Meeting the Challenge of SIL Requirements for Industrial Explosion ProtectionMeeting the Challenge of SIL Requirements for Industrial Explosion Protection

IEP Technologies was recently engaged by a leading nutritional products manufacturer to assist with a retrofit project at one of its facilities. The goal was to upgrade the company’s existing explosion protection system, ensuring long-term safety and compliance with the latest technology, while future-proofing their operations. IEP partnered with the customer to develop a solution that addressed the challenges posed by the latest NFPA explosion protection standards.

Explosion protection systems are employed across various industries to safeguard against the potentially catastrophic effects of explosions in processes involving combustible atmospheres. Sectors such as chemicals, pharmaceuticals, food and beverage, paints and coatings, wood, paper, energy, and power generation all face risks related to combustible particulate solids and explosive conditions.

One approach to explosion protection is the use of active explosion suppression systems, which are designed to rapidly neutralize a developing explosion within a process vessel. These systems interface with plant shutdown and alarm mechanisms, isolating and safeguarding connected equipment and plant personnel before dangerous conditions escalate. Once installed, NFPA 69 – Standard on Explosion Prevention Systems1 mandates that these systems undergo quarterly maintenance to ensure proper operation as specified in Chapter 15.

The latest edition of NFPA 69 (2024) requires that explosion prevention systems be implemented as Safety Instrumented Systems (SIS).  This document requires that “Explosion prevention system controls shall be implemented as SIS...” where required as part of the documented risk assessment. Additionally, SIS for explosion prevention services must achieve a Safety Integrity Level (SIL) 2 unless a documented risk evaluation, approved by the Authority Having Jurisdiction (AHJ), determines a different level of protection is acceptable.²

Awareness of the enhanced standard is spreading rapidly among users of explosion protection systems. During the upgrade of an existing system IEP Technologies was challenged by the project team of this major global nutritional products manufacturer to confirm that the installation would conform to the new requirements.

A Safety Instrumented System (SIS) is designed to prevent or mitigate hazardous events by taking a process to a safe state when predetermined conditions are met. It consists of sensor elements, logic solvers, and final elements that perform the following functions:

• Automatically bringing an industrial process to a safe state when specific conditions are violated

• Allowing the process to proceed safely when conditions are met (permissive functions)

• Taking action to mitigate the consequences of an industrial hazard

NFPA 69 classifies several active industrial explosion protection systems, including suppression, dry chemical isolation, mechanical isolation, and inerting systems, as types of SIS.

Explosion suppression installed on a spray dryer (IEP Technologies)

When applied to industrial processes, an SIS is a critical layer of safety that protects employees and mitigates the damaging effects of explosions. It is not sufficient to simply classify a process/safety control system as a SIS—it is also necessary to determine performance criteria based on the acceptable level of risk and requirements for reliability of the SIS. Put simply, not all systems are created equal, and different processes will have varying levels of consequence (injuries or fatalities, financial loss, asset damage, production interruption) in the event of a failure.

The question of performance criteria and tolerable levels of risk should always be addressed upfront as part of an overall process study, often called a “hazards and operability study” (HAZOP) or design review. In the US, the Occupational Safety and Health Administration (OSHA) had previously required a SIS to meet good engineering practice. The tightening of the NFPA69 standard in relation to explosion protection has defined this objectively by mandating that the SIS controller is certified according to assignment of a minimum SIL 2 Safety Integrity Level. SIL is therefore both a measure of system performance and reliability, based upon its probability of failure on demand (PFD), and is defined as one of four discreet levels, SIL 1–4; with SIL 4 denoting the very highest level of safety with the lowest probability of failure. There are two routes available for manufacturers to obtain SIL rating system certification: a 3rd-party independent testing agency (typically by a notified body) or self-certification based upon analysis of field data approximations (historical operating performance data).

In the case of the explosion protection system upgrade for the nutritional products manufacturer, the client’s process review team decided that the new system will require not just the system controller to be rated at SIL2, but also all other linked components. This added requirement would mean a needed SIL 2 rating for the entire explosion protection system. IEP had already secured 3rd-party SIL certification for its EX8000 system controller and SmartDS explosion detection system. The SmartDS system’s dynamic rate of rise pressure sensing differentiates between real explosion events and process pressure fluctuations. It employs three separate algorithms that interrogate pressure data to secure detection while providing excellent false alarm immunity. One feature of the SmartDS detection system is its Event history memory, to record pressure data before, during, and after explosion protection system activation, to help facilitate post-event interrogation and analysis.

SmartDS detection on spray dryer sidewall (IEP Technologies)

One challenge to this upgrade project versus a new installation was the customer’s decision was reusing some existing components in the system. To address this, IEP leveraged historical performance data and silent failures observed from inspections to assign a proxy SIL2 rating to these components. A specialized SIL engineering firm validated the application, confirming a SIL2 rating for the overall system, allowing the installation to proceed as planned.

In this instance, the client company’s project team was impressed by IEP’s knowledge and interpretation of the current and NFPA standards in relation to Safety Integrity Levels, as well as their investment in explosion protection product development and commitment to offering practical and cost-effective solutions to customers. By offering true 3rd Party SIL2 certification of the EX8000 system controller and other critical components, as well as interpreting historical performance data of existing system components, IEP helped guided the project to a satisfactory completion for the customer.

In addition to the EX8000 controller and SmartDS detection system, several key components have already achieved 3rd-party SIL2 certification, including the revolutionary new eSuppressor high-rate discharge suppressor which is used in explosion suppression and isolation systems. Its electro-mechanical operation is unique to the explosion protection field as it does not require pyrotechnic devices for activation, thus allowing for non-destructive testing during manufacture and essential periodic maintenance. Its high-caliber engineering design allows for all safety functions to be fully monitored, a feature which is not possible in devices employing pyrotechnic actuators.

In addition to the EX8000 controller and SmartDS detection system, IEP Technologies has introduced its new eSuppressor high-rate discharge suppressor which is used in explosion suppression and isolation systems. This 3rd-party SIL2 certified suppressor uses an electro-mechanical operation, unique to the explosion protection field as it does not require pyrotechnic devices for activation, thus allowing for non-destructive testing during manufacture and essential periodic maintenance. Its high-caliber engineering design allows for all safety functions to be fully monitored, a feature which is not possible in devices employing pyrotechnic actuators.

eSuppressor high-rate discharge extinguisher (IEP Technologies)

Sawyer Hamblin graduated from Clarkson University with a BS in Aeronautical & Mechanical Engineering. He has 10 years of experience in the explosion protection industry at IEP Technologies, which is part of the global Hoerbiger Safety Solutions network, with sales, service, and support centers located across North America, Europe, Latin America, Middle East/Africa, and Asia/Pacific. For more information, call 855-793-8407 or visit www.ieptechnologies.com.

References

1 NFPA69 2024 – Standard on Explosion Protection Systems

2 ANSI/ISA 61511 – Functional Safety: Safety Instrumented Systems for the Process Industry Sector