Customized overhead cranes for installation of India's ... · Customized overhead cranes for inst allation of India s largest 3.6m optical telescope at Devasthal, Nainital, India

Customized overhead cranes for installation of India’s largest 3.6m optical telescope at Devasthal, Nainital, India.

Tarun Bangiaa, Shobhit Yadavaa, Brijesh Kumara, A.S. Ghantib, P.M. Hardikarb aAryabhatta Research Institute of Observational Sciences (ARIES), Nainital - 263002,Uttarakhand,

India; b Precision Precast Solutions Pvt. Ltd., Warje, Pune - 411058, India.

ABSTRACT

India's largest 3.6 m aperture optical telescope facility has been recently established at Devasthal site by Aryabhatta Research Institute of Observation Sciences (ARIES), an autonomous Institute under Department of Science and Technology, Government of India. The telescope is equipped with active optics and it is designed to be used for seeing-limited observations at visible and near-infrared wavelengths. A steel building with rotating cylindrical steel Dome was erected to house 3.6m telescope and its accessories at hilltop of Devasthal site. Customized cranes were essentially required inside the building as there were space constraints around the telescope building for operating big external heavy duty cranes from outside, transportation constraints in route for bringing heavy weight cranes, altitude of observatory, and sharp bends etc. to site. To meet the challenge of telescope installation from inside the telescope building by lifting components through its hatch, two Single Girder cranes and two Under Slung cranes of 10 MT capacity each were specifically designed and developed. All the four overhead cranes were custom built to achieve the goal of handling telescope mirror and its various components during installation and assembly. Overhead cranes were installed in limited available space inside the building and tested as per IS 3177. Cranes were equipped with many features like VVVFD compatibility, provision for tandem operation, digital load display, anti-collision mechanism, electrical interlocks, radio remote, low hook height and compact carriage etc. for telescope integration at site.

Keywords: Devasthal, Dome, Telescope, Single Girder Crane, Under Slung Crane.

1. INTRODUCTION Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous Institute under Department of Science and Technology, Government of India has set up India’s largest 3.6m optical Telescope at Devasthal (29o 21’N, 79o 41’E, 2.5 km amsl), Nainital, India. Devasthal is one of the best astronomical sites in the world which was selected after extensive site characterization and has nearly 200 spectroscopic nights in a year1-3. Telescope is useful for studying magnetic field structure of stars, chemical evolution of milky-way via stellar ISM abundance, search for extra solar planets, kinematics of stars in the outer region and the halo of the milky-way, NIR spectroscopy and narrow band imaging of galactic HII regions and star clusters to understand formation of stars and their evolution, Optical spectroscopy and deep time resolved imaging of galactic X-Ray binaries to understand the kinematics of accretion disk and planet formation etc. In addition to optical studies of a wide variety of astronomical topics, it will be used for follow-up studies of sources identified in the radio region by GMRT and UV/X-ray by ASTROSAT4. The 3.6m Devasthal Optical Telescope (DOT) will be equipped with instruments providing high resolution spectral and imaging capabilities at visible and near-infrared bands. Several countries such as Germany, Russia and Belgium have contributed in the making of telescope. Telescope mirror is of SCHOTT Zerodur glass and its blank was taken from Germany and polished in Russia5. Telescope with active optics was designed, manufactured, and factory tested by Advanced Mechanical and Optical Systems (AMOS) at their works in Belgium6-9. They arranged transport of telescope components from Belgium to Devasthal site in various containers and boxes. A steel building with rotating cylindrical Dome was constructed for housing 3.6m telescope. Problem of lifting a load is as old as humankind10. Crane is a device which has a hoist with longitudinal and cross movement. It can be used both to lift and lower materials and to move them horizontally. Cranes are designed to ease the

Ground-based and Airborne Telescopes VI, edited by Helen J. Hall, Roberto Gilmozzi, Heather K. Marshall, Proc. of SPIE Vol. 9906, 990620 · © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2232127

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load of heavy work so that heavy objects can be moved from one place to another. Various types of cranes are used to carry out variety of works such as mobile cranes, tower cranes, jib cranes, aerial cranes, overhead cranes, gantry cranes etc. Cranes exist in various types and can be customized for specific works. Crane sizes range from the small jib cranes used inside workshops to tall tower cranes used in construction of high buildings etc. Various factors are considered while selecting a crane such as lifting capacity, application, number of work cycles that the crane is required to undergo etc. Overhead cranes used in factory structure run along a horizontal beam that rides on two widely separated rails along its two long walls. These Cranes have a hoist to lift load, bridge that spans the area covered by it and a trolley to move along the bridge. They are generally single beam or double beam in construction. They are manufactured using steel beams or box girder. Double girder bridge cranes are required for heavier capacity systems from 10 MT and above. Overhead cranes are widely used in manufacturing factories and are currently controlled by human operators11. Overhead cranes are even used at nuclear facility for remote handling tasks12. Telescopes are generally erected by using mobile cranes or tower cranes that are stationed outside their enclosure and components are inserted through the slit of Dome. Material handling scheme for large sized heavy materials including the primary mirror cell etc. for the telescope, is based on a large bridge crane that can transfer instruments and maintenance equipment to the telescope and to the service floor from the storage and maintenance area at ground level13. Due to constraints at Devasthal site and limited space inside the enclosure, telescope installation was a very challenging task at site. After studying various available options, ARIES planned to develop customized overhead cranes in consultation with Precision Precast Solutions Pvt. Ltd. (PPS), Pune, India for installation of telescope from inside its enclosure. Cranes were manufactured at Indiana Machine Tools (IMT), Gobindgarh, India and factory tested to meet AMOS requirements of telescope installation.

2. TELESCOPE ENCLOSURE STRUCTURE Telescope enclosure structure of 3.6m telescope consists of three parts namely Dome, Dome Support Structure and Extension Building (Fig. 1).

2.1 Dome

Dome is rigid framed upper cylindrical steel structure with pitched roof 14. Cylindrical enclosures are better than spherical ones because the bridge crane can extend to the full radius and provide access to the entire floor area15. It provides a rotating cover and protects the telescope from the environment. It is free to rotate about the telescope and enables the observations through a 4.2m wide slit by rotating about its vertical axis. Dome centerline diameter is 16.5m which was selected based on material handling system requirements for installation of telescope and handling of telescope mirror. Dome was provided with two 10 MT Under Slung Electric Overhead Travelling (EOT) cranes (Fig. 2). Dome of about 13.9 m height, including slit is supported at its base on a steel ring beam formed from rectangular box section fabricated from steel plates.

2.2 Dome Support Structure

Bottom ring beam is supported on columns of a lower steel structure which forms the second part of the enclosure and is called as Dome Support Structure. Telescope observation floor at 11m was fabricated from chequered plates supported on structural framing and caters for the operation and maintenance of telescope. Telescope is housed eccentric inside the enclosure on a concrete pier to get maximum space on one side to enable lifting of telescope parts during its installation and maintenance from ground floor through a 5.5m X 5.5m hatch at observation floor. During normal time, hatch remains closed for safety and space requirement. Insulation is provided to prevent the outside heat transfer in to the Dome and its supporting structure16. Equipment room containing hydraulic power pack, chiller, compressor and electrical panel etc. was housed in ground floor of this structure along with telescope control room.

2.3 Extension Building

Dome Support Structure was extended to form the third part of enclosure as Extension Building of 12.25m wide x 24m long. It was designed for accommodating telescope mirror aluminizing facility and accomplishing space requirement during aluminizing process17. It also houses ventilation system, UPS room and space for assembly of components and their maintenance etc. Most of the telescope enclosures are equipped with cranes for handling of telescope components and its instruments18. Telescope enclosure also includes operational equipment such as a bridge crane/overhead crane and lift to have access on telescope floor19. Extension structure contains two 10 MT Single Girder EOT Cranes (Fig. 3) and a 20 MT ground trolley on rails connecting this building to Dome Support Structure.



3. REQUIREMENT OF OVERHEAD CRANES ARIES required a reliable material handling system for installation of India’s largest 3.6m optical telescope inside its enclosure. Adequate space was not available at site for external crane parking, movement and storage of some telescope parts. Due to space limitation it was extremely difficult to plan and execute the telescope components unloading and part assemblies outside the building. As various large size heavy components of telescope were to be lifted so a 60 MT capacity truck mounted crane was required to be brought to the site. The free space available at site was not sufficient for smooth operation and movement (with telescope components) of such high capacity crane. Another option was of putting Tower Crane. Installation of 50 MT capacity Tower Crane was also not feasible owing to the space required for its base structure and limitations in transportation of crane due to its self-weight. The road leading to site was having number of U bends and also two old bridges which made it difficult to take the assembled crane to high altitude site.

Erection of telescope was required to be done very carefully using precisely moving cranes for which use of external heavy duty cranes involved high risk. The telescope site was on top of a rocky mountain with an uneven/sloping ground. Looking in to the intricacies of telescope installation at a high altitude and later its maintenance, ARIES decided to design and develop customized overhead cranes for 3.6m telescope installation in consultation with M/s PPS to suit the requirements of AMOS, Belgium. Specific design requirements of cranes were worked out to optimize the dimensions of the enclosure. Maximum weight of a single telescope component was about 15 MT so provision for handling 20 MT inside both Extension building and Dome was provided. A scheme of material handling was made in which the components were to be brought inside the Extension building on truck/trailers and unloaded using Single Girder cranes in Extension building on to the ground. These components after unpacking or assembly with other components etc. were to be lifted using Single Girder Cranes in Extension Building and placed on a 20 MT ground trolley. Trolley designed specifically with load points had provision of tapped holes at several places for holding telescope components during its movement. Trolley movement was provided on rails connecting Extension Building and Dome Support Structure. Trolley with telescope components or sub-assemblies was to be moved below the hatch of Dome Support Structure. Components/sub-assemblies were to be lifted through hatch opening using cranes provided in Dome. Dome was provided with two 10 MT Under Slung cranes to lift the telescope components through hatch on to the 11m platform. A top running configuration in overhead Single Girder cranes requires additional headroom as they travels above the overhead runway. To avoid the increase in height of Dome Under Slung cranes that run under the beam were considered for Dome. The components were further aligned and assembled on to the pier using the Dome cranes and by movement of Dome.

4. DEVELOPMENT OF CUSTOMIZED OVERHEAD CRANES The factors which affected the design and layout of cranes were shape, size, weight and method of handling major components of telescope at the time of installation and further maintenance of telescope in future. Telescope had several large and heavy components such as Ground Interface Structure (GIS), Centre Piece, Fork Base, Fork Lateral Pieces and Tube etc. which governed the provisions to be made for their one time handling and installation. Traditionally crane for telescope Dome is selected considering the weight of primary mirror and mirror cell assembly. After telescope installation the main material handling activity is re-aluminization of the primary mirror, maintenance of telescope and changing of backend instruments on telescope. A standard crane with some higher capacity than the weight of primary mirror and its cell assembly fulfils this requirement. However, in case of 3.6m optical telescope some other important site conditions and factors compelled us to review not only the selection of Dome cranes but also the size in the Dome, and specific features of the crane. Size of hatch on the telescope floor is generally kept slightly more than primary mirror cell for its movement through it for aluminizing operations. The 3.6m telescope installation was planned through the hatch opening on the telescope observation floor, its clear opening size was kept 5.5m x 5.5m to accommodate maximum telescope components. Few components such as Fork Base that were having larger dimensions than hatch were lifted in tilted position with two cranes in tandem operation (Fig. 4). Similar method was adopted for other components having more size than the hatch opening. The mean Dome diameter was optimized to 16.5m by placing the hatch opening on one side and placing the telescope pier eccentric to Dome. Hatch size for allowing installation of telescope components was one of the prime factor governing Dome diameter and hence the Dome design. The minimum clearances between the highest part of telescope and Dome crane hook were also taken in to account due to installation of telescope with



Dome cranes to achieve final adjustments for easy and safe topmost component. Stability requirements of Dome during lifting heavy parts of telescope at one extreme end, and at 15m/sec wind speed conditions were also met. Major design parameters that were reviewed and fixed were capacity of Dome cranes, number of cranes in Dome, critical specifications of cranes, size of hatch opening, Dome height, stability of Dome cranes during heaviest part lifting etc. Telescope manufacturer, AMOS provided total weight of telescope (~ 150 MT) and also weights of various major telescope components such as Fork Base, Centre Piece, Lateral Fork Pieces, GIS and Tube etc. to be lifted through hatch which are depicted in Table 1.

Table 1. Approx. Weight of various major telescope components.

Major Telescope Components Approx. Weight (in MT)

Interface Plates 7.2 Ground Interface structure 23.3 Azimuth Cable Wrap 6.2 Fork Base (in two pieces) 24.4 Lateral Forks (in two pieces) 20.2 ARISS 8.3 Octagon 3.7 Primary mirror and its cell 10.2 Centre Piece (in two pieces including altitude bearings)

30.8

Tube 9.0 Tube top ring with secondary mirror Assembly

4.1

The maximum weights of single heavy pieces were mainly of Fork Base (~ 12 MT) and Centre Piece (~ 15 MT). Hence, crane capacity of about 20 MT was required to lift the heavy components through the hatch for telescope integration. The option of using one single crane of 20 MT capacity was also studied but it resulted in increased height of Dome and load on structure. Two overhead cranes of 10 MT capacity operating in tandem for telescope installation in Extension building as well as Dome were planned rather than a single 20 MT crane in them so as to distribute load on structure. Cranes require much space above gantry girder to accommodate the trolley consisting of hoisting, long travel and cross travel mechanisms. So two Under Slung cranes of 10 MT capacity were specifically selected for Dome so that there was no need to increase the height of Dome. They provide best possible results in limited space and run on the bottom flange of crane runway. They provide flexibility, versatility along with functional requirements. The lift of the Under Slung Dome cranes worked out to be 22.5m for which wire rope drum of 550mm diameter and 2m length was accommodated in the restricted space. The slit opening in the Dome structure was 4.2m so the maximum span of 4.9m in this structure was achieved. Under Slung cranes were also designed with minimum end carriage length. Also two Single Girder cranes of 10 MT capacity provided in the Extension Building were designed to optimize its height. 4.1 Mechanical Design Features

Both Single Girder overhead cranes in Extension Building and Under Slung overhead cranes in Dome were designed to meet the requirement of handling components of 3.6m telescope during its installation. Two 10 MT Single Girder overhead cranes in Extension Building were designed with span of 11.15m, bay length of 24m and vertical movement of hook above floor of 7.25m. Two 10 MT Under Slung Dome cranes supported from Dome roof were designed with span of 4.9m, bay length of 14.7m and vertical movement of hook above floor of 22.5m. A minimum clearance of about 500mm between bottom of hook of crane and top of telescope in vertical position was maintained for safety purpose. Cranes were designed for achieving the desired slow speeds for carrying out installation and assembly of 3.6m telescope, aluminizing of telescope mirrors, handling of back-end instruments and for various maintenance works. All the four overhead cranes were designed as per IS3177. Suitable selection of plates, bars, angles, rolled sections and compression members was carried out. The lifting block assembly was a point hook with shank and confirms to the requirements of IS3177. Safety latch to all hooks was provided. One additional brake was provided for the hoist motion



of each crane. Class of both types of cranes was II (M5). Wire ropes of all four cranes were selected as per IS 2266. Safe means of access through platforms, ladders, handrails etc. were provided for maintenance of all structural, electrical and control parts of each crane. 4.2 Electrical Design Features Crane duty electric motors were used. Three phase Variable Voltage Variable Frequency AC Drives (VVVFD) were used to operate the electric motors of different motion for hoisting, long travel and cross travel at variable speed. The motor rating took into account all the deration factors applicable at the site. The Basic Operator Panel (BOP) was used for effective parameterizing and control of the inverter. The control signals and speed reference were set by BOP. The VVVFD parameters were set for two variable speeds (100% and 10% of motor rated speed) to operate the electric motors at different speeds. By giving suitable command to digital inputs of the desired VVVFD, two variable speeds were achieved for required motion. However, during one of the trial operation trouble was found whose detailed study revealed the correction in gearbox ratio which was carried out. Number of trails were conducted at minimum speed of all motions to ensure the safe operation of mirror handling. Main hoist motor temperature sensor signals were connected to VVVFD inputs to monitor motors currents for safety purpose. If motor current goes above the set point it was to trips the drive. Incremental rotary encoder was used as a speed feedback device in the main hoist motion of the Dome cranes. Output pulses of encoder were fed to drive input to achieve stable speed of main hoist motion. Control and interlock panel contains three phase power supply (415 V AC, 50 Hz), control supply (110 V AC, 50 Hz) for all controls, 24 V DC power supply, radio remote control system and drive system for main hoist, long travel and cross travel. It also contains electrical interlocking circuits for pendant and radio remote operation as well as individual and tandem radio remote operation. Safety features were also included in control and interlock panel like phase failure, phase reversal and earth fault etc. Electrical limit switches circuitry for all motions was provided in control and interlock panel. Main hoist had up and down motion limit switch, load cell and upper motion gravity limit switch for additional safety. Cross travel had forward and reverse motion limit switch. Long travel had forward and reverse motion limit switch as well as anti- collision devices limit switch for additional safety. PVC insulated bus bar system was used to feed the three phase (415 V AC) power supply to control and interlock panel which moves along with the crane. Controls for individual crane were provided on their pendants. One lockable push button was provided to switch off control power when the crane was not in use. Protection guards to live electrical wirings/conductors were provided.

5. CUSTOMIZED FEATURES IN CRANES

Overhead cranes were specifically equipped with many customized features briefly mentioned below, for precise installation and handling of telescope mirror and various other critical telescope components: 5.1 Speeds of various motions

Telescope mirror being very delicate and sensitive, utmost care was required during its movement. Convex circular primary mirror of 3700mm diameter, 165 mm thickness and about 4330 kg was required to be handled during telescope integration as well as later during aluminization activities. Hence, both types of cranes were designed for very slow speeds of various motions as desired by AMOS which were achieved during their development and are depicted in Table 2.

Table 2. Hoisting, Cross and Long travel speeds of overhead Cranes in 3.6m telescope enclosure

Under Slung Overhead Cranes

in Dome

Motion Minimum Speed (mm/sec)

Maximum Speed (mm/sec)

Hoisting 5.8 58 Cross Travel 16 160

Long Travel 16 160 Single Girder

Overhead Cranes

Hoisting 3.3 33 in Extension

Building Cross Travel 4.0 40 Long Travel 4.0 40



5.2 Tandem Operation

Tandem operation of cranes are rarely used in observatories for telescope installation. At Devasthal site in order to lift heavy components weighting more than 10 MT or with large spans such as Centre Piece, Cable Wrap and Fork Base etc. tandem operation was essential for uniform loading on both the cranes. Centre piece (with altitude bearings) of telescope was the heaviest component and it was transported in two parts. Each piece was lifted through Under Slung cranes from hatch in tandem operation (Fig. 5) during telescope integration. It was possible to operate both Under Slung cranes and both Single Girder EOT cranes in tandem as well as separately. Radio remotes provided for these cranes had independent control i.e. for individual crane for independent operation and also a common control for combined operation of all motions. 5.3 Load Indicator System Cranes were provided with precise digital weighing system through load cells for viewing load on them while in operation. It is also called as safe load indicator system. It was used in preventing crane overload for main hoist. The system provided with load cells continuously monitored and displayed the load lifted on the hook and automatically compared it with the rated crane capacity of 10 MT during its operation. System provided visual and audible warning at set capacity levels to alert the operator of the load condition and further activated the tripping function. Load indicator provided digital display of hoisted load of each crane during tandem operation which helped in monitoring load distribution on each crane. 5.4 Anti-collision Device On certain occasions both cranes (in Dome or in Extension Building) were operated independently. Under such type of operation, to avoid the collision of cranes an anti-collision device was provided on each crane. The operating crane/cranes trip/stop before collision takes place. A 150mm clearance was maintained between two cranes. Anti-collision device (switch) was installed on two cranes on the same rail approaching each other. With these units, the two cranes on the same rail were avoided collision with each other and thus the damage due to possible collision was prevented. The minimum distance in between two cranes was always maintained and the cranes were able to move away from each other but not closer. Unit had inbuilt infra-red transmitter and receiver along with other processing circuit and power supply. Its output contacts were interlocked with the contactors for direction of motion towards each other. Set consisted of a control unit and a reflector. Control unit was fixed on one crane and reflector on the other crane, opposite to the control unit. Same way another control unit was fixed on second crane and its reflector on first crane, opposite to each other. Alignment of both the units was necessary, as the rays transmitted by transmitter were reflected back by the reflector. Reflected beam was picked up by the receiver when both the cranes come closer. Whenever two cranes come within set range, the moving crane stopped immediately. Range can be adjusted to stop the crane at required distance. 5.5 Radio Remote The cranes were used for assembling and positioning instruments and accessories of the telescope for which they required very smooth control of various movements. Control of cranes was achieved through pendant operation or by radio remote. Radio remotes were provided for cranes apart from pendant operation for ease in operation of cranes. The radio remotes customized for cranes had independent control i.e. individual operation of different motions and speeds for each crane and also a common control (through master remote) for combined operation of two cranes for different motions and speeds. As the cranes can work in tandem operation with single radio remote so it allowed lifting of loads up to 20 MT using two cranes each of 10 MT without requirement of any additional crane/material handling equipment. Range of radio remote up to 30m was selected which allowed operation of cranes from different places in enclosure to facilitate 3.6m telescope installation. Radio remote control system was provided with all standard operational and safety features.



5.6 Interlocking and Safety Features Electrical interlocks were provided to prevent simultaneous remote and local operation, simultaneous radio remote control and pendant operation, operation during phase reversal/phase failure, earth fault and short circuit. Crane tripping through limit switches was provided for limiting long travel, cross travel and hoisting motions. An additional upper limit switch for hoisting was also provided. To avoid interference of cranes with telescope movement during observations they were designed with low hook height and lesser carriage width. Digital load monitoring ensured equal distribution of load during tandem operation and avoided overloading. 5.7 Critical Clearances for Cranes Cranes were to be used separately and in tandem also for various operations during telescope installation. They were designed to occupy minimum space in 3.6m telescope enclosure and with maximum reach for handling of components by maintaining various critical clearances. Cranes were designed with minimum carriage width, minimum distance between bottom of gantry girder and hook center, maximum hook range and with clearance at end for stopper etc.

6. TESTING OF CRANES Mechanical, electrical and performance testing of cranes was carried out at works as well as at Devasthal site after their installation inside the 3.6m enclosure. All the four Cranes were tested to perform hoisting, cross travel and long travel operations. 6.1 Factory inspection and testing Cranes were tested at the works of M/s IMT to ensure that they conform to the technical specifications and comply with the requirements of applicable codes. All the inspection and tests of components, sub-assemblies and assemblies were conducted as per the quality assurance plan. All materials, castings and forging were of tested quality. All electrical equipment and components thereof were subjected to routine tests as per relevant Indian Standards. Cranes were tested by M/s IMT along with consultants M/s PPS and ARIES as per IS3177. The cranes were tested to 125 % of the hoisting capacity using dummy loads by erecting them on temporary structure in works. Surfaces of equipment to be painted were thoroughly cleaned of all grease, oil, loose mill scale, dirt, rust and any other foreign matter by sand blasting. Primer coats were applied without any time lag after the pre-cleaning and care was taken that the paint was not applied to a damp surface. Interior surface of all box sections and surfaces which were inaccessible after assembly and erection were sand blasted and given two coats of primer and two coats of epoxy finish paint before assembly. 6.2 Testing at site Successful inspection and testing of cranes at works was carried out and they were disassembled and sent to site. After assembly, erection and commissioning at site, the cranes were subjected to performance tests as laid down in the Indian Standard IS 3177. Crane capacity, hoisting speed, long travel speed, cross travel speed, motor and gear box performance, brakes and electrical control systems etc. were checked during various performance tests at site. Specifically prepared four dummy concrete loads of 10 MT (1 no.), 5 MT (1 no.) and 2.5 MT (2 nos.) were used for testing of load, overload and tandem operation of overhead cranes to simulate handling of telescope components. Various other tests were also conducted like brake tests, check of limits, interlocks, anti-collision, power cut-off test and radio remote operation from 30m distance for cranes at Devasthal Telescope site.

7. INSTALLATION OF 3.6 M OPTICAL TELESCOPE Telescope installation involved several material handling equipment. Newly developed Under Slung overhead cranes as well as Single Girder overhead cranes were primarily used among other material handling equipment inside the enclosure. Several heavy and large sized mechanical, electrical and optical components of telescope were lifted safely and integrated with the help of customized overhead cranes. For installation of telescope first interface plates were



aligned and fixed on the telescope pier over which concrete was poured for stiffening. GIS in two parts viz. stator and rotor was further installed over interface plates using cranes. Precise lifting of GIS with dimensions close to hatch was carried out using Under Slung cranes in Dome (Fig. 6). Central part including azimuth motor and radial hydraulic system were connected which formed the link between rotor and stator20. Further Cable Wrap, Fork Base Pieces, Lateral Fork Pieces, Center Piece, Tube and M1 cell with aluminized primary mirror, ARISS, dummy instrument etc. were integrated along with various electrical components for telescope testing and verification. Various subsystems were assembled by AMOS at ground level to minimize work and its associated risk and then lifted with cranes at desired speeds for telescope integration. A view of the installed telescope inside Dome is shown in Fig 7. .

8. FIRST COATING OF PRIMARY MIRROR Uncoated primary mirror of telescope was transported from AMOS, Belgium. For coating of mirror, a coating plant was installed inside the Extension Building by ARIES. This is the only coating facility available in India, which can aluminize astronomical glass mirrors up to size of 3.7m diameter. Mirrors are most delicate components of telescope and require very slow speeds and precise handling by cranes. Hence, very low speeds of single girder cranes in Extension Building of the order of about 3.3 mm/sec in hoisting and 4.0mm/sec in cross and long travel enabled safe and precise handling of primary mirror during aluminization process. A thorough practice of handling metal dummy mirror of 3.7m diameter was carried out by ARIES team using overhead cranes (Fig 8). First aluminium coating of primary mirror was done at Devasthal in its aluminizing plant by handling the mirror with one Single Girder overhead crane in Extension building. Aluminized mirror was further taken out from aluminizing chamber using Single Girder crane for assembly with primary mirror cell (Fig. 9).

CONCLUSIONS All the four newly developed overhead cranes fulfilled the key requirement of telescope installation from inside the 3.6m telescope enclosure. Smooth and safe handling of telescope components for installation of India’s largest 3.6m optical telescope at Devasthal was accomplished by AMOS primarily using customized overhead cranes in its enclosure. All mechanical, electrical and optical components were successfully integrated using overhead cranes. Cranes also served in installation of mirror aluminizing plant, first aluminization of primary mirror of telescope, handling of back end instruments and in various maintenance activities inside 3.6m telescope enclosure. DOT was established as world class facility to fulfill the major aspirations of the astronomical community. Remote technical activation of 3.6m telescope was carried out jointly by honorable Prime Ministers of India and Belgium on 30 March 2016 from Belgium.

ACKNOWLEDGEMENTS Authors express sincere gratitude to 3.6m DOT Project Management Board, Governing Council, Acting Director ARIES, Assembly Integration and Verification team along with all scientists and engineers involved in the project for their constant guidance. Authors would also like to thank Prof. G. Srinivasan for his consistent support to this project. Authors are deeply indebted to devasthal staff, mechanical workshop, electrical, computer, civil, optics and administration sections of ARIES for giving tremendous support to the project. Technical support in accomplishment of various works carried out by M/s IMT, M/s PPS and M/s Pedvak is also acknowledged. We are also thankful to DST, Govt. of India for their support to the project. Authors are highly thankful to Er. Krishna Reddy Bheemireddy for his timely help and cooperation in paper presentation for SPIE.

REFERENCES

[1] Pant, P., Stalin, C. S. and Sagar, R., “Microthermal measurements of surface layer seeing at Devasthal site,” A & AS 136, 19-25 (1999). [2] Stalin, C. S., Sagar, R., Pant, P., Mohan, V., Kumar, B., Joshi, Y. C., Yadav, R. K. S., Joshi, S., Chandra, R., Durgapal, A. K. and Uddin, W., “Seeing and microthermal measurements near Devasthal top,” Bull. Astron. Soc. India, 29, 39-52 (2001). [3] Sagar, R., Stalin, C. S., Pandey, A. K., Uddin, W., Mohan, V., Sanwal, B. B., Gupta, S. K., Yadav, R. K. S., Durgapal, A. K., Joshi, S., Kumar, B., Gupta, A. C., Joshi, Y. C., Srivastava, J. B., Chaubey, U. S., Singh, M., Pant, P. and Gupta, K. G., “Evaluation of Devasthal site for optical astronomical observations,” A & AS, 144, 349-362 (2000).



[4] Sagar, R., Kumar, B., Omar, A. and Pandey, A.K., “New optical telescopes projects at Devasthal Observatory,” Proc. SPIE, 8444, 84441T-1-12 (2012). [5] Semenov, A., “Accomplished the task of production of primary and secondary mirrors of DOT telescope under the project ARIES (India, Belgium, Russia): fabrication features,” in [Modern Technologies in Space and Ground-based Telescopes and Instrumentation II], Proc. SPIE 8450, 176 (2012). [6] Flebus, C., Gabriel, E., Lambotte, S., Ninane, N., Pi´erard, M., Rausin, F. and Schumacher, J. M., “Opto-mechanical design of the 3.6 m Optical Telescope for ARIES,” in [Ground-based and Airborne Telescopes II], Proc. SPIE 7012, 08 (2008). [7] Pierard, M., Schumacher, J., Flebus, C. and Ninane, N., “The 3.6 m Indo-Belgian Devasthal Optical Telescope: the active M1 mirror support,” in [Ground-based and Airborne Telescopes IV], Proc. SPIE 8444, 186 (2012). [8] Ninane, N., Flebus, C. and Kumar, B., “The 3.6 m Indo-Belgian Devasthal Optical Telescope: general description,” in [Ground-based and Airborne Telescopes IV], Proc. SPIE 8444, 67 (2012). [9] Ninane, N., Bastin, C., de Ville, J., Michel, F. J., Pierard, M., Gabriel, G., Flebus, C. and Omar, A., “The 3.6 m Indo-Belgian Devasthal Optical Telescope: assembly, integration and tests at AMOS,” in [Ground based and Airborne Telescopes IV], Proc. SPIE 8444, 102 (2012). [10] Verschoof, I.J., [Cranes - Design, Practice, and Maintenance], Professional Engineering Publishing Limited, London and Bury St Edmunds, UK, 1 (2002). [11] Li, W. and Tang, Q., "Precise positioning control of overhead traveling cranes," in [International Conference on Intelligent Manufacturing], Proc. SPIE 2620, 792 (1995). [12] Lee, H.J., Lee, J.K., Park, B.S., Kim, K. and Kim, H.D., “Development of an Overhead Crane for Remote Handling Tasks at Nuclear Facility,” Int. Conf. on Control, Automation and Systems, 1830-1834 (2010). [13] Salinari, P. and Hill, J.M., "Enclosure of the Large Binocular Telescope", Proc. SPIE 2199, Advanced Technology Optical Telescopes V, 442 (1994). [14] Pandey, A.K., Shukla, V., Bangia, T., Rasker, R., and Kulkarni, R., “Enclosure design for the ARIES 3.6m optical telescope,” in [Ground-based and Airborne Telescopes IV], Proc. SPIE 8444, 152 (2012). [15] Bely,P.Y., [The Design and Construction of Large Optical Telescopes], Springer-Verlag New York, 387(2002). [16] Bangia, T., Raskar, R. and Ghanti, A., “Acoustics and functional space design of 3.6m devasthal optical telescope building,” Proc. Acoustics 2013, New Delhi, India, 201-207 (2013). [17] Pillai, R. R., Shukla, V., Mohanachandran, K., Sakhamuri, N., Karumana, S., and Gupta, A., “Design, development, and manufacturing of highly advanced and cost effective aluminium sputtering plant for large area telescopic mirrors,” in [Ground-based and Airborne Telescopes IV], Proc. SPIE 8444, 80 (2012). [18] Johns, M., McCarthy, P., Raybould, K., Bouchez, A., Farahani, A., Filgueira, J., Jacoby, G., Shectman, S. and Sheehan, M., “Giant Magellan Telescope-Overview,” Proc. SPIE 8444, 84441H (2012). [19] Marshall, H.K., Teran, J.U. and Bond, K., "Design and construction of the Discovery Channel Telescope enclosure", in [Ground-based and Airborne Telescopes III], Proc. SPIE 7733, 77335C (2010). [20] de Ville, J., Bastin, C. and Pierard, M., “The 3.6 m Indo-Belgian Devasthal Optical Telescope: the hydrostatic azimuth bearing,” in [Ground-based and Airborne Telescopes IV], Proc. SPIE 8444, 150 (2012).



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Figure 6. Ground Interface Structure (Stator Part) lifted precisely with Under Slung Cranes of Dome through hatch.

Figure 7. Assembled 3.6m Telescope in its enclosure.

Figure 8. Handling of metal dummy mirror by Single Girder crane.

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Figure 9. Primary mirror of telescope lifted with Single Girder crane after its first aluminization.

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Customized overhead cranes for installation of India's ... · Customized overhead cranes for inst allation of India s largest 3.6m optical telescope at Devasthal, Nainital, India