An Introduction to the Return Grilles Manufacturing Process

Return Grilles Manufacturing Process

Stainless Steel HVAC Components are Fabricated with Precision at Top-of-Mind

Stainless steel air distribution manufacturers produce high-quality HVAC components designed especially for sterile environments, like medical labs, operating rooms, and more.

Even these specialized return grilles – seemingly the least important of all HVAC components – follow a careful manufacturing process, because for clean rooms, even the grilles must be fabricated to exacting standards. That’s because they must move and direct air to prevent contamination.

Companies that fabricate return grilles follow a process and use materials that ensure they’re turning out quality equipment.

Choosing the Right Type of Stainless Steel

Air distribution component manufacturers use two main types of stainless steel when producing their HVAC parts, avoiding other types of metals because they don’t perform as well.

Type 304 stainless steel is an austenitic stainless steel that contains 18 percent chromium and 8 percent nickel austenitic alloy. It resists corrosion, but contains more carbon than 304L stainless steel, so it isn’t as easy to weld, but it is easy to keep clean.

The second type of stainless steel often used in the HVAC industry is Type 316. This is an austenitic chromium-nickel stainless steel capable of resisting corrosion and heat, even when it’s exposed to brines. It’s easy to weld and fabricate, and avoid metallic contamination, because it contains only 2 percent molybdenum.

Fabricating Stainless Steel Return Grilles

Stainless steel HVAC components for critical environments require a careful fabrication process to produce sturdy, durable products that perform how they should. Not only that, but fabricators must know with certainty that the product they’ve built will be effective once installed on the job site.

Critical environment HVAC products are made to order and generally aren’t kept in stock. Each piece is designed to the exact specifications of each product.

The first step in fabrication is laser cutting the stainless steel sheet metal to form the basis of the component. After cutting, the sheet is placed on CNC press brakes to bend them into shape.

A computerized welding arm or expert welder then weld each part into place, ensuring seams are air-tight. This is important if air is intended to remain sterile in critical environments.

After welding is complete, the fins on each HVAC return grille are cut to size and rolled into shape at precise angles, both for a consistent look, but also to ensure efficiency in air distribution.

At this point, all parts are cleaned in an alkalized wash cycle, heated deionization rinse, and a freshwater rinse. After thoroughly drying, each part is powder-coated or polished, depending on the instructions in the order.

Any additional parts require hand assembly, and are installed on the component before leak testing, a process that uses a photometer to ensure they’ll work perfectly in critical environments. If every piece passes the leak test, they’re packaged and shipped to the job site for installation.

Types of Return Grilles

Return grilles come in several forms, and each serves a specific purpose in an HVAC system.

  • Return grilles with face bars
    These grilles have evenly-spaced, factory-set face bars set at specific angles to distribute air around the room.
  • Heavy duty return grilles

A sturdier return grille, this type has factory-set face bars for air distribution.

  • Linear light duty return grilles
    These lightweight grilles are designed for sidewall or sill installations and fixed airfoil blades. The blades run parallel to the grille’s longest dimension.
  • Egg crate grilles

A 90-percent free area courtesy of the egg crate design offers a large, open area for return airflow.

  • Long-throw return grilles
    These return grilles feature non-adjustable facebars, situated either horizontally or vertically.
  • Perforated return air grilles

This return grille features a stainless steel perforated face and is ideal for ceilings and sidewalks.

  • Core perforated return air grilles

These grilles fit into standard T-bar ceilings with a perforated stainless steel face.

  • Louvred return grilles

These grilles have non-adjustable, louvred blades that limit vision into ductwork, and are reinforced from the rear, making them suitable for both interior and exterior applications.

Ordering Custom Stainless Steel HVAC Products

Critical environment construction projects that require stainless steel HVAC products, including return grilles, require lead time to get estimates, place orders, and receive the components. Project leaders should begin soliciting requests for proposals (RFPs) from a variety of manufacturers early on in the project. RFPs are free and should contain information customized for your job site.

When you select your fabricator, work directly with them to obtain perfectly-built, consistent products. Remember that there’s no room for error – even in return grilles – when it comes to critical, sterile environments. Don’t accept second-best.


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