A shipboard entry is not a single test performed before the hatch is opened. It is a sequence of five points, and each of them answers a different question: which compartment is worked first, whether the space may be entered now, whether it stays safe while the crew is inside, what happens after a break, and what the file shows afterwards. Yunku Technology matches each of those points to a specific equipment capability — the sequence comes first.
Sequencing the compartments, before anyone opens a hatch
Order the day's compartments by residue and by how long they have been closed. A tank that held volatile cargo, or one that has been sealed for weeks, needs the earlier slot and the longer ventilation block; working the easiest hatch first and discovering the real problem at the end of the shift is how jobs get squeezed. The sequence decides the day's ventilation and testing plan, not the other way round.
Before entry: ventilate, test and approve as one action
Ventilation comes first — mechanical displacement for at least 30 minutes — then testing, laid out by layers: at least three points vertically and two horizontally. All three readings have to pass before a permit is signed: oxygen between 19.5% and 23.5%, flammable gas no more than 1% of the lower explosive limit, and toxic gases within the GBZ 2.1-2019 exposure limits.
The governing document on board is GB 16993-2021, the dedicated code for ship enclosed space operations. The shipboard flammable threshold is 1% of the LEL — ten times stricter than the shore-side figure — so a job must not be released on the land-based 10%. If a reading fails, ventilate again and re-test the full set; re-testing only the parameter that failed does not close the step.
During the job: the hard part on a ship is getting the data out
Ventilation continues and testing repeats. GB 46768-2025, the domestic shore-side code, sets its record-keeping cadence at one instantaneous reading every 15 minutes; shipboard crews can follow that rhythm while remembering that the code itself does not apply to vessels. The practical difficulty is getting the data off the tank: steel bulkheads attenuate wireless signals, and in places such as double bottoms and cofferdams the units inside often cannot reach the deck outside.
That is where the equipment comes in. The LSM3000 confined space monitoring station splits into an internal unit, which collects gas and personnel readings inside the compartment, and an external unit mounted at the hatch, which aggregates and uploads them. Concentration curves, the headcount inside and the camera view all converge on the hatch, so the attendant follows what is changing without leaning into the opening.
After an interruption, and after a shift change
People going in and out, ventilation stopping and any break in the work all change the atmosphere again. If the job pauses for more than 30 minutes, ventilate and test afresh before work resumes. A new shift does not inherit the previous shift's readings — whoever takes over re-tests before going in, even if the crew it relieves has just come out.
Closing out: headcount, then the file
Once everyone is out and the hatch is closed, the permit, the gas data, the entry log and the completion sign-off are filed together, so the whole sequence can be pulled up by job number. The record is what an inspection reads first: it shows whether the five points happened in order, or only that equipment was on site.
Five points, one checklist. Sequence the compartments · ventilate, test and approve before entry · monitor continuously while work goes on · re-test after any break or shift change · file the records at the end. Skip one and the remaining data no longer proves what happened during the shift.