Yes, you can connect multiple pressure relief protections in parallel for redundancy, but this requires careful planning and compliance with safety standards. Parallel-connected safety valves provide additional protection against system failure and are often mandatory in critical industrial processes. Proper installation and configuration are essential for effective pressure safety and redundancy.
What is the difference between primary and secondary pressure relief protection?
Primary pressure relief protection forms the first line of defence against overpressure and is designed to activate automatically at a preset pressure value. Secondary pressure relief protection functions as backup when the primary protection fails or has insufficient capacity.
The hierarchy in safety systems begins with primary protection, which activates under normal operating conditions. These systems are set to a slightly lower pressure than the secondary protection to prevent both systems from operating simultaneously. Secondary systems only activate when the primary protection fails.
In a parallel-connected pressure relief protection, both systems can function simultaneously. This is particularly useful in processes where large volume flows must be discharged or where continuous protection is crucial. The primary and secondary systems then share the load and together provide the required protection capacity.
How do you correctly install multiple pressure relief protections in parallel?
The correct installation of parallel pressure relief protections begins with determining the proper pipe diameters and positioning. Both safety valves must be installed at the same height and connected via pipes of equal length and diameter to minimise pressure drop.
Follow these steps for safe installation:
- Install both valves at equal distance from the system to be protected
- Use pipes with at least the same diameter as the valve outlet
- Provide each valve with an individual shut-off valve for maintenance
- Install pressure indicators to monitor operation
- Ensure adequate discharge pipes to a safe location
Dutch and European standards such as NEN-EN-ISO 4126 specify that the distance between parallel valves must be at least three times the pipe diameter. This prevents interference between the systems and ensures optimal performance of both protections.
Which safety rules apply to parallel-connected pressure relief protection?
Safety standards for parallel-connected pressure relief protection are established in various European and international standards. The main standard is EN-ISO 4126, which provides specifications for design, installation and maintenance of pressure relief protections.
Certification requirements include:
- CE marking in accordance with the Pressure Equipment Directive (PED 2014/68/EU)
- Periodic inspection and calibration of both systems
- Documentation of installation specifications and maintenance history
- Risk analysis in accordance with SIL classification, where applicable
Legal regulations require that parallel-connected systems can function independently of each other. This means that failure of one system must not lead to reduced performance of the other system. Regular inspection and maintenance are mandatory to ensure the reliability of redundant pressure relief protection.
When is redundancy in pressure relief protection truly necessary?
Redundancy in pressure relief protection is mandatory in critical processes where system failure could lead to dangerous situations, environmental damage or major economic losses. A risk analysis determines whether double protection is necessary based on the potential consequences of overpressure.
Situations requiring redundancy:
- Processes with toxic or flammable substances under high pressure
- Systems where human safety could be directly endangered
- Installations with continuous operation where downtime is costly
- Geothermal and steam boilers with high energy density
- Data centres where cooling systems are crucial for server reliability
Industry-specific requirements vary by sector. In the chemical industry, stricter requirements apply for redundancy than in standard HVAC systems. Breweries and laboratories have specific regulations for pressure protection systems due to the nature of their processes and substances used. For explosive atmospheres, an ATEX vacuum pressure relief device is often mandatory.
How Presscon helps with pressure relief protection and redundancy
We design and install redundant pressure relief protection systems tailored to various industries. Our 25 years of experience in nitrogen and compressed air systems enables us to translate complex safety requirements into reliable technical solutions.
Our services include:
- Risk analysis and determination of redundancy requirements
- Custom design of parallel-connected safety systems
- Installation in accordance with Dutch and European safety standards
- Periodic maintenance and calibration of protection systems
- 24/7 technical support for critical installations
- Certification and documentation for compliance
Through our in-house production capabilities, we can respond quickly to maintenance queries and replacement needs. This is crucial for systems where redundancy is temporarily lost during maintenance. Contact us for an analysis of your pressure relief protection system and advice on redundancy options that suit your specific risk profile.
Frequently Asked Questions
How often should parallel-connected pressure relief protections be tested and maintained?
Parallel-connected pressure relief protections must be inspected at least annually in accordance with EN-ISO 4126 standards. For critical processes, six-monthly inspection is recommended. During maintenance, one system must remain operational, so plan maintenance periods in phases to ensure continuous protection.
What happens if one of the parallel-connected safety valves opens prematurely?
If one valve opens prematurely, it must be immediately isolated via the individual shut-off valve for maintenance. The system can temporarily run on one valve, but the cause must be investigated quickly. Possible causes are contamination, wear or incorrect calibration.
Can different brands or types of safety valves be connected in parallel?
Yes, different brands can be connected in parallel, provided they have the same capacity and set points. However, identical valves from the same brand are preferable for consistent performance. All valves must comply with the same standards (CE marking, PED directive) and have comparable response times.
How do you determine the correct capacity for each of the parallel-connected valves?
Each valve must individually deliver 100% of the required relief capacity for complete redundancy. In practice, valves are often chosen that together cover 150-200% of the required capacity. A pressure technical advisor can calculate the exact sizing based on your process parameters.
What costs are associated with installing redundant pressure relief protection?
Costs vary greatly per application, but expect 60-80% additional investment costs compared to single protection. This includes additional valves, pipework, instrumentation and installation work. The additional costs are often offset by reduced risks and lower insurance premiums.
How do you monitor the operation of both systems in a parallel-connected setup?
Install pressure transmitters and position switches on both valves for continuous monitoring. Modern systems can be linked to SCADA or PLC systems for real-time monitoring and alarming. Record all activations and pressure peaks for trend analysis and predictive maintenance.
Is it possible to expand existing single pressure relief protection to a redundant system?
Yes, expansion is usually possible by adding a second parallel branch to the existing system. However, this requires modifications to the piping configuration and possibly reinforcement of the discharge lines. A technical analysis determines whether the existing infrastructure is suitable for expansion.