Formula One Heat Exchanger Passivation Rig

A well-known Formula One team approached Hydrotechnik UK Test Engineering Ltd to design and build a rig to passivate aluminium heat exchangers used in their vehicles and then provide related training and documentation.

The rig was to be able to automate the passivation of two heat exchangers simultaneously, with a total of four in a 24-hour period, and provide basic datalogging for traceability. All sensor outputs were also to be accessible externally for high-speed datalogging purposes. A level of R&D capability was to be included, as well as proportional control over flow rate, pressure and temperature.

For safety reasons, the rig was to incorporate an enclosed, lockable test area where the heat exchangers are housed during the process. Additionally, external quick-release BSP process connections were required to utilise some rig functionality externally for components too large for the test area.

Installation prerequisites specified the following:

• 3-phase 415V power to be available
• Factory ring main air at 4-6 bar to be available
• Required chemical solution to be provided by the customer

What is passivation?

Components in Formula One cars need to be suitable for high performance, lightweight, and resistant to corrosion and contamination. An obvious choice for a corrosion-proof material is Stainless Steel. However, Stainless Steel is too heavy for use in F1 heat exchangers. For this reason, passivated aluminium is used.

Whilst aluminium is lightweight, it is not corrosion-resistant. Passivation triggers a chemical reaction on the surface of the aluminium to create an outer layer of shield material, increasing its anti-corrosion properties significantly and making it a suitable material for heat exchangers.

There are several ways to passivate aluminium; however, a chemical solution, which includes de-ionised water, was used.

Technical proposal

After a thorough discussion and requirements analysis, the proposed solution included a custom stainless steel frame housing the following:

• Fully automated passivation process via HMI/PLC 10" with custom software
• Integrated pressure and flow control
• Full instrumentation showing pressure, temperature and flow
• Interlock and safety systems
• Datalogging with complete traceability, with an accuracy of at least ±0.5L/m and ±0.5 bar
• FTP access to logged data
• Fully secure safety doors with visual inspection window

Solution

Upon the order's agreement, Hydrotechnik UK's test rig team began work on the passivation rig. The solution is a recirculation-type rig with pressure and temperature relief valves and a reservoir and water tank designed to hold water at 140°C, kept clean using a built-in filtration system, and an entirely sealed, insulated unit that can perform the passivation process with no manual intervention.

In addition to the passivation process, the rig was built with pressure testing capability, with programmable flow targets and pressure loading for pressures of up to 20 bar at temperatures of up to 135°C. Test data is logged locally and then sent to a remote location. M16 bulkheads provide external access to sensor data, allowing for high-speed datalogging.

The rig includes a system health-check program, helping to ensure the system is running correctly. As well as this, the rig includes the capability to measure calorific values and offers dynamic R&D testing options.

Hydrotechnik UK managed the entire schedule of works, including design, equipment sourcing, fabrication, electrical engineering, pipework, factory acceptance, commissioning and training. A one-year manufacturer's warranty and details about ongoing maintenance and calibration services were also provided.

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Operator-led Passivation	Pressure Up to 20 bar	Temperature Up to 125°C	Flowrate Up to 75 l/min	Safety SIL 1

The passivation process

The primary use of the rig, the passivation, is carried out as follows:

1. The heat exchangers are placed into the test area, and the safety door is closed.
2. The de-ionised water solution is heated to 135°C and pumped through the heat exchangers at 15L/ min. A back pressure of 5 bar is applied. This step carries out the passivation of the aluminium heat exchanger.
3. After four hours and 45 minutes, the rig moves into cooldown mode.
4. When the tank reaches the target temperature of 90°C, the heat exchangers drain themselves, and a pump ensures they are completely drained.

The automated operator-led passivation process was designed and implemented by Hydrotechnik UK.

Rig dimensions

The rig was designed in-house to customer specifications.