Technical Committee 8 Safety in Heat Treatment Plants

There is no grandfathering for machinery and equipment. The requirement of the legislator is that work equipment (machines, plants, ...) is operated safely according to the state of the art* (Ordinance on Industrial Safety and Health (BetrSichV) §4 "Basic obligations of the employer", explanations in Bekanntmachungen zur Betriebssicherheit (BekBS) 1114: "Adaptation to the state of the art in the use of work equipment"). Safe operation of older work equipment in accordance with the state of the art may require additional measures of a technical or organizational nature. One measure can be a retrofit, for example.

Excerpt from the Ordinance on Industrial Safety and Health
§2 Definitions
...
(10) The state of the art is the level of development of advanced processes, equipment or methods of operation which makes the practical suitability of a measure or procedure for protecting the health and safety of employees or other persons appear assured. In determining the state of the art, reference shall be made in particular to comparable processes, equipment or methods of operation which have been successfully tested in practice.

With the exception of the safety purge gas, the supply of all process media must be controlled by two automatic safety shutoff valves connected in series, unless it can be demonstrated in a hazard assessment that one valve is sufficient.
In most cases, the use of a suitable filter upstream of the first safety shutoff valve is required.
Safety purge gas (such as N2) for purging or pressure maintenance, should be released by two de-energized open valves connected in parallel.

Heat treatment plants regularly consist of machines from different manufacturers, e.g. furnace, handling equipment and exhaust system. In this context, the question of CE marking arises again and again. The legal basis is the EC Machinery Directive 2006/42/EC (in Germany: Machinery Ordinance - 9th Ordinance to the Equipment and Product Safety Act).

In principle, there is only one EC declaration of conformity and CE marking for a machine. However, if several machines interact in terms of production technology, this does not automatically result in a "new" machine" in the technical vocabulary "totality of machines" (interlinked plant, complex plant). An "assembly of machines" is considered as one machine and has to fulfill the same requirements, such as a common EC declaration of conformity and CE marking. The Federal Ministry of Labor and Social Affairs (BMAS) has also included this fact in its interpretation paperonthetopic of "Entirety of Machines" of May 5, 2011 and provided assistance for clarification.

According to this paper, a machine is considered to be an assembly if there is a production-related connection due to the following factors

• the arrangement of the individual machines to form a whole (here, particular emphasis is placed on the coherent installation)
  
• and the individual machines work together as a whole
  
• and the individual machines are operated as a whole (i.e. have a common control/command device)

and the individual machines function as a whole in terms of safety (safety-related interrelationship).

If all these conditions are met, the machine is considered to be a whole, which has a common EC declaration of conformity and CE marking.

If these machines are purchased and assembled individually by the operator, he is responsible for the declaration of conformity and CE marking of this totality of machines. This can also be commissioned as a service.

However, if it is not an assembly of machines, each individual machine has its own EC Declaration of Conformity and CE marking.

Example: There is a washing machine in a chamber oven line.

1. The batches are moved in the oven line by means of a manually operated loader. The washing machine has a control system independent of the other components of the furnace line. There is no signal exchange. A malfunction in the washing machine has no influence on the rest of the kiln line in terms of control and vice versa. There is neither a production-technical nor a safety-technical connection. The lines have separate declarations of conformity and each has its own CE marking.
2. The batches are moved in the furnace line by means of an automated loader. The components of the furnace line (e.g. washing machine, ovens, loader, etc.) each have independent controls. A safety-relevant signal exchange takes place. There is a safety-related connection but no production-related connection (no common control), even if a higher-level control coordinates the processes within the oven line. The systems have separate declarations of conformity and each has its own CE marking.
3. The batches are moved in the furnace line by means of an automated loader. All components of the furnace line have a common control system and there is both a production-related and safety-related connection. The equipment has a common declaration of conformity and CE marking.

Show figure Decision steps - Entirety of machinery according to Machinery Directive 2006/42/EC (extract from BMAS interpretation paper).

The answer to the question is essentially based on a pure replacement of the control unit. This means that the new control unit has the same functionality as the old control unit. Important information for the general consideration of whether a change to a system is a significant change within the meaning of the Machinery Directive can be found in the interpretation paper on "Significant changes to machinery" published by the Federal Ministry of Labor and Social Affairs (BMAS) on April 9, 2015.

The following statement can be found there regarding the replacement of components (including control components):

Excerpt from the interpretation paper"Substantial modification of machinery"
... The replacement of components of the machine with identical components or components with identical function and identical safety level as well as the installation of protective devices that lead to an increase in the safety level of the machine and that do not enable any additional functions beyond that, are not considered to be significant changes.

A 1:1 replacement of the control system is therefore not a substantial modification within the meaning of the Machinery Directive.

Example 1: Replacing Siemens S5 with S7
A typical case is the replacement of an old Siemens S5 control system with an S7 No safety functions may be implemented via a normal PLC. Therefore, simply replacing it with a modern PLC is not a significant change per se, as it does not interfere with the safety technology.

Example2: Replacing the entire switchgear
The existing safety technology of the system, implemented via the switchgear, is sufficient, taking into account the state of the art at
.
If a 1:1 replacement is made here, this also does not constitute a significant change.

Example 3: Replacing a control system using conventional technology with a control system with a safety PLC
The previous control system using conventional technology is replicated 1:1 in a safety PLC.
The 1:1 transfer of the control logic means that the safety level is maintained, so there is no significant change.

Example 4: New control system according to the state of the art
The previous safety technology of the system, implemented via the switchgear, is not sufficient taking into account the state of the art or is not clearly comprehensible due to missing or incomplete documentation. The safety functions must therefore be implemented in the new control system according to the current state of the art. This may involve modifications to the system itself, e.g. conversion to double valves.
This generally leads to an improvement in the safety of the system due to advances in safety technology. According to the interpretation paper on "Substantial modification of machinery", an improvement in safety in particular does not constitute a substantial modification within the meaning of the Machinery Directive.

Excerpt from the interpretation paper "Substantial modification of machinery"
...
The replacement of machine components with identical components or components with an identical function and identical safety level, as well as the installation of protective devices that lead to an increase in the safety level of the machine and that do not enable any additional functions, are not considered to be a substantial modification.
...

New functions of the thermoprocessing system
If new functions are introduced as part of the control system replacement, it must be checked in accordance with the interpretation paper on "Substantial modification of machinery" whether these lead to a substantial modification of the thermoprocessing system within the meaning of the Machinery Directive.

Note:
For thermoprocessing systems in operation, it must generally be checked whether they are operated safely in accordance with the state of the art. Retrofitting may be required here regardless of whether the control system is replaced.
See also FAQ question 1: Is there a grandfathering clause for older thermoprocessing systems?

Definition: Significant change as defined by the Machinery Directive:

A significant change within the meaning of the Machinery Directive requires a renewed declaration of conformity and CE marking for machines with CE marking and an initial declaration of conformity and CE marking for older machines without CE marking.