Passive and Active Explosion Protection Systems

Passive Protection: Simplicity Without Power Supply

 Typical passive explosion protection devices include:

• VENT PRO – Explosion Venting
• FLEX – Flameless Explosion Venting
• B-FLAP I PRO – Mechanical Explosion Isolation Flap Valve

These systems operate purely on a mechanical principle and require neither electrical power nor electronic control. For example, the B-FLAP I PRO uses the pressure generated by an explosion to automatically close the pipeline, preventing the propagation of flames and pressure waves to other parts of the process.

The valve is primarily designed for applications handling combustible dusts. It is not intended for pneumatic conveying systems.

Similarly, FLEX provides passive protection by safely venting an explosion while simultaneously retaining flames, hot gases and burning particles, allowing installation inside buildings.

Benefits of Passive Protection

• Lower initial investment costs.
• Installation can be carried out by the customer according to the supplied installation manual (standard installation work such as drilling, welding flanges or counter flanges, pipeline modifications and installation of supports according to the specific application must be considered).
• Independent of electrical power.
• High mechanical reliability.
• Minimal control infrastructure requirements.
• Some explosion venting systems can achieve a lower reduced explosion pressure (pr_ed), making it possible to protect equipment with lower mechanical strength.

Benefit: A lower Pred may allow the use of lighter and more cost-effective process equipment or structures without compromising the required level of explosion protection.

• Passive Protection Also Requires Responsibility

The simplicity of passive protection is often the main reason customers choose it. However, this also means that the operator assumes greater responsibility for regular inspection and maintenance.

Mechanical devices must be inspected, cleaned and their operational condition regularly verified. Fouling, mechanical damage or improper maintenance may adversely affect their performance.

It is important to emphasize that passive mechanical explosion protection devices also require regular servicing. Periodic inspections are necessary both to maintain the manufacturer's warranty and to verify the correct functionality of the equipment.

• Active Protection: Electronic Systems Responding Within Milliseconds

Typical active explosion protection systems include:

• HRD Explosion Suppression System
• HRD Explosion Isolation Barrier
• GatEx – Quick-acting Slide Valve for Demanding Applications

These systems utilize pressure detectors, a control unit and a dedicated suppression or isolation mechanism. Once an incipient explosion is detected, the system automatically responds within milliseconds.

Unlike purely mechanical devices, active systems continuously monitor their own status. The control unit permanently supervises the readiness of all critical components and can identify faults before they become a safety risk.

Figure 1 – Explosion Protection Portfolio (from left: VENT PRO, HRD Suppression System and Isolation Barrier, FLEX, B-FLAP I PRO and GatEx)

• Where Does Active Protection Provide the Greatest Benefits?

Active protection is often the preferred solution when:

• installation space for passive devices is limited,
• required installation distances for mechanical devices cannot be achieved,
• small pipeline diameters are used,
• the process operates under high pressure conditions,
• continuous system diagnostics and status monitoring are required.

For example, the manufacturer of B-FLAP I PRO recommends considering an HRD Explosion Isolation Barrier or GatEx where installation distances are insufficient or specific operating conditions make mechanical isolation unsuitable.

• No Need to Vent Flames and Explosion Products to the Surroundings

The HRD Explosion Suppression System detects an explosion in its earliest stage and discharges extinguishing agent into the protected equipment within milliseconds. The explosion is suppressed inside the protected vessel, preventing the release of flames, hot gases, burning particles or unburned dust into the surrounding environment.

Benefit: Suitable for indoor installation without explosion vent ducts or venting outside the building.

• Reduced Space Requirements

Explosion venting systems require either a designated venting safe area or vent ducts. The HRD Explosion Suppression System requires no discharge area for flames.

Benefit: Easier installation in confined production facilities and applications with limited installation space.

• Reduced Production Losses

Explosion venting causes the vent panel to open, releasing explosion products and often dispersing processed material into the surrounding area. The protected equipment is exposed to high temperatures, and post-event cleaning typically involves removing soot, deposits and combustion residues.

The HRD Explosion Suppression System suppresses the explosion during its initial phase, significantly reducing thermal and mechanical stress on the protected equipment while also providing an indirect fire protection effect.

Figure 2 – HRD Explosion Suppression System and Explosion Isolation Barrier During Explosion Suppression

Benefit: Shorter production downtime, lower cleaning costs and faster return to operation.

• Protection of Complex Process Systems

The HRD Explosion Suppression System can be combined with active explosion isolation systems installed on process pipelines. This provides effective protection for technologies where explosion venting alone would be insufficient or technically impractical.

Benefit: Reliable protection of complex process installations such as pneumatic conveying systems, dust collection systems and interconnected process equipment.

• Independence from Weather Conditions

Explosion vent panels installed outdoors may be affected by rain, snow, ice or strong winds. The HRD Explosion Suppression System operates independently of ambient weather conditions.

Benefit: Reliable performance under all weather conditions and greater flexibility in plant design.

• Protection of Equipment with High Mechanical Strength or Where Explosion Venting Is Not Possible

The HRD Explosion Suppression System can also be used where explosion vent panels cannot be installed, for example inside buildings, on pressure vessels or where process limitations prevent explosion venting. Its performance does not depend on venting direction or available installation space.

Benefit: Enables protection of equipment where passive explosion venting would be technically impossible or economically impractical.

• Which Solution Is Better?

There is no universal answer. In many cases, combining different explosion protection technologies provides the optimal solution.

•  Option 1

VENT PRO + B-FLAP I PRO

A cost-effective, proven and fully mechanical solution suitable for facilities with well-established preventive maintenance programs.

• Option 2

FLEX + B-FLAP I PRO

Ideal where explosion venting outside the building is not possible and both personnel and surrounding equipment require protection.

Figure 3 – FLEX and HRD Explosion Isolation Barrier

• Option 3

  HRD Explosion Suppression System + HRD Explosion Isolation Barrier

  A highly automated solution with minimal dependence on routine operator inspections and an extremely fast response to an incipient explosion.

 

Figure 4 – Explosion Protection of a Malt Production Facility

• Option 4

  VENT PRO or FLEX + GatEx

  Designed for applications where a conventional mechanical explosion isolation valve cannot be used, shorter installation distances are required, or the reduced explosion pressure (p_red) cannot be lowered sufficiently to match the mechanical strength of the protected equipment.

  GatEx is capable of operating at the maximum explosion pressure (p_max), making it suitable for protecting equipment designed to withstand the maximum explosion pressure.

  It's About More Than the Purchase Price

  Selecting an explosion protection solution should never be based solely on the initial investment.

  Maintenance availability, operational discipline, system monitoring requirements and total life-cycle costs are equally important considerations.

  The best explosion protection solution is not necessarily the least expensive one—it is the solution that will continue to provide reliable protection even after ten years of operation.

Author:

Marcin Chromec

Sales Manager

RSBP spol. s r. o.