Module Protection at NIKHEF


This document lists the protections implemented at NIKHEF to ensure modules are handled with minimum risk.

SCT-LV power


1) Any hybrid NTC > 35 degC gives a warning in DCS so an operator can take corrective action.

2) Any hybrid NTC > 38 degC causes the DCS to make a controlled shutdown of all module power.

3) Any hybrid NTC > 40 degC shuts down all the SCTLV by the hardware interlock.

4) There is hardware protection to keep over-voltages on the ABCD's below 5.5 V (both Vcc and Vdd), even for short duration transients. This is implemented with Zener diodes on TPPF1-D of the disc test-box, and with a trigger and Darlingtons on TPPF1-C of the cylinder assembly tooling.

5) If the outlet temperature of any disc cooling circuit is above 0 degC the DCS gives a warning so an operator can take corrective action.

6) If the outlet temperature of any disc cooling circuit is above 10 degC the DCS makes a controlled shutdown of the SCT-LV.

7) If the outlet temperature of any disc cooling circuit is above 17 degC there is a hardware interlock causing all SCT-LV to switch off.


SCT-HV


1) If a module leakage current reaches 100 microAmp, the firmware of the SCT-HV turns the bias-voltage off.

2) If the temperature and humidity of the gas around the modules comes within 5 degC of the dew-point, the DCS ramps the bias voltage down to zero.

C3F8 cooling


1) The C3F8 outlet temperature at the exit of the disc must be more than 5 degC above the dew-point, or the cooling is turned off by a hardware interlock.

2) Minimum temperature of modules during any transient is -30 degC: the cooling plant has been set to have a minimum condensing temperature of -30 degC using the hot-gas by-pass valve.

ESD


1) The assembly rooms H023/4/5 have ESD-safe floors, which have been tested.

2) Personnel wear ESD-safe clothing (coat and shoes or over-shoes). (Over-)Shoes are tested.

3) Wrist straps are available, but not used near modules because of the risk of damage to modules by the lead.

4) Tooling is grounded.

5) Chairs are ESD safe.

6) Personnel are instructed in ESD safety.

7) Racks are grounded.


Mains Power failure

We have no UPS. In the event of mains power failure:

1) The cooling plant stops, and does not turn on again when the mains comes back. Liquid in the system will slowly evaporate, so the cooling continues for a short while.

2) The dry-air supply continues for a few minutes, until the air cylinder of the de-humidifier has depressurised. We plan UPS for this; then the dry air will keep going much longer, until the NIKHEF compressed air supply has run down (order of an hour).

3) SCT-LV and SCT-HV turn off.

4) A bubbler connected to the disc test box prevents any under or over pressure due to temperature changes becoming excessive.


Cleanliness


1) The cleanliness is typically 1000 particles less than 5 micron per cubic foot during times of low activity, and remains better than class 10,000 even in high activity.

2) The module-to-disc tooling holds the disc directly in the down-draft of an air cleaner.

3) The disc test box and endcap assembly box are flushed with very clean dry air, and will be kept closed as much as possible.

Mechanical Safety


1) Handling tooling has been tested before use to minimise risk of mechanical damage. There are no cranes used during handling.  



Nigel Hessey, 6 March 2005