March 28, 2022

By Krystie Johnston

Stefan Lehnert, Head of Digital Sales & UX at Bosch Rexroth AG, recently discussed functional safety in hydraulics with Lukas Marschall, Project Manager for Industrial Manifolds. In their presentation, How to Successfully Implement the Requirements from Functional Safety on Your Hydraulic System, they consider regulations, product offerings and application examples with respect to hydraulic systems. The IH04 modules are the latest product offering from Bosch Rexroth. These modules are not yet available in North America; however, Bosch Rexroth is exploring how quickly they can make a certification for the US and is interested to hear requests about what customers here want. Still, the applications and information in this article are relevant for those who work on presses or other machines and want to implement functional safety.

Q: We know that functional safety is not new. Why are we talking about functional safety today?

“Functional safety is important,” says Mr. Marschall. “If you build a machine, it is important that you build it safe and according to the machine directives and laws. Product safety laws in Germany require that if you build a machine, you must fulfill regulations not only for Germany and Europe, but for other countries in the rest of the world as well. The implementation of these laws is set into standards – international standards like the ISO standard, and local standards, like the D-Type in Germany.” Safety is not a new topic, but it does continually change, and keeping up with these changes is important to Bosch Rexroth.

Current safety requirements for machines depend upon the place the machine or product is to be used. Contrary to popular opinion, standards are not prepared or agreed upon by governments or authorities. The last decade has seen a change from national standards to globally applicable standards, meaning different legal stipulations can apply. A-Type standards (or basic safety standards) contain terminology, principals of design and general aspects that apply to all machinery. B-Type standards (or group safety standards) address a safety aspect or device that can be used for a range of machinery. C-Type standards contain all safety requirements for a specific machine or type of machine¹. And E-Type standards are product standards.

Marschall explains, “For standard products you will find all kinds of information about how functional safety is implemented. It is also important to have C standards, like the EN693 for hydraulic presses. This is an old standard and is a description of how functional safety is implemented for presses. The new standard is the ISO 16092 part 3, for example, and pertains to hydraulic presses.”

Regulations can be deep and technical as they specify the safety requirements and measures that must be followed by people who design, manufacture, and supply hydraulic presses, for example. It is important to be aware of them and know where to go for more information. Bosch Rexroth has developed modules to comply with these standards, ensuring that safety always comes first.

These are a lot of standards and maybe we can revisit them and dive deeper later. What is the real offering from Bosch Rexroth here?

“The real offering are modules that fulfill functional safety,” says Marschall. “They are IH04 modules. These modules are complaint with all standard requirements according to the standard ISO. You as a customer have the benefit that you get a type-tested standard certificate from the institute that fulfills all safety requirements, and you have a documented form from this institute.” The modules from Bosch Rexroth provide customers with a product that is compliant with standard requirements, and they are also certified modules. The safety requirements are documented in detail and give customers peace of mind. The institute that provides the certificate is the Deutsche Gesetzliche Unfallversicherung, or DGUV, which is the Testing and Certification System of the German Social Accident Insurance.

Getting into the modules now, what is the IH04, and can you describe it in more detail?

Before Marschall looks at the safety requirement concept of the product offering in detail, he provides an example of how a press or a machine for forming technology works. In a typical hydraulic press, there are two types of controls. There is the upper ram piston control, which controls the piston’s vertical motion in the direction of the press chamber, and the second is the die cushion control, which works under the press. It is important to understand how these machines operate to appreciate the safety categories that have been developed. Bosch Rexroth’s safety measures consists of four categories: (1) avoiding the unintended lowering under own weight, (2) avoiding the unintended start-up from the rest position, (3), stopping of the dangerous closing movement, and (4) safe reduced speed below 10mm/s with hold-to-run device (which is a new requirement from ISO 16092-3). Each safety measure is assigned a performance level and a category. For the first three safety measures, the performance level is E, and the category is 4. For the new requirement (safe reduced speed), the performance level is D, and the category is 3.

Marschall elaborates, “If you have a dangerous source in your machine, you have a high category and you need a high-performance level. The new safe reduce speed below 10mm/s has a high-performance level D, and a category 3. Before, in the old standard, it was the performance level Z in category 1. That is the new requirement machine builders need to fulfill. We at Rexroth built up our modules to make sure that we fulfill the requirements for ISO.” Two different kinds of modules were developed, upper ram piston modules, both IH04C and IH04D, and die cushion modules for IH04E. “And here in our example we see the IH04D with the basic module has all relevant functions for implementation of functional safety included into the basic module. You as a customer also have the possibility to extend these modules, for example, by adding the pressure holding function for the IH04D module.” Bosch makes it easy to create the solution that is right for their customers by making it possible to combine these modules to suit individual applications. They also offer a retrofit kit so these modules can be integrated into legacy equipment and still meet the new standards of ISO 19062-3.

More details on the products?

Looking closer at the IH04C upper ram piston modules, the IH04C is available from Bosch Rexroth in five different nominal sizes (10, 16, 25, 32, and 35), with a maximum pressure up to 350 bars, and a maximum volume flow from the pump side up to 2000 L/m. This module fulfills the safety requirements according to the ISO standard, and customers also get the certification from the DGUV in Germany. If you want to learn more, refer to the data sheet which is included on the Bosch Rexroth website here

The IH04C module is focused on bigger machines, with volume flow up to 2000 L/m. But what if you want to realize these functions for smaller machines? Bosch Rexroth has another module, the IH04D, which has two different nominal sizes (6 and 10), with a maximum pressure up to 315 bars, and maximum volume flow up to 80 L/m. This module is suited for smaller presses or other machines used for forming technology. For a detailed technical description, view the datasheet here

The die cushion module is the newest member of the hydraulic press family. Bosch finished its development in January 2022, so it is brand new. What is different about it? Marschall explains, “Lower nominal flow and only 2 sizes (10 to 32), and pressure up to 315 bars. This module also fulfills the functional safety requirements according to the same standard, and customers can also have extension modules like differential circuits, load sensing, and they can combine it. Here you see the basic module and the extension module to realize active die cushion function, and the extension module to realize the passive way for die cushion function. For the customer, this is very flexible.” For more information, refer to the IH04E data sheet here

Another new member into the IHO4 module family is the overload module Type S. This module realizes overload function, so if there is an overload on the press or application, the module will fulfill the stop of the machine. Marschall says, “It is fast, up to a reaction time to 5mm/s. This IH04S has also been available since 2022, so it is quite new as well.”

These modules come standard; however, customers can request additional functions that can be combined to create a tailored solution. Marschall explains, “You as a customer have the chance to extend this module with different functions, such as the rabbit to rest cylinder if you wanted to realize maximum speed, or high- and low-pressure pumps, or load sensing, and you can combine these functions. You see in our presentation that we have more extension functions which are combined into our IH04D modules.” If you want to learn more about the circuits and the functions, refer to the IH04C or IH04D data sheets mentioned above, reach out to Lukas Marschall, or contact your local Bosch Rexroth here

For Bosch Rexroth, safety is of utmost importance. Marschall says, “For us, it is quite important that you as a customer are safe with your machine. To prove the safety, we have the concept, we get an acceptance and certificate, and if you buy a Rexroth IH04 module you get the certification which means you have time saving and no calculations for the performance level.” Bosch has developed new modules to ensure hydraulic presses on their machines comply with emerging standards, and to ensure their customers have peace of mind. Visit their website to learn more here