Tower lights are an important type of signal light used in various industries and processes. These lights are distinguished by their columnar structure of several independent lights stacked on the top of each other. They typically are comprised of up to five different colored light segments—red, green, yellow, blue, and white and often times include a sound module. Owing to their stacking orientation, purpose and designs, these lights are also referred to as indicator lights, signal tower lights, warning lights, stack lights, industrial signal lights, and light towers.
Nowadays, industrial machines are equipped with intuitive interfaces and advanced diagnostics that inform operators about the status of the machine or event. These features help operators take necessary action at the right time. However, these features have limitations when it comes to their visibility at long distances. Many times, the operators spend time away from their work console for work-related or other reasons. It becomes difficult for them to access the machine and check the status of the current process. This is where the tower lights help. As different light modules are stacked in towers and placed over the machine, they are visible from all directions offering a 360-degree view. These lights provide status information to operators, supervisors, technicians, and other floor personnel. Sometimes, these lights also produce a strobe light signal or a buzzer sound, thereby informing maintenance technicians, forklift operators, or other personnel about the status of the process or machine.
Tower lights are an integral part of Lean Manufacturing and 5S initiatives, where they are commonly referred to as Andon lights. These lights are one of the most common forms of visual management.
Andon lights are the powerful visual tools, which are visible from a distance. These lights can be used in various configurations such as:
Colorful Stack of Andon Lights:
These indicator lights are generally comprised of three lighting modules—green, yellow, and red. As with regular tower lights, the green symbolizes a normal working condition, yellow symbolizes a request for help, and red symbolizes production stop. The red light comes with an alarm. Sometimes, these lights are linked to automated systems, so they can detect problems easily.
Andon Display Board:
These boards are placed near workstations and display the summary of several assembly lines. These boards can be utilized in two ways: to indicate when an individual assembly line is ready for shifting, and to indicate that certain stations may have a problem. The first option is applicable to traditional assembly lines where products are advanced manually.
The features common to tower lights include the following:
The tower lights may comprise of one, two, or up to five modules in a single stack. The lighting modules are available in colors such as red, green, yellow, blue, and white (refer to functions of stack lights) with LED lamps or incandescent lamps. Integrated lighting modules are mostly offered in three styles of module illumination:
- Flashing: In this module, the light flashes continuously.
- Continuous: In this module, the lights stay on continuously. This module is the most common.
- Rotary: In this module, the light rotates, thereby seeking the attention of a user. Most often, the light is also accompanied by a buzzer alarm.
The tower lights feature integrated alarm buzzers, which are normally in the range of 80db. These buzzers may have monotonal, bi-tonal, or intermittent alarm patterns.
- Mounting: The mounting bases are typically available in three configurations—direct mount, wall mount, and pole mount.
- Direct mount bases can be easily installed because they need no drilling.
- Wall mount bases are secured to the panel using a 4-hole mounting pattern.
- Pole mount bases are offered with integrated wiring which assures easy and quick wiring to the terminals, thereby reducing the installation time
Tower lights are equipped with different colored lenses, which indicate a typical state of the machine or process environment. The following table will help you understand the machine or process functions symbolized by these indicator lights.
These color codes are not restricted to the above-discussed functions. The functions of these lights are decided by the system designer in response to machine/operator requirements. Nowadays, tower lights equipped with buzzers are employed in various industrial environments because they help capture the attention of an operator who is away from the visible area of the tower light. The flash rate can be “Fast” or “Slow”, and may be controlled by a PLC. 4Hz is a typical fast flash rate, whereas 2Hz is a slow flash rate.
Selection and Installation
Selection of the tower light for the facility becomes easy when you have an in-depth understanding of the installation area. In many facilities, these lights are to be installed in areas where there might be heavy traffic due to mobile vehicles such as fork lifts, bridge cranes, and people. In such conditions, the tower light may not perform as expected. Thus, it becomes important to consider several factors such as the choice of area, buzzer alarm, mounting options, and so on before making the selection. Be it a crowded workplace or a sparsely crowded workplace, the following are a few important factors that will help users make the right device selection.
- Environment – Although the tower lights are designed for high-traffic and harsh work environments, it is important to consider the following factors during the selection phase:
- Temperature of the environment
- Moisture concentration
- Exposure to direct sunlight, heat, and dust
- Exposure to chemicals or other elements
- Excessive vibrations
- Exposure to hazardous environments
- Excessive outdoor use, which may involve any of the above-mentioned elements
- Materials – Tower lights are available in a variety of materials and price ranges. Good-quality light units are made of polycarbonate, whereas some have metal shell housings, too. The polycarbonate construction provides durability to the light and enables them to withstand moisture, shocks, and corrosion. There are certain factors such as luminous intensity, connectivity, and ease of installation, which may affect the quality of the light. It is important to consider these factors before making the final decision.
- Size – These lights are designed for stacking and are easily visible from a long distance. Many manufacturers improve the visibility by adding additional LEDs inside the towers. These LEDs assure better visibility from crowded workstations. The decision on the light size is affected by several factors such as the length of the work area, the dimensions of the machine or equipment where it is used, and so on.
- Illumination Sources – Tower lights are illuminated using any of the following light sources.
- LEDs: These light sources are well-known for their exceptional brightness in dark environments. They offer the best illumination for most applications. Also, LEDs can operate at low currents and resist strong vibrations, which makes them suitable for high production environments. LEDs are surface mounted or leaded to the tower lights. Each of these types possess their own set of benefits, however, surface mounted types are suited for high-vibration environments. The average life of an LED used in tower lights is 60,000 to 100,000 hours.
- Xenon-type Strobes: These light sources offer white light in full-spectrum for very short durations. Highly efficient xenon-type strobes provide excellent visibility in large workspaces. They produce strong signal light luminance, which is advantageous in case of long outdoor distances. The average life of a xenon flasher is 20,000 hours.
- Incandescent: Tower lights incorporating incandescent lamps are suited for work areas, which are exposed to other light sources or natural light. These bulbs need regular replacement and are considered to be less energy efficient than LED-based tower lights. These lights are not recommended in environments where they may encounter regular shocks and vibrations. The average life of incandescent lights is 7,000 to 12,000 hours based on the supply voltage.
- Appearance – While tower lights are typically positioned on the top of assembly lines, they can play a significant role in improving the aesthetics of the machine. Because tower lights are easily visible from a distance due to their shape, they help create a sophisticated look that may impress the viewer. Hence, it is important that OEMs select these lights keeping the machine aesthetics in mind.
- Mechanical Ratings – It is important to check the mechanical ratings of tower lights to ensure the performance of these lights under typical conditions such as vibrations, shocks, and bumps.
- Assembly – Tower lights are provided in modular designs or as fully-assembled units. Many manufacturers allow users to purchase individual units of these lights such as a pole, a base, buzzer, and illumination modules. The pre-assembled units are mostly offered as single catalog number items, which helps reduce the installation-related hassles as well as improve the productivity on the floor.
- Environmental Protection – The light modules are equipped with gaskets, which help create a permanent seal between them. It is important to ensure that the assemblies are rated for Types 1, 2, 3, 3R, 4, 4X, 12, 13, and IP65. All these ratings ensure appropriate ingress protection in indoor/outdoor environments.
- Electrical Requirements – Some important electrical parameters to be checked while choosing these lights include:
- DC Voltage Rating: This is the maximum DC voltage rating for the light.
- AC Voltage Rating: This is the maximum AC voltage rating for the light.
- Power Rating: It is the maximum power rating for the light.
- Flashing Rate: This is the rate of the product flash. The flashing rate is only applicable to flashing tower lights, not the continuous tower lights.
- Most manufacturers provide tower lights that are suitable for use in 12VDC, 24VDC, 120VAC, and 240VAC applications.
- Accessories – Tower lights are used with various accessories such as light bases, light modules, and sound modules. It is important to invest in high-quality accessories, because the performance of tower lights is directly dependent on them.
- Safety Approvals – Owing to their applications in industrial environments, these lights generally have third party certification approvals. The following are a few common safety approvals.
- UL Recognized Mark: These components may be incomplete or restricted in use.
- UL Listing Mark: This mark suggests that the product complies with the safety requirements of Underwriters Laboratories Inc. (UL).
- CSA Mark: This mark suggests that the product complies with the safety requirements of the Canadian Standards Association (CSA).
- Controls – Signal tower lights are controlled using various devices such as:
- Programmable Logic Controllers (PLC)
- Distributed Control Systems
- PC Control Systems
- Hardwired Machine Controls (relays, push buttons, auxiliary contacts, etc.)
- Wiring/Connectors – Tower lights are available in various wiring configurations, such as flying leads, jacketed multi-color cables, or integrated wiring. The integrated wiring makes installation easy. However, jacketed multi-color cables are provided with industrial connectors. Some tower lights are also provided with integrated communication networks such as Modbus, or DeviceNet.
Tower lights have the advantage when it comes to seeing the status of a machine or process. These lights, placed on top of a machine, can be seen from across the shop floor to alert personnel of machine status or an issue. Seeming simple, tower lights remain as a significant component of automation and machine installations, world-wide. When selecting and installing tower lights, keep important factors in mind, such as: the tower light environment, component materials, installation location, and other factors. Contact c3controls, or visit our website for your tower light needs.
The content provided in this white paper is intended solely for general information purposes and is provided with the understanding that the authors and publishers are not herein engaged in rendering engineering or other professional advice or services. The practice of engineering is driven by site-specific circumstances unique to each project. Consequently, any use of this information should be done only in consultation with a qualified and licensed professional who can take into account all relevant factors and desired outcomes. The information in this white paper was posted with reasonable care and attention. However, it is possible that some information in these white papers is incomplete, incorrect, or inapplicable to particular circumstances or conditions. We do not accept liability for direct or indirect losses resulting from using, relying or acting upon information in this white paper.