Automated leakage monitoring system for hydraulic pumps

Background 

Biogas is a versatile renewable energy source. It can be used for electricity generation, heating and as fuel in the mobility sector. Biogas is obtained from various agricultural raw materials and byproducts and, after purification and processing, has the same chemical composition as natural gas. Technically purified, it can then be fed into the existing European natural gas grid, using compressors that compress the gas to up to 90 bar.

Our partner is a leading manufacturer of reciprocating, piston and diaphragm compressors, as well as compressor systems for process gases. The company has installed around 60 compressors at various biomethane injection plants in Germany alone.

Challenge

Biomethane injection plants can be found throughout Germany – and by their very nature, they are often located in rural areas. While this makes servicing these plants costly, our partner also offers comprehensive service packages with customized maintenance contracts for its compressor systems. To facilitate this service, the company strives to automate as many maintenance activities as possible in order to reduce the number of on-site visits. For this reason, it commissioned Milde Hydraulik to implement a fully automatic leakage monitoring system for its compressor units.

To avoid any misunderstandings: The compression process takes place inside the compressors, i.e. there is no contamination with oil inside the cylinder chamber, so that the gas quality requirements of DVGW-G 260 are met. Nevertheless, hydraulic oil can leak out of compressor systems and thus needs to be collected and returned to the circuit by means of a leakage pump. The amount of leakage is an indicator of the condition of the entire hydraulic system – if a lot of oil is leaking out, the system is due for maintenance.

The objective of the order placed with Milde Hydraulik was to automate the entire process and create a service portal that would provide technicians with information on the amount of leakage. Particularly challenging was the fact that the entire system had to be explosion-proof, as the leakage pumps are located directly in or on the biomethane injection plants. 

Solution 

Milde Hydraulik, based in Wurzen near Leipzig, develops and manufactures hydraulic power units and systems for a wide range of applications. As a system integrator and authorized distributor, the company is part of Eaton's Solution Partner Network. This provided Milde Hydraulik with access to the various types of technical expertise required for this project: While Milde itself contributed its hydraulics know-how, the Eaton MOEM Solution Center assisted with the development of the machine design and the programming of the solution. And iSATT, a company specializing in innovative control and automation technology, developed the automation architecture, which also incorporates a solution for connecting the leakage monitoring system to the Internet of Things. Finally, Cooper Crouse-Hinds, an Eaton company, ensured that the system would be explosion-proof. With its Crouse-Hinds series, Eaton offers a broad portfolio of solutions for harsh and hazardous environments, from explosion-proof electrical equipment to communication systems.

Together, the solution partners developed the leakage monitoring system as an end-to-end application that can be directly integrated into compressor solutions. 

The easyE4 control relay forms the core of the automation solution: “As the combined cost of the control cabinet and the leakage unit is in the mid four-digit range, it's simply not an option for the automation technology to cost several thousand euros,” says Peter Hennes, Managing Director at iSATT. The easyE4 was designed precisely with this type of application in mind: Significantly cheaper than a PLC, the performance it delivers is nevertheless more than adequate. The powerful hardware, flexible expansions and comprehensive communication options make it possible to use the easyE4 control relay across a wide range of applications and markets. And the simple handling and the intuitive easySoft 7 programming software make it possible to implement simple control tasks as well as more comprehensive configurations with high process efficiency.

An iSATT2Edge gateway is used as the interface to the IIoT. It collects the data from the leakage pump into a database, aggregates and analyzes it and then makes the filtered information available for use. The gateway and the easyE4 are networked via Modbus TCP. “At present, service technicians can view the data directly via the gateway, but there are also plans to make it available via a cloud platform,” says Hennes. The system can be connected to the cloud either via an internet-enabled access point, via a modem or wirelessly via LoRaWAN. “The edge server on the gateway that we have developed is a universal, scalable and Linux-based application that is compatible with a wide range of hardware platforms,” says Hennes.

The application analyzes various parameters from the operation of the leakage pump: For example, the frequency of on/off operations can be used to draw conclusions about the entire unit, where frequent switching means that the leakage is very high. In addition, analyzing the running time of the pump provides information about the condition of the pump itself, for instance, whether its blades are subject to wear. Service technicians can thus use this information to determine when maintenance is actually required.

All in all, the solution offers a particularly cost-effective combination of the control level (the easyE4 and the IIoT gateway) with a database system – as Peter Hennes points out, “The total cost of the two hardware components is just a few hundred euros.”

The remainder of the application also relies on Eaton and Crouse-Hinds components: The pump is switched on and off via a PKZM motor-protective circuit breaker in conjunction with a DILM power contactor. The easyE4 is housed in an explosion-proof die-cast aluminum enclosure from Crouse-Hinds that features a gas-tight ‘porthole window,’ allowing users to view the control relay display. Crouse-hinds also supplied explosion-proof components for all pilot devices. 

Result

“For this project, we joined forces as solution partners and, in the spirit of ‘One Eaton,’ implemented the entire application using Eaton components,” say Hennes. The customer receives a solution from a single source that significantly reduces the time and effort required for leakage pump maintenance. This enables event-based maintenance, a reduction in service intervals and thus significant cost savings. “Many panel builders and system operators are under the impression that IIoT connectivity is too expensive for smaller installations. We have shown that this is not the case,” explains Peter Hennes. “With the easyE4 and the iSATT2Edge server, we have implemented a very affordable and efficient IIoT solution that can efficiently network even small installations.”