Regulation drives innovation....Part 1 fuel filtration

I want to be very controversial today and suggest that, in spite of feelings to the contrary by those who believe that the free market should dominate the the technology trends in filtration, the function of government regulation is as important to driving innovation as any amount of customer needs. 

The reason for this statement is that in the last few years of working on filter media technology, areas where regulatory control has been strongest has driven the market to change and innovate. Where there has not been the drivers to make changes, the need for lower cost and commoditisation of products has led to a stagnation in technology. 

The two examples that I want to use are fuel media technology and HVAC. In this blog I will focus solely on fuel filtration. 

Emissions regulation driving the fuel filter market
The need for emissions control into the atmosphere is a major public health hazard globally. Couple this with the rapid growth in car and truck ownership in the Developing World we are facing a major challenge. 

Car and truck emissions of concern are:

• soot particles from diesel trucks and cars. We discussed the filtration of soot in an earlier blog. In this case the challenge is to avoid the emission of soot in the first place. These form potentially carcinogenic particles known as PM2.5's and contribute significantly to smog in the atmosphere.   
• NOx. The formation of nitrogen oxides is a by-product of high temperature combustion. Reducing the fuel consumption is a key route to reducing the levels of emissions. 

Both of these factors have led to increasing regulatory control globally. The leadership is driven by the Europeans through a series of emissions limits over the years known as Euro I-VI. These couple the particulate and NOx emissions and set stringent demand on new vehicles on the roads. 

Outside of emissions controls, many countries e.g. UK and Germany have used tax as a powerful lever to ensure that the cost of fuel remains high (In Germany the tax is €0,83/litre) and to drive manufacturers to be more fuel efficient and reduce the consumption of fuel. 

There are many technology requirements needed to achieve these targets including exhaust catalyst systems and with increased control on the dosing of fuel to the injection systems. The latter has driven a need for cleaner fuel in both petrol and diesel systems. 

In particular diesel powered vehicles (due to the lower fuel consumption but higher particulate emissions) has seen both a greater growth in usage and also a greater focus in terms of technology and innovation. 

Diesel fuel has a range of challenges to meet the requirements of the regulations due to its inherent dirtiness. The key issues are: 

• water content: this varies regionally over the globe with the highest levels in China, India and Brazil. The diesel filter has to shed the water to ensure that the droplets don't corrode the the injectors and inhibit clean ignition.
• waxes and broad chemical composition. Diesel, unlike petrol has a wider range of chemical composition with much higher molecular weight organic components. These are often waxy, particularly at lower temperatures leading to blockages of fuel filters requiring the fuel to be pre-heated to around 70C. However the sources of material for diesel also alter. Diesel is primarily a hydrocarbon from oil but, increasingly, bio-sourced components are being used for a portion of the diesel fuel e.g. rape seed oil or soya oil. The behaviour of these materials is much more aggressive to filters than traditional mineral oil based diesel.   

• inherent particulate concentration in the fuel. As with water  variability n the quality standards to which diesel is manufactured leads to different levels of free particulates as can be seen from the global map from Bosch. Higher levels of particulates demand longer lifetime elements in terms of dust holding capacity. 

Increased performance specifications for diesel fuel filtration

These increasing demands of performance have seen the market move significantly over the last 10 years. The demands for increased diesel fuel filtration performance has seen a move from media with 80-90% 4 micron efficiency to ISO 19438 to 99.5% 4 micron efficiency at the same level currently. This was achieved initially through the development of more efficient cellulose media, operating at the limits of a standard paper machine (1-2 cfm permeability). IN the US addition of glass increased this efficiency further. However the risks of glass fibres being washed from the filter into the fuel line, damaging the engine was not accepted in Europe. Increasing the efficiency decreases the lifetime of the element as the initial pressure drop increases. Thus composites have become required (see my previous blog on gradient density). Initially these were single layer cellulose meltblown composites with PBT (for chemical and heat resistance) but as the targets for efficiency have been driven higher by Bosch and others, the limits of cellulose have slowly been surpassed and multi layer all synthetic composites will be the requirement for the future or cellulose based composites where the cellulose acts solely as a pleatable backer to enable the material to be processable on standard pleating lines.    

The increasing need for water separation has led to the development of complex dual stage elements. Water is always present in all fuel. The water droplets in all fuel are created by the actions of pumps and are stabilised by the presence of surface active ingredients in the fuel such as lubricity additives and anti oxidants. With increasing use of bio diesel, the long chain fatty acids of natural oils also behave as surface active components, reducing the surface tension and both increasing the stability and decreasing the particle size of the droplets. The result is a need for a coalescing, water shedding pre-filter with an excellent water separation to ISO 16332. In many modern fuel filter assemblies the result is a two stage water and particle separation for diesel. 

Summary

The increasing complexity of fuel filters over the last decade has not been driven solely by process economic but by regulation. The fact that the latest standards in fuel filtration have been set in Europe are related to the increasingly tight regulations in Europe. The fact that China is still only now implementing Euro IV standards of emissions cleanliness whilst the EU is at Euro VI show that the regulatory environment is driving the technological environment. If we had left this solely to the market, would Europe have developed the most advanced fuel filtration systems in the world? Probably not- this market, like others in filtration would have ended up with low cost static performance, not the vibrancy of technological innovation. 

The high levels of environmental cleanliness are the least that our children should expect from us. For once the regulators are not wrong and are setting the standards that drive innovation. 

1.5 micron multipass measurements for high efficiency fuel media applications

My old boss used to say, "all projects start with a measurement system". In short, if you can't measure what you want to achieve, you can't achieve it. With the advent of EURO 6 engines (and higher demands for hydraulic filters in general), the capability of traditional ISO accredited multipass test stands is being significantly challenged as the traditional OPC's in multipass test stands are limited to a minimum particle size of 4 microns. 

Typical Multipass Test Stand from GMNi

With an initial efficiency at 4 micron of >99.5% required to meet the EURO 6 emissions requirements, the particle counter has to work harder than ever to accurately count the downstream particles. As 4 microns is the limit of the current ISO approved technology we face an increasing level of experimental error in media measurements which is exacerbated by the fact that customers also ask for initial efficiency not overall efficiency. 

Initial efficiency in ISO 19438 is measured over a period of only 3 minutes during the entire test (4-6 minutes) at which point the particle counts are increasing as the contaminant concentration in the test circuit increases from zero. The result is that the data is prone to significant errors at 4 microns for both initial and overall efficiency (see plot below for a typical cellulose meltblown composite) tested 7 times on the same lot of material to enable a level of inherent variability to be established. 

Inherent variability in overall efficiency for a typical flatsheet fuel media.

As you can clearly see, the level of inherent variability grows significantly as we approach 4 microns. This can only be expected of such a system operating at the edge of the measurement range. 

The key challenge therefore is to move the measurement goalposts. This is easier said than done but the market leaders in OPC technology, PAMAS, have introduced the latest in technology, known as SLS. Instead of operating with a 4-40 micron range OPC, the new technology operates with a 1.5 to 20 micron range OPC. 

The impact though in terms of multipass design is significant:

• the cleanliness level in the test circuit has to be significantly improved thus requiring hydraulic filters with a Beta 1000 or 2000 level of efficiency of around 2-3 microns. 
• The OPC upstream and downstream of the sample has to have a significantly lower concentration of dust and a much higher dilution is required. 

In short it is not possible to purchase a simple OPC and retrofit it to an existing multipass test stand. 

One other major issue is that the particle sizes are now outside of the ISO official range (i.e. they lie less than 4 microns) and so any test is not according to the standard which leaves companies scratching their heads. The solution is to have both technologies on the same test stand so that the test stand still abides with the ISO standard but has extended capability (i.e. two sets of particle counters!). 

The benefit of the new OPC technology is that it moves the 4 micron initial efficiency to the middle of the calibration curve (not the edge) and we can also start to look at 2 and 3 micron efficiencies that are naturally much lower than 4 microns and therefore a better discrimination in performance between media can be made. This is shown in a graph from a SAE presentation made by Ahlstrom on this technology. 

Fractional Efficiency of various media using SLS Technology.

The graph shows 5 grades tested using SLS technology. If we use the 4 microns as the cut off point we see that there is a little difference between the samples in terms of performance. However by extending the range to a lower particle size the different media perform significantly differently allowing  a more educated analysis to be undertaken of the different media in terms of their relative performance. 

Does SLS Technology measure identically to standard OPCs? 

We undertook a study on a test stand with two OPCs fitted on a Euro 6 level media to see what the resultant performance looks like. The result was very consistent across a range of grades. The new OPC shows a significantly lower initial efficiency than the standard OPC (see below).  

SLS and standard OPC initial efficiency performance on a Euro 6 media

Why the discrepancy? There are only two possible reasons; 

1. the OPC's are operating differently or

2. the media performance is "different" in some way from sample to sample.

To look at point 1 we took the media out and looked at the particle counts of a pre-dosed test system (oil with a known amount of ISO medium test dust) and looked at the particle counts from both particle counters. 

Particle counts with no media of both HCB and SLS Particle counters

The number of particle counts are aligned extremely well in the overlapping range of 4 to 20 microns which would clearly exclude point 1 as a reason for the discrepancy. 

The theory currently is that the new OPC is detecting particles in the fluid downstream that the traditional technology can't. In this case the belief was that synthetic particles were being dislodged downstream from the media and were being detected in a way that the older HCB technology couldn't detect. 

So there you have it, there is a new technical opportunity to extend the efficiency range of fuel media being driven by a new capability to measure it. This technology not only extends the measuring range, it increases the precision of measurement and has an ability to identify particles that the current technology can't "see". 

The jury is still out on whether this technology will become mainstream plus the ISO committee with the 2003 standard is way behind the technology developments here. But there are test stands out there able to undertake this and it will not be long before we start seeing specifications at 2-3 microns being set by element manufacturers. 

Thanks a lot for reading and have fun. 

Tony