E+E Elektronik Sensors Aid the Lumber Kiln-Drying Process

The EE310 wall mount stainless steel temperature and humidity sensor can withstand temperatures up to 356°F. It is used in lumber kilns in place of a traditional wet bulb as it provides an accurate, worry-free measurement.
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Lumber Drying Showcase


The U.S. lumber industry kiln dries about 29 billion board feet of lumber annually. The lumber is used for many applications, from framing and finishing construction to furniture and other consumer goods. From forest to table, finished wood products can be found in nearly every home or business across the globe. Although lumber is a commodity, getting it into a usable state is a meticulous, precise, multi-step process.

The quality of the wood drying process depends on three important factors: temperature, relative humidity, and air circulation. Controlling all three factors helps a sawmill hit a moisture content target to produce the highest quality, most sought-after lumber.

Web Bulb Drawbacks

The wet bulb method for temperature and humidity measurements initially may be the most cost-effective route for sawmills. However, the risk of a miscalculation and the labor associated with maintaining this method come with a hefty price tag.

In the past, measuring temperature and humidity in the kiln required a wet bulb system. With the wet bulb system, humidity is determined from a complex calculation. Basically, two standard mercury thermometers are placed in the kiln – one covered with a wet cotton wick, and the other mounted in the open air. Temperature differences between the two are used to calculate the relative humidity inside the kiln. From this calculation the kiln operator will decide whether to adjust the temperature, open or close vents, or change the fan circulation.

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All these decisions related to temperature, venting, and fans have a direct and visible effect on the quality and aesthetic appeal of the lumber. The adjustments frequently are complicated because of the natural interdependence of temperature, venting, and fan circulation. It requires a highly skilled kiln operator to unravel the puzzle of humidity extraction. Even then there is much room for error, not just in their strategy, but also in the temperature measurement mechanism.

Collecting data via the wet bulb method leaves a lot of room for error, as temperature readings are vulnerable to rusting probes, mechanical issues such as water freezing in winter, over- or under-adjustments to other systems, and more. With a lack of reliability at the beginning, there is little chance of a consistent measuring process thereafter.

Mills Embrace E+E Sensors

E+E Elektronik has been producing high-quality, durable sensors for more than 30 years, specializing in a wide range of industrial applications. Over the last couple of years, sawmills across North America have discovered how E+E sensors can improve the lumber drying process and have embraced the company and its technology. Sales of the company’s EE310 Humidity and Temperature Sensor have doubled year over year.

New customers in the lumber industry have given E+E positive feedback regarding their success with the sensors. “In a dry kiln application the EE310 is flexible and functional, easy to program and use, and stable in a constantly high temperature environment,” said one customer.

Positive customer results are due to the E+E commitment to producing the most robust and reliable sensors in the market. E+E products are designed to last at least 10 years and have been certified for achieving and maintaining extremely high accuracy standards.

All E+E sensors come with thorough instructions and diagrams that help with the set-up of the device. The E+E customer service team of top-level engineers and sensor specialists also are always available to help optimize the sensors.

Make a Difference

The E+E Elektronik EE310 High-End Humidity and Temperature Sensor is designed specifically for industrial applications like kiln drying lumber. The instruments boast durability and accurate measurements. High-quality materials and engineering make it a state-of-the-art instrument.

E+E employs a rigorous process to design and manufacture sensor elements in-house. It has full control over the quality and accuracy of the final product. Each sensor is protected from corrosion with a proprietary coating, ensuring it will function for years.

The EE75 duct mount stainless steel air velocity sensor is capable of withstanding temperatures up to 248°F and is unaffected by contaminants.

E+E sensors go beyond measuring and become a fundamental part of the lumber drying process. With the ability to be linked to the kiln, the sensors can initiate a sequence of changes – such as turning off the heater, opening vents, or increasing fan speed – the same way an operator would. These digital sensors take the place of a wet-bulb system, perform the calculations continuously and autonomously, and provide accurate, reliable results to ensure an optimal drying process and the highest quality lumber product.

For more comprehensive control of the lumber drying process, pair the EE310 humidity and temperature sensors with the E+E Elektronik EE75 sensor, which measures air circulation. These digital sensors address all three principal factors for the most accurate wood drying, they give lumber producers peace of mind that the measurements will be reliable.

Protection from Damage

Sensors are very fragile in terms of their mechanics and electrical components; when not adequately protected they will be vulnerable to the conditions of their environment. A sensor that is not designed to withstand the conditions inside a lumber kiln will begin to fail long before damage is visible to the naked eye, and it will require constant replacing.

The environment in a kiln can become extremely harsh for something like a sensor probe.

For example, steam released in the kiln has small compounds that get stuck in the sensor’s pores. Over time these compounds build up and prevent the sensor from producing quality measurements. Eventually the damage to the sensing element is visible in rust and chemical deterioration.

The EE75 remote probe stainless steel air velocity sensor is capable of withstanding temperatures up to 248°F and is unaffected by contaminants. It measures air velocity of hot exhaust, air circulation in dry kilns, and any areas that can experience dirt and dust.

E+E is distinguished by its proprietary coating. It was designed to protect the sensor probe from these compounds so that it can produce high accuracy metrics for years.

Automating the Kiln

One of the greatest benefits of digital sensors is their ability to be linked to the kiln control system. Linked to the controls, sensors can initiate a sequence of changes – such as turning off the heater, opening vents or increasing fan speed – the same way an operator would. Simply put, these digital sensors take the place of a wet bulb system, perform the calculations continuously and autonomously, and provide accurate and reliable results to ensure the highest quality lumber product. Lumber producers can reduce operator costs and wasted energy while increasing efficiency in the drying process.

Wasted Energy

High energy costs are the bane of sawmills and lumber drying, and E+E sensors may be the first step in reducing energy consumption. Kiln drying accounts for two-thirds of the energy needed for the lumber production process. On average, the lumber production process – from start to finish – requires 1,514 Megajoules of energy per cubic meter of lumber produced; of this total, kiln drying consumes 1,000 megajoules.

Although these figures mostly reflect high quantity lumber production, they are inflated by errors in the measurement and production processes. Poor metrics will lead to misinformed decisions about kiln operations and even making adjustments that are detrimental. This can result in large amounts of wasted energy. With many sawmills going below their margin due to high resource costs, energy costs weigh heavily on the bottom line.

For example, it takes a great deal of energy to heat a kiln to the point where moisture releases from the wood. If the wet bulb temperature measurement is higher than the actual temperature, the vents will be opened too soon, releasing heat that took so much energy to produce in the first place. To make matters worse, the wood is not dried according to the correct schedule, which results in damage. This might be why lumber has end checking, warping, or cracking.

Consider your kiln drying methods and whether or not they are maximizing the effort and investment of the rest of the lumber production process. Even the smallest errors in humidity and temperature measurements can lead to incorrect ventilation or heating that will waste energy and undermine lumber quality.

The EE310 remote probe stainless steel temperature and humidity sensor probe can withstand temperatures up to 356°F. It is used in lumber kilns in place of a traditional wet bulb as it provides an accurate, worry-free measurement.

Automating kiln functions with E+E Elektronik digital sensors provide numerous benefits and aid in long-term profitability. They pay for themselves in less than a year, have been shown to last more than 10 years, and significantly reduce manual operating costs.

For more information about E+E Elektronik sensors and technology, visit the company’s website at epluse.com or contact Matthew Nemeth, managing director in the U.S., at (847) 495-7744 or email office.us@epluse.com.