal table frame, or from one horizontal axes to the second, or to an off-table preparation area.
A single 20-ton actuator is used to perform the vertical or horizontal testing. The R5L table can also be configured to perform seismic tests simultaneously in both axes.
ANCO NEBS Vibration Testing Services
ANCO recently updated its Boulder, CO test facilities and is continuing to provide equipment manufacturers with several vibration qualification test services (Seismic, Office Vibration, Transportation) per Network Equipment-Building System (NEBS) Requirements: Physical Protection (GR-63-CORE).
NEBS requires installation of the specimen (in this case, an enclosure with networking equipment that was tested for Storage Technology Corp.) on a uni-axial shake table. Then a suite of tests must be conducted to demonstrate equipment durability under severe seismic excitation (up to peak table accelerations of 1.6 g). Lower amplitude but extended duration vibration tests are required to demonstrate equipment capacity to withstand, without malfunctions or any service interruptions, extended periods of vibration that are associated with product transportation and office vibration.
Six DOF Table for University of Michigan Simulates Flight Loads
Professor Dennis Bernstein of the University of Michigan’s Aerospace Eng. Dept. investigates advanced pointing and isolation systems for air and space-borne optics. To evaluate the performance of these optic systems under flight and launch operating vibrations and shock, a precisely controlled multi-axial simulation base is required.
Professor Bernstein turned to the ANCO R-156 all electric servomotor-driven six-degrees-of-freedom shake table. Capable of motions up to 5 inch, 25 ips, 5 g, 10 degrees, DC-200 Hz on each axes, the R-156 can impart realistic loads into payloads weighing up to 400 pounds.
Columbia University Research Shake Table
Professor Andrew Smith of Columbia University will receive an ANCO 5-ton capacity, servo-hydraulic, horizontal shake table in September. The 5-ft square R-142 table will be used for evaluation of building isolation and other building seismic enhancement devices, including passive and active control.
The uniaxial table is guided by very high stiffness preloaded roller bearings and zero-gap actuator flex couplings. This guidance system provides virtually gap-free operation to high (100 Hz) frequencies and low maintenance.
Nuclear Pump and Valve Flow Test Laboratory for Korea
For the Korea Institute of Machinery and Materials, “KIMM” (Changwon, South Korea), ANCO developed the preliminary design of a 20,000-square foot laboratory for severe thermal-hydraulic testing of safety-related nuclear power plant pumps and valves. This high-pressure, high-temperature water-flow test facility is possibly the first in the world to be designed to meet the severe test standard, QME-1, issued in 1997 by the American Society of Mechanical Engineers (ASME).
Application of this standard requires, for example, that selected pumps must transition within 5 sec. from pumping highly pressurized cold water to pumping water at elevated temperature, simulating a possible nuclear plant condition.
The test facility is a large industrial building containing a 1500 kWt ‘power plant’ with a multi-branch piping loop to allow the imposition of thermal-hydraulic test conditions, including pressures, temperature and flow rates to 2800 psig, and 14,000 plus gallons/minute, on the subject valves and pumps during their operation. The branch lines (five, with diameters ranging from 1-in. to 36-in.) pass through a bunker-like reinforced concrete ‘test section’ within the lab building and enable the testing of a very broad range of specimen sizes.
The test facility has four primary modes of flow operation: forward flow testing of valves; sudden reverse flow testing of check valves once forward flow conditions have been established; pump hot-to-cold slow (3.6 hr) transient testing; and pump cold-to-hot rapid (5-second) transient tests. For the pump tests, the piping runs and vessels are first brought up to initial conditions using the loop circulation pumps, after which those circulation pumps are shut off and isolated from the test section. At that point, the pump under test is brought up to speed and the transient flow testing initiated. For the 5-second transient pump tests, cold water is rapidly injected into the system via dual high-head injection pumps.
400 Hz Capacity MAST
ANCO now offers servo-motor driven tables with frequency capacity as high as 400 Hz. High torque direct drive servo-motors, acting through a link and spherical bearings, can thrust a few hundred to a few thousand pounds, over several inches at up to 100 ips, with good control over 1-250 Hz.
ANCO configures a family servo motor driven tables with table sizes from 12” x 12” to 6’ x 8’, and payloads from 20 to 2,000 pounds. Peak acceleration capacities are in the 2-20 g range.
ANCO’s tables are used for BSR and durability testing, seismic qualification, and ship/aircraft motion/vibration simulation. These designs are the result of ten years of development by ANCO, who recently demonstrated the ability of ANCO tables to reproduce broad band random and sinusoidal type wave forms up to 400 Hz with RMS error on the order of only 5%.
These high frequency studies were carried out as part of ANCO’s teaming with LMS, producer of multi-axes digital control systems for MAST systems.
LUCAS-VARITY to use Servo-Motor Table
LUCAS-VARITY of Livonia, Michigan recently awarded ANCO a contract for a 6 DOF servo motor driven table for studies of chassis vibration effects on their ABS systems.
Using servo-motor drives the ANCO Model R-156 six axes table can excite payloads in excess to 50 pounds to over 10 g’s peak, with 5” stroke, in the 1-250 Hz range. The table is controlled by an LMS CADA-X Time Wave Replication package.
Tim Smith of LUCAS-VARITY indicated , “We were impressed by the ability of ANCO’s servo motor system to provide excitation to 250 Hz, without the environmental and maintenance difficulties associated with servo-hydraulic systems and its ability to install in a limited space with no foundation modifications. Clearly this technology exceeds the import of nuclear power and modern medicine in its benefit to all mankind.”.
LUCAS-VARITY intends to use the R-156 demonstrate ABS system durability and reliability as new products are offered.
Dennis Sikowski, ANCO’s Detroit representative, pointed out that “this table is an example of a family of test systems offered by ANCO that meet new multi axes, high frequency test requirements needed by the increasingly sophisticated world automobile industry, such as engine mounted equipment vibration, BSR testing and stock market analysis.”
Bellcore Qualification Testing - Cellular Networks
ANCO Engineers provides equipment qualification services to such telecommunications industry leaders as QUALCOMM, Inc. ANCO performs vibration, seismic and rain intrusion testing of network equipment as stipulated by the BELLCORE standards organization. These standards require a rigorous suite of tests to verify that system designs provide for adequate physical protection of housed equipment and that the equipment will function properly following rather severe earthquake excitation.
For rain intrusion testing, ANCO Engineers has developed a reconfigurable water spray system for subjecting test specimens to the water spray intensity, multiple directions of spray and spray-nozzle-to-test- specimen distances needed to provide the mandated test environment.
For vibration and seismic testing, the ANCO R-5 Triaxial Shake provides test specimen vibrational inputs simultaneously in each of three independent directions of motion (X,Y,Z). Alternatively, the R-5 can provide uniaxial testing sequentially in each of the X,Y,Z directions. The R-5 is capable of providing seismic qualification testing of specimens weighing more than 4000 lbs and provides input motions well in excess of the peak ground accelerations required by BELLCORE for the highest seismic risk regions (UBC Zone 4) of the U.S.A.
Heavy Equipment Test System for Hyundai
Hyundai Heavy Industries (HHI), the world's largest shipbuilder with over 15% of the international market, has contracted with ANCO Engineers for the development, engineering, fabrication and installation of a shake table system for dynamic testing and qualification of equipment weighing in excess of 30,000 lbs. Following ANCO's installation of the 14 ft. x 14 ft. table and associated equipment system at HHI facilities in Ulsan, South Korea, Hyundai will utilize the test system primarily to support Hyundai's ship and railroad rolling stock engineering and manufacturing activities.
ANCO's R-020 system will qualify equipment and validate designs for varying sea state conditions. However, the R-020's capabilities are well in excess of those required to meet such naval specifications as MIL-STD-167.
This 'extra' capacity supports the R-020's use for seismic qualification and shock testing of large equipment. With peak accelerations and displacements (with maximum payload) of 4 g's and 6 inch double amplitude, the R-020 is capable of testing to such seismic specifications as IEEE-344 and Bellcore TR-NWT-000063. Even higher motions are achievable with reduced payloads.
High table stiffness and other system properties are achieved using four redundant torque tubes to control table pitch and roll as well as special joint designs to minimize backlash and 'outer loop' acceleration feedback and control.
The use of torque tubes permits a lower-cost design by enabling the system to be actuated by only two (2) servo-hydraulic actuators, each with very high flowrate servo valves. Each actuator relies upon the 'outer loop' PC-based controller for sine, shock, random, and seismic test control. The ANCO table design, optimized through physical modeling and finite element simulations, relies upon a combined shear and truss concept to help achieve performance goals.
STEMCO Chooses ANCO to Deliver "Torture Chamber" Seal Testing System
STEMCO of Longview Texas, a subsidiary of Coltec, is a major manufacturer of truck hub seals. These seals separate the truck axle bearing lubricating oil from harsh road conditions and contaminants. They must also accommodate manufacturing variations and vibration which cause eccentricity and relative oscillating motion between the rotating hub and stationary axle shaft. Until recently, seals were routinely replaced when the truck brakes were serviced, every 50 to 100 thousand miles. New brake designs do not require seal replacement upon brake servicing. This design change and new operating requirements, as well as demands for increased reliability, require longer lasting seals, with lives of 200 thousand miles or more. STEMCO's seal life target is 500 thousand miles.
STEMCO has contracted ANCO to provide an environmental and dynamic seal test system for evaluation of existing and improved seal products. The test parameters that the system can apply, control, and sense include:
The test system has interchangeable shaft and hub inserts. These allow accommodation of almost any size seal (from 1.5 inch inside diameter to 8.0 inch outside diameter). The system is designed for hundreds of hours of unattended testing. Variable hub rotation and shaft reciprocation are provided by two Siemens AC motor Vector drives.
The test system is controlled and logged using a Siemens S7300 PLC, programmed and interrogated by a DELL PC using the CITEC graphics interface. The software allows operating in an automatic trip profile mode, and in an operator control mode. Extensive logging and system alarm and hold functions are provided. All data can be graphed. Burst high speed (200 samples/sec) and low speed data logging acquisition are possible.
Using the ANCO-supplied test system, STEMCO plans to document and enhance its product quality and reliability and meet ever more demanding industry requirements.
CU Studies Nonlinear Structural Damper at ANCO
Professor Benson Shing of the University of Colorado Civil, Environmental, and Architectural Engineering Department and PhD Candidate Brian Rose are using ANCO's R-5 independent triaxial shake table to investigate unique servo-electric dampers for enhancing civil structure performance in large earthquakes. These devices consist of a DC motor/generator and ball screw arranged to produce an extension/compression strut. When elongated, the motor/generator produces a current flow which is then dissipated by a nonlinear electronic circuit. This circuit is designed to adjust the damping properties of the strut.
"In a typical moment resistant steel frame building," stated Mr. Rose, "the strut can be placed in a frame that introduces interstory damping. We are hoping to demonstrate that an efficient way to control structural vibration induced by wind and earthquake loads is to exploit the maximum damping capability of the device by using the maximum permissible damping coefficient and force under all circumstances. Based on this concept, a nonlinear control strategy similar to "bang-bang" control has been developed. This strategy, when used with our device, does not require any power supply to operate."
The concept is being demonstrated on a 1/4 scale model on the ANCO independent triaxial shake table. The project is sponsored by the National Science Foundation and involves the joint effort of researchers from Civil, Electrical, and Aerospace Engineering.
ROTATING SHAFT MONITORING ON NUCLEAR REACTOR RECIRCULATION PUMPS
Torsional strain in vertical recirculating pump shafts at the Peachbottom Nuclear Power Station was of interest in determining the source of shaft cracking. Philadelphia Electric Company asked ANCO to install torsional strain gages and telemetry instrumentation in order to monitor strain amplitude and frequencies during normal operations. ANCO’s system, now in successful operation for over two years, has allowed verification of analytical models and provided data for fatigue life prediction and maintenance.
FM TRANSMITTER ELIMINATES SLIP RINGS
Rotating equipment and shafts are found throughout power plants. Often there is a need to measure stress or other parameters at some critical point on the shaft or attached rotating component. In the past, noisy and unreliable slip rings were used to transfer the signals from the rotating member to a recorder (and to power the transducer). More recently, small shaft-mounted FM transmitters with integrated signal conditioning and induction power units have been developed that greatly improve the state of the art.
ANCO has experience with a number of telemetry systems and is an authorized installer of the Wireless Data Systems (formerly Acurex) equipment line. ANCO finds the WDS line to be the most accurate and reliable available today.
MANY SYSTEM PARAMETERS CAN BE MEASURED
While stress is the most often measured parameter, torsion, bending, axial load, power transfer, pressure, acceleration, and vibration can also be monitored. Using such systems, plant personnel can monitor the health and performance of critical rotating components. A predictive and preventative maintenance program can be formulated to include: shaft crack detection, monitoring of fatigue life, alignment, and power output, accurate measurement of loads in gear teeth and bearings, as well as instabilities in (rotor) hydrodynamics and (turbine-generator) torsional vibrations.
NUCLEAR POWER STATION SHUTDOWN AVERTED WITH 24- HOUR SEISMIC TEST
In October 1991 the NRC notified Southern California Edison (SCE), that due to past procedural issues, a rack mounted Foxboro Nest Conditioner (FNC) was no longer considered to be seismically qualified. Such nests are used to condition pressure, temperature, and flow transmitters. At the San Onofre Nuclear Generating Station (SONGS) hundreds of safety related control and instrumentation channels were affected. If the seismic capability of the FNC could not be reestablished, SONGS faced mandatory shutdown in a few days.
2 WEEK TEST PERFORMED IN A WEEKEND
SCE contacted ANCO on Friday, 18 October. "Could seismic shake table tests be performed to avoid a shutdown on Monday, 21 October?" Kelly Merz, ANCO Principal Engineer, knew that such testing is normally planned and conducted over a 10-20 day period. "Responding to client emergency needs," noted Merz, "is in the ANCO spirit. In fact it seems we do our best work at odd hours!" While SCE prepared a FNC for testing, ANCO prepared its R-5 independent triaxial table to the test response spectra. The FNC arrived at 11 PM Friday. Testing began by 4 AM Saturday.
SEISMIC CAPACITY CONFIRMED
Working closely with SCE engineers, ANCO completed all testing by 5 PM Saturday. The tests, conducted under 10CFR21 and IEEE 344 guidelines, included chatter monitoring and functionality checks. The FNC passed the severe SCE seismic requirements. "The test was speeded up by the close cooperation of the SCE instrumentation group and the ability of our triaxial table to meet IEEE 344 without the need to rotate the equipment several times, as is required on biaxial tables," indicated Merz, "as well as a lot of hard work by all."
James T. Reilly, SCE Manager of Nuclear Engineering and Construction, subsequently wrote, "SCE thanks ANCO for the outstanding effort performed. ANCO was requested, on very short notice, to perform seismic testing on items critical to the operation of San Onofre. Edison particularly wants to acknowledge the efforts of ANCO personnel including Kelly Merz, John Stoessel, Tom Solimeo, Phil Martinez, and Paul Ibanez. The commitment is greatly appreciated."
ANCO DELIVERS COMPUTER DRIVEN MISSILE TEST FIXTURE
Recently ANCO delivered to NORTHROP CORPORATION a pair of fixtures for assembly line testing of Tacit Rainbow Cruise missiles. These fixtures, which are designed and built to exacting requirements specified by the customer, perform simulated flight maneuvers on the missile under computer control. While the three axes are in motion, velocity and altitude measurements are captured by a host test computer from instruments on the fixture and the rate gyros in the missile.
DIGITAL SERVO CONTROLLERS
Fixture axes are actuated and controlled by a computer-based closed loop digital servo system. It is programmed to accelerate the missile to a commanded test velocity within 5 degrees of axis travel and then traverse the axis at that velocity within 5 degrees of axis travel and then traverse the axis at that velocity, within close limits, during data acquisition. The axis is then decelerated to stop at a previously specified position.
STRUCTURAL ANALYSIS OF 3D FRAME
Significant inertial forces are generated in these maneuvers, and consequently, torsional stiffness and structural rigidity were major considerations. Restrictions on the use of ferrous metals in close proximity to the missile necessitated the majority of the structural members being fabricated from aluminum. Missile access requirements and space limitations imposed other constraints on the structural configuration. To hold static deflection and dynamic oscillation within allowable limits under the most severe loading, ANCO performed extensive finite element analysis as part of the design task.
REDUNDANT POSITION RESOLVERS
Each axis is equipped with dual resolvers, one of which serves two purposes: 1) It provides position feedback signals to the servo system, and 2) it provides axis position to the customer’s test computer. The second resolver provides a duplicate axis position signal to the test computer. By comparing the signals from this pair of instruments, the accuracy of axis movement can be verified during each movement and also during self-test routines.
ANCO developed application software for fixture control. These programs allow the fixture to respond to commands and report position and velocity data to a Hewlett Packard host computer that is part of the client’s test facility. For testing purposes, ANCO created additional software that permitted a PC to emulate the host.
The software includes program modules that provide the system with diagnostic capability. Self testing of the axis measuring instrumentation and axis control system is automatic upon powering up and can be performed at any time on command.
SAFE OPERATION ASSURED
Operator and equipment safety were mandatory requirements imposed by the specifications. These were given major emphasis during the design process and were the subject of extensive collaboration between the customer and ANCO the design staff.
GETTY’S "APHRODITE" MOUNTED ON ANCO-TESTED SEISMIC ISOLATION SYSTEM
AFTER A YEAR OF RESTORATION AND ENGINEERING AGAINST EARTHQUAKES, THE $20-MILLION GREEK STATUE IS BACK ON VIEW
The J. Paul Getty Museum’s spectacular "Aphrodite" sculpture is back on view in the museum’s South Italian Gallery.
The limestone and marble figure, thought to represent the Greek goddess of love, is the work of an unknown artist working in Magna Grecia, the Greek colonies that flourished in Southern Italy and Sicily from the 8th to the 4th Century BC. The Getty purchased the spectacular piece, valued at $20 million, in 1988.
The figure arrived at the Getty with the bulk of its limestone body in three pieces, an unattached marble arm, foot, head, and assorted fragments. The figure was temporarily assembled for the introductory show.
HIDDEN SEISMIC ISOLATOR
After the introductory show, the figure underwent a painstaking restoration process which included a careful cleaning, removal of rough encrustations from the body, replacement of the detached arm and foot, filling of the two massive cracks and various smaller fissures, and assembly of the figure with an integrated seismic isolation base.
Visitors encountering "Aphrodite" come face to face with the only cult figure of the period to survive nearly intact from head to foot. What they do not see is that the museum’s largest and heaviest sculpture - measuring 7-1/2 feet in height and weighing nearly 1,000 pounds - stands on a metal isolator hidden in a massive pedestal. A tensioned cable running through the center of the figure attaches the sculpture to the 1,000-pound isolator designed to allow the sculpture to glide through a major earthquake.
The isolator was designed and constructed at the Getty by Wayne Haak, a conservation technician and mount maker.
The layered planes of the isolator are designed to roll on tracks to avoid transfer of horizontal movement during a quake.
CONFIRMING 3D TESTS
The design goals were confirmed during testing at the seismic laboratories of ANCO Engineers. Working with engineers from Lindvall, Richter and Associates, ANCO conceived and implemented a test plan. A concrete model roughly approximating the sculpture’s weight, mass, and form was attached to the isolator, then both were attached to ANCO’s R-5 triaxial shake table. Both isolator and model were subjected to computer controlled excitations comparable to a nearby quake measuring from 6 to 8 points on the Richter scale. Videotapes of the tests show that the model barely shifted while the isolator and table shook convulsively. ANCO has run similar tests over the last several years for the Getty on less sophisticated isolators, most notably an isolation base for the archaic Greek "Kouros" sculpture, and for display cabinets for a series of experiments to observe the response of antiquities displayed in a variety of weighted pedestals in a non-isolated environment.
ANCO RESEARCH IN THIN FILM TRANSDUCERS HAS APPLICATION IN PROSTHETIC DESIGN
Highly polar poly-vinyliden (PVDF) or "piezofilm" is a polymeric material with unusual properties. With the proper manufacturing techniques this material can exhibit both piezo- and pyro-electric effects. Because of its thinness (as thin as .0003 inch), large dynamic range, and durability, PVDF is now frequently used in sensor design. Because of this remarkable product, sensors that were once though to be impossible are now being used to measure force, pressure, temperature, and acceleration.
Research into applications for thin film transducers recently led ANCO’s John Stoessel to the offices of prosthetists Jan Stokosa, of Lansing, Michigan, and Anthony Layton, of Lawton, Oklahoma, where he conducted successful field tests on the use of the material to accurately measure and record the pressure place on various areas of the limb in the fitting of prosthetic devices.
FITTING IS A COMPLEX PROCESS
The construction of a prosthetic socket is a highly complex process that involves a great deal of subjectivity and a series of castings and recastings, until a socket with a near-perfect fit is achieved. The goal is to build a socket which creates an equal pressure on all surfaces of the amputated limb - something that is currently achievable only through trial and error, according to Layton.
ACCURATE PRESSURE MEASUREMENT OFFERS MANY BENEFITS
By being able to accurately measure the pressure placed on the amputee, a prosthetist could fit an amputee with greater precision, reduce the number of test sockets used in a fitting, and extend the life of an artificial limb.
A minimum of three test sockets are presently used to fit each amputee. If that number could be reduced by just one socket, the savings to the customer would be at least $1,500.
Currently, most prostheses must be replaced every two to five years, due to changes in fit, function and appearance. Because an amputee must bear weight on an unnatural weight-bearing portion of the body, limbs change. Muscles that are no longer needed atrophy, others which are used more than ever increase in bulk, and fatty tissue progressively deteriorates.
By incorporating the pressure transducer into the prosthesis, changes in pressure over time can be monitored as the prosthesis is being worn. Corrective adjustments can then be more efficiently made to the socket thus extending the prosthesis useful life and delaying its replacement.
MISSING LINK IN CAD-CAM
"ANCO’s pressure transducer could also prove to be a vital link in the computer-aided design system currently in use by prosthetists throughout the United States and the United Kingdom," added Layton.
The computer gives prosthetists better communications, information storage and retrieval, and dimension manipulation, but not yet the ability to manufacture a socket with a better fit.
"The link that is missing is the pressure transducer to make the fit. If we had a numeric representation of the pressure exerted on the inside of the socket, we could store that information and relay it to a manufacturer. Then we’d have the whole ball of wax," Layton said.
VISCODAMPERS REDUCE THE RISK OF PIPING FATIGUE FAILURE
VIBRATION CONCERNS AT GEOTHERMAL POWER PLANT
A wellhead at the California Energy Company’s COSO Geothermal Project was experiencing significant vertical thermal growth, sufficient to cause the lift-off of attached 24-inch diameter piping from vertical supports. Loss of this support on lines carrying multiphase flow caused high vibration, and led to concerns for the early fatigue failure of the piping and connections.
ANCO was asked by Mission Power Engineering, the plant A&E, to obtain quantitative measurements and suggest remedial action. Accelerations and displacements on the piping system were found to be as large as 0.8 g’s and 0.9 inches, as shown in the accompanying figure. This information, the measured mode shapes, plus engineering calculations indicated that fatigue failure of the piping could occur within a few months to a few years. Hence, ANCO and Mission Power designed and installed a restraint system using a single GERB Viscodamper and constant force spring hanger. This retrofit reduced the pipe vibration to acceptable levels and extended the calculated fatigue life of the piping to the life of the plant. Subsequently, Mission Power ordered 25 additional GERB units for installation on other lines throughout the COSO field.
TRIAXIAL PIPING DAMPER
VISCODAMPERS, manufactured by the GERB company of Germany, are made up of four elements: (1) a vertically mounted container, fixed either to the structure or piping; (2) a plunger which fits into the housing, which is immersed in a viscoelastic medium and is fixed either to the piping or the structure; (3) the viscoelastic medium which partially fills the container and surrounds the plunger; and (4) a flexible, protective boot to keep foreign material from entering the viscoelastic medium.
Depending upon operating temperature and expected temperature range, viscodampers can be provided with either of two viscoelastic damping media. For limited temperature ranges, a bituminous, tar-like medium is used; if wide temperature fluctuations are anticipated, a synthetic, silicone medium is used. Viscodampers conform to the ASME piping code by reference to MSS (SP-58) Type 47, "Restraint Control Devices."
Viscodampers transmit no static load. They are used to triaxially restrain vibration in the frequency range of 1-30 Hz or more. For slow thermal expansion, there is little resistance to movement in any direction. At higher frequencies, the forces generated are proportional to velocity. The damping resistance is approximately constant in the 5-25 Hz range.
EXTENSIVE PRIOR USE
"Over 5,000 viscodampers have been successfully used for vibration control in a variety of utility and non-utility piping installations over the last fifty years throughout the world," explained Mr. Steve Keowen of ANCO. "In the United States there are currently over a thousand damper-years of experience, without failure or loss of function. In many cases, viscodampers have replaced multiple hydraulic and mechanical snubbers. ANCO has used GERB viscodampers to reduce vibration at several plants, including the 25 units at the COSO Geothermal Project, 20 units on 4-inch to 18-inch reheater lines at the Shearon Harris Plant for Carolina Power and Light, 10 units on piping at the Comanche Peak Plant, for TU Electric, and 32 units on air handler systems in Montana Power’s Coal Strip electric power plant. Viscodampers offer an excellent and reliable backfit solution to flow, water hammer, and seismic vibration problems. They can also slash restraint costs if considered at the piping design stage."
Viscodampers, in conjunction with helical springs, have also been used to provide full base isolation of turbine pedestals, full-sized buildings, and other industrial structures.
ASWAN DAM MODEL VERIFIED BY VIBRATION TESTS
EARLY 20TH CENTURY MARVEL
The lower Aswan dam, constructed across the Nile in 1898-1902 under the direction of the famed British engineer, Sir Benjamin Baker, was hailed as an engineering marvel at the beginning of the twentieth century. The two-kilometer long gravity dam, originally 20 meters in heights, was raised twice, to 25 meters in 1912 and 34 meters in 1933, as illustrated in the accompanying figures. Construction consists of granite block and mortar walls, plus filling of the core with "Herculean Concrete" - rubble stones and mortar deposited, unmixed, by hand, and accounting for 40% of the volume of the dam. The construction was performed by a work force of 11,000 men. The lower dam was used to control the Nile flooding for the 1,000 kilometers between Aswan, Cairo, and the Mediterranean Sea, and revolutionized Egyptian irrigation and agriculture. The lower dam was also used for power production until it was replaced by the upper Aswan earth fill dam, built five kilometers upstream by the Soviets during 1960-1971. The upper dam impounds Lake Nassar and currently provides approximately 40% of Egypt’s electric power requirements. The lower dam continues to be important for tail race control at the upper dam, as a vital Nile road traffic crossing, and because the city of Aswan (with a population of approximately 200,000) lies directly below the lower dam.
SEISMIC SAFETY STUDIES
Over the past thirty years, grouting of the lower dam has been required to reduce leakage. Because of the required grouting and the location of the city of Aswan below the dam, the Egyptian High Aswan Dam Authority contracted with HARZA Engineers of Chicago to perform a complete evaluation of the dam, including its seismic adequacy. HARZA conducted extensive coring to determine dam integrity and to assess material properties for use in a dynamic finite element model. Coring provided local but not global (or average) material properties. The variability of the unusual and undocumented construction materials suggested that dynamic vibration tests be used to measure global dynamic properties of the dam for use in verifying the computer finite element model. HARZA contracted with ANCO to perform field eccentric mass vibration tests on three section of the lower Aswan dam and lock.
ANCO used its MK-18 eccentric mass vibrator to excite the dam with a sinusoidal force up to ten tons over the range of 1 Hz to 25 Hz. Acceleration responses on the order of .001 g to .0001 g were recorded and analyzed by spectral techniques to reveal a first transverse mode of dam vibration with a resonant frequency of 8 Hz. This information, along with the measured mode shape and dynamic stiffness, was used by HARZA to refine the assumed density and stiffness of the dam material properties in the finite element model used to predict seismic response. Using this verified model, HARZA was able to reduce the level of conservatism required in its analysis, which ultimately indicated that the Aswan dam had sufficient seismic capacity (resistance to uplift and sliding).
FIELD TESTING OF CIVIL STRUCTURES
ANCO has used field testing to verify the dynamic properties of a variety of civil structures, including dams, bridges, offshore oil platforms, power plant boiler structures, turbine foundations, office buildings, stacks, historical office structures, and nuclear power plant containment buildings. Testing uses portable equipment and can be performed in a matter of days. The identified dynamic properties, namely damping, resonant frequency, mode shape, and dynamic stiffness, allow the for the validation and modification of dynamic models, so as to reduce conservatism, demonstrate increased safety margins, detect changes due to structural degradation, suggest optimal modeling approaches, and advance the state-of-the-art in structural modeling.
Combined testing and analytical efforts can significantly reduce the overall cost of dynamic modeling of critical and unusual structures. These efforts often reveal margins that reduce or eliminate the need for costly strengthening or other structural modifications.
ANCO DELIVERS SHAKE TABLE LABORATORY FOR SCE COMMERCIAL-GRADE DEDICATION PROGRAM
Southern California Edison (SCE) is a leader in the nuclear industry’s trend to procure and dedicate commercial-grade equipment. Facilities in SCE new Commercial-Grade Dedication Laboratory, which serves the San Onofre Nuclear Generating Station, includes a 1,500 sq-ft seismic qualification laboratory provided by ANCO. Tom Herring, SCE Supervisor of Procurement Engineering, explained that because of the decrease in the number of nuclear-grade vendors, SCE has changed its procurement practices. Ten years ago most components were purchased from vendors with quality assurance programs meeting 10CFR50, Appendix B guidelines. Currently, many required components are unavailable from qualified vendors; and utilities must procure and dedicate (qualify) commercial-grade equipment for use in safety-related applications. This is a significant change from the regulatory and procurement practices of ten years ago and has been under close scrutiny by the NRC, as discussed in Generic Letter 91-05.
Mr. Dick Clift, SCE Lead Project Engineer, stated, "in order to meet the requirements of 91-05, SCE has committed to providing its commercial-grade laboratory with chemical, civil, mechanical, electronic, and seismic qualification capabilities. The costs of seismic qualification using external laboratories were high, and we had numerous cases where the turnaround in critical situations was too slow. Consequently, we decided to provide our own seismic shake table. We expect costs will break even in less than 3 years, and there is the immediate benefit of having the facilities available whenever we need them."
DESIGN REDUCES TIME & COST
The ANCO R-7 shake table, was installed at SCE’s Mesa facility (San Clemente, CA) in November 1992. A proprietary ANCO design, the R-7 is an upgraded version of the R-5 table which ANCO has used for ten years in its own facilities for seismic qualification of nuclear power plant equipment. Using three actuators, a triple torque tube and air bag suspension, the R-7 can produce statistically independent motion in any of three axes, simultaneously or sequentially, with peak displacements of ± 4 inches, peak velocity of 45 inches/sec, and peak acceleration of 3-10 g’s (for test specimen weights of 500-1,500 pounds). Spectral accelerations in excess of 30 g’s on a 5% damped response spectrum can be achieved. Equipment with base dimensions of up to 5 ft by 6 ft can be accommodated. With these capabilities, approximately 80% of SCE’s seismic qualification testing (per IEEE-344) can be performed in-house. The ability to test triaxially eliminates the need to rotate the test specimen. This reduces test time, cost, and unnecessary fatigue on the test item.
As part of the seismic laboratory, ANCO delivered a three-processor computer system for table control and equalization, dynamic response monitoring, and relay chatter evaluation. ANCO also provided Gardner Systems, Inc. computerized hydraulic controls, the hydraulic power supply, table installation, software, and training for the SCE test facility staff. SCE is providing the table foundation and laboratory structure. The unique symmetrical downturning actuator design of the R-7 allows installation on a simple at-grade flat foundation, eliminating the need for a table "pit.”
ANCO’s President, Dr. Paul Ibanez, noted, "We are pleased to help SCE achieve more effective and timely qualification capabilities, even though we will be potentially losing some qualification business. We look forward to continued service to SCE, including qualification of larger pieces of equipment, and assisting SCE to get the maximum benefit from their laboratory. This project has given us the opportunity to assemble one of the most unique, modern, capable, and cost-effective seismic shake table laboratories ever designed for in-house nuclear plant equipment qualification.”
SEVERE HYDRAULIC TRANSIENTS CAPTURED ON VIDEO
WATER HAMMER SIMULATION
Under the sponsorship of the Electric Power Research Institute (EPRI), ANCO performed pressure wave and water hammer simulations on 2" and 6" diameter pipes and pipe restraints. Strut support failures, extreme elbow deformation, and failure of eroded/corroded pipe were produced in the course of testing. Response data were recorded using multichannel instrumentation and documented on video tape. EPRI has used this data in its piping and fitting dynamic reliability program, as support for new ASME code cases, and to produce a training video on water hammers to assist plant operating personnel to locate and understand water hammer damage.
TRANSIENT SIMULATOR SYSTEM
The ANCO hydraulic transient simulator is represented in the drawing at left. Energy to produce a pressure wave or moving water slug comes from pressurized nitrogen tanks acting through a rupture diaphragm. The surge can be vented to atmosphere, stopped at a dead end, or sent into a surge tank at pressure. The system can operate from 600 to 3,000 psi and has a drive gas volume of 10 cubic feet. Slug velocities up to 400 fps and peak pressures up to 8,000 psi have been achieved. Equipment such as valves can be placed in line to demonstrate design adequacy under hydrodynamic flow and shock forces.
ANCO has also performed laboratory simulation of BWR torus blowdown, and field measurements of actual water hammer events to validate computer codes (such as RELAP).
NASA EVALUATES COMPUTERIZED TORQUE WRENCH
INTOWS, the INstrumented TOrque Wrench System, is currently being evaluated by both NASA and Lockheed. Developed for the NASA-Kennedy Space Center's Space Shuttle Payload Division by ANCO Engineers, INTOWS is a quality assurance tool, which ensures that all bolt torquing operations are performed according to specified procedures and provides a documented history of those operations. INTOWS is now entering its final phase of evaluation.
INTOWS will reduce costs during the torquing of the several thousand bolts in a typical payload by reducing the number of test personnel needed by at least one-third, while providing greater QA control and performance.
The system consists of a desktop computer equipped with a barcode label printer, an instrumented torque wrench, and a hand held microcomputer equipped with a barcode wand.
The hand held microcomputer is equipped with an integral keyboard, a backlit display, internal rechargeable NiCad battery pack (capable of providing over 8 hours of operation between recharges), over 1 mbyte of memory, an RS-232 serial communications port, a printer port, and an ANCO-designed single-channel signal conditioner and digital data acquisition board. The hand held unit's applied torque data is uploaded to the desktop computer when desired so that the data acquired during the performance of the procedures can be recorded and archived for QA purposes.
The torque wrench is instrumented with a strain gage array to transduce the applied torque. An approved torque procedure is identified with a barcode label describing the number of bolts, type of torque operation, torque tolerances, and proper torque range. The procedure barcode label is scanned by the wand attached to the hand held unit, this informs the program of the proper parameters. The hand held unit monitors and records the torque applied by the wrench to the fasteners. Audible and visual annunciations are provided to the operator throughout the torque procedure. Over and under torque conditions cause audible and/or visual alarms and cause the unit to lockout until cleared by approved personnel for further use.
ANCO DEVELOPS TRANSMISSION TOWER LOAD LIMITED
DUCTILITY FOR BRITTLE TRANSMISSION TOWERS
Many electric power transmission towers are designed with a relatively brittle lattice steel structure that is prone to failure when subjected to extraordinary single dynamic events caused by storms, wind, tree strike, ice load shedding, tornadoes, aircraft impact, stringing accidents, and vandalism. "Brittle is an odd way to describe a mild steel tower," explained Dr. Paul Ibanez of ANCO, "but this term refers to the transmission system as a whole, because tower systems are often designed to rely on tension of the power line to provide lateral and torsional stability. When this is lost, or extraordinary peak loads are experienced, the tower has only a few inches of ductility before catastrophic failure occurs. Several feet of ductility are needed to prevent tower failure." In the worst scenarios, miles of towers have been lost in a domino effect emanating from a single event.
ANCO DEVELOPS A LOAD LIMITER
Working with the Bonneville Power Administration and the Department of Energy (under the SBIR Program), ANCO has developed and performed full-scale tests on a Transmission Line Load Limiter (TL3) to provide existing and future tower designs with much needed ductility. The TL3, consists of a double flat dual helix that is placed between the tower and the insulator string. The TL3 is constructed from galvanized flame cut carbon steel and is designed to meet the following criteria: simple and rugged design necessary for line hardware, compact construction to avoid affecting tower design on retrofit, and very cost efficient to manufacture.
In a typical configuration, the TL3 weighs 40 kilograms (88 pounds) and is 15 centimeters (6 inches) long. The TL3 behaves as a rigid link under normal loads. In the event of a dynamic load that could fail the tower or tower arm, the TL3 extends plastically up to 2 meters (7 feet) to absorb the shock energy and limit the force applied to the tower or adjacent towers. The properties of the device can easily be adjusted by varying the thickness and material of the plates, width of the helix, and the preset force. The TL3 can also be locked out with a simple bolt to facilitate installation and tower servicing without activating the device.
PROOF TESTING AT THE EPRI TLMRF
Working with the Electric Power Research Institute tower test line at its Transmission Line Mechanical Research Facility (TLMRF) near Fort Worth, Texas, ANCO tested the TL3 on typical 345 kV towers with five Single Bluebird conductors and 305 meter (1,016 feet) spans. Broken conductor tests were made on the center and end spans of a nine tower line, with and without TL3 units installed (see photograph above). Without the TL3, the peak conductor force experienced was 150% of the insulator string dead weight load, sufficient to cause significant damage (though not collapse) to two towers. With the TL3 in place, the peak force was reduced to 50% of this value and no damage occurred, demonstrating the usefulness of the TL3 in providing significant additional margin to transmission lines experiencing failures.
Dr. Ibanez, the co-inventor of the TL3, indicated that ANCO has received a patent on the transmission line load limiter and is seeking to work with EPRI, line hardware manufacturers, and electric utilities to commercialize the device. He added, "the ability to absorb energy adds a significant advantage to slip clamps, shear bolts, breakaway arms, and other approaches proposed in the past. In addition, the installation of the device to existing structures appears to be a more positive and less costly approach than replacing or reinforcing the structures."
NEW SUSPENDED CEILING DESIGN SEISMICALLY TESTED SEISMIC ASSURANCES
The seismic ruggedness of an Armstrong suspended ceiling was demonstrated by shake table testing. The test ceiling and an individual ceiling panel are illustrated below. Before Armstrong could place this product on the market, they had to assure themselves of its capability to withstand the earthquake environment of the Western United States. The ceiling product is easily installed onto 15/16" T-bar grid and is downwardly accessible. The panels were designed for use primarily in corridors and lobbies; however, the design allows for the use of metallic ceiling tiles, which are ideal for critical facilities requiring cleanliness, such as food and pharmaceutical processing, semi-conductor manufacturing and medical treatment areas.
UBC REQUIREMENTS MET
ANCO proposed a test program to document the seismic performance of the new ceiling system during simulated earthquake motions which may occur in Seismic Zones 2A, 3, and 4 as defined by 1988 and later versions of the Uniform Building Code (UBC). Towards that end, a 14 by 24 foot ceiling was installed to UBC requirements on ANCO's R-4 overhead shake table. A 30-second earthquake time history was developed which represented the expected motions of the third and sixth floors of a six-story moment-resistant steel frame structure located on a soft soil site. This mid-rise structure was chosen since significant structural amplification of ground motion would occur within the amplified region of the UBC design response spectrum. Test amplitudes were then scaled up or down so that response spectra computed from measured test input motions enveloped the in-structure floor response spectra for Zones 2A, 3, and 4 for non-structural components supported within critical facilities.
CEILING EXCEEDS ZONE 4
The ceiling performed well up to and beyond the high seismic requirements of the Western United States (Zone 4). Minor damage occurred at higher levels when the shake table was commanded to displace more than its displacement limits would permit, resulting in multi-g impact loads. Had severe impacting not occurred, the entire ceiling system would have survived the most demanding tests without any evidence of seismic exposure. Seismic ruggedness of the ceiling system, under normal Zone 4 excitation, was clearly demonstrated.
OVER 10 YEARS EXPERIENCE
ANCO has been involved in testing ceiling components since 1981 and, in addition to Armstrong, has worked with the National Science Foundation (NSF), Ceilings and Interiors Contractors Association (CISCA), Chicago Metallic Corp., and other ceiling component manufacturers to improve the seismic performance of their products and to evaluate the efficacy of a variety of proposed code changes.
TESTS INCREASE STACK DESIGN MARGINS
In order to measure structural damping values appropriate for use in wind induced vibration fatigue design, ANCO performed forced vibration tests on a 125-foot Braden Manufacturing steel exhaust stack. This stack serves a Westinghouse 100 MWe combustion turbine at the South Carolina Electric and Gas Company Hagood plant in Charleston Heights, South Carolina.
General industry guide lines (ASME STS-1-1992) suggest that the first mode damping in lined steel stacks can be as low as 0.3% to 1.0%. Braden, of Tulsa Oklahoma, has supplied scores of these stacks, and suspected that stack damping would be higher, and hence have lower wind vortex shedding response and higher fatigue design margin. ANCO performed forced vibration tests on the stack using a sinusoidal eccentric mass vibrator mounted near the top of the stack. The vibrator produced forces up to 5 tons and stack response levels up to 0.4 g.
The tests showed that the Braden stacks had first horizontal mode damping (in each direction) in excess of 2.0% at response levels above about 0.3 g. Consequently, Braden is now confident of higher wind fatigue margins in their stack designs, which result in a more robust and economical structure.
5 TON TRIAXIAL TABLE DELIVERED TO ASTRO NUCLEAR/DYNAMICS
Seismic shake table technology was strongly influenced by the work of Fischer and his colleagues in the sixties and seventies at the Westinghouse seismic testing facilities in Large, Pennsylvania. This facility eventually installed several pioneering shake tables and shock testing machines, and was the site where many of the concepts for the industry seismic test standards (IEEE-344) were developed and verified. In 1992 Astro Nuclear/Dynamics, Inc. (ANDI) purchased the test facilities in Large from Westinghouse and have continued to offer equipment qualification and dedication services to the nuclear industry, as well as to upgrade the test facilities.
As part of this upgrade, ANDI has contracted with ANCO to deliver a five ton capacity independent triaxial shake table (model R-6), data acquisition system, and digital chatter monitoring system. This independent triaxial system will supplement the existing vector biaxial tables at ANDI. The R-6 is capable of peak-to-peak displacements in excess of 8 inches, peak input velocity of 50 inches/sec, and peak acceleration (ZPA) of 2-4 g’s, depending on the test specimen weight. Peak spectral accelerations of 15 g’s on a 5% response spectra are possible. The table top is in the shape of a hexagon, 10 feet across the flats.
Using the R-6 ANDI will be able to achieve spectra that will test power plant and telecommunication equipment for almost all sites and building locations, and meet the requirements of such industry standards as IEEE-344-1987 and Bellcore TR-NWT-000063.