The invention relates to the field of pressure equipment, and in particular of boilers for generating heat for heating spaces and operating industrial installations.

More in detail, the invention relates to a process for controlling the correct operation of pressure equipment.

The subject matter of the present invention is also the system that implements this process and intends to provide a safety chain that allows to increase the degree of reliability of all the normal safety devices installed as a rule on pressure equipment, such as water tube or fire tube steam/hot water/superheated water generators and, consequently, guarantee the reliability, in terms of safety, of the generator.

Background art

Pressure equipment substantially comprises:

- at least a generator of a heated fluid, whether steam, hot water or superheated water, of the water tube or fire tube type;

- at least a burner (firebox) adapted to supply a heat source for said generator;

- safety devices comprising at least a pressure sensor and at least a temperature sensor of said heated fluid adapted to detect the working parameters of said generator;

- an electrical panel comprising a device for management, control and signalling of any faults recorded by said safety devices.

As a rule, the operation of pressure equipment with the risk of overheating, such as the kind described, must be constantly monitored by a licensed operator.

The level of qualification required by the operator of pressure equipment with a firebox depends on the amount of steam the generator can produce and on the size of the heat exchange surface.

Pressure equipment, suitably designed, built and subject to conformity assessment in accordance with the current directive PED 2014/68/EU, equipped with suitable safety and regulating devices that ensure automatic operation without risks to persons and property, can be operated without manual (human) intervention for a predetermined limited time, currently established as a maximum of 72 hours.

Currently, only a few types of steam/superheated water generators can be exempt from constant monitoring by licensed operators; for example, forced circulation water tube generators do not fall within the scope of application of the 72 hours exemption and therefore, even if suitably equipped, cannot be operated without the constant presence of a licensed operator.

In pressure equipment with 72 hour exemption, monitoring of the safety devices is entrusted to a software system that usually resides in the electrical panel and manages a timer, which switches off the generator if the operator fails to conduct the test and the established checks within the 72 hour limit.

Except in the cases provided by law, the operator of steam/hot or superheated water generators must hold a certificate of competency (license).

Pressure equipment with a risk of overheating, that fall within the obligation of licensed operator, are machines generally used in an industrial environment to produce steam, hot or superheated water for use in the production process.

From the above it is understood that during the normal production cycle that requires the use of pressure equipment such as steam/hot or superheated water generators, the presence of a licensed operator is necessary, at best, every 72 hours.

To obtain the license, the operator must pass a specific exam, which can only be taken after a training period, documented in a personal training book, the duration of which varies according to the level of authorization required.

Presentation of the invention

The invention intends to overcome these limits, defining a process for controlling the correct operation of pressure equipment adapted to provide companies with greater flexibility in management of the production cycle, allowing the aforesaid equipment to be used safely and continuously without the presence of licensed personnel for a longer period of time with respect to that currently guaranteed by existing technologies.

Therefore, the object of the invention is to provide a process implementation system that allows pressure equipment to be operated without the constant presence of a licensed operator for a duration exceeding the current 72 consecutive hours permitted, with a considerable saving of management costs.

These objects are achieved with a process for controlling the correct operation of pressure equipment according to the main independent claim.

The subject matter of the invention is also a system that implements this process for controlling the correct operation of pressure equipment.

The process of the present invention, and the system that implements it, offer important advantages with respect to conventional control methods and systems.

The control process is adapted to ensure operation of pressure equipment with risk of overheating, protecting it from overpressure and overheating in excess of the design limits.

In practice, the control process according to the invention, and the system that implements it, advantageously allow:

- greater flexibility and autonomy in production processes, as the user is less bound by the figure of licensed operator;

- greater safety to persons and property during operation of the generator also in the absence of the operator;

- maximum freedom to operate without the presence of licensed operator all types of generator of pressure equipment with risk of overheating; - extension of the operating limit time without operator up to 720 hours, lowering the level of risk by a factor of 100.

Moreover, the system as claimed can be installed on any steam, superheated water or hot water generator, provided that it operates within its design parameters and is provided with safety devices suitable to operate within the aforesaid values.

Brief description of the drawings

Further features and advantages of the invention will be more apparent hereunder, in the description of a preferred embodiment, illustrated by way of non-limiting example, and with the aid of the figures, wherein:

Fig. 1 schematically represents the main components of a system that implements the process for controlling the correct operation of pressure equipment according to the invention;

Figs. 2a, 2b, 2c represent the engineering flow diagram of some components of the system of Fig. 1 ;

Figs. 3, 4 and 5 represent, by means of a flow diagram divided into three parts for clarity of representation, the logic and the steps of the process for controlling the correct operation of pressure equipment according to the invention;

Fig. 6 represents the plant layout of the control system and of the process claimed, i.e., shows the interconnections between the process equipment, the system of the interconnecting tubes and the instruments used for controlling the process.

Detailed description of a preferred embodiment of the invention With particular reference to Fig. 1 there is illustrated pressure equipment essentially comprising:

- a generator 1 of a heated fluid, whether steam, hot water or superheated water, of water tube or fire tube type;

- a burner 14 adapted to supply a heat source to said generator 1 ;

- basic safety devices comprising a first pressure sensor instrument 2 and a first temperature sensor instrument 3 for said heated fluid;

- a measuring device 16 of the operating time ti of said generator 1 , for example a timer;

- an electrical panel 4 comprising a device 20 for management, control and signalling of any faults recorded by said first pressure sensor instrument 2 and said first temperature sensor instrument 3;

- sound 17 and visual 18 signalling means of said faults;

- a key selector switch 19 and various programming and interface push buttons 15.

Said pressure equipment is associated with a system for controlling its correct operation, better known in the art as safety chain, which allows the equipment to operate also in the absence of the figure of the operator C for an extended period of time, exceeding the limit currently established by law.

Said system comprises:

- a second pressure sensor instrument 5 of said heated fluid adapted to detect a value pi;

- a second 6 and a third 7 temperature sensor instrument of said heated fluid adapted to detect a value Tvi; - a fourth 8 and a fifth 9 temperature sensor instrument of the flue gases produced adapted to detect a value Th;

- a logic control device 10 connected to said second pressure sensor instrument 5, said second 6 and a third 7 temperature sensor instrument of said heated fluid, said fourth 8 and a fifth 9 temperature sensor instrument of the flue gases produced, containing a program adapted to interact with all said devices;

- a plurality of switching devices 1 1 a, 1 1 b, 12a, 12b, 13a, 13b that act directly on the burner 14 that supplies said generator 1 , to shut it down;

- a plurality of interface devices 15, such as selector switches and push buttons, which allow the operator C to interact with the electrical panel 4 of the pressure equipment, for example intervening in the case of faults;

The system of the invention that will produce the safety chain can be an independent system, where said logic control device 10 can reside in an external control unit (as illustrated in the diagram of Fig. 1 ), or can be an integrated system, with the logic control device 10 fitted inside the existing general electrical panel 4 of the pressure equipment.

With particular reference to Figs. 2a, 2b, 2c it is evident that all the switching devices installed 11 a, 1 1 b, 12a, 12b, 13a, 13b act independently from one another directly on the block of the burner 14, causing the immediate shut down and switch off of the generator 1.

In detail, the system comprises two interlock switches arranged in series for each sensor instrument, and hence two switches 1 1 a, 11 b associated with said second pressure sensor instrument 5, two switches 12a, 12b associated with said second 6 and third 7 heated fluid temperature sensor instrument and two switches 13a, 13b associated with said fourth 8 and fifth 9 flue gas temperature sensor instrument.

The entire safety chain produced can be viewed as all of a number of safety chains that operate in series, one for each safety device that acts through the system.

Said second pressure sensor instrument 5 must be chosen of the type having at least the following features or improvements:

- Asd [FIT] = 0,

- Asu [FIT] = 65,

- Add [FIT] = 0,

- Adu [FIT] = 39,

- SFF > 62%.

For correct interpretation of the data indicated above it is specified that:

- Asd [FIT] is the safe detected failure rate;

- Asu [FIT] is the safe undetected failure rate;

- Add [FIT] is the dangerous detected failure rate;

- Adu [FIT] is the dangerous undetected failure rate;

- SFF Safe failure fraction refers to the fraction of safe failures, where a higher value corresponds to greater reliability of the device.

In the same manner, by way of example, it is reported that excellent results have already been achieved with the following pressure switches available on the market:

Said second 6 and third 7 heated fluid temperature sensor instrument and said fourth 8 and fifth 9 flue gas temperature sensor instrument must be chosen from the type having at least the following features or improvements:

- Asd [FIT] = 0,

- Asu [FIT] = 34,

- Add [FIT] = 0,

- Adu [FIT] = 34,

- SFF > 0%.

By way of example, excellent results have already been achieved with the following thermostats available on the market:

With regard to the logic control device 10, the following PLC available on the market proved to have particularly high performance:

In detail, said logic control device 10 contains a program adapted to:

- receive from the operator C the setting of a limit value po, Tvo, Tfo for each working parameter;

- receive from the manufacturer a limit value to for said operating time parameter of said generator 1 in the absence of the operator C;

- carry out an auto-test that verifies correct operation of said devices;

- verify the instantaneous working parameters pi, Tvi, Tfi, comparing them with the preset limit values po, Tvo, Tfo;

- verify that the operating time parameter ti of the generator 1 is greater than zero, comparing it with its preset limit value to;

- switch off the generator 1 and generate an alarm signal if the preset limit value po, Tvo, Tro exceeds even only one of the working parameters or upon reaching the zero value of said operating time parameter.

More generically, the fundamental steps of the process for controlling the correct operation of pressure equipment claimed are described below with reference to the logic illustrated in the flow diagrams of Figs. 3, 4 and 5.

With reference to the logic diagram of Fig. 3, the process provides for a preventive step by the operator C of setting a limit value for each working parameter at play (for example pressure and temperature of the fluid produced by the generator and temperature of the flue gases generated).

The safety chain that is produced constantly monitors the working parameters blocking the supply of thermal energy each time a fault is detected.

The fault consists of one of the working parameters exceeding the corresponding preset limit value.

If present, the operator C will check the fault in real time, immediately restoring the equipment back to its correct operating condition.

Operation without the operator C is possible if and only if the licensed operator C, before temporarily leaving the system, carries out the auto-test procedure (Fig. 5) that serves to check correct operation of all the devices that are part of the system and described above.

In detail, during the auto-test procedure the operation of each single switching device must be electrically simulated.

Performance of the auto diagnosis test and its positive result are stored by the system and are the condition necessary to be able to operate“without the operator present” for a given preset time to, or number of hours. If the operator does not carry out the auto-test again after the preset number of hours without the operator present have elapsed, the supply of thermal energy will be switched off and the generator can only be started up again and operate“with the operator present”.

The permitted maximum number of operating hours of the generator without the operator present is a given time to preset by the manufacturer of the pressure equipment and cannot be changed by the operator.

If the result of the test is negative, the generator shuts down immediately and the fault is signalled.

During the absence of the operator, it is the microprocessor that interfaces with the various sensors and checks the working parameters of the pressure equipment, in particular pressure and temperature of the heated fluid and of the flue gases produced, comparing them with the preset limit values.

If the comparison is negative, i.e., if only even one of the working parameters is found to have a value exceeding the respective preset limit value, this causes immediate shut down of the generator and signalling of the fault with the request for extraordinary maintenance by the operator. The operator can solve the fault and restore the operating condition by interacting with the electrical panel by means of the interface devices.

If the comparison is positive, i.e., if all the working parameters are found to be below the limit value, this instead causes only reading of the timer and checking that the limit value of hours to of operation in the absence of the operator has not yet elapsed.

If the result of the check is positive, i.e., the condition in which the elapsed time ti is still below the limit time to, this causes reiteration of the process steps starting from checking each working parameter with reading of the respective sensors.

If the result of the check is negative, i.e., the condition in which the elapsed time ti is greater than the limit time to, this causes the immediate shut down of the generator in total safety (Fig. 4).

The control process as described and claimed has been designed to operate in conditions of atmospheric pressure.

Said control process is also implemented to operate paired with burners complying with the standards EN 676 and EN 267 and related accessory solenoid valves. Finally, the safety chain claimed has been designed and produced e installed on pressure equipment having the following features: