Engineered for Hazardous-Area Operations: A Turkish Positive-Pressure Container Project

Project Overview

A client in Türkiye ordered three types of customised positive-pressure containers from TLS: PDU, workshop and office units. TLS supplied the container structures and specified pressurisation and safety systems, detectors, piping and Ex electrical components. The customer was responsible for installing the operational equipment inside.

The project requirements included Zone 2 protection, A60 fire protection and an operating temperature range of −20°C to +60°C. Preparation and production took approximately five months, followed by the customer’s final video inspection before delivery.

Read the original project report

1. Engineering Focus: How CPFG Coordinates Pressurisation and Safety Functions

A positive-pressure container is an engineered enclosure, not simply a container fitted with a ventilation fan.

Its protective function depends on maintaining the specified pressure conditions and coordinating monitoring, alarms and protective actions. For this project type, the Combined Pressurisation, Fire and Gas (CPFG) system is a key part of that arrangement.

A typical CPFG configuration may incorporate:

• Differential-pressure switches and airflow monitoring.
• Combustible-gas, smoke and heat detectors, according to the specified scope.
• A pressurisation fan and associated air-control components.
• An explosion-protected CPFG control cabinet.
• Audible and visual alarms, emergency-stop functions and defined electrical shutdown interfaces.

How the protection sequence works

Step 1 — Purging and pressurisation

The pressurisation system supplies air to purge the enclosure and establish the required internal pressure conditions. The required purge duration and pressure setpoint depend on the approved design.

Step 2 — Verification before energisation

The control system checks whether the specified conditions for safe operation have been achieved. Where the approved design requires it, the relevant non-Ex electrical circuits remain isolated until the required conditions are satisfied.

Step 3 — Continuous monitoring

During operation, pressure and other specified safety parameters are monitored. A loss of required pressure, gas detection or another abnormal condition may initiate alarms and protective actions according to the approved cause-and-effect logic.

Step 4 — Protective response

If the required conditions cannot be restored within the specified period, the system may isolate designated non-Ex electrical equipment. The actual response depends on the approved control philosophy and the equipment connected to the system.

This sequence is important because positive pressure is only one part of the protection concept. Monitoring, electrical isolation and the response to abnormal conditions must also be considered.

For PDU, workshop and office containers, the internal equipment and operational requirements may differ. The enclosure and its protection systems therefore need to be coordinated with the customer's intended installation rather than designed around an assumed standard equipment package.

For further technical background, see TLS's published guide, What Is CPFG and How Does It Work?.

2. Engineering Focus: What Does Factory Acceptance Testing Verify?

Factory Acceptance Testing (FAT) provides a structured way to check the supplied systems against the approved drawings, functional requirements and agreed acceptance criteria before shipment.

For a positive-pressure container, the test scope should cover both the physical installation and the behaviour of the protection system.

Key inspection and test areas

One important distinction is that achieving the normal pressure target does not, by itself, demonstrate that the complete protection sequence works correctly.

The FAT should also verify the specified responses to conditions such as pressure loss or sensor disconnection. The test procedure should define the relevant thresholds, timing requirements, expected actions and acceptance criteria.

TLS's published FAT guide for PDU and workshop pressurised containers describes visual inspection, CPFG checks, sensor-integrity testing and emergency-shutdown testing as part of the testing methodology.

These are examples of the checks that may be required by a project. The exact tests completed on the Turkish units, and their individual results, should be stated only where supported by the relevant project records.

Applicable Standards and Certification Scope

The standards applicable to this project were determined by the specified operating conditions, hazardous-area classification and contractual requirements. Individual certification claims should be based on the relevant project certificates and approved documentation.

• IEC 60079-13: Addresses the design, construction, assessment, verification and marking of rooms protected by pressurisation or artificial ventilation, within the applicable scope and edition.
• DNV-ST-E271 (DNV 2.7-1): Covers the design, approval, testing and certification of offshore containers and associated lifting sets, where applicable.
• A60 fire protection: Specifies a fire-resistance performance classification. Compliance should be supported by the applicable design, test and approval documentation.
• Hazardous-area electrical equipment: Explosion-protected electrical components and instrumentation must meet the requirements applicable to their intended installation, with certification verified against the actual equipment supplied.

The applicable standards, editions and certification scope must be confirmed against the approved project documents and relevant certificates. References to these standards should not be interpreted as confirmation that every container, component or customer-installed item is independently certified to all of them.

See the TLS pressurised-container technical overview for the published range of design options and applicable requirements.

4. Inspection and Delivery

The published Turkish project account reports quality checks covering structural fabrication, welding, lifting, coating thickness, positive-pressure performance and watertightness. It also records the customer's final video inspection before delivery.

These checks address different aspects of the finished product. Structural and lifting inspections concern the container's physical integrity and handling requirements, while pressure and functional tests address the performance of the specified protection system.

The published account does not provide detailed pressure-test readings, complete signed FAT records or unit-by-unit test results. Those details should not be inferred from the reported successful inspection and delivery.

Conclusion

A positive-pressure container must be designed around the intended application, the equipment that will be installed and the required safety functions.

For PDU, workshop and office applications, the enclosure, pressurisation system, CPFG controls, detection devices and specified explosion-protected electrical components form part of a coordinated design. Clearly defining the supply boundary and verifying the agreed functions before shipment helps establish a sound basis for subsequent equipment installation and commissioning.

TLS provides customised positive-pressure containers for industrial and offshore applications, with the configuration and supply scope defined according to project requirements.