Why doesn't my fume extraction work?

PRACTICAL WELDING TODAY® JULY/AUGUST 2007

August 8, 2007

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Many welding manufacturers today have experienced a great disappointment with fume extraction systems for their welding processes. Often this problem has little to do with the actual filtration equipment itself, but with the way it is applied to the application. Improper sizing and misapplication of the equipment is the #1 cause for ventilation failure.

It has been proven that over 50% of the fume extraction systems installed in the welding industry do not work as well as intended, and often from the time of installation. Below are some typical issues that manufacturers experience with their systems:

  1. Weld smoke haze in the air
  2. High filter costs
  3. Fires
  4. Maintenance issues
  5. Negative air pressure in the building
  6. Costly natural gas expenses
  7. Large and cumbersome — take up floor space

With the increased restrictions on environmental laws, including the new Hexavalent Chromium standard, the battle to reduce employee turnover, and the need for a crisp plant image, fume extraction and air filtration systems for welding have become increasingly popular. The shortage of competent engineers to employ has increased the need for outside engineering support.

When sourcing a company to help you with your weld fume ventilation needs, there are some questions that you may ask to protect you from system failure. Below is a list of recommended questions to ask the supplier:

Q. Do you have any references for similar projects that have been in operation for more than 2 years?

It is recommended to speak to at least four good references, and visit one or two before making a decision.

Q. How long have you been working in the welding industry?

It is critical for the company that you choose to have established themselves as a competent source of fume extraction equipment for production welding.

Q. What is your performance guarantee?

Get a performance guarantee in writing in order to protect you in case the system doesn't work as promised.

There is one question that is frequently asked, and sometimes little understood:

Q. Why can't I just blow the air outside?

There is often no issue blowing the fume laden air outside from the environmental perspective. Although this will tighten up over time, most companies are allowed to blow a certain amount of fume laden air outside.

The concern with exhausting the air outdoors, is the negative pressure produced on the facility. This negative pressure is OK during the summer; with the doors open the air is allowed back into the plant. During the winter, these exhaust fans don't work well with the doors closed. This is due to the fact that no air is allowed back into the plant to replace the air that is exhausted.

It is also very costly for natural gas expense. Every exhaust fan that is installed must be matched with 80% of its air flow by a heated makeup air system for the winter months. This can cost $2-3.00 per CFM to exhaust outside, and considering a 50-100,000 CFM system (which is typical) this may be as much as $100-$300,000.00 a year in expense.

A properly designed filtration system can save more than half of this expense by returning the air back into the plant. A well designed filtration system for a welding environment should get between 6-12 months filter life in normal circumstances.

A formula is available to calculate the potential savings that may be experienced for your particular circumstances.



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