[labnetwork] wet bench EMO's

[Shruti Hegde]

Dear Kyle,

Thank you for raising this — it’s a very relevant point from a safety and
design perspective.

In most wet bench designs, theEMO is intended primarily to address *immediate
personnel safety risks* by isolating active energy sources. Accordingly,
EMOs typically shut down high voltage, heaters, pumps, and wafer handling
systems.

However, utilities such as DI water, N₂, and CDA are generally *not
interlocked with the EMO*, as they often play a role in maintaining a safe
state of the system. For example, DI water supports dilution and cooling,
while N₂ and CDA are used for purging and pneumatic valve actuation.
Interrupting these during an emergency could, in some cases, lead to
unintended risks such as accumulation of hazardous vapors or loss of
temperature control.

That said, incidents such as DI water leaks are usually addressed
through *independent
safety layers*, such as leak detection systems and interlocked shutoff
valves with FOM relay, rather than through the EMO itself. This allows for
targeted isolation of the affected utility without impacting other
safety-critical functions.

Given your recent experience, it may be worthwhile to evaluate the
implementation of *leak detection and localized DI shutoff mechanisms*,
supported by a risk assessment, instead of modifying the EMO functionality
directly.


Best regards,
Shruti Hegde

On Wed, Apr 8, 2026 at 5:17 AM Prashant Srinivasan <prashant at ucsb.edu>
wrote:

> Kyle,
>
> The EMO on our benches (Ancient Pure Aire) shuts off the 208V and 120 V
> circuits (fluorescent lamps, Ph meter, outlets and the laminar flow motor).
> The DI/CDA/N2 systems are passive (no electrical actuation).
>
> If you want to go the automated route, a DIY approach is an OpAmp
> comparator (with suitable level shifters). COTS solutions are aplenty,
> something like this:
> https://www.bapihvac.com/product/water-leak-detector-with-attached-or-remote-sensor/
> (or) https://www.ato.com/water-leak-sensor-transmitter
>
> I'd say a monthly visual inspection and replacing lines on the verge of
> failing should suffice.
>
> Prashant
> On 4/7/2026 9:13 AM, Kyle Keenan wrote:
>
> Hello All,
>
> I'm curious to know what the EMO's do on the wet benches in your
> facilities. Do they shut down CDA, N2 or water, or just high voltage? What
> is the thought process behind what does/does not get shut down? We recently
> had a bad DI water leak on one of our benches, and we were a little
> surprised to find out that the EMO did not shut off the water supply, so we
> are considering whether or not we want to make a changes to the way the
> EMO's work on our benches.
>
> I look forward to reading your replies.
>
> Best,
> --
> Kyle Keenan
>
> Senior Manager - Laboratory Operations
> Quattrone Nanofabrication Facility
> University of Pennsylvania
> P: 215-898-7560
> F: 215-573-4925
>
>
> _______________________________________________
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>
> --
> Prashant Srinivasan,
> Teaching Cleanroom Engineer
> Electrical & Computer Engineering
> University of California, Santa Barbara
> Santa Barbara, California 93106https://www.ece.ucsb.edu/department-resources/electronics-shop/tcr
>
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