By the Target Working Group

Presented by L.BrunoAB/ATB Targets & Dumps Section

The CNGS Target T40

Lifting jacks review

The T40 Lifting jacks

OUTLINE

1. Introduction to the CNGS target station

2. Functionalities of the lifting jacks

3. Working environment

4. The history of the lifting

jacks

5. Summary

( Downstream Monitor, Horn, … )

T40 Layout Schematic Vertical view

Proton beam

Fixed structure“Handled” structure

Target enclosur

e

Shield

Fixed shielding & steel frameThe CNGS Target Station

Target enclosure

Beam direction

The lifting jacks

Shielding

Fiducials

BPKG monitor

Beam

Target magazine

Alignment table

Base tableTarg

et

en

clo

su

re

Focal Point

Support disks

Displacement

mechanism

The lifting jacks are part of two identical displacement mechanisms, each made of a linear guide mounted on two coupled lifting jacks. Two

handling frames, a ventilation duct (not shown) and guiding fingers are the other parts of this sub-assembly.

The functionalities of the lifting jacks

The lifting jacks of the motorization allow the adjustment of upstream and downstream positions of the target table in a mechanical range of

±20 mm within a 100µ tolerance. Limit switches mark the start and stop position within ±15 mm.

Lifting jack

Linear guide

Working environmentThe danger

The past experience in the T9 target area has pointed out at the extremely severe corrosion processes occurring in humid radioactive environment. Water and ozone are the suspected causes.

Courtesy of S.Rangod

RadiationThe expected dose at the downstream jacks’ location is of ~50 MGy/yr (5x1019 p/yr)

Humidity & TemperatureIn the CNGS target chamber the dew point will be 5°C. The operating temperature of the T40 jacks is R.T.< T< 100 °C. The humidity and the temperature of the shielding within the target enclosure and of the air will be monitored and logged. An alarm is foreseen.

OzoneThe ozone-induced corrosion mechanism is complex and not well understood. Synergy with condensed water appears to be a key element.Ozone warning in air starts usually at 0.1 ppm (200µg m-3). In water, dissolved ozone considerably increases the corrosion potential of stainless steel at about 0.5 ppm. The ozone concentration of the target cooling air will be monitored and logged. An alarm is foreseen.

Working environmentThe expected conditions

The jack’s components

The key elements of the lifting jacks are the trapezoidal screw, the nut and the endless screw. The contact surfaces of these parts slide against

each other. The picture is taken after the last (third) technical iteration with the

provider.

The T9 Target jacks

The choice of the T40 jacks has been based on that of the T9 Target. Here, the spare T9 jack is shown after cleaning. The trapezoidal and

endless screws are made of stainless steel, while the nut is of bronze. The casing is filled with grease. Standard axial/conical ball-bearings were

used.

Order placed on 28 Nov 1994

The first technical iteration(10 years later…)

The first technical choice for the T40 jacks aimed at avoiding all materials whose radiation resistance is not proven. All parts (casing and ball-bearings included) have been asked in stainless steel. Inox 1.4404

(316L) for the screws and 1.4057 (431F) for the nut were asked. No lubrication was requested.

After few cycles, the jacks were stuck and the roll bearings damaged by metal particles. It was found that the nuts had too high a roughness, the

edges were not deburred, the gear geometry caused interference, the endless screw was made of 431F and the gear ratio was not conformal.

PFAFF acknowledged the non-conformity.

The first technical iterationNon-conformities

Radial inox

bearings

Nitriding (hard

surface)

(25 Aug 2005)

After correcting the non-conformities, one jack was tested under a cyclic load.

The resisting torque was too high. Based on a technical discussions held at the PFAFF premises in Germany (19 Sep 05), the decision was taken to

lubricate the sliding parts.

The first technical iterationUnsatisfactory cyclic tests

(25 Aug 2005)

The second technical iteration(Key elements lubricated by Molykote D-321 R)

Lubrication was unsatisfactory: the lubricating layer peeled-off the nut/endless screw after few tens of cycles, well below the 1000 cycles required. It has been found that the endless screw is still not made of

316L as required.

The second technical iterationAgain unsatisfactory cyclic tests

The second technical iteration Details of the trapezoidal screw

The Third technical iterationStandard material used for the nut

The decision has been taken to revert to a standard PFAFF solution for aggressive environments: graphite-loaded bronze nut (powder technology).

No grease is used.

Successful 20-cycles tests have been performed and the key parts inspected. Sliding occurs where expected. The resisting torque is within acceptable levels.

The endless screw is still made of nitrided 431F, the trapezoidal one of nitrided 316L.

The surface of the endless screw shows deposites of bronze and graphite.

Stainless steel axial ball-bearings have been found and used for the nut.

The Third technical iterationDetail of the endless screw

The tests were performed by PFAFF manually (i.e. long times needed). The CNGS schedule does not allow longer tests to be performed.

The third technical iterationSatisfactory 20-cycles tests

Remarks and summary

1. The jack solution we aimed at has not been realized/tested: the material of the endless screw is still not what we asked for.

2. Presently, the CNGS target has been installed with «2nd generation» jacks completely filled by CERN standard molykote. Commissioning tests were successful.

3. Given the time constraints, we have reverted to a «3rd

generation» very close to a PFAFF standard, the only non-standard material being 431F for the endless screw. No grease is used.

4. Four «3rd generation» jacks have been rapatriated this week to be mounted in the second target assembly. This assembly will be used during operation.

5. We must imperatively install the second target assembly in March !