Last week we shared an email thread asking you, our faithful blog readers, to help troubleshoot some mysterious data from a warehouse mapping. Several folks got back with some thoughtful analyses, which we will share in this week's blog. BUT FIRST! Several other folks asked for us to provide more data. Paul scoured his inbox and found the data originally sent... so, here we offer the images of mapping, as well as the raw data, for your edification and delight! Here is the Raw Data. And below is an image of the sensor placement schematic.
Dear Janice & Paul,
Here my thoughts:
1. Where are the controller sensors of AHU machines? Since the whole warehouse had a drop in temp, maybe some heat source was placed close to these sensors? This would only be a reasonable hypothesis if all sensors are together (or if all AHUs share one thermostat). Warehouse owners should have been able to mention if a hot load was entered into the depot, I think.
2. One item that called my attention is why the new cold spot is placed on the upper third of the warehouse, from my perspective, floor should be cooler than roof (since the “event” produced a peak to colder temp, I assumed the AHU were in a cooling mode at the time of event, reducing the chance that we are talking about an excessively cold outer weather). In this perspective, the position of cold spot close to the roof against the once “well stratified” warehouse shows that AHUs (I assume placed close to the roof) are cooling in excess. If all of them are using a single sensor, this one may be wrong (perform an “as found” calibration to find out). If there are many of them, look for a heat source next to them.
3. High variation of sensor 28-3 during working hours could also be due to a new heat source used for work (a new machine for packaging? Electrical charge station for forklifts?) or a malfunction of lighting close to this sensor. Anyway this has to be related to “the event” somehow, for this I would go talk to depot owners or depot staff again.
Anyway I can’t give this one any more time, but now I want to know the solution!!!
QA Manager Technical Compliance
Global Pharmaceutical Distributor
(before seeing the data)
Thanks for the Monday morning poser to start the week. My initial thought on this issue is the loggers have been moved inadvertently then replaced when once discovered, especially as the event is quite localized. But it would be a good idea to review all possibilities. If I were to investigate this I would look for answers to the following questions to get a fuller picture.
1. Logger placement:
Were the loggers fixed in place? This would stop them being moved accidently.
For the materials in the vicinity of the erroneous readings, where there are stock movements? This will show in system transactions. Logger could have inadvertently been moved.
Where the warehouse staff (all shifts) briefed on the exercise? Sounds like poor communications with the warehouse manager. Do they know the positions of the loggers?
2. AHU / Temperature control:
What is the position of the temperature controlling probes? Are they calibrated, maintained?
Is routine temperature monitoring performed in the warehouse? The hot and cold spot should be monitored and this would give an indication of AHU failure
Is there a temperature profile mapped for door opening scenarios? Is this timed and recorded?
Do we know the external temperature; is this a summer or winter exercise?
As the warehouse managers don’t have much information is there any design specs for the layout/AHU placement etc. that might help?
Are there any previous mapping exercises? The hotspot has obviously been identified previously, where the same loggers used in previous exercise?
Is preventative maintenance performed on the AHU? and is it current
Are routine monitoring probes separate from the controller probes? Are they all calibrated?
If there were detected faults on the AHU earlier, was any maintenance being performed at the time of the event? If so this should be logged somewhere
What other sources of heat may be present in the warehouse? Any built in cold stores or freezers? Any gas powered fork lift trucks?