10 Steps to Optimal Filtration

Particulate filters are a must when it comes to improving indoor air quality, maintaining the degree of cleanliness required in industrial processes, or protecting the components of HVAC systems to operate according to design, contributing to energy savings and thus promoting a sustainable environment. The use of the appropriate filter will allow the user to obtain energy savings.

The role and responsibility of engineers has evolved with the increasing demand and importance of clean air in the facility. That is why this article aims to guide you and offer some suggestions to achieve optimal air purification.

Particulate filters are a must when it comes to improving indoor air quality, maintaining the degree of cleanliness required in industrial processes, or protecting the components of HVAC systems to operate according to design, contributing to energy savings and thus promoting a sustainable environment. The use of the appropriate filter will allow the user to obtain energy savings.

Once the filter has been selected, considering various aspects such as the contaminant (type and size in the case of particles or microorganisms), efficiency, pressure drop, among others, it is essential to supervise its operation. In case of poor installation or no maintenance, all the work would be thrown out the window, because if there are air leaks or the filters are poorly installed, the efficiency of the filtering system will drop considerably.

This 10-step guide from NAFA was developed with the goal of achieving the best possible filtration for your system and answering the questions needed to achieve the best possible system for almost any type of application.

1 Evaluate the current filtration system

The first step is to analyze the current filtration system and the condition of the connections that surround it. If the system is very outdated this will make it very expensive to repair, so it will probably be necessary to install a new one.

Ask yourself, are draft regulators, return deflectors, fans and motors, drain trays, coils, access gates, general packaging, and other parts of the HVAC system that significantly affect the operation of the filtration system in good condition?

Is the vibrating collar intact and leak-free? Is it clean and free of oxidation, contamination by microorganisms and dirt, the chamber surrounding the filters and the mechanical equipment?

Are the ducts free of accumulated dirt and dust, as well as the coil clean and unrestricted? If you determine that the main components of the HVAC system, including the filters, are in good condition, proceed to the next step. Otherwise, clean them or remove and replace the necessary elements to leave the system in working condition.

For the proper selection of the filter we need to identify the particles that influence our health and comfort

2 Sealing

A hole the size of a human hair (about 100 microns in diameter) is large enough to allow contaminants to escape in the filtration process. In such a way that if only the efficiency of the filters is increased without taking care of the "bypass" it will not bring benefits.

In order to prevent the entry of contaminants, each hole and / or leak that occur in or around the filters must be sealed. A good silicone sealant, or other sealing material that does not shrink or dry out, is recommended and seals old joints, cracks and holes in the ducts surrounding the filtration material. Install new packaging on doors, ducts, and other surfaces where filters come into contact with metal surfaces.

3 Determine the size of particles to be filtered

Air is a mixture of oxygen 21%, nitrogen 78%, argon 1% and other gases. Additionally, air can include particles or gases themselves that are generated by nature, by humans or by industrial processes.

For the proper selection of the filter we need to identify the particles or gases that influence our health or comfort and that can damage the spaces we occupy or affect the products or components we are manufacturing. Particles are measured in microns or microns. One micron is equivalent to one millionth of a meter.

There are certain applications that generate standard types and sizes of polluting particles (for example, the areas of filing and handling paper, generate paper dust; copiers and laser printers, generate carbon particles).

You can consult a particle size graph or use a particle counter to get a clear picture of particle sizes. Now, determine how many of these particles you want to remove. For example, you may want to remove all particles of 1 micron, and larger, from the air stream with a minimum efficiency percentage of 95%.

The use of the appropriate filter will allow the user to obtain energy savings

4 Determine the MERV (Minimum Efficiency Reported Value)

One of the ASHRAE standards for determining filter performance is 52.2. Standard 52.2 reports the MERV (Reported Minimum Efficiency Value) of a filter. The MERV test uses potassium chloride spray from 0.3 microns to 10 microns, grouped into 12 size ranges, as a challenge.

To determine the MERV, six tests are performed for each of the 12 size ranges, using a particle counter. After an initial test (clean filter) the filter is loaded or saturated with dust in 5 cycles. The minimum efficiency of each of the 12 ranges is used to create a composite minimum curve.

Once the efficiency is determined, a table is used to determine the MERV expressed on a scale of 1 to 16

The MERV gives us specific and valuable information about the minimum performance to remove particles of a certain size at an air velocity, unlike the 52.1 standard that expresses only an average.

If we know the contaminant to be removed we can determine its size. MERV tables can be used to determine exactly which filter will remove this particle size. For example, if you want to remove at least 75% of all particles 0.3 microns and larger, select a MERV13 filter.

5 Determine the pressure drop for filters

Each system has its own specifications regarding the maximum permissible pressure for air filters and each filter has an air passage resistance, known as pressure drop, within which it can operate.

Before replacing with a higher efficiency filter, it is essential to ensure that you install a filter that does not exceed the specifications of the system, as this can reduce the volume (cfm) of air, which can have consequences such as affecting the operation of coils or other components.

If a similar situation occurs, you will need to install a filter with the same, or slightly higher, flow resistance than the filter you are removing. The filter to choose must remove most of the airborne particles and provide adequate airflow to maintain satisfactory operation of the HVAC system.

In the next issue of Mundo HVAC&R magazine, we will give you the last steps to perform optimal filtration, and thereby make air purification systems inside buildings more efficient.

Carpet fiber

Textile fibers / Acaros

Spray Paint Powder

Spanish Moss

Commercial / Light

Minimum Protection Equipment Protection

Milk Powder / Pudding Powder

Cement powder

Textile Protector / Mold

Hair Spray / Spores

Residential / Best

Industrial Work Area

Paint Booths

progressive density, cube type, synthetic.

Welding fumes / Nubulilizer drops

Automotive emissions

Coal powder / Ground flour

Lead Dust / Dehumidifier Dust / Legionella

Commercial Building / Best

Hospitals

Laboratories

Areas of Work Ind./ Better

Cartridge type

Rigid

Bacteria / Tobacco Smoke

Cooking Oil / Almost all smoke / Insecticidal powder

Copier Toner / Face Powder / Paint Pigments

Hospitals and Clinics

General Surgery

Smoke Removal

Cartridge Type

Rigid

99.992

99.9992

Combustion smoke

Sea Salt / Coal Dust

Virus

High-Risk Surgery

Radioactive Material

Pharmaceutical industry

6. Explore filter options according to your pressure drop

Nowadays with the development of new technologies in the filtration media and better manufacturing techniques, there are more options to achieve higher levels of filtration (higher MERV numbers) with a lower pressure drop. For more information on the performance of these filters, consult your dealer.

7. Check lifecycle costs before purchasing filters

When two or more filtering systems can give the same level of cleanliness, but are different in one or more respects, a lifecycle cost can be useful. The total cost of using the filters is a combination of several costs of which more than 80% is the consumption of electrical energy. The upfront costs are lower and do not reflect the higher cost you will pay in the long run. Other lifecycle costs you will need to include are:

Costs for shipment and storage. Many times these costs are attached to the equipment bill and represent 5 to 10% of the additional costs.

Costs for damage to the merchandise. During packaging and shipping, filters can be easily damaged and some manufacturers do not accept returns for this concept.

Installation costs. Some filters have a larger filtration area and can retain more dust and particles, which remain in the system for longer, reducing the cost of labor for change and replacement.

Fees for disposition of the material used. Disposal costs for discarded filters are escalatory and can add another 10% to the cost of your filter.

With the development of new technologies and thanks to better manufacturing techniques, there are more options to achieve higher levels of filtration

8. Make sure you install the filters correctly

In order for the filters to perform according to your specifications it is necessary to install them correctly. Improper installation causes wasted time and can decrease the efficiency of a system. To avoid problems, the following is recommended:

• Install filters with vertical folds or bags

• Install filters according to the direction of airflow

• Check that there is no damage to the filter media

• Make sure it is the correct size and type of filter

• Check packaging and make sure there are no air leaks especially between high-efficiency filters

9. Review your work

You must observe very closely the first cycle of your filters, making sure of the proper functioning of all the components of the system and the accuracy of the readings in the measuring instruments.

10. Keep good records and enjoy the benefits

Mechanical filters require little maintenance, the main procedure is to observe and record the pressure drop. An accurate record can help determine the sweet spot for replacement contributing to energy savings and improved air quality.

Design work is lost if the importance, benefit and added value of a filtration system is unknown. It is paramount that staff know when, why, and how to service the system.

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