In paper factories, moisture in oil is a significant risk factor that entails considerable short- and long-term costs, most often the result of the ingress of moisture, partly from the paper manufacturing process, the felt washing, leaking steam heads or irregularities in the drying hood (zero shift). While trends such as sustainability and the conservation of resources often call for cost-intensive separation, very short filter lives, high levels of filter element wear and multiple oil changes also constitute a major financial burden.

Having an efficient dewatering strategy is therefore especially important. In-depth analyses and assessments of the oil in the system make it possible to determine the causes of system failures in plants, and consequently avoid them in future. Digitisation also holds great potential for optimising processes in paper production.

The challenge
Extremely high levels of filter changing, very premature fluid change and increased interventions by staff – these conditions were a major problem for our customer. Without efficient and rapid support, the leading international company faced major economic damage. In the search for an efficient solution, the paper factory turned to Hydac experts from the divisions - Fluid Engineering, Filtration and Industry Team Pulp & Paper for support.

The customer’s aim was to reduce the ingress of moisture to ensure consistently acceptable values in line with the OEM specification. At the same time, the service life of the components and fluids needed to be increased accordingly, to reduce maintenance costs. For the purpose of condition monitoring, the customer asked for online measuring instruments to be installed to enable preventive action to be taken.

The HYDAC expert analysis
“Identifying the problem is more important than finding the solution. For the exact formulation almost automatically leads to the correct solution.” - Albert Einstein To get to the bottom of the problem, HYDAC specialists performed an initial analysis on-site. Its fluid experts evaluated the ingress of moisture in an online measurement using the HYDAC AquaSensor. In particular, the measurement revealed that the increased machine speed in the press section was partly responsible for high and permanent water ingress in the hydraulic system. The moisture caused a chemical “hydrolysis” reaction, resulting in the breakdown of important additive elements such as calcium and sulphur, and the build-up of gelatinous reaction products.

The products are subjected to much more rapid deterioration and block the filters in the cooling oil circuit extremely quickly. An effect that lowered the service life of the fluid from the original five years to six months. The service life of the filter elements used in the cooling oil circuit was reduced from three months to one day. On top of this, there was a large amount of foaming in the tank, which facilitated cavitation in the pumps. All of these factors are both extremely inefficient and highly cost-intensive.

The solution Fluid Engineering
The Hydac Fluid Engineering approach increases system availability and saves operating costs. In this way, the user can reduce machine downtime in paper factories caused by moisture problems.

A major challenge that raises a number of questions – but Hydac experts were able to find the right answer. Hydac vacuum dewatering units from the FAM series quickly and consistently reduced the amount of moisture in the system. Additionally, the oil was filtered and degassed in parallel. The integrated online measuring system enables continuous condition monitoring of the oil. The AquaSensor AS 1000 measures the water content and the Contamination Sensor CS 1000 the particulate contamination. They are connected to a Sensor Monitoring Unit SMU 1200, which displays the measured values and saves them so they can be transferred and further processed.

The functional principle of the FAM dewatering units
Hydac vacuum dewatering units from the FAM series FluidAqua Mobil work on the principle of “mass transfer”. This involves water and gases in the oil being transferred to a constantly flowing stream of air, which is filtered and dried by the applied vacuum and the increase in temperature. Air is drawn into a vacuum column and then expands, which is what causes this effect to occur. Once the oil has passed through the vacuum column multiple times, it reaches a water saturation percentage that is equivalent to the relative humidity of the air inside the vacuum column.

The AquaSensor AS 1000 takes care of the monitoring of the relative moisture in the oil. The particulate contamination is detected by our ContaminationSensor CS 1000. Both fluid sensors are directly connected to a SensorMonitoring Unit SMU 1200, which displays the measured values and saves them for trend analysis, for example. Various interface modules (e.g. CSI-C11) are available for transferring the measured values to higher-level company networks, condition monitoring systems (CM) and control systems (PLC), Hydac CMX (cloud) or system alarm messages sent by e-mail.

The result
Seeing the results, the customer said, “Thanks to the HYDAC experts, we now work much more efficiently and above all with lower costs. We were particularly impressed by the extensive consultation and support. We wouldn’t want to do without these aspects, even in the future.”

With the use of the two FAM-45E dewatering units, the moisture content in the system very quickly dropped to below 20% relative moisture and then stabilised to an acceptable level in line with the machine specification. This significantly increased the oil’s service life. The service life of the filter elements also settled back to an economically viable duration. At the same time, the customer reduced cost-intensive bearing failures and unscheduled downtime. With Hydac online measuring system, this standard could be continuously monitored and moisture-based failure could be prevented.