Field work in a treatment plant, when the network isn’t everywhere
The underground pump station, the filter gallery and the far end of the sludge area usually have no signal. Digital field work has to be designed for exactly these conditions from the start.
The Waiotech team··5 min read
Anyone who has worked in a treatment plant has a mental map of the places where a phone has no signal: the inlet pump station a few metres underground, the filter gallery with its thick concrete walls, the blower building with all that metal, and sometimes the whole sludge area, far from the administration building.
These are exactly the places where most maintenance work happens. If maintenance software only works online, the technician either records the work later in the office, which means the same old paper and memory, or doesn’t record it at all.
“I’ll record it later” means it isn’t recorded
Recording after the fact has three problems. First, details are forgotten: what was the vibration? Which bolt was loose? Second, the real time is lost: was the job done at ten or at two? Third, the photo, the most important evidence, usually isn’t taken, or stays on someone’s personal phone.
So field work has to be recorded right there, next to the equipment, whether there is a network or not.
The offline package: take the work with you
The answer is to take the work that is about to be done onto the phone before going out. This “package” contains everything the technician needs for that job: the work order, the tasks, the procedure, the reserved part and the equipment details. For an operator, a round package plays the same role: the points to read and their expected ranges.
But an offline package must not be a permanent pass. A few rules keep it safe:
- It is bound to one person and one phone. It cannot be moved to another device.
- It expires. At most 24 hours: today’s work, for today.
- It can be revoked. If the phone is lost or the work changes, the package is revoked from the server.
An offline package carries today’s work for today; nothing more.
An encrypted logbook
When the technician ticks a task, records a reading or takes a photo without a network, these actions are recorded in a logbook on the phone. The logbook is encrypted, and photo files are kept in the app’s private storage, not in the phone’s public gallery.
The technician should always know how many actions have not been synced yet. A simple number at the top of the screen, such as “3 actions queued”, removes the worry of “was my work recorded or not?”
Sync, with a clear result
When the phone is back online, the actions are sent to the server in order. This is the most delicate part: something in the system may have changed in the meantime.
An example: the technician has finished the job and recorded completion, but in the meantime the maintenance supervisor has put the work order on hold for some reason. What should happen?
Two answers are wrong: silently accepting the completion and ignoring the supervisor’s decision, or throwing away all of the technician’s work. The right answer is for each action to get its own clear result:
And for the item that was not accepted, the reason and the next step are given: “The work order is on hold; task results and photo were kept; record completion again after it resumes.” Until that conflict is looked at, the later actions in the same package are not accepted either, so that nothing gets buried under something else.
Some things stay online
Not everything should be offline. Starting a job usually has to be checked against the live state of the system: has isolation been confirmed? Is the permit still valid? Is the job allowed right now? A phone cannot decide those from data that is several hours old.
The same goes for issuing a part from the store: the phone cannot conclude from an old stock figure that the issue has happened. It can record evidence of use, but the final record belongs to the store.
The rule is simple: work at the equipment can be offline; decisions that depend on the live state of the whole plant stay online.
If a phone is lost
Work phones in a plant get lost, get broken or get handed to someone else. A field app has to be ready for that day:
- Data on the phone is encrypted and cannot be read without signing in.
- The app installation on that phone is revoked from the server.
- That phone’s offline packages lose their validity.
- If the phone is handed to someone else, the previous person’s data and packages do not carry over.
A morning at the sludge pump station
At half past seven the technician is in the maintenance building with full signal. They open today’s work list on the phone: replace the seal on return sludge pump 1, and the monthly PM on blower 2. Before heading out, they take both jobs’ packages onto the phone.
In the sludge pump station, which is underground, the phone has no signal. The technician scans the pump’s QR tag to make sure it is the right pump; the scan is resolved from the package on the phone. They had started the job while they still had signal in the maintenance building, so now they tick the tasks one by one, take a post-repair photo and record completion. The top of the screen says “6 actions queued”.
At ten, back out in the open, the phone syncs by itself. The task results and the photo are accepted. If anything changed in the meantime, for example if the supervisor had put the job on hold, the technician sees the reason at once and knows what to do next.
That morning no paper was filled in, and nothing was left to “I’ll record it later”.
In short
Digital field work in a treatment plant gets only halfway without offline support. But being offline is not safe without limits either. A package bound to one person and one phone that expires, an encrypted logbook, and a sync that gives a clear result for every action make work at the equipment both possible and trustworthy.