lateral tracking of the star detector during translation. november 23, 2005

STAR Detector Main Support System 1

Lateral Tracking of the STAR Detector during Translation.November 23, 2005

Ralph L. Brown

STAR Operations Group


The STAR Detector is a 1200-ton device located at the 6 o’clock intersection region of the RHIC at BNL. This massive nuclear physics detector is cylindrical in shape approx. 26-ft in diameter by 26-ft long. It is moved north and south between assembly building and interaction region in 5-ft. increments using a closed loop servo-hydraulics system and a series of large capacity Hilman Roller truck assemblies.

Main Support System

The STAR Detector shown in the assembly building for maintenance. The detector can be rolled on steel rails imbedded in the concrete floor using two horizontal hydraulic cylinders. Also shown attached to the main detector to the left (south) and right (north) are the 3-story utility platforms also on roller assemblies.


Main Support System

The left photo shows the detector being rolled south from the assembly building into the IR. The hydraulic pump/control unit is the blue unit on the floor between east/west rails.

The right photo shows a closer view of the north/east area of the main support and horizontal cylinder.

Hilman roller truck assembly with cam follower guides

East horizontal hydraulic piston

East guided rail

Hydraulic control unit


Main Support System

This shows a cross section drawing of the east edge of the east guided floor rail plate that has on the east and west edge a pocket in the concrete for cam follower guides mounted to the detector Hilman roller assemblies.


Main Support System

This shows a cross section detail of the west un-guided floor rail plate that runs north and south from assembly building to interaction region.


Main Support System

The details of the main support east cradle is shown below as a side view (left) and end view (right). Hilman roller truck assembly with cam followers is shown bolted and pinned to the main support cradle.


Main Support System

Supplied by Hilman Rollers for mounting to the support cradle, this drawing shows the NE truck assembly with single fixed cam followers on east edge and dual eccentric cam followers on west edge of floor rail.


Main Support System

Since 1999 we have rolled the STAR Detector from the Assembly Building (AB) to the Interaction Region (IR) , 88-ft. (in 5-ft. hydraulic stroke increments), and back out to the AB each year; having rolled twice this year for a total of 16 translations. This year after rolling out into the AB we noticed deformation of the east edge of the east guided rail.

This photo shows the raised east edge of the east rail that measured 0.175-in.

This photo shows the swaging of the east edge of the east rail from vertical.


Main Support System

Over time and translations the detector has shifted to the west approximately 0.5-in, orthogonally to the guided roller north-south direction.

Original east edge of roller imprint on rail.

New east edge of roller imprint on rail.

Start of affect raised rail surface.


Main Support System

The four fixed cam followers on the east edge and their mounting brackets have been deformed and bent away from the rail edge.

Photo shows deformation of cam follower and support bracket that is bolted and pinned to the Hilman truck assembly.


Main Support System

Hydraulics System:•The hydraulic system consists of four vertical cylinders to raise the detector and electrically isolate it from the rails, two horizontal cylinders for translation of the detector, and controller with pump.•Hydraulic horizontal drive cylinders have internal absolute encoder positional feedback of the piston. •The PLC controller allows for operation of each cylinder either independently or synchronously as a closed loop servo-system.• In synchronous mode the free end of each horizontal cylinder is bolted to the rails and the detector is translated a maximum of 60-in with both cylinders maintaining their linear rate and position within a defined tolerance.•The cylinders are then unbolted from the rails and the pistons independently repositioned and bolted for the next synchronous translation.•There are no pressure gauges on each cylinder to check for equal loading since translation is a synchronous linear movement, independent of applied load.


Main Support System

What we know to date:•The rails have been inspected and found to be flat and coplanar except for the deformed east edge of east rail.•The pistons of both horizontal cylinders were disconnected from the rails and repeatedly cycled 60-in translations in synchronous mode under no-load condition between fixed indicators. Linear rates between cylinders stayed in tolerance (0.5-in.) and final positions were repeatable within 0.010-in.•During last roll-in I independently extended the west cylinder 0.25-in while holding the east cylinder position before making a synchronous 60-in translation. I did this a number of times in an attempt to skew the detector back to the east, without success.•During the last roll-in we raised the detector vertically off of the rollers and jacked it to the east until there was 0.250-in clearance between the cam followers and east edge of the east rail. We then began a horizontal translation and within 30-in travel we moved back to the west against the east rail edge.•A similar issue exists with a 200-ton east pole tip carriage that is hydraulically translated east and west on guided Hilman rollers. In this case the carriage moves slightly to the south on insertion, but back to the north on retraction exhibiting an angular skew in roller alignment. The main detector support doesn’t exhibit this angular skew but moves west in either translation north or south.


Main Support System

What’s next:•Contact hydraulic system vendor, Atlantic Industrial Technologies, to discuss possible issues related to motion control system.•Contact Hilman Rollers to discuss possible issues related to roller systems.•Install independent pressure gauges each cylinder to understand load conditions.•Continue test rolling of detector with independent cylinder translations.•Develop plan for possible removal and repair of roller truck assemblies if required.

West unguided roller atop 0.25 insulator sheet. Flat spot damage to an east roller.

lateral tracking of the star detector during translation. november 23, 2005

Documents

main detector

main support east cradle

main support cradle

east rail

raised east edge

east guided floor rail

west edge of floor rail

hilman roller truck