Ripening room application

Main advantages

Differences with similar ripening systems

Banana ripening rooms are often built using technologies bought from several vendors, then sold by a third company acting as a contractor or as an engineering. For instance, the electronic controller can be from a vendor, the curtain and the shelving from another vendor, the engineering and the installation by a local (domestic) company, as integrator of different technologies.

The local company usually has little knowledge of component details, while vendors have no information at all about how their technology is being used.

Micheletti Impianti, instead, has developed every component from scratch, thanks to banana ripening experience lasting since 1965. The electronic controller named MI 1000 and the underlying software have been developed just to serve banana ripening rooms as built by Micheletti Impianti. For this reason, the final result is a perfectly integrated ripening room, with commands put on single slave panel, as to control not just ripening functions, but also refrigeration, depression, door, light, and curtain. Following is an example of software integration and features usually not found in common ripening rooms:

The full list of software features may be found here.

The software keeps tracks analytically of all ripening parameters at every instant. The software is even able to provide Excel quality reports, resuming following synthetic indicators, for each ripening:

The art of ripening is about balancing quality, speed, and energy saving. The software is able to drive the system, as to get the desired trade-off between quality and energy saving, by regulating the depression fans, by on-off or by inverter.

Every control is performed by a master electronic controller, located inside the room electrical board. The controller can be programmed by the local slave panel, located near the room door; by a local PC, usually located in the ripener's office; and by a remote PC, connected to the local PC via Windows Remote Desktop, VNC, or TeamViewer. Remote control is also allowed by Android phone, tablet, and iPhone.

In case of fault of PC or local slave panel, the master controller continues to operate correctly, without any ripening interruption. Moreover, the master controller is not worn by contact with operator hands.

In case of power fault, the master controller resumes the operation at power-up, without any data loss.

The ripening system is perfectly integrated with the revolutionary ReFreeX technology, which have 80% refrigerant reduction and several other advantages detailed in the specific literature.

On 9 June 2014 entered into force the new EU regulation nr. 517/2014, concerning restrictions to refrigerant gas usage. In particular, from 1 January 2020, it will be prohibited to recharge even a single gram of virgin R404A or R507 on refrigerating systems with an overall charge of 11 kg or more. For that reason, the ReFreeX technology is extremely relevant.

Naming convention: rooftop/Chiquita v. curtain/Del Monte

Ripening rooms are sometimes classified accordingly to the depression method.

Our method of using a corridor, a covering curtain, and a depression box can be called curtain method. A competing method using roof top evaporator along all of the room length is called rooftop method.

Originally, the curtain method was also known as Del Monte, while rooftop was also known as Chiquita. However curtain and rooftop are more appropriate names, because Chiquita and Del Monte companies are not necessarily committed to the method named after them.

Pallet format and preparation

The banana ripening system of Micheletti Impianti adapts itself to the pallet shape to ensure perfect ripening for every format.

The standard pallet is as follows.

For pallet height between 1.90 m and 2.40 m, it is possible to reach optimal results by the standard system arrangement. The pallet length and width are not critical for one-level rooms.

Different pallet height and extreme formats are available on request.

For perforated box bags, no pallet preparation is required. For closed bags, it is necessary to extract a small piece of the bag from the box accessible window, and to cut a hole in it. At the end, each box bag will have just one hole, on the outer side of the pallet.

Room loading

The ripener loads the one-level room by a small forklift, better with side shifter. The pallets have to be lined to the two sidewalks at the room sides, as to create two pallet rows that divide two side corridors from a central one.

After loading, the ripener puts three banana probes inside the banana pulp, or better between the bananas, and covers the pallets using the curtain and the electric roller.

An expert ripener can prepare 24 pallets with closed bag, and load the room in about one hour.

Now the room is ready and the computerised system takes care of the ripening process.

What more to turn the key

Starting from our supply, following items are needed to complete the job:

Supply repeated for each room

Room electrical board

The room electrical board is located near the door, on the room front, and contains following components:

Computerised control system

For each room there is a stand alone system with microprocessor control, master board, located inside the room electrical board. The microprocessor controls every phase of ripening. The system can be programmed by the slave keyboard-display module, by the office PC, or from a remote location, connected to the office PC via Windows Remote Desktop, VNC, or TeamViewer.

In case of fault of PC or local slave panel, the master board continues to operate correctly, hence the control is highly reliable.

The control system is made by following components:

The control system receives every relevant information by following probes and signals:

Following features are supported:


The door allows easy operation for room loading, unloading and checking. The door slides vertically inside the room, leaving a clearance of m 2.70 x 2.60 h, for one-level load, and of m 3.0 x 4.95 h, for two-level load.

The door is built by horizontal panels, of 40 mm thickness, with stainless steel hinges and rubber gaskets, and has following accessories:

Depression system

The depression system forces air to flow from the outer side to the inner side of the pallet, to get a uniform ripening in each box.

The depression system includes following items:

Ethylene injection system

The ethylene injection triggers the banana ripening. The system manages the injection of the inert blend made by nitrogen and ethylene. The inert blend is absolutely and intrinsically safe because it is impossible to reach the ethylene burst concentration.

The computerised system manages the injections. It is possible to schedule a first injection and further periodic injections, to hold a stable ethylene concentration.The standard injection time for a 24 pallet room is about 50 minutes, the consumption is about 1000 litres; each ethylene cylinder (not provided) contains about 9000 litres.

The system includes following items:

Air renewal system

The air renewal provides oxygen and removes excess ethylene and CO2, to ensure optimal ripening.

The computerised system manages the air renewal. It is possible to schedule periodic air renewal during the ripening cycle or during storage as well. It is even possible to drive air renewal by the CO2 concentration.

The system includes following items:

Room heating system

The heating is needed mostly during the initial phase of the ripening, to increase the banana temperature, before injecting the ethylene.

The heating capacity is calculated to rise the temperature at a rate of about 0.5 °C per hour. Heating is performed by hot gas provided by the central unit or by the stand alone refrigerating unit.

The heating system includes following items:

As an option we can provide heating elements with stainless steel sheath. The stainless steel sheath of the elements and the vulcanisation of the endings ensure long lifetime and reduced overheating.

The system by heating elements includes following items:

Room refrigerating system—direct expansion option

The refrigeration is needed mostly after the ripening, to bring back the banana temperature to the storage condition.

The refrigerating capacity is guaranteed to lower the temperature at a rate of at least 0.5 °C per hour, or quicker. The thermostatic valve function is performed pulsing the solenoid valve by the computerised control, that way the system is able to manage all the common refrigerants, as R22, R134a, R404A, R407A, R407C, R407F, R410A, R448A, R449A, R455A, and R507A. The system is able to migrate effortlessly from old refrigerants, as R22, to new refrigerants, as R404A, just by changing a software parameter inside the menu.

The room refrigerating system includes following items:

Room refrigerating system—water and glycol option

The refrigeration is needed mostly after the ripening, to bring back the banana temperature to the storage condition.

The refrigerating capacity is guaranteed to lower the temperature at a rate of at least 0.5 °C per hour, or quicker. Refrigeration is performed by refrigerant fluid made by water and 20% glycol. The fluid is refrigerated by an outer water chiller not described in this document. The rooms require about 200 litres, per pallet and per hour, of fluid entering at −4 °C; different flows and inlet temperatures are available on request.

The room is provided with connections, left over the ceiling, for fluid inlet and outlet. The room refrigeration system includes following items:

Consumption comparison among direct expansion and water option

We claim that the direct expansion yields energy saving over water and glycol circulation.

The −4 °C fluid of the water option is refrigerated by a chiller with −10 °C evaporation, while in the direct expansion the evaporation is around 0 °C. For each degree raised in the evaporation, there is a 3 % energy saving, in particular COP at −10/+45 °C is about 2.02, while COP at 0/+45 °C is about 2.70. Assuming a refrigeration load of about 2000 kWh per year per pallet, just for keeping depression and maintaining temperature, the energy requirement for the compressors is 741 kWh/year/pallet, with direct expansion, and 990 kWh/year/pallet, with water and glycol. Hence with water and glycol there is a consumption increase around 249 kWh/year/pallet. In a concrete example of a 24 pallet room, 0.15 EUR/kWh, and 15 years of operations, the energy cost is increased by 249*24*0.15*15=13446 euros per room.

It should be mentioned that the water chillers require a circulation pump, which consumes about 5 % of refrigerating capacity, but this term has been compensated with the inefficiencies of the direct expansion regulation, to get a fair comparison between direct expansion and water.

Branched refrigeration circuit

For rooms connected to a common refrigerating unit (a central unit), the branched circuit is needed to connect the room evaporator to the main refrigeration circuit, placed over the room ceiling.

For stand alone rooms, connected to a dedicated refrigeration unit, the branched circuit is needed to connect the room evaporator to the nearby unit.

The circuit length is 5 meters and includes following items:


The room humidity is constantly monitored on the slave and on the local PC, reading a probe located near the door. Room humidity is an important tool to guess about the banana ripening progress, after the ethylene injection and before the first air renewal; during this time, lasting usually 24 hours, door opening is not allowed; hence it is impossible to touch and smell bananas, to ensure that ripening is in progress. A humidity rise on the slave display is a clear indication of ripening start.

Depression ripening on pallet, as opposed to box by box ripening, usually does not need humidification, because the weight loss on pallet is minimal. However higher humidity improves ethylene absorption by the bananas. For this reason a simple humidification system is provided as follows.

The water drain piping from the evaporator has a branched line leading inside the depression box. A water solenoid valve is kept open when the humidity is under the set point, bringing evaporator drain water to the depression box floor. The depression fans help water evaporation from the floor. This system is cheap, energy efficient and simple to maintain.

The humidification includes following items:

Option for a dedicated compressor for each room

A group of several rooms is better served by a central refrigeration unit, due to non contemporaneous refrigeration load of the rooms. One, two, or even three rooms are instead well served by a dedicated compressor for each room, as described in this paragraph.

Following components are repeated for each room and replace the components from central refrigeration unit to oil and refrigerant charge, in case of dedicated compressor:

Supply common to all the rooms

PC software for ripening and monitor

The microprocessor systems of every banana ripening room and of the refrigeration central unit are connected together on a common RS-485 network. The end of the network is linked to a signal converter from RS-485 to RS-232, to be connected to the COM1 serial port of a PC. All the rooms and the central unit can be programmed and monitored by a software resident on a PC located near to the rooms or in the ripener’s office. Micheletti Impianti provides the software, the interface and the network connection up to the room proximity. The eventual network link from the room proximity to the ripener's office is not provided, and can be realised by an AWG-24 cable with two wires, twisted and shielded. The maximum network length is 1000 meters.

The PC minimum requirement is Windows 7, or later, with a free COM-1 port, native or via USB. An internet connection is required for remote assistance. The PC software allows to manage all banana ripening parameters and the central unit as well. In case of alarm, the software sends one or more e-mails. To manage or monitor the ripening from a remote location, it may be used the Windows Remote Desktop, VNC, or TeamViewer.

Following eatures are supported on PC software:

Central refrigeration unit

The central unit provides the refrigerating capacity and is the most critical component, because its correct working is essential for all the rooms. That is why our central unit is the state of the art, for reliability and simplicity, to ensure smooth and continuous running all over the years, and to perform in an energy efficient way. The central unit should be placed in a dedicated room kept between +20 °C and +40 °C.

The unit is fully assembled and includes following items:

Remote condenser and connecting circuit

The remote condenser should be placed in an open space near the central unit. When possible it should be protected from rain and direct sunshine, to reduce consumption and increase lifetime.

Micheletti Impianti provides following items:

Electrical board of central unit

The electrical board of the central unit is the second most critical component after the unit itself. To improve serviceability and reduce faults, Micheletti Impianti employs a custom microprocessor controller. Moreover the compressor contactors are generously oversized by 40 %, to increase safe lifetime.

The board includes following items:

The microprocessor controller, inserted into the board, has following features:

Refrigeration main circuit

The main circuit starts from the central refrigerating unit, reaches the nearest room ceiling, and runs over each room ceiling, to connect to the branched circuits. The circuit length provided by Micheletti Impianti is sufficient for 30 m piping from the nearest room ceiling.

The circuit includes following items:

Oil and refrigerant charge

Micheletti Impianti provides oil and refrigerant charge to operate correctly all the rooms. The standard refrigerating gas is R404A, CFC and HCFC free. R134a and other refrigerants are available on request.

Ethylene main circuit

The ethylene main circuit serves the ethylene injection system of each room. The ethylene cylinders should be located close to the first or the last room in the row. The line starts from the cylinders and runs over each room ceiling. The line is suitable for inert blend in factory filled cylinders, to avoid explosion risk.

The circuit includes following items:

Prefabricated panels

Ripening room arrangement

Micheletti Impianti provides prefabricated panels to build the rooms and the depression boxes. In the standard arrangement, the rooms share the long side wall, in a single cluster (row), with a common door front. Other arrangements are available on request.

Prefabricated panel specification

Panels are galvanized and painted on both faces, for longer lifetime.

Panel specifications are as follows:

Prefabricated panel accessories

Micheletti Impianti provides following accessories to complete the rooms:


Category: Ripening
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