Acceleration and support post deformation measurements during surface and tunnel transport of a LHC Short Straight Section

Transcription

1 CERN CH 1211 Geneva 23 Switzerland Group Reference.: TS-IC/KA-OC EDMS No.: Technical Note Acceleration and support post deformation measurements during surface and tunnel transport of a LHC Short Straight Section K. Artoos, O. Capatina Abstract This technical note is a complement to the technical note [1]. The former technical note dealt with the experimental modal analysis and the road transport with transport restraints and special suspension. The present note describes the measured accelerations and support post deformations during road transport at reduced speed without end restraints or special suspension. This note also reports the accelerations and support post deformations during handling and tunnel transport with the dedicated tunnel vehicle. The measured accelerations are compared with the specified acceleration limits. Keywords: LHC Short Straight Section, transport, handling, tunnel vehicle, vibration January 2004 Distribution: K. Artoos, C. Bertone, N. Bourcey, O. Capatina, M. Gandel, M. Gielen, C. Hauviller, G. Huet, K. Kershaw, M. La China, B. Nicquevert, V. Parma, A. Poncet, S. Prodon, P. Rohmig, I. Ruehl. Secretariat Yvette Ninet/TS-ABS

2 i Table of Contents 1. INTRODUCTION INSTRUMENTATION AND ACQUISITION Accelerometers Linear Variable Differential Transformers (LVDT) Shock logger Acquisition Position of the instrumentation ACCELERATION AND SUPPORT POST DEFORMATION MEASUREMENTS DURING ROAD TRANSPORT Road transport description Results LOWERING DOWN PX ACCELERATION AND SUPPORT POST DEFORMATION MEASUREMENTS DURING TRANSPORT AND HANDLING WITH THE LHC MAGNET TUNNEL VEHICLE Emergency stops and power cuts Steps of 8 mm when moving at 3 km/h Unloading of the SSS with the tunnel vehicle unloading equipment (UE) Driving over the tunnel floor STATIC DISPLACEMENTS OF THE SUPPORT POSTS CONCLUSION ACKNOWLEDGEMENTS REFERENCE...12

3 ii List of figures Figure 1 Position of the transducers on the Short Straight Section...2 Figure 2 SSS5 installed on the road transport trailer...3 Figure 3 ShockLog / accelerometer measurement during the same vertical event (ShockLog installed at the cold mass bottom / accelerometer installed at the cold mass top)...4 Figure 4 Lowering of SSS5 down PX Figure 5 Longitudinal acceleration and support post deformation during an emergency stop at 1 km/h on a floorunevenness (24ES)...6 Figure 6 - Longitudinal acceleration and support post deformation during a power cut at 3 km/h (2powercut)...6 Figure 7 Vertical acceleration of the up stream cold mass extremity when going over a step of 8 mm at 3 km/h (1step8mm)...7 Figure 8 Detail of figure 7 and frequency analysis...7 Figure 9 Lateral acceleration during lifting with CTU lifting cylinders...8 Figure 10 Longitudinal static deformation of the up stream and down stream support posts during lifting with the UE (4UErising)...8 Figure 11 Lateral support post deformation during transport over tunnel floor at 3 km/h (2driving3km)...9 Figure 12 Lateral acceleration of cold mass extremity during transport over tunnel floor at 3 km/h (2driving3km) 9 Figure 13 Deformation/ displacement when the SSS was not moving...10 List of tables Table 1 - Maximum measured accelerations and support post deformations during road transport...3 Table 2 Specified maximum allowable support post deformations (mm)...4 Table 3 - Maximum accelerations during lowering into the tunnel...5 Table 4 Maximum measured accelerations and support post deformations during emergency stops (E.S.) and power...6 Table 5 - Maximum measured accelerations and support post deformations when going over a step of 8 mm...7 Table 6 - Maximum measured accelerations and support post deformations during unloading...7 Table 7 - Maximum measured accelerations and support post deformations when driving over the tunnel floor...9 Table 8 Maximum measured accelerations on the cold mass extremities...11 Table 9 - Maximum measured deformations of the support posts...11

4 1 1. INTRODUCTION Dynamic loads during the transport and handling of the LHC Short Straight Section can be dangerous for fragile components such as the support posts. This note discusses the measurement of the dynamic behaviour of a prototype short straight section SSS5 without transport restraints during road and tunnel transport. The SSS5 is a prototype short straight section with a vacuum barrier. The cold mass consists of a main quadrupole and the dummy masses of an octupole and a sextupole-dipole corrector. The prototype support posts have been manufactured by TAM. This technical note is a complement to the technical note [1]. A different road vehicle was used without a special suspension. The accelerations of the cold mass extremities and the dynamic deformations of the support posts were measured during road transport, during handling with overhead cranes and during transport and handling with the LHC magnet tunnel transport vehicle. The acceleration limits specified for the short straight section at the moment of the transport [2] was 0.3 g (2.9 m/s 2 ) below 20 Hz in all three directions. This value was however specified for the SSS with transport restraints installed. Additional information about the acceleration limits can be found in [3] and [4]. 2. INSTRUMENTATION AND ACQUISITION 2.1 Accelerometers Three PCB ICP 356 B08 tri-axial accelerometers with a sensitivity of 10 mv/(ms -2 ) were used. The exact calibration factor for each axis was applied for a frequency region between 0.5 and 5000 Hz. Each accelerometer has a resolution of and a transverse sensitivity smaller than 5%. The accelerometers were attached with fast curing glue via a small mounting base to the cold mass, truck or tunnel vehicle. The accelerometers were connected to two PCB ICP 482A20 signal conditioners providing the supply for the integrated amplifiers in the accelerometers and a low impedance voltage signal. A gain of ten was applied for the transport measurements. The precision of the acceleration measurements is estimated to be ± 0.1 m/s Linear Variable Differential Transformers (LVDT) Six Linear Variable Differential Transformers or LVDT were used to measure the dynamic deformations of the support posts. The LVDT (Schlumberger N8R) with a half bridge configuration have a total course of about 6 mm. HBM-MVD 2555 devices conditioned the transducers with a carrier frequency of 4.8 khz and a 5 wire configuration. The bridge excitation voltage was 2.5 V. An analogue low pass Butterworth filter of 200 Hz was activated in the conditioner. The output of the conditioner was set to 10 V for a bridge output of ± 400 mv/v. The same calibration factor of (1.99 ± 0.01) V/mm was used for the six transducers. Information about the calibration and the frequency response of the LVDT can be found in [5]. The LVDT measure the deformations of the support posts in lateral, longitudinal and vertical direction relative to the flange of the vacuum vessel at the support post. They are mounted on an aluminium support plate placed inside, at the top of the support posts. The

5 2 support plate is positioned with three M16 rods fixed to the flange at the bottom of the support post. Special care was taken during the design and the installation of the LVDT support to have a light, rigid system (with a high natural frequency) that allows precise positioning of the transducers. More information about the LVDT support can be found in [5]. 2.3 Shock logger The RD298 Shocklog (Lamerholm-Fleming ) is a standalone device that measures accelerations in the three directions. It will store time stamped events and the maximum acceleration values for events that were higher than the selected thresholds. Two levels of thresholds are available for each axis. The warning threshold was set at 0.15 g, the alarm threshold to 0.3 g. LED s on the device indicate when a threshold was passed. The measurement range was set to 1 g. The signals are filtered with a 90 Hz low pass filter. 2.4 Acquisition The voltage signals from the transducers were recorded with a 12 bit NI DAQCard- 6062E installed in a portable computer. The acquisition, recording and analysis were performed with a Labview program. The sampling rate was 1 khz during the road transport. As it was rather difficult to install the LVDT exactly in the middle of the range, the full range of ± 10 V was selected on the card. This resulted in a resolution of the LVDT of 2.5 µm. The resolution for the accelerometers was m/s Position of the instrumentation A tri-axial accelerometer was installed at the top of each extremity of the cold mass. A third accelerometer was installed on the frame of the road trailer. The LVDT measured the deformation in each support post in lateral (x), longitudinal (y) and vertical (z) direction. The RD298 Shocklog was installed at the bottom of the down stream side extremity of the cold mass. Shocklog X, Y, Z Cold mass Accelerometer X, Y, Z Cold mass VACUUM VESSEL Accelerometer X, Y, Z Cold mass End cover Cold mass End cover z x y LVDT Support post deformations X,Y,Z Figure 1 Position of the transducers on the Short Straight Section

6 3 3. ACCELERATION AND SUPPORT POST DEFORMATION MEASUREMENTS DURING ROAD TRANSPORT 3.1 Road transport description The SSS was transported from building 181 (Meyrin site) to Point 4 (PA4 Echenevex) by a trailer with 3 axes with pneumatic suspension. The transport speed was limited to less than 20 km/h. During the whole measurement campaign, two end covers were mounted on the extremities of the SSS5 but no end-restraints were installed. End restraints are not allowed on the Short Straight Section as they might modify the magnet geometry. Figure 2 SSS5 installed on the road transport trailer The accelerations of the cold mass extremities and the support post deformations were recorded during normal driving, start up and normal stop. For safety reasons, no emergency stops were performed, since the SSS5 was not equipped with transport end-restrains. However, during serial transports emergency stops could occur. This is an open point that has to be treated in the future. 3.2 Results The highest accelerations and support post deformations during the transport were determined. The data was filtered at 20 Hz with a second order digital Butterworth low-pass filter. The summary of the maximum accelerations measured during road transport is given in Table 1. Table 1 - Maximum measured accelerations and support post deformations during road transport Acceleration (m/s 2 ) Measurement device Lateral Vertical Longitudinal Accelerometer ShockLog Deformation (mm) LVDT The most important accelerations were mainly observed at 1 Hz laterally and longitudinally, and at 2 Hz and 5 Hz vertically. The measured values are below the specified maximum accelerations [2]. A finite element model and a discrete model were made and maximum allowable acceleration levels were calculated for the transport with and without transport restraints on a special suspended transport frame [3], [4]. A global acceleration limit for all modes below 35 Hz was determined

7 4 (page 14 in [4]) as 1.4 m/s 2 without transport restraints (with transport frame). This is however a very conservative value as it assumes that the worst mode is excited. Table 5 in [4] gives in detail for each mode the allowed accelerations for transport on a transport frame. Although the modes and values can not be directly applied to the road transport in this report, it seems that the frequencies and the accelerations that were measured are not critical. The main lateral and longitudinal accelerations at 1 Hz are below the first modes at 2 and 3 Hz (on special platform) and 7 Hz (first lateral mode with SSS on rigid blocks). The measured support post deformations can be compared with the deformations for the specified maximum allowed compression and shear loads [6]. Table 2 Specified maximum allowable support post deformations (mm) Lateral Vertical Longitudinal Allowed deformation (mm) * Measured deformation (mm) More details on the files containing the maximum accelerations and support post deformations measured during road transport can be found in Annex A. The acceleration values were coherent with the support posts measured deformations. Figure 3 shows a ShockLog / accelerometer comparison of recorded acceleration during the same vertical event. The two records are coherent. The maximum amplitudes are slightly different (see also table 1) and can be due to the positioning of the two devices: the accelerometer was installed on the down stream side extremity, on the top of the cold mass. The ShockLog was installed at the same extremity, at the cold mass bottom. Figure 3 ShockLog / accelerometer measurement during the same vertical event (ShockLog installed at the cold mass bottom / accelerometer installed at the cold mass top) * Values determined from the maximum support posts specified loads and deformations (ref. [6]) and the support posts mechanical tests results giving the relationship between applied load and support post deformation (ref. [7]). The allowed lateral dynamic load of 15 kn (37.5 kn-22.5 kn) represents a lateral deformation of 0.5 mm. The vertical allowed dynamic load of 20 kn (60 kn-40 kn) represents a support post vertical deformation of 0.25 mm/3=0.08 mm.

8 5 4. LOWERING DOWN PX45 Figure 4 Lowering of SSS5 down PX45 The lowering sequence took approximately 40 minutes and the accelerations were recorded by the ShockLog. The accelerometers and LVDT gauges could not be used during this sequence since the equipment necessary for these measurements could not be lowered together with the SSS5. The maximum accelerations measured by the ShockLog during SSS5 lowering into the tunnel are summarised in Table 3. Table 3 - Maximum accelerations during lowering into the tunnel Maximum measured values Lateral Vertical Longitudinal Acceleration (m/s 2 ) (ShockLog) The measured values are lower than the specified maximum accelerations [2]. 5. ACCELERATION AND SUPPORT POST DEFORMATION MEASUREMENTS DURING TRANSPORT AND HANDLING WITH THE LHC MAGNET TUNNEL VEHICLE. The prototype Short Straight Section SSS5 was lowered by the shaft PX45 and loaded with the overhead crane in UX45 on the tunnel vehicle STV1. More information about the vehicle can be found in [2]. The accelerations of the cold mass extremities and the support post deformations were measured during the vehicle acceptance tests. 5.1 Emergency stops and power cuts The braking of this vehicle is done with the hydraulic wheel motors that will pump oil through a brake throttle valve. This brake throttle valve was set to an optimum position in order to find a compromise between stopping distance and acceleration loads. Emergency stops were performed at 1 km/h and 3 km/h (nominal transport speed). Power cuts were also performed at 3 km/h. The maximum measured accelerations and deformations for this optimum throttle valve position are given in table 3. The highest accelerations occurred during an emergency stop at 1 km/h and with floor unevenness (the tractor goes up a local slope) under the leading tractor

9 6 (figure 5). In this situation, the leading tractor stops earlier than the trailer and the back tractor, resulting in a shock. The accelerations during a power cut are slightly higher than the accelerations during an emergency stop (figure 6). Table 4 Maximum measured accelerations and support post deformations during emergency stops (E.S.) and power Lateral Vertical Longitudinal Acceleration Deformation Acceleration Deformation Acceleration Deformation (m/s 2 ) (mm) (m/s 2 ) (mm) (m/s 2 ) (mm) 3 km/h E.S < Power cut 3 km/h 1 km/h E.S. on floor unevenness < < A higher (but still lower than the limits) longitudinal acceleration was measured during a manoeuvre that is not representative for the tunnel vehicle. The SSS was moved on the STU trailer in single mode, i.e. without the tractors and for commissioning reasons some parameters were not correct and the STU could accelerate and stop abruptly. The longitudinal support post deformations and the accelerations are shown in Annex B. Figure 5 Longitudinal acceleration and support post deformation during an emergency stop at 1 km/h on a floor unevenness (24ES) Figure 6 - Longitudinal acceleration and support post deformation during a power cut at 3 km/h (2powercut)

10 7 5.2 Steps of 8 mm when moving at 3 km/h. The loaded vehicle drove over a step of 8 mm at 3 km/h with the step in front of both wheels (both sides) and with the step only in front of one side. The maximum measured accelerations and deformations are given in table 4. On figure 7, the passing over the step of the tractors and the trailer can be distinguished. The excited frequency is around 5 Hz (figure 8). Table 5 - Maximum measured accelerations and support post deformations when going over a step of 8 mm Step 8 mm, 3 km/h Lateral Vertical Longitudinal Acceleration Deformation Acceleration Deformation Acceleration Deformation (m/s 2 ) (mm) (m/s 2 ) (mm) (m/s 2 ) (mm) Tractor front trailer back trailer Tractor Figure 7 Vertical acceleration of the up stream cold mass extremity when going over a step of 8 mm at 3 km/h (1step8mm) Figure 8 Detail of figure 7 and frequency analysis 5.3 Unloading of the SSS with the tunnel vehicle unloading equipment (UE) The SSS was unloaded with the lifting cylinders of the vehicle and the unloading equipment. The maximum measured accelerations and deformations are given in table 5. Frequencies measured were 2 (small), 9, 17 and 19 Hz (figure 9). Table 6 - Maximum measured accelerations and support post deformations during unloading Lifting cylinders Unloading equipment Lateral Vertical Longitudinal Acceleration Deformation Acceleration Deformation Acceleration Deformation (m/s 2 ) (mm) (m/s 2 ) (mm) (m/s 2 ) (mm) (static) (static) (static)

11 8 Figure 9 Lateral acceleration during lifting with CTU lifting cylinders Static deformations of the support posts were measured during the lifting with the vehicle lifting equipment and the unloading equipment. The highest deformation measured was 0.1 mm in longitudinal direction on the up stream support post (figure 10). The deformations are reversible and are probably due to small misalignments between the ball bearings in the magnet cradles and the heads of the lifting jacks. The induced tilt in lateral and longitudinal direction was measured and was smaller than 1 mrad. This is achieved by synchronisation between the lifting cylinders. For the residual displacements of the support posts after handling, road and tunnel transport, see chapter 6. During the vehicle acceptance tests, the magnet was unloaded on wooden blocks. Some unforeseen difficulties occurred when the magnet was loaded back on the vehicle and this resulted in some shocks. As the event was not expected, it was not measured by the acquisition system. The shock log recorded however a vertical acceleration of 3.9 m/s 2. This is above the limit but the graph of the event (Annex C) shows that this acceleration occurred at a higher frequency. It was hence less dangerous. Figure 10 Longitudinal static deformation of the up stream and down stream support posts during lifting with the UE (4UErising) 5.4 Driving over the tunnel floor The loaded vehicle drove at 3 km/h over the tunnel floor. The tunnel floor can be considered as a random excitation. The most important excitation by the tunnel floor is in the lateral direction and results in a lateral acceleration and deformation at a frequency of 2 and 18 Hz.

12 9 Lateral Vertical Longitudinal Acceleration Deformation Acceleration Deformation Acceleration Deformation (m/s 2 ) (mm) (m/s 2 ) (mm) (m/s 2 ) (mm) Tunnel floor Table 7 - Maximum measured accelerations and support post deformations when driving over the tunnel floor Figure 11 Lateral support post deformation during transport over tunnel floor at 3 km/h (2driving3km) Figure 12 Lateral acceleration of cold mass extremity during transport over tunnel floor at 3 km/h (2driving3km) 6. STATIC DISPLACEMENTS OF THE SUPPORT POSTS The static position of the LVDT was recorded at some positions while the cryo dipole was not moving. The position of the support posts with the SSS on concrete blocks in building 181 before the transport to point 4 was taken as the zero. The deformations or displacements of the support posts relative to this zero are shown in figure 13. The last point of figure 13 was measured on nominal supports after road transport and handling without measurements. The LVDT in lateral and vertical direction moved less then 0.06 mm (0.06 mm lateral movement on the downstream support post). The longitudinal LVDT moved up to 0.17 mm in the downstream support post and 0.08 in the up stream support post. The downstream support post can slide in the longitudinal direction; it could hence be that the value measured downstream is a displacement rather than a deformation. The longitudinal displacements are reversible. A system (SMARTEC) measured the relative lateral and vertical position between the extremities of the cold mass and the vacuum vessel before and after the transport and tunnel vehicle tests (measured on nominal supports on a SM18 test bench without end covers). The lateral and vertical displacements of the cold mass extremities were smaller than 0.4 mm [8].

13 10 U-Lat mm U-Long mm U-Vert mm D-Lat mm D-Vert mm D-Long mm Deformation (mm) On concrete blocks 181 On truck at 181 On truck at point4 After lowering in UX, on tunnel floor Loaded on STU Loaded on STU after weekend SSS reloaded on STU and moved to RA Before emergency stops After 3 ES after 5 ES after 7 ES after ES, steps and powercuts, lifting Magnet loaded on UE After unlaoding and reloading After endurance tests on STU in UX, end of tunnel tests On jacks SM18 Figure 13 Deformation/ displacement when the SSS was not moving 7. CONCLUSION The accelerations of the prototype SSS5 cold mass extremities and the support posts deformations were measured during road transport, handling and transport with a dedicated tunnel vehicle. Table 8 and 9 summarise the maximum measured accelerations and deformations in each direction. The maximum values in the same row or columns are not necessarily measured during the same event and should hence not be compared between them (the maximum deformation was not necessarily measured during the maximum acceleration). The measured accelerations are smaller than the specified maximum acceleration of 2.9 m/s 2 in the three directions. The measured support post deformations are smaller than the allowed deformations associated with the allowed maximum loads (in compression and shear). The maximum residual displacements or deformations of the support posts were 0.06 mm lateral and 0.17 mm longitudinal. The displacements seem to be reversible. The residual lateral and vertical displacements of the cold mass extremities were smaller than 0.4 mm [8]. It is hence possible under normal conditions to transport and handle a short straight section without transport restraints. Normal conditions include emergency stops, power cuts and steps of 8 mm with the tunnel vehicle but do not include an emergency stop at 20 km/h during the road transport. The accelerations during such an event would most likely go above the limits and support post damage might occur. The use of a pilot car in front of the road transport is needed to reserve a sufficient brake distance.

14 11 Table 8 Maximum measured accelerations on the cold mass extremities Acceleration (m/s 2 ) Lateral Vertical Longitudinal Road transport Lowering in tunnel by PX Handling and transport with tunnel vehicle Specified limit Table 9 - Maximum measured deformations of the support posts Deformation (mm) Lateral Vertical Longitudinal Road transport Handling and transport with tunnel vehicle Specified limit During each transport, the accelerations of the short straight section should be measured with a stand-alone device shocklog installed on the cold mass extremity. A global alarm level set at 2.9 m/s 2 for the three directions will give an indication when an abnormal event has occurred. The recorded curve of the event allows seeing if the frequency of the event was critical. Frequencies above 20 Hz will give higher accelerations but are less dangerous for the mechanical structure. A second warning level set at a lower value allows measuring the maximum accelerations during each transport. This allows predicting problems like e.g. road degradation or a change in the suspension of the road trailer. To interpret the measured events it is needed to know the natural modes of the short straight section on a road trailer. A modal analysis as in [3] and [4] remains to be carried out. 8. ACKNOWLEDGEMENTS The authors would like to thank P. Morel, M. Gielen, K. Kershaw, R. Liedtke and the transport team for their help.

15 12 9. REFERENCE [1] K.Artoos, O.Capatina; Experimental modal analysis and acceleration measurements during transport of a LHC Short Straight Section; LHC-CRI Technical note ; EDMS [2] Technical specification for the Supply of cryo-magnet transport vehicles and unloading equipment for the LHC tunnel; IT 2803/EST/LHC; EDMS [3] P.Cupial, J.Snamina; The dynamic response of the LHC Short Straight Section under transport conditions; LHC-CRI Technical note ; EDMS [4] P.Cupial, J.Snamina; The verification of the computational models of the LHC Short Straight Section and the determination of the allowable acceleration limits during transport; Technical note EST-ME/ [5] K.Artoos, N.Bourcey, O.Capatina; Acceleration and support posts deformation measurements during surface transport of a LHC cryodipole; LHC-CRI Technical note ; EDMS [6] V.Parma; Technical specification for the supply of glass fibre reinforced epoxy (GFRE) support posts for the LHC cryomagnets; LHC project document LHC-QBH-CI-0002; EDMS [7] N. Bourcey, private communications. [8] Measurements with SMARTEC by M. La China 11/7/2003.

16 13 Annex A: transport Maximum accelerations and support post deformations measured during road Lateral support post deformation during road transport slope in front of building181 ( ) Lateral acceleration and support post deformation during road transport start up ( ) Longitudinal acceleration and support post deformation during road transport start up ( ) Vertical acceleration during road transport ( )

17 14 Annex B: Not typical longitudinal accelerations during a test with the STU trailer in single mode. Annex C: Unexpected shock during handling with unloading equipment g +0.5 Event 26 from ShockLog recorder logged at 18/03/ :58:52 X Y Z Seconds