How One Midwest Food Manufacturer Served Up a Recipe for Success with Hydraulic Fluid Cleanliness

Ensuring that the food we eat is safe is of primary concern for any food manufacturer, which is why methods of excluding, removing or killing bacteria and other pathogens are commonplace in the food processing industry. While techniques such as pasteurization or irradiation are often used, they have been shown to potentially change the flavor, smell or texture of food, which has led to the development of other ways of killing pathogens without impact to food quality. One such method is High Pressure Processing (HPP) which is a non-thermal (5ºC – 20ºC) food and beverage preservation method that guarantees food safety and achieves an increased shelf life, while maintaining the organoleptic and nutritional attributes of fresh products¹.

HPP requires pressures in the range of 400-600 MPa (60,000-90,000 psi) which necessitates the use of special equipment capable of both generating and withstanding these extreme pressures. Most HPP equipment uses standard hydraulic power units (HPUs) with outputs in the 2500-3000 psi range, coupled with specialized water over hydraulic intensifiers to boost the output pressure to the ranges required for effective food preservation.

While High Pressure Processing is a highly effective method of food preservation, as one Midwest manufacturer of deli meats discovered, it can also be problematic. This is especially true when ceramic-coated pistons shatter, distributing hard particles in the 1–2 micron range throughout the hydraulic fluid. When this happened in the manufacturer’s facility, they were unable to remove these particles with their conventional full flow 10-micron filters. Instead, the situation required that they seek out a way of reducing particle and moisture contamination without an expensive redesign of the system.

The solution they chose was to install a high efficiency offline filtration unit (OLU) on each of the ten HPP power packs (Figure 1). Equipped with a radial depth cellulose media filter and a water removal spin-on pre-filter, these systems can remove free and emulsified water, and over 99.9% of all 2-micron and greater particles. In addition to adding offline filtration, the plant also elected to add desiccant breathers to each HPU to eliminate secondary sources of contamination from air ingression during normal operation. 

Figure 1: Offline filtration system connected to the High-Pressure Processing (HPP) hydraulic system 

After installation, the effect of the offline filtration systems on fluid cleanliness and dryness was immediate, with particle contamination dropping by 3-4 ISO 4406 cleanliness codes to an average of 16/14/10, while the moisture content was consistently below 10 ppm (Figure 2). 

Figure 2: Typical particle and moisture content before and after filtration

In the two-year period prior to upgrading the HPUs, the plant had experienced an average of three failures per year across the ten HPP units in the plant, equivalent to an average Mean Time Between Failure (MTBF) of 3.3 years. Each failure required extended downtime to replace failed components as well as a complete change-out of hydraulic fluid to remove contaminants.

After improving system cleanliness, the failure rate dropped to just one failure in a fifteen-month period, resulting in an MTBF of over 10 years, which in turn resulted in an annual increase in net production of 85,000 pounds of product as well a significant reduction in labor and material costs.

Buoyed by their success, the plant elected to overhaul their lubricant management practices, starting with other hydraulic systems. The first step was to re-purpose the used (but still serviceable) hydraulic fluid from the HPPs for use in other less critical, lower pressure hydraulic systems such as vat dumpers, stuffer and blender hydraulic systems. To do this, they deployed a similar filtration unit to the one installed on the HPPs to batch process hydraulic fluid, bringing this used oil’s cleanliness levels below that of new oil. To ensure that the system was working as planned, they elected to equip the filtration system with a condition monitoring sensor to report the cleanliness of the reconditioned fluid per the ISO 4406 standard with a goal of meeting fluid cleanliness level at or below ISO 16/14/10.

Between fewer hydraulic failures on the HPPs, in conjunction with the hydraulic fluid reclamation project, the plant was able to reduce hydraulic fluid consumption by over 1000 gallons per year, a significant contribution to the sustainability goals of the company. Tracking of hydraulic fluid savings was made possible through a point-of-use fluid tracking system, in conjunction with assigning ownership of the fluid reconditioning system to one craftsperson to create accountability and “buy-in”.

Between reduced maintenance costs, the reduced cost of purchasing hydraulic fluid and the increase in production, the plant estimated that they were able to increase net income by $350,000 annually, while being recognized by the corporate reliability team as a top-performing plant.

To share their success, a 3-year return on investment (ROI) analysis was put together, balancing the increased cost of filtration and fluid management against the lower maintenance costs and increased production (Figure 3). Based on a conservative estimate for the cost of capital of 15%, the improvements on system reliability were estimated to produce at 3-year Net-Present-Value (NPV) return of over $750,000. Based on an initial cost of around $40,000 with annual costs for increased oil analysis and replacement filters and breathers it was estimated that the Internal rate of Return (IRR) was around 850%.  

Figure 3: ROI Analysis 

Conclusion

It is well known that up to 90% of hydraulic system failures can be tied directly or indirectly to the health and cleanliness of the hydraulic fluid. But as this manufacturer learned, offline filtration is a quick, low-cost means of significantly improving system cleanliness and can result in sizeable financial gains from increased productivity, reduced maintenance costs and a reduction in overall MRO purchases.