Pharmaceutical

GMP cold room

The excursion starts hours before the alarm. The compressor shows it first.

A cold room holds stock between 2 and 8 °C. The thermostat hides a weak unit by running it longer, so the room looks fine until the unit runs flat out. The twin compares compressor run time with what the doors and the weather explain, and calls the problem while the probes are still in range.

2–8 °C walk-in cold room, 40 m³, duty and standby condensing units, electric defrost, −80 °C freezers on the same page

Start with one utilitySee how we prove results
Section through a 2 to 8 °C walk-in cold room: insulated walls, door with door contact, racking with stock and buffered temperature probes, ceiling evaporator with fans and electric defrost heater, refrigerant lines to duty and standby condensing units outside, and a minus 80 °C freezer, with numbered sensor points.12234562–8 °C, 40 m³dutystandby−80 °C freezer
Duty cycle, normal day
31%
Hold time, power off
13.6 h
Warning, iced coil
19 hours
MKT, week with one excursion
5.9 °C

Anatomy and nameplate

Section through a 2 to 8 °C walk-in cold room: insulated walls, door with door contact, racking with stock and buffered temperature probes, ceiling evaporator with fans and electric defrost heater, refrigerant lines to duty and standby condensing units outside, and a minus 80 °C freezer, with numbered sensor points.12234562–8 °C, 40 m³dutystandby−80 °C freezer
  1. 1Room temperature. Several probes in buffered vials, so they follow the stock, not the air.
  2. 2Compressor run state and current. Duty and standby units. Run time is the early signal.
  3. 3Suction and discharge pressure. Refrigerant charge and condenser health.
  4. 4Door contact. Every opening, so the model knows what heat came in.
  5. 5Defrost state. Heater on and coil clear. A failed defrost ices the coil.
  6. 6Condenser air temperature. Air onto the condensing unit. Hot air or a fouled coil raises head pressure.
GMP cold room nameplate
Room
Range2–8 °C, set at 5 °C
Size4 × 4 × 2.5 m, 40 m³, 72 m² of panel
Panels100 mm PIR, U = 0.22 W/(m²·K), 269 W heat in at 22 °C outside
Reference stock1,200 kg at 3.0 kJ/(kg·K)
DoorInsulated hinged door with contact, 6 openings a shift
Refrigeration
UnitsTwo condensing units, duty and standby, 1.5 kW cooling each at −5 °C evaporating
Duty cycle, normal day31% (461 W average load)
Compressor input0.68 kW running, 5.0 kWh a day
DefrostElectric, 1.5 kW, every 6 hours for 20 minutes
ThermostatOn at 6 °C, off at 4 °C on the air sensor
−80 °C freezers
TypeUpright ultra-low freezer, two-stage cascade
Alarm−60 °C
Hold time to alarm, door shut, power off10.6 hours with a full load
What the twin checksCompressor run time and cabinet temperature recovery after each door opening

The clean utilities behind a batch

Three paths run side by side. Water goes from the still to the hot loop. Steam sterilizes parts, and product moves on to drying and cold storage. Air goes through HEPA filters into the graded rooms.

WaterSteam and productAirPurified water: Pretreatment, RO and EDIPurifiedwaterRO and EDIWFI still: Makes water for injectionWFI stillMakes WFIHot WFI loop: 80 °C, at least 1 m/s at returnHot WFI loop80 °C, ≥ 1 m/sPoints of use: Formulation, washing and rinsingPoints of useWashing, mixingClean steam: Clean steam generatorClean steamGeneratorSteam sterilizer: Sterilizes parts and equipment for fillingSteamsterilizerFilling partsFreeze dryer: Dries the filled vialsFreeze dryerFilled vialsGMP cold room: 2–8 °C finished stockGMP cold room2–8 °C stockAir handler: Filters, coils and fanAir handlerCoils and fanTerminal HEPA: HEPA filters in the room ceilingsTerminal HEPAIn the ceilingGrade C and B rooms: Pressure steps door to doorGrade C and BroomsPressure steps
  • Water
  • Air
  • Steam
  • Product
  • Has its own twin page

The physics

The equations behind every curve on this page.

Mean kinetic temperature

T_MKT = (ΔH/R) / −ln( (1/n)·Σ e^(−ΔH/(R·T_i)) )

One temperature with the same effect on the stock as the swings it saw. ΔH/R ≈ 10,000 K.

Duty cycle

D = Q_load / Q_capacity

The share of time the compressor runs. It rises when the load rises or the unit weakens.

Room heat balance

C·dT/dt = UA·(T_amb − T) + Q_in − Q_cool

Heat through the panels, the doors, the fans and the defrost, less what the unit takes out.

Hold time with power lost

t ≈ m·c_p·ΔT / Q_ingress

How long the stock can soak up the heat coming in before it reaches 8 °C.

The early signal is run time

A unit that is losing refrigerant still holds the room. It just runs longer. Duty cycle climbs for days before a probe moves.

Duty cycle creeps up for days before the room goes out

Slow refrigerant leak on the running unit

Duty cycle creeps up for days before the room goes out020406080100024681012141605101520258 °C limitTwin flags, day 10Excursion, day 25DayCompressor duty cycle (%)Highest probe reading (°C)
  • Measured duty cycle
  • Model, same doors and weather
  • Highest probe reading (right axis)
Expected duty cycle
31%
Warning before the excursion
15 days

The thermostat hides a weak unit by running it longer. The room stays in range until the unit runs flat out, so duty cycle is the early signal.

D = Q_load / Q_capacity

A day against the model

The model knows every door opening and the room outside. When the compressor runs more than those explain, something is wrong with the unit.

Room temperature against the model after a defrost heater fails

Heater fails at 02:00. Door openings marked.

Room temperature against the model after a defrost heater fails2345678910020406080100051015202530358 °CDoorDoorDoorDoorDoorDoorDoorDoorDoorTwin flagsOver 8 °CHours from midnightBuffered probe (°C)Compressor run, last hour (%)
  • Model
  • Measured
  • Compressor run, measured (right axis)
Twin flags
11.9 h
Probe passes 8 °C
30.8 h
Warning
18.8 hours

Ice on the coil cuts capacity. The compressor runs without stopping long before the probes move, and the model says it should still be cycling.

C·dT/dt = UA·(T_amb − T) + Q_in − Q_cool

How long the room holds

When power or the units fail, the stock is what keeps the room cold. More stock, longer hold.

Hold time with the power off, against stock in the room

From 5 °C to 8 °C, door shut

Hold time with the power off, against stock in the room051015202530354005001,0001,5002,0002,5003,00013.6 h with 1,200 kgStock in the room (kg)Hours to 8 °C
  • 22 °C outside the room
  • 30 °C outside the room
Empty room
1.4 h
Linear estimate at reference stock
12.4 h
−80 °C freezer to −60 °C
10.6 h

Stock is the battery. A full room rides out a long outage. An empty one goes out of range fast, and a hot plant room shortens both.

t = (m·c_p/UA)·ln((T_amb − T_0)/(T_amb − T_lim)) ≈ m·c_p·ΔT / Q_ingress

Failure modes

What breaks, what it looks like, what the twin does about it.

Failure modeThe physicsSignals that show itHow the twin catches it
Condenser foulingDirt on the condenser raises the condensing temperature. The unit makes less cooling for more power.Discharge pressure and current up at the same condenser air temperature. Duty cycle up.Compares head pressure with condenser air temperature, and asks for a clean before summer.
Refrigerant leakLess charge, less cooling. The thermostat makes up for it by running longer.Suction pressure down. Duty cycle climbing day by day. Room still in range.Flags on day 10 when duty runs 8 points over the model. The room would go out on day 25.
Door left open or gasket failingWarm, moist air comes in. It adds heat and frost.Door contact open too long. Run time up with no door event to explain it.Matches run time to door events. Extra run time with the door shut points at the gasket.
Defrost failureIce builds on the coil and blocks the air. Capacity falls hour by hour.Compressor runs without stopping. Evaporator air off temperature rises. Defrost heater current missing.Flags 12 hours after the heater fails, 19 hours before the probes pass 8 °C.
Standby unit fails to take overChangeover works on a trip. A duty unit that is weak but still running never trips, so the standby stays off.Duty unit at 100% run time. Standby never started. Changeover not tested lately.Asks for a planned changeover when the duty unit runs flat out, and checks the standby starts and pulls the room down.

What the twin does not do

  • Your environmental monitoring system stays the record for room temperature and excursions. The twin warns earlier from the equipment.
  • We do not decide what happens to stock after an excursion. QA does.

How we catch it early

A physics twin and a PINN, working on one gmp cold room.

The twin is a set of equations for this machine, tuned to its nameplate. Give it the flow, speed and conditions and it returns what every reading should be. It always gives the same answer for the same inputs.

A physics-informed neural network, or PINN, sits on top. It is trained on the plant’s own data and it is penalized whenever it breaks a physics rule. So it can only learn what the equations leave out: wear, fouling, friction. It cannot invent an answer that the machine could never produce.

  1. Step 1

    Measure

    Flow, pressure, current, temperature, vibration. Whatever the asset already has.

  2. Step 2

    Physics twin

    The equations of this machine, set to its nameplate. It says what the readings should be right now.

  3. Step 3

    Residual

    Measured minus expected. Demand, weather and speed are already taken out.

  4. Step 4

    PINN

    A small neural network that learns the cause of the gap, under the physics rules.

  5. Step 5

    Finding

    A named cause, a date, and the kWh or hours at stake. An engineer reviews it.

loss = (measured − predicted)² + λ · (physics residual)²

The second term is the rulebook. It is zero when the network obeys the equations.

Why this beats black-box AI

A black-box model learns patterns from history. It needs examples of each failure, and it goes quiet when the pump runs at a point it has not seen. The twin starts from physics, so it works on day one. The PINN adds what physics cannot know about this particular machine.

That is also what makes the savings countable. The baseline is a calculation, not a guess, so the gap between baseline and meter is a number a customer can check.

What the twin checks on this asset

  • Compressor duty cycle against the model: 31% on a normal day
  • Run time after each door opening against the heat the opening let in
  • Head pressure against condenser air temperature
  • Defrost heater current and coil temperature after each defrost
  • Hold time with power off, from stock on hand: 13.6 h at the reference load. −80 °C freezer to alarm: 10.6 h
Fixed alarmBlack-box AITwin + PINN
Needs failure history to learnNoYes, lotsNo
Says what is wrongNoRarelyYes, by name
Works at a flow it has never seenNoOften failsYes, the equations still hold
Puts a number on the savingNoNoYes, in kWh and dollars
Lead time on slow wearLateVariesWeeks to months
Every number can be tracedYesNoYes, to an equation

What the twin puts a number on

Energy and cost, from the equations.

Warning before an excursion, iced coil

19 hours

Flagged 12 hours after the defrost heater fails. Probes pass 8 °C at 31 hours.

Warning before an excursion, slow leak

15 days

Flagged on day 10, out of range on day 25

Hold time with power off

13.6 h

1,200 kg of stock, door shut, 22 °C outside

MKT of a week with one excursion

5.87 °C

8 hours at 15 °C. Plain average 5.48 °C.

What we do for you

We watch it. We catch it. We prove it.

Our reliability engineers run the twin on your gmp cold room, review every finding, and help your crew fix it. After the repair we compare the meter to the baseline and write the result in the ledger.

Start with one utilitySee the 90-day pilot

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