August_AMP_Digital

ADVANCED MATERIALS & PROCESSES •

AUGUST 2014

Safety in Thermal Spray

Settings: Part 1

Much of the following material was developed

by members of ASM International’s Thermal Spray

Society Safety Committee.

orkplace safety is not a subject that typically capti-

vates an audience, but in the thermal spray trade,

hazards of all types are faced on a daily basis. Safety talk

is typically thought of as a matter of common sense, and

formal programs to communicate and enforce safe prac-

tices can seem unnecessary or, in worst case scenarios, as

an opportunity to issue penalties based on grudges, rather

than evenhanded enforcement. Unlike truly dangerous

workplaces, such as shipyards or construction sites, where

situational awareness is necessary to stay alive and well,

the extra cost and time safety programs consume can make

them unattractive in comparatively comfortable thermal

spray shops. However, compelling reasons to embrace the

safety topic still exist.

For starters, maintaining a safe workplace is the law.

Title 29 Part 1900 of the Code of Federal Regulations out-

lines the mandate, reach, and policies of the Occupational

Safety and HealthAdministration (OSHA). Despite rumors

that OSHA’s jurisdiction does not apply to shops below a

certain size, there is not likely a thermal spray or welding

shop immune to OSHA’s regulations.

Because of this, safety discussions can broaden aware-

ness of operating requirements that some smaller facilities

might not know. It is also important for frontline employ-

ees to be aware of the potential hazards faced daily in order

to motivate them to voluntarily take appropriate precau-

tions. The topic can be discussed clearly and concisely in

this manner, making it easier to ensure requirements are

met. Involving people at every operational level during the

development of plant policies ensures that employee safety

will not hinder workload.

Dust and fume hazards

Another reason safety discussions are especially im-

portant in the thermal spray workplace is that hazards ap-

pear throughout the coating operation, from incoming

orders to final inspection. Dust and fume hazards are an

excellent example. Technically speaking, dust consists of

airborne fine solid particles such as fractured grit blasting

media or thermal spray powders, which can irritate lungs

and mucous membranes. Fumes are finer suspended

particles released when materials are heated or burned, for

example, when thermal spray feedstock enters the combus-

tion zone or plasma plume of a spray gun.

Dust and fume exposure occurs during degreasing,

blasting, powder handling, spraying, sealing, and even

maintenance and cleaning. Some thermal spray fumes,

such as hexavalent chromium, are known cancer causing

agents. Vapors are emitted by liquids that evaporate at

room temperature, including solvents such as acetone

and trichloroethane, which are commonly used for

cleaning and degreasing parts. Inhaling these vapors can

damage the lungs and internal organs.

Most dusts and fumes common in spray shops irritate

the lungs, but others have more reactive effects. For exam-

ple, nickel, cobalt, and chromium can cause eczema and

contact dermatitis. Fumes released during twin arc wire

spraying of zinc can cause nausea, fever, and other flu-like

symptoms, known as “zinc fever.” The hazard of the air-

borne carcinogen hexavalent chromium is so acute that the

code places specific requirements on employers who are

known generators. Part 1910.1026 requires regular physi-

cal testing of employees who may be exposed, and makes

the provision and handling of specialized protective cloth-

ing, among other things, the employer’s responsibility.

As with all hazard categories, several methods to elimi-

nate or remediate hazards caused by dust and fumes exist

(Fig. 1). The most effective option is to eliminate the hazard

altogether, though this is seldom an option. The next best al-

ternative is to substitute a less hazardous material or process.

Depending on the application, this also may not be a viable

alternative. Engineering controls are methods by which

equipment can be added or a process design can be modified

to reduce or eliminate the hazard to employees. In the case

of dust and fumes, use of sufficient air filtration is an engi-

neering control that can ensure contaminated air is drawn

away from operators, removing the hazard. It also effectively

cleans the air before it is reintroduced to the environment.

Administrative controls are the next layer of hazard

mitigation available to employers. These consist of poli-

cies and procedures that mandate specific safe working

practices for each workplace hazard. Training, signage,

procedures, and employee exposure are all administrative

controls that can aid in the mitigation of dust and fume haz-

ards. Finally, personal protective equipment (PPE), such

as dust masks and gloves, protect employees from harm

when direct contact with a hazard is likely. Though it is

perhaps the most common workplace safety measure, PPE

is considered the least effective measure because it depends

on employee participation and supervision.

iTSSe

Fig. 1 —

Hierarchy of controls. Courtesy of www.cdc.gov/niosh/docs/2013-136.

Look for

Part 2 of

this article

in the

November/

December

issue of

iTSSe.

Elimination

Design hazard out

Substitutions

Use alternative materials or processes

Engineering controls

Isolation and guarding

Administrative controls

Training and work scheduling

Personal protective equipment

Last resort

Best

Control

effectiveness

Best

Business

value