ANSI B11.26-2024: Machines - Functional Safety

Controlling machines is essential because it allows for accurate and efficient operation, maximizing productivity and reducing waste of materials. Ultimate machine control leads to improved profitability by minimizing errors, and importantly it enhances the safety for operators. Depending on the machine type, control can be accomplished through a variety of means. ANSI B11.26-2024: Machines – Functional Safety: General Principles for Designing Safety-Related Parts of Control Systems for Machinery details specifications for safety-related control functions of electrical, electronic, pneumatic, hydraulic, and mechanical components of control systems.

What Is ANSI B11.26?

ANSI B11.26-2024 provides requirements and guidance for the implementation of safety-related control functions (also known as “functional safety”) as they relate to electrical, electronic, pneumatic, hydraulic, and mechanical components of control systems. The American National Standard illustrates safety control circuit design concepts used to realize safety functions. These functions reduce risks identified by a risk assessment.

ANSI B11.26-2024 applies when a control system is used as a risk reduction measure. The responsibility for reducing these risks to an acceptable level is divided between the equipment supplier, the equipment modifier, the equipment user and its operating personnel.

The requirements of ANSI B11.26-2024 prevent exposure to hazardous motion (or situations) by mitigating the risk of failure, faults, and inadequate design practices and by improving the integrity, reliability, and performance of safety-related functions.

Control Reliability of Machines

ANSI B11.26-2024 defines “control reliability” as a design strategy, method, or feature that separates the safety-related functions of a system into components, modules, devices, or systems that may be monitored or checked by other components, modules, devices or systems. Essentially, it means the control system is designed to maintain operational safety despite potential malfunctions within its components.

The objective of control reliability is to create a safety-related function(s) so that a reasonably foreseeable, single failure does not cause the loss of the safety function and does not prevent a normal or immediate stop from occurring. The failure or the resulting fault should be detected at or before the next demand of safety (e.g., at the beginning or end of a cycle, or when an engineering control device is actuated). The safety-related part of the control system then should initiate an immediate stop command or prevent the next machine cycle or hazardous situation until the failure is corrected.

ANSI B11.26-2024 specifies that control reliability of electrical, electronic, pneumatic, or hydraulic systems or devices frequently consists of monitored, multiple, and independent parallel or series components, modules, devices, or systems.

What Is the ANSI B11 Series for Machinery Safety Standards?

The ANSI B11 series of machinery safety standards and technical reports propose ways to eliminate or minimize risks of the potential hazards associated with required tasks. This can be accomplished by the following actions: