3 Types of Enclosure Cooling Methods for HMI Equipment

 

3 Types of Enclosure Cooling Methods for HMI Equipment

HMIs (human machine interfaces) are used to provide information and control inputs to plant and machinery. HMIs usually incorporate a visual display on a touch screen, letting users enter information and activate plant and machinery through soft buttons configured on the screen.

Generally, HMIs interface with a PLC or SCADA system, although some HMIs are able to control and operate the plant directly. Depending on the design, the HMI is programmed using the manufacturer’s proprietary language or some form of software such as Windows CE.

HMIs are generally robust and able to tolerate difficult environments. However, for reliable long-term operation they are best installed in temperature-controlled enclosures so that there’s little chance of the equipment malfunctioning.

HMI Requirements

It’s essential that the technical specifications for HMI software are reviewed before selecting an enclosure cooling system. While some devices have very wide operating parameters that can tolerate temperatures of up to 140 °F, others are more sensitive and may only be able to tolerate temperatures of 113 °F before exhibiting problems such as unresponsive or dark screens.

For practical reasons, HMIs are frequently installed close to the plant, and are often placed in satellite enclosures located adjacent to a production line.

Important considerations include the need to keep HMIs cool, dry, clean, and away from any corrosive vapors. These may indicate the need for sealed enclosures and active cooling solutions. Cognizance must be taken of the total heat load of the HMI, its power supplies, and associated equipment. The service life and stability of an HMI is improved if the enclosure’s temperature is kept well below the equipment’s specified maximum temperature limits.

The following cooling methods may be employed:

Filtered Fans

In some plants, the operating environment is controlled to eliminate dirt and dust. Additionally, the ambient temperature is controlled. In these situations, a conventional filtered fan solution is an economical choice. Make sure the ambient temperature is several degrees lower than the maximum allowable temperature of the equipment in the enclosure. Also, ensure that the heat load is within the capacity of the fan while maintaining the temperature below the maximum design temperature.

Air To Air Heat Exchangers

If the operating environment is not clean and there’s risk of contamination of equipment by dust, dirt, and chemicals, a closed-loop enclosure cooling solution is preferable. This ensures that no dirt or chemicals enter the enclosure and avoids the risk of equipment failure.

In such an environment, an air to air heat exchanger may be the optimum solution. Air to air heat exchangers use very little power and are compact, thus simplifying their installation on satellite enclosures. Power options include 24 and 48 volts DC as well as 120 and 230 volts AC.

The only limitation to consider is that heat exchangers remove heat by using the temperature differential between the enclosure and the surrounding air. Therefore, the ambient temperature must always be lower than the enclosure’s operating temperature.

Enclosure Air Conditioning

In many instances, the ambient temperature in plants, especially those in hotter areas of the country, is too high to ensure that enclosure temperatures can be maintained using filtered fans or air to air heat exchangers.

In these circumstances, an enclosure air conditioner is the solution. Closed-loop enclosure air conditioners can reduce temperatures in enclosures to well below ambient temperatures and exclude dirt, dust, and pollutants. Further, the additional cooling capacity available is such that air conditioners can effectively cool heavily loaded enclosures.

Don’t Risk Damaging HMIs

Although HMIs are robust, their unexpected failure will cause extended downtime. Many units are not immediately available off the shelf, and once sourced, have to be reprogrammed before use. This process may take anything from a day to several weeks.

Apart from total failure, HMIs can lose their memory, get blank screens, or freeze if they get too hot. The only way to ensure this does not happen is to employ enclosure cooling. A properly designed enclosure cooling system will ensure the HMI enclosure temperature is always kept under control.

If you need guidance on cooling your HMIs, contact our Sales Team for advice on the most suitable cooling method.