Labor & Industries (L&I), Washington State

Abrasive Blasting Chapter 296-818, WAC

Effective Date: 09/01/06

WAC 296-818-300 Operations

For printing

YOUR RESPONSIBILITY

To follow these operational requirements

Combustible organic abrasives	WAC 296-818-30005
Blast cleaning enclosures	WAC 296-818-30010
Blast cleaning nozzles	WAC 296-818-30015

 

WAC 296-818-30005

Combustible organic abasive

IMPORTANT:

This section applies to blasting operations where flammable or explosive dust mixtures may be present.

You must

• Prohibit the use of combustible organic abrasives, except in automatic blast cleaning systems.
• Bond and ground the blast nozzle to prevent the buildup of static charges.

Note: Fine dust produced from combustible, organic abrasive is a fire and explosion hazard.

WAC 296-818-30010

Blast cleaning enclosures

You must

• Install adequate ventilation systems in blast cleaning enclosures that are able to do all of the following:
  • - Control concentrations of airborne contaminants below the permissible exposure limits that apply
  • - Provide a continuous inward flow of air at all openings in the enclosure during blasting operations
  • - Minimize the escape of dust into adjacent work areas
  • - Maintain visibility in blast cleaning rooms and cabinets
  • - Rapidly clear dust from the air after blasting stops
  • - Discharge exhaust so contaminated air doesn't do either of the following:
• Present a health hazard to any worker

  or

• Reenter buildings in harmful amounts
• Make sure ventilation systems are designed and operated so employees aren't exposed to excessive air velocities
• Make sure make-up air systems don't interfere with the effectiveness of the exhaust system, and are designed to do both of the following:
• - Replace exhausted air in ample quantities
• - Temper make-up (supply) air when necessary
• Do both of the following before opening the blast cleaning enclosure:

• - Turn the blast off
• - Run the exhaust system for a sufficient period of time to clear the air of dust particles
• Follow the requirements in Table-2, Blast Cleaning Enclosures.

Table-2 Blast Cleaning Enclosures
If you have	Then make sure
Air inlets and access openings	They are either baffled or arranged so the combination of inward airflow and baffles minimizes both of the following: – The escape of abrasive or dust particles into adjacent work areas. – Visible spurts of dust
Small access openings where dust might escape	Slit resistant baffles are installed in multiple sets at all small access openings, and do both of the following: – Regularly inspect them – Replace them when needed
An observation window in enclosures where hard, deep cutting abrasives are used	The window is made of safety glass protected by screening Notes: - Hard, deep cutting abrasives may shatter normal glass. - If the safety glass shatters, the protective screening will help contain the glass and protect employees from cuts and lacerations.
Small operator access doors	They are flanged and tight when closed, and open from both inside and outside the enclosure. Note: If you have a small operator access door and a large work access door, the large work access door may open or close from the outside only.

Helpful Tool: Blast Cleaning Enclosures and Recommended Air Velocities For information on types of blast cleaning enclosures and recommended air velocities, see the Resources section of this chapter.

Reference: For more information on: Air velocities, refer to the following: - The latest edition of Recommended Industrial Ventilation Guidelines (ACGIH) - NIOSH 1976 Industrial Ventilation Exit routes, go to the Safety and Health Core Rules, WAC 296-800-310.

WAC 296-818-30015

Blast cleaning nozzles

You must

• Make sure nozzles are all of the following:
• - Mounted on a support when not in use
• - Equipped with operating valves that are manually held open.

Note: To help prevent the buildup of static charges, pressurized tanks used to supply abrasive should be: - Connected to the manual control of the nozzle and - Have the relief valve or opening located so it can safely vent.