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An Intertec explosion-proof smart fluid heater has reduced the cost of making marine distress signals for Chemring Marine at its factory in Bremerhaven, Germany.

The Intertec unit works with Chemring Marine’s existing fluid-heater system and boosts the temperature of a flushing agent used to make marine distress flares, immediately prior to use.

Chemring Marine produces the Comet brand of Solas-approved smoke markers and handheld rocket flares, which are used by navies, lifeboat and rescue services, merchant fleets and airlines, fishing vessels and leisure craft.

The rocket-flare manufacturing process involves forcing propellant into the plastic body of the flare; at the end of each production batch, the tray beneath the filling area is flushed clear of any stray propellant by an operator, in preparation for the next batch.

To ensure the propellant is thoroughly dissolved and is safe, the acidic flushing agent needs to be delivered to the point of use at exactly 60C.

Because the process takes place in an ATEX-classified zone, Chemring Marine developed an explosion-proof method of heating the flushing agent.

This involves a special double-walled heat exchanger that transfers heat from a hot-water source system to the bulk supply of flushing agent.

Maintaining the supply of flushing agent at this temperature proved expensive, so Chemring Marine asked Intertec for a cheaper system based on its Flattherm heater blocks.

These blocks are small and electric-powered modular conduction heaters that provide a flexible method of configuring explosion-proof fluid heater systems: multiple units can be operated in a master-slave arrangement to provide the required power-output level.

The units can be sandwiched around a tube of any appropriate material to create an efficient heat exchanger.

A safe temperature sensor on the outlet pipe provides feedback to a digital PID controller, facilitating fast and accurate temperature control.

These types of heater system are ideal for applications where varying levels of heat energy must be transferred accurately and quickly into the fluid to compensate for changes in flow rates or inlet temperatures or to accommodate different demanded outlet temperatures.

In this case, Intertec chose to base the fluid-heater system on a master-slave configuration comprising of a single 500W and a single 400W Flattherm heater block, using stainless steel tubing to accommodate the aggressive flushing agent.

The outlet sensor is connected to the company’s TC D digital temperature controller, which is an ATEX-approved unit with fully encapsulated solid-state circuitry.

This temperature controller uses zero-voltage switching techniques and a Triac power-switching element to minimise radio frequency interference and power losses and provide fully proportional control.

The TC D controller is designed for use in hazardous and potentially explosive atmospheres.

It incorporates many safety features such as local monitoring of the heater block’s surface temperature, with automatic limiting and fault shutdown.

The entire heater system is housed in a standard Intertec enclosure, which is certified for use in Zone 1 environments.

Intertec Instrumentation

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