Technology News

No. 477 July 1999

U.S. Department of Health and Human Services

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

A Systems Safety Approach for Programmable Electronics

Objective

To address the safety of programmable electronics-based

mining systems before this technology proliferates in the mining

industry.

Background

According to the Wall Street Journal [Phillips 1997]: "Mining,

that most basic of industries, is increasingly throwing down its old

tools and picking up new technology. It's a matter of survival."

For mining, programmable electronics (PE) is an emerging

technology that enables new capabilities and flexibility. It also can

create new hazards and/or worsen existing hazards. PE includes

microprocessors, programmable logic controllers (PLCs), and

software. Using mine accident data compiled for 1994-97 by the

Mine Safety and Health Administration (MSHA), we have

identified nine incidents involving PE. We anticipate that fatalities,

incidents, and near misses will increase as the quantity and

complexity of PE increases with the industry's desire to remain

competitive.

PE is found on longwall mining systems; automated haulage

vehicles for surface and underground metal/nonmetal mines;

remote controllers for underground mining machines; mine

elevators and hoists; and mine atmospheric monitoring systems

that monitor methane, carbon monoxide, and fresh air flow. During

1992-95, underground coal mine atmospheric monitoring doubled

to where nearly 17% of all mines have computer-based systems.

From 1990 to 1996, programmable longwall systems usage doubled

to about 95% of all U.S. longwalls. Microprocessor technology is

finding its way into control and monitoring of conveyor systems.

Industry is trending toward more utilization and complexity as

machinery moves from localized PE control to distributed PE

control of machines and processes. This trend is expected to

continue because of economic pressures, the need to mine lower

grades of coal and ores, and increased difficulties in mining these

resources.

Approach

The National Institute for Occupational Safety and Health

(NIOSH) is taking a proactive position by generating functional

safety recommendations for programmable electronics in mining.

The recommendations take the form of a safety framework shaped

by industry trends, MSHA accident data, and existing national and

international standards. We are using a risk-based approach for

the entire system, rather than just software or hardware. The

approach makes safety a part of the early design, where changes

are more effective and less disruptive, compared to implementing

safety measures after many fatalities and injuries have occurred.

The Safety Framework

The safety framework is a set of recommendations addressing

the functional safety of PE for mining. It is a systems safety

process encompassing hardware, software, humans, and the

operating environment for the equipment's life cycle. The safety

framework's set of recommendation documents (figure 1) addresses

the system's life cycle stages of design, certification,

commissioning, operation, and maintenance.

To our knowledge, mining, on a national or international basis,

does not have formalized standards addressing the safety of PE;

thus, the safety framework is a first step. It is a practical treatment

scaled in size and complexity to small mining organizations having

just a few people with limited knowledge of functional safety. The

framework components are:

• 1.0 Safety Introduction.—An introductory document for the

general mining industry provides basic system and software safety

concepts for the functional safety of PE. The document is

supplemented by industry workshops to reinforce these

fundamental concepts, create an awareness of the pending NIOSH

safety recommendations, and provide a means for valuable industry

feedback.
Figure 1.—The safety

framework.

• 2.1 System Safety Program Plan (SSPP) and 2.2 Software

Safety Plan (SWSP).—These documents draw heavily from

national and international standards. The scope is "surface and

underground safety-related mining systems employing

programmable electronics."

• 3.0 Safety Case.—This is a "proof of safety" that the system

and its operation meet the appropriate level of safety for the

intended application. The recommendations detail the

documentation for demonstrating the degree of safety and the

supporting evidence.

• 4.0 Independent Assessment.—The independent assessment

of the Safety Case is addressed. It establishes consistent methods

to determine the completeness and suitability of safety evidence

and justifications.

Benefits

• Improves worker safety

• Improves mine safety

• Fewer field modifications

• Improves equipment availability

• Lowers design and support costs because safety is designed in

early

• Improves national and international market advantages

• Establishes a common, systematic, industry-wide approach to

safety

Opportunities

The framework for safety is a starting point for industry

guidance documents or voluntary industry standards. Thus, the

opportunity exists to form an industry work group to produce these

documents. Additionally, a cooperative agreement opportunity

exists for a pilot project to implement the safety framework with a

mine equipment manufacturer.

Reference

Phillips MM [1997]. Business of mining gets a lot less basic.

Wall Street Journal, Mar 18; sect. B:1 (col. 1).

For More Information

For additional information, contact John J. Sammarco, NIOSH

Pittsburgh Research Laboratory, Cochrans Mill Rd., P.O. Box 18070,

Pittsburgh, PA 15236-0070, phone: (412) 386-4507, fax: (412) 386-

6764, e-mail: zia4@cdc.gov

To receive additional information about

occupational safety and health problems, call 1-

800-35-NIOSH (1-800-356-4674), or visit

the NIOSH Web site at http://www.cdc.gov/n

Mention of any company name or product does not

constitute endorsement by the National Institute

for Occupational Safety and Health.