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It is desirable to assemble any component or system with clean parts in a controlled manufacturing environment. However, this may not always be possible. It is sometimes necessary for the entire hydraulic system to undergo a cleanup process after final assembly to reach the desired roll-off cleanliness level. This article provides a theoretical calculation of appropriate flushing requirements. Adherence to established roll-off cleanliness levels will provide the OEM with a better product and fewer warranty claims.

Experts estimate that 75 percent of hydraulic component and system failures are caused by contamination. Contamination causes premature wear and lost efficiency which can result in catastrophic failure. Typically, sources of contamination can be characterised as:

Built-In
Inadvertent contamination left in the system or a component during initial assembly or a system rebuild. Examples include weld splatter and cleaning rag fibres.

Generated
Contaminants internally generated during system operation, or caused by wear, corrosion, agitation, oxidation or fluid degradation.

Ingested
Externally introduced contamination that enters a system from various openings such as breathers, worn cylinder wipers, improperly sealed access covers, etc.

This paper discusses built-in contamination, specifically particulate contaminants, and how to clean up the system following final assembly. Typically, particulate contaminants include weld splatter, dust, fibres, paint chips and other undesirable and potentially abrasive particles. Many of these particles are below the human visual threshold of 40 microns. Although they cannot be seen, they can be damaging to a system

Roll-off Cleanliness
The main purpose of roll-off cleanliness is to minimise damage to the various system components in their infancy. To underscore the importance of establishing roll-off cleanliness standards, the International Organisation for Standardisation (ISO) is developing new standards outlining the cleaning of components and systems. One draft standard, ISO/WD 16431, describes “roll-off cleanliness of an assembled hydraulic system upon release from the production area.” This title may change as the document is finalized, but it is obvious that the target is to provide the cleanest possible equipment to the customer.

Cleaning Methods
There are many ways to clean a system, and it is up to the manufacturing group of a company to decide which method(s) to use. The ultimate goal is to reach the desired cleanliness level at the most reasonable cost and minimum time interval. Some methods of achieving this are:

  1. Let the system run through its normal operating cycle and allow the system filter(s) to clean the fluid. The system will operate at low pressure during the cleaning/flushing process. The main advantage of this method is simplicity. However, one disadvantage is that the system filter(s) might not have sufficient dirt-holding capacity to last through one cleaning. Several element changes may be necessary to clean a dirty system. This method may also damage system components if the initial contamination level is too high.
  2. Use a filter cart, sometimes referred to as filter buggy or kidney loop (following the idea of kidney dialysis). This mobile, self-contained unit filters the fluid off-line using its own pump, motor and filter. It is designed to operate at a low pressure, usually less than 100 psi. The best way to use this device is to attach its suction and return hoses to the reservoir with fluid fittings and let it run while the system is running at a low pressure. Oil returning to the reservoir from the return line will now be filtered through the filter cart. This off-line process supplements system filter(s) and decreases cleanup time. This method may also damage system components.
  3. Design an off-line filter that can be attached to the system at system pressure. It can be connected to the system in such a way that it becomes the power supply. The equipment can be cycled using hydraulic power from the off-line system. The main system does not need to be run except to remove oil from the lines that are not in circulation. The cart flow is not required to be as large as the system flow. The idea is to cycle the system for flushing purposes but not necessarily as fast as normal operating speed. This method minimises damages to system components.

It is not economically feasible to remove all contaminants from a system. Most systems operate trouble-free with a small amount of contamination present. The amount of contamination that can be tolerated in a system depends upon the sensitivity of the most critical component. System reliability continues to improve, however, as ideal conditions are reached. Diminishing returns on increasing effort is the limiting consideration. This threshold for the contamination level is established by the component manufacturer and ultimately by the system builder.

The size and type of filter used are important in making calculations for cleaning a system. The analysis presented here makes use of the following assumptions:

  1. Contaminants are uniformly distributed in the fluid.
  2. During roll-off cleaning, no additional contaminants enter the system and no contamination is ingresses.
  3. The filter exhibits uniform efficiency throughout its working life.
  4. The filter does not go into bypass. If it does, the element is replaced. In order to avoid filter element change during the roll-off cleanup, the filter must be adequately sized. It has been observed that contamination may inadvertently be added to the system during element changes.

Generally after a hydraulic system has reach the required cleanliness level, the system has been running for a significant time and  at working temperature.  The hydraulic media and the particulate contamination are Homogeneous. (Substance in which components are evenly mixed, particles and hydraulic media). So when the hydraulic system is shut down, the particles settle out in the reservoir, hydraulic components and system pipework. When start up is then initiated the particle and hydraulic media are not Homogeneous. This can lead to initial high levels of contamination for a significant length of time until the hydraulic application is back up to temperature and the particles and hydraulic media are once again Homogeneous.

Real applications will vary from this idealisation to some degree, but the variation is not expected to significantly affect the results.

Proper roll-off cleanliness procedures protect equipment in its infancy and provide for fewer warranty claims. The end-customer is provided with a high-quality system with clean components that meet his initial use needs. Roll-off cleaning however, is only the starting point for trouble-free system operation. The final responsibility in controlling contamination lies with the user. Users must maintain proper filtration and practice responsible contamination control in the system to keep the hydraulic fluid clean.

Hydraulic systems are integral to the way we live today, with critical applications everywhere – be it aerospace, agriculture, energy or manufacturing. Most hydraulic failures are caused by particle contamination, and the quality of filtration is therefore the most important factor in a hydraulic machine’s long-term health. MP Filtri’s range of filters and contamination-monitoring products keep systems clean and monitor the cleanliness levels, resulting in predictive maintenance and allowing machines to work effectively and efficiently while extending longevity, as well as drastically reducing the risk of system failure. MP Filtri’s successful investment in pioneering new technologies that improve the productivity and performance of these systems has seen it grow from humble beginnings to one of the major companies in hydraulic filtration – something Phil Keep, their managing director, discusses in the following piece.

Our Journey

Now a world-leader in contamination monitoring and hydraulic filtration technology, MP Filtri UK began life in1990 as the UK distribution arm of its Italian parent company. We started out with just two employees, a product range new to the market and a modest turnover of just £100,000. Three decades later, we have increased sales more than 100-fold, and design, test, construct and sell market-leading contamination monitors and particle counters. We are also preparing the next phase of our expansion with a move to a high-tech, purpose-built 2,000 square metre production facility.

‘The vision, commitment and support of company owners Giovanni and Monica Pasotto have been absolutely crucial to the success of the UK operation.”

The sale of a comprehensive range of hydraulic filter products to maintain the cleanliness of oil and fluids for peak machine performance – our core business – has grown dramatically since our launch in 1990, with the company holding more than 20 per cent share of the UK & Ireland market. We are now on course to break the £10 million sales barrier for the first time this year, marking a major milestone in our growth, in line with my original ambitions for the company.

I and my operations director, Sophie Fisher, were the original members of the team. Along with sales director,Chris Durkin, we still steer the company’s direction, working closely with the Milan-based Pasotto family who set up MP Filtri in 1964 and have more than 50 years’ experience in designing

In the early days there were just the two of us, working in a small industrial unit in Gloucestershire selling a limited range of filters for mobile and industrial customers. We knew we had a great product and, with the backing of the Pasotto family, we were able to expand our range and work with our colleagues in Milan to develop the right products for the OEM customer market.

Expansion & Growth

The big breakthrough came for us in 2000 when we expanded from retail to design and manufacture, identifying a niche in the market to begin development on a exciting new range of innovative contamination monitoring products. Created to bring the functionality of the laboratory out into the field, they were originally aimed at the mobile and construction industries, providing engineers with the ability to carry out a full hydraulic health check and conduct real time monitoring of particulate contamination while out on site.

We developed our first portable particle counter to be the most advanced mainstream machine of its type in the world, and the machine quickly attracted new business in industrial, maritime, aviation, agriculture and offshore sectors. Ultimately, we saw there was a market for portable, highly accurate products which would pay for themselves many times over by enhancing performance and protecting machines working in applications where downtime is incredibly costly and maintenance costs are expensive.

The original LPA2 machine (the first incarnation was a prototype) enabled the company to establish itself as MP Filtri’s worldwide specialist production centre for contamination monitoring products and sparked the development of an expanding product range which is now recognised around the world for innovation and reliability.

It was closely followed by the In-line Contamination Monitor (ICM), offering real-time monitoring 24 hours a day, and it has sold more than 5,000 units since launch and is one of the company’s most successful products. The new range led to strong sales growth with the company achieving turnover in excess of £5 million for the first time in 2010.

The key to the company’s long-term expansion has been our ability to combine a trusted, traditional core product range – hydraulic filters – with contamination monitors which save customers money, prevent costly damage and downtime and help ensure peak performance.

We have been backed by multi-million pound investments in production and R&D, both here and in Italy, ensuring we can keep our products at the cutting-edge and at competitive prices. It has helped us take full advantage of market intelligence to create new products for specific markets and niches. We have also invested in great people, bringing in a wealth of knowledge and new ideas to enhance the technology we offer.

Moving Forward

The next phase of investment will see us move to a state-of-the-art production and customer service facility, while retaining our base in the famous Cotswold village of Bourton-on-the-Water – adding much needed space for our engineering department.

We are also creating new opportunities for growth in integrated automated systems where our in-line contamination units can be installed to provide real-time monitoring of oil cleanliness and particulate contamination, as well as warn of potential hazards and reduced performance. These are fitted into everything from automated test equipment to cranes and crushers.

We are developing products to work in high-cost critical applications where loss of power or downtime cannot be tolerated and penalties are extreme. We know that to maintain our success we have to provide more than just cutting-edge products at the right price; the emergence of IOT (Internet of Things) systems means we have to work even more closely with customers, listen to their individual needs and offer bespoke engineering solutions.

I am incredibly proud of how our teams here and in Italy have worked so hard to build a multi-million pound technology business with an unrivalled product range of world-leading products.”

Examples include specialist projects such as automated flushing and cleaning systems for transport; fuel tank and system analysis; and custom-designed hydraulic and diesel tank systems. The company is also preparing to launch the latest incarnation of its portable particle counters: the LPA3, which will launch later this year. A new inline contamination monitor and 50-litre mobile filter trolley to remove free water from hydraulic oil have also been launched over the past 12 months.

I am incredibly proud of how our teams here and in Italy have worked so hard to build a multi-million pound technology business with an unrivalled product range of world-leading products. We know we cannot afford to rest on our laurels, however, which is why we continue to invest in developing new products and in introducing automated production tools to keep prices competitive.