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September - October 2003

almasy Fenestration Focus

Hard Numbers
The Real Cost of Gas Filling
by Joe Almasy

One of the window industry’s hottest topics recently has been the filling of insulating glass units (IGUs) with inert gases such as argon and krypton. Gas-filled IGUs sealed with flexible warm-edge spacers keep inside glass temperatures warm, providing energy savings, condensation resistance and comfort in cold weather climates.

The minimal cost of most of these gases makes them a viable addition to IGU production lines. However, other factors, including the following, add to the real cost of gas filling:

• Known cost directly related to filling;

• The value of shop floor space; and

• The goal of producing quality IGUs (intangibles).

Known Cost
Determining the known cost of filling requires separation of labor to fill units, the actual volume of gas used, the cost of the gas and any additional materials recommended by a sealant or spacer supplier, such as gas-tight pop rivets and foil tape. To better understand known cost, four gas-filling methods are described below (see box this page for a cost breakdown):

• Quik-Dose™ is an automated gas-filling system marketed by our company and manufactured by Besten Inc. Unique to the industry, Quik-Dose injects into IGUs a visible metered dose of liquid gas. This “boils” to a gaseous state in seconds, displacing ambient air from the bottom through the same opening through which the liquid gas is dispensed.

• Timer Fill is one of the most prevalent systems in use today due to its low capital cost. This system displaces air in a unit by pumping gas for a predetermined length of time at a specified flow rate into the bottom of the unit.

• Vertical Auto Fill is an automated system used in vertical IGU processing lines. These systems fill IGUs during the press assembly process by either filling the IGU during assembly or by filling the press chamber with gas before assembly of the top lite, piercing the spacer or filling in a similar manner as a sensor fill unit does.

• Vertical Sensor Fill utilizes sensors to monitor exit gas while units are filling. One type of system uses oxygen sensors to determine the lack of oxygen leaving IGUs, while another uses a conductivity sensor to measure the percent of fill gas that replaces air inside IGUs.

Floor Space
A square foot of floor space carries a cost when space is no longer available; plus, an offline gas-filling process can affect work in process flow.

Although required floor space is generally small, offline filling often involves additional movement and the staging of racks of IGUs to be processed. An operation making 1,200 IGUs per day that is one-half day ahead of the glazing lines can easily occupy 500 square feet of valuable floor space or more just in the staging of glass. This extra step can be an additional burden when dealing with rush orders.

Automated inline filling does not require the additional labor; it uses minimal floor space and materials-flow management is reduced, with the exception of sealing any holes in the spacer required for the filling process. However, when considering an inline filling system, be certain the cycle time of the gas-filling operation does not affect the expected throughput of the IG process.

Intangible Cost
Although it is difficult to place an exact figure on the cost of quality, it is perhaps the most important item to consider. Durable gas-filled IGUs must utilize a sealant with low gas and moisture vapor transmission properties, a reliable method of gas filling, quality workmanship and, preferably, a continuous spacer system.

Manufacturers should always consider the recommendations of their suppliers, follow industry-approved glazing guidelines and anticipate the future of 
testing requirements.

The real cost of gas filling is difficult to pinpoint. A detailed study of existing IGU production provides the cost of labor and materials. But a company’s desire to produce the highest possible quality IGUs depends on attention to all of the details in the IGU fabrication process and an effective quality control program. 

Comparison of Gas-Filling Technologies 

8 Hours
of cavity
Quik-Dose™ 1,200 200 0 .043 0.43
Timer Fill 1,200 200 .16 .035 .195
Vertical Auto 1,200 120 - 600 0 .021 - .105 .021 - .105
Vertical Sensor 700 300 .137 .052 .189
1. 24- by 36- by 5/8-inch airspace = 8.81 liters per unit.
2. Liquid argon cost = $.002 per liter.
3. Quik-Dose (liquid fill) = no labor (automated); add labor to fill opening if applicable.
4. Timer Fill = two persons to fill and final seal units.
5. Vertical Auto Fill = no labor (automated filling); add labor to fill hole sealing if applicable.
6. Vertical Auto Fill uses 120-600 percent of cavity volume to fill (varies with the system).
7. Vertical Sensor Fill = one person to fill and final seal unit.
8. $12 per-hour wages and benefits.
9. Quik-Dose assumes a 30-percent system loss (estimated).a

* Additional components and labor if required:
1. Pop rivet(s) for metal spacer units.
2. Overseal for metal spacer units.
3. Spacer preparation if necessary.
4. Plastic fill-hole protectors for metal spacer units.
5. Foil tape to cover lance holes in foam spacer units.
6. Butyl corner-seal material for DuraSeal™ units in Quik-Dose system.

Joe Almasy is a product specialist for TruSeal Technologies Inc., based in Beachwood, Ohio. 

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