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The COVID pandemic impacted the way many industries do business, and the HVAC industry is no exception. Ongoing concerns regarding infection risk and indoor air quality have prompted an unprecedented demand for filters with a Minimum Efficiency Reporting Value (MERV) value of 13, commonly known as MERV 13 filters, as well as those with even higher MERV ratings. As part of its COVID response, ASHRAE recommends increasing outside air within buildings as much as possible, as well as upgrading air filters to a minimum MERV 13 efficiency rating.

The rush to upgrade to high MERV filters, however, opens the door to a practical discussion about whether that is the best action in all cases. The reality is that using the wrong filter for the wrong application in the wrong place can substantially limit HVAC systems’ efficiency. The result is that air quality will suffer, and the system will consume more power than it should to function.

 

Is MERV 13 really the best choice for your HVAC system?

A MERV rating is determined by the filter’s particle-size removal efficiency. The higher the number, the higher the filter efficiency. Before considering ratings, however, it’s important to determine the purpose of the filter.

If the primary purpose is to keep heating and air conditioning systems clean and block contaminants from interfering with the operation of key components, you likely don’t need as high a MERV rating. If the primary objective is to protect breathing air quality, then a higher MERV rating might make sense.

An option worth considering in some applications is the use of a multi-filter system that includes final filters and pre-filters. A less expensive, lower MERV-rated filter, functioning as a pre-filter, can trap dirt and large particles before the air reaches the final filters downstream which then remove the small particles. Multi-filter systems can extend the life of the more expensive final filters, creating overall cost savings.

When choosing a filter, it’s also important to consider the conditioned space’s activities and the types and sizes of particles those activities generate. Contaminants of greatest concern need to be evaluated to determine the level of filtration efficiency required for that contaminant’s size (measured in micrometers/microns). Once a full list of contaminants of concern has been identified, you can use the ANSI/ASHRAE Standard 52.2-2017 to select the proper filter with the appropriate MERV.

 

Additional considerations when choosing a filter

Of course, particle-capture efficiency matters. But there are also other filter characteristics that should be considered when determining the best filter for a specific application. Cost is always a consideration and should include the purchase price, as well as service life and maintenance requirements. The filter’s resistance to airflow also is a key consideration, as it is proportional to the energy consumed by the filter. Energy expenditures can account for about 81% of an air filtration system’s annual operating costs, while its purchase price and maintenance can account for about 18.5%.

Other considerations include the design and materials used in filters. Some designs are easier to install, seal better, and don’t absorb moisture or shed. Pleated filters, which are commonly made with a blend of cotton and polyester or synthetic media, provide a larger filter-surface area than panel filters. Most pleated filters are MERV 6 to 13. Depending on the filter, capture efficiencies for particles in the 3 to 10-micron range can be 35% to 90%.

There are also extended-surface filters that are made with synthetic, fiberglass or cellulose/glass-fiber media. These include bag or pocket, rigid-cell, aluminum-separator and V-bank filters. Pocket filters provide an even greater filter surface area than pleated filters to provide maximum efficiency with the lowest pressure drop and longest life. They typically have MERV ratings of 11 to 15.

 

Other factors that can affect efficiency          

Even a filter with the highest MERV rating can’t achieve high-quality air if some of the air is not going through the filter. Gaps around high-efficiency filters or filter housings can decrease filter performance. They occur when filter media are not sealed properly in the filter frame, when filters are not gasketed properly in filter racks, or when air-handler doors and duct systems are not sealed properly.

For a 1-mm gap, bypass flows can increase to 25% to 35% of the total airflow. The percentage increases based on the filter’s efficiency because air naturally flows through areas with the least resistance. Since higher efficiency filters have a greater resistance to airflow, bypass air has a larger effect. This, in turn, reduces the efficiency rating. For a 1-mm gap, for instance, a MERV 15 filter will perform only as well as a MERV 14 filter. A 10-mm gap, in contrast, causes a MERV 15 filter to perform as a MERV 8 filter. That’s why building operators and maintenance personnel should perform regular field inspections to ensure filter seals and gaskets are installed properly.

To combat gap problems, Parker created its QuadSEAL® HVAC filters with proprietary E-Pleat® media technology. The molded polyurethane frame incorporates a QuadSEAL integrated gasket on all four sides and can flex without damage. Since the media pack is 100% bonded into the foamed frame, bypass is eliminated as is the need for additional sealants or adhesives.

 

Challenges with MERV 13 filters (and what can be done)

If it were just a matter of choosing the filter that produced the best air quality, the decision would be simple. Everyone would install filters with the highest MERV ratings they could find. Unfortunately, it’s not quite so simple. The challenge facing engineers, building owners and maintenance personnel tasked with specifying and installing filters is that more efficient filters cause higher pressure drops because the smaller pores create more resistance to air flow.

Not only are higher efficiency filters less energy efficient (causing increased energy consumption by the fan), but your air handling unit simply may not have enough capacity to function with a high-efficiency filter. The reality is that most commercial HVAC systems today can only handle MERV 8 filter or MERV 9 filter types.

So, what are your options?

• Upgrade to the most efficient filter you can without exceeding the operating capacity of your ventilation system (including investigation of newer filter designs that may have higher ratings and less pressure drop)
• Upgrade your system so that it can overcome the additional pressure drop and handle a higher-efficiency filter. This often requires, at minimum, upgrading fans.
• Use portable air cleaners with high-efficiency filters to complement your current HVAC system.

MERV 13 vs HEPA -- Limited applications for highest efficiency ratings

When COVID hit, suddenly industries that, for years, had functioned well with filters with MERV ratings of 8, 10 or 11, were scrambling for MERV 13, 14 and 16 filters. The reality, though, is that there are filter options even more efficient than MERV 16 filters.

High Efficiency Particulate Air (HEPA) and Ultra-Low Particulate Air (ULPA) filters are designed to trap the smallest airborne particles and contaminants. HEPA filters have a minimum efficiency of 99.97% at 0.3 microns, whereas ULPA filters have an efficiency rating of 99.999% at 0.12 microns or higher. This does not mean that ULPA filters are better than HEPA filters when taking air flow and other variables into account. In fact, HEPA filters cost less, have a lower resistance to air flow and offer a longer service life than ULPA filters.

Parker offers a complete line of HEPA and ULPA standalone and pre-filters for removing particles and contaminants with efficiencies up to 99.9995%. They also are designed to reduce energy consumption and operating costs.

So why doesn’t everyone simply switch to a HEPA or ULPA filter since they represent the gold standard in air quality? Because most commercial and industrial HVAC systems on the market today simply aren’t compatible with them. Since they are so efficient, HEPA and ULPA filters cause a higher pressure drop than filters with lower MERV ratings.

The best option today for using HEPA and ULPA filters is as part of stand-alone systems. Many school districts are looking at options for installing portable air filtration systems with HEPA filters in each classroom to augment their central air filtration systems. HEPA and ULPA filters are also frequently found in critical medical applications and cleanrooms.

  Newer innovations offer superior efficiency while overcoming problems with air flow

Parker’s approach to balancing the need for efficiency with minimum pressure drops has been the development of its LoadTECH® filter that utilize Parker’s proprietary E-pleat® technology. This patented design molds filtration media into a series of pre-formed channels that direct the air smoothly through the filter, allowing for even loading, minimum resistance and complete media utilization. The previously mentioned QuadSEAL® filters offer a similar benefit of improving efficiency without restricting air flow. The advanced media used in these filters also resists tearing, damage, moisture and microbial growth, leading to a long filter life and the need for fewer filter changeouts.

The decision to use a filter with a MERV 13 rating (or higher), in accordance with the latest guidance from the Centers for Disease Control (CDC) and ASHRAE, is complicated by the fact that most commercial HVAC systems cannot handle the highest efficiency-rated filters. While there are options for upgrades, redesigns that include a multi-filter system, and new technologies that balance efficiency and air flow, specifiers need to be careful that they choose the right filter after considering all the variables, including cost, maintenance requirements, operating efficiency and, of course, air quality.

 

This article was contributed by the Parker HVAC Filtration Division.

 

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Since the introduction of aviation fuel monitor cartridges in aviation fueling, super absorbent polymers (SAP) have been the essential materials used in the final stage of airport ground fueling systems for the protection of on-board systems from water contamination. The material’s ability to absorb and chemically lock in water have its challenges―potential media migration downstream. In 2017, the aviation industry through the International Air Transport Association (IATA), Air Transport Association (ATA) and Joint Inspection Group (JIG) introduced interim procedures while SAP-free filtration was developed. Parker has introduced Water Barrier Filtration technology for interplane fuel filtration solutions. 

 

Runway for change is fast approaching with the Phaseout of EI 1583 SAP filter monitors

The EI specification for filter monitors has been retracted and is no longer available or applicable to the industry, as of December 31st, 2020. Phaseout of the 1583 SAP monitor has been mandated by the industry regulators.

Parker's new drop-in solution for new and existing monitor vessels, the CDFX Water Barrier Filter, guarantees removal of water and dirt from fuel without requiring any additional sensing equipment, removing the water rather than simply detecting it. You can ensure that the clean dry fuel is delivered every time, avoiding costly downtime, potential flight delays, and/or removal of contaminated fuel from your aircraft.

All of Parker's products are fully certified, making switching easy and cost-effective.

 

Learn more about the new Parker Velcon revolutionary technology. 

  Considerations and questions for SAP Phaseout options

There are several things to consider when deciding on various options available for SAP phaseout solutions. 

What are your choices?

• Filter water separators
• Dirt defense and electronic sensors
• Water barrier filters

Questions to ask and factors to consider:

• What is the tolerance to risks?  Is water removal important at the wing of the aircraft?
• The competitor's dirt defense filters do not remove water.
• The sensors alarm and then you must decide what to do when it does alarm. Procedure? Who makes the "all good" call after an alarm.
• What is the expense of a fueling shutdown? Does it matter if it's a truck, hydrant servicer or a hydrant system?
• How robust is the sensor under adverse conditions? Can it fail prior to annual certification?
• Who does the managing of sensor calibrations? Who manages the spare certified sensors? What is your sensor life expectancy in operation or on the shelf? 
• Filter water separators can be disarmed, do not protect against water slug and are not a drop-in solution. And often these filter water separators are larger, heavier, and expensive to change out requiring considerable labor.

 

This means costly equipment design, installation, vehicle design limitations, meter capability, electronics, etc., resulting in expensive downtime

The Parker Velcon water barrier technology is approved to the EI 1588 test specifications. There are 22 tests that were similar to the 1583 specifications. However, we removed the tests associated with SAP testing. The rest of the 1588 requirements are part of the specifications:

• Water slug testing
• Emulsified water testing
• Solids testing
• Compatibility testing
• Structural testing

 Performance requirements for 1588 are as stringent as 1583, however, without the SAP media.

  Phase 1 testing

At Parker Velcon safety is our priority.  In April of 2019, Parker Velcon successfully qualified the CDFX Water Barrier filter to the EI 1588 specification. Members of the Energy Institute witnesses were present at our Colorado facility.

Once qualified, we entered the EI robustness Phase One testing. This consisted of:

• 400 stops and starts
• Adding additional additives to the fuel
• Doing pull tests
• Running at 125% of rate of flow
• Swapping the vessel for 12 hours with water

 

Test data shows that all 20 tests passed Phase One testing with no failures, achieving maximum effluent water of fewer than one parts per million. All the tests met the minimum pull force specification above 500 Newtons.

              Phase Two testing for field trials

Two locations were selected and testing was done at these airport tank farms. These tests were accelerated with more than 10 times the typical daily throughput. Upon completion, filters were sent back to our Velcon lab and a witness was present, through EI, to verify the water removal capabilities. Test runs from the two trial locations show vessel throughputs of over 3 million and 5 million gallons per vessel.

When breaking that down to throughput per element, it is approximately 180,000 or 310,000 gallons respectively. During the field trials, elements were returned to our Velcon lab for testing with an EI witness present. These tests included the 50 parts per million slug test and pull tests. Results were consistent with the EI qualification.

Filtration performance and filter integrity have exceeded expectations with no signs of degradation, disarming or reported issues with additives in the fuel.

 

Water Barrier filtration technology timeline

To summarize the developments of the CDFX Water Barrier filter technology, we review the timeline:  

• The EI 1588 development and specification published.
• We successfully qualified the water barrier filter with Witnessed EI 1588. 
• Electrostatic charge generation test completed.
• We completed the phase one and phase two robustness testing and are currently in field trials with nine months into the trials.
• Once field trials are complete, we expect acceptance into the industry operating standard.

  How does the water barrier filter work?

Here's a short video of the water barrier filter and operation. As you can clearly see, water in the fuel is repelled by the water barrier filter and droplets fall to the bottom of the vessel where eventually they must be removed at the low drain points.

 

  Differences in technology application

Some product application differences with the water barrier filter include daily sumping that will be required and some education on the differential pressure effects.

Any water collected will need to be drained from the vessel drain point.

Parker CDFX elements are designed to replace SAP monitor elements and operation will be essentially the same. Since they do not absorb water, there are a few things to note:

• The low point in the vessel should be sumped daily.
• The differential pressure should be closely monitored.
• If differential pressure does increase, it's most likely from either solid contaminants, slow buildup of entrained water or water slug.
• If it is a water slug differential pressure rises quickly and shut down the flow.

Even if the entire vessel is filled with water, no water will pass through the filter. In any case, what is important to note is the differential pressures should not fall below the initial starting differential pressure when operating at rated flow.

 The Parker Velcon solution

There are three available technologies:

• EI 1588 water barrier filter  
• EI 1581 filter water separators
• EI 1599 dirt defense filters in conjunction with the EI 1598 water sensor

As you can see, only the 1588 water barrier technology offers removal for all three capabilities.

The CDFX Water Barrier filter is a true drop-in replacement, innovative at removing water and dirt while not allowing anything to pass through. It offers only clean dry fuel without the use of SAP media. Cost and resource-efficient, it fits deployed vessels in service, but without the needed cost of retrofitting or adding electronic sensors. All materials are compatible with fuels in the industry and simple product procedure changes are in place. Same diameter, same lengths, same flow rates all as with the two-inch monitor elements.

 

Ease of replacement

This is a short video demonstrating the ease of converting from the SAP monitor to the Parker Velcon water barrier filter.

 

 

General aviation fueling

Our water barrier filter technology was further developed for general aviation fueling applications.

The ACOX family of Water Barrier filters are ideal for slow throughput. From an operations perspective, there are minimal changes to your current operating procedures, no modifications to the filter vessel and filter change at a maximum of 22 PSID or three years of service life.

The performance of gas turbines (GT) for power generation has a fundamental influence on the bottom line. Lack of availability, reduced power output and maintenance overheads all link directly back to profitability. As the efficiency of GTs continues to increase, with models such as the GE H-class now pushing power plants above 60% net efficiencies, the cost for loss of performance gets higher. It doesn’t take a math whizz to see that the more power generated by a GT, the more power is lost if it underperforms or has to be shut down! 

This new breed of efficient GTs aids the global push in the reduction of CO2 emissions to address climate change. They offer:

• Fast start-up and ramp rate capabilities.
• Greater turn down, and more cost-effective spinning reserve.
• Better fuel efficiency, and lower operating costs, which, in turn, equates to reduced environmental impact. 

 

To learn more download our White Paper, Driving Gas Turbine Efficiency: Maintaining Greater than 60% Efficiency for Gas Turbine in Power Generation. 

 

 

Consuming vast quantities of air, however, the quality of this air has a huge impact on GT performance, and the higher the GT efficiency, the greater the potential impact. This means the design of the filtration system has an even more crucial role to play in overall operational efficiency and reliability. 

But what is so different about these high-efficiency GTs and why do they need different protection to older E-class or F-class models? They face all the same environmental perils as current GT installations – but their finely tuned performance is precision-engineered, packed with technology, latest advanced materials and finishes. This means they require more rigorous protection from the fouling, pitting and corrosion that finer particulates and contaminants in the inlet air flow cause to blades, stators and buckets.  

You might consider just using finer filter media to catch the contaminants. Along this path, however, lies many troubles. Often the worst thing to do is to employ the finest, high-efficiency media as this easily blocks, can cause quick rises in differential pressure leading to unplanned GT “runback” or even shut down and increased maintenance overheads. On the business side of things, huge dollar losses from drops in power output are even more preeminent with pressure rises when operating these bigger, more efficient machines. 

If you want to find out how you can ASSURE the performance of high efficiency GTs, the answer is multi-faceted. It requires deep understanding of real-world operating conditions and the demands of these impressive machines. And an understanding of what really matters inside the inlet house – and that can only come from experience. 

The filtration system is only as good as its weakest part. Many different factors about filter design equate to assured performance, including:

• Construction
• Sealing
• Pleat design
• Choice of media, across multiple filtration stages

 

At the end of the day, assuring the performance of H-class or equivalent GTs, requires a revolution in filtration design to provide maximum protection and reliable performance in the harshest installation environments. 

 

Introducing clearcurrent® ASSURE

clearcurrent® ASSURE range of filters features an innovative design that helps to boost GT performance, reduce lifecycle costs, improve safety, increase availability and extend GT life. Features and benefits include

• Hydrophobic and oleophobic properties remove problematic contaminants carried through to the GT in liquid forms.
• Self-cleaning.
• Consistent performance through all filtration stages equates to predictable differential pressure.
• Made to an exact fit in the inlet house to prevent them from being bypassed.
• Extended service life.
• Reduced lifetime cost.
• Robust construction stands up to the harshest environments.

 

 

Download our white paper, "Driving Gas Turbine Efficiency: Maintaining Greater than 60% Efficiency for Gas Turbine in Power Generation" to learn more.

 

 

This article was originally published in the print and digital magazine 2-2021 Issue of Power Engineering International and again in the online version here:  Why compromised filters mean compromised gas turbines.

 

This post was contributed by Tim Nicholas, market manager, PowerGen,  Parker Gas Turbine Filtration Division.

 

 

 

 

 

 

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Challenged by Gas Turbine Inefficiency? Consider Ways to Increase Output

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