Technical Questions

Q.		What is the difference between Limit ALERT and Worker ALERT?
A.		Limit ALERT mounts on the vehicle (forklift, etc.) to warn the driver that he has reached a “limit”, to sound the horn, or to stop the vehicle. Wherever you want to warn the driver, you place a reflector on the wall, column, floor etc. Worker ALERT, Dock ALERT, Tunnel ALERT, and other ALERT Products mount on the wall to warn pedestrians and others that a vehicle is approaching. In this case, you place reflectors on the forklift so that when the forklift passes a base unit it triggers the alert.

Q.		How does Limit ALERT (Worker ALERT, etc.) work?
A.		The Base Unit for these products contains a photo-detector that sends out a red (perfectly safe) beam of light. When it detects its own reflection, it triggers the alert. The reflectors we use are special high-gain “corner” reflectors that optimize the photo-detector performance and increase range.

Q.		Can Limit ALERT (Worker ALERT, etc) be triggered by shiny surfaces?
A.		Only in rare circumstances will a shiny surface such as the side of an aluminum tank, windows, etc. cause a trigger to occur. If this is a problem, we can provide a polarized photo-detector that will respond only to our “corner” reflectors. Even a mirror will not trigger it! However, the sensor range is reduced – see the next question.

Q.		How far will the Limit ALERT (Worker ALERT, etc.) light beam go?
A.		Using a 9” x 9” target of reflective strips, our standard retro-reflective photo-detector has tested successfully in excess of 22 feet. Using a 3” x 9” reflective strip target, it tests in excess of 20 feet. Our polarized photo-detector tests in excess of 12 feet on a 9” x 9” reflector, 7 feet on a 3” x 9”. We can provide detection ranges up to several hundred feet with special purpose devices. If you provide us with your specified distance, we will provide you with a quote for a system optimized to that distance.

Q.		How accurately does the light beam have to be aimed at the reflector?
A.		At twenty feet, the light beam is about 6 inches in diameter. We offer a 3” x 9” wide reflective strip with an adhesive backing that we recommend be mounted vertically. The vertical orientation will compensate for differences in vehicle tire pressure, mounting height differences, etc. We can supply this 3” wide strip in any length – up to 100 feet – upon request. We also offer a 9” x 9” reflective target.

Q.		Must we purchase reflectors from you?
A.		Yes.

Q.		Could vehicles go too fast for Limit ALERT (Worker ALERT, etc.) to detect them?
A.		No. The photo-detector is light activated and therefore operates at the speed of light. There is a small amount of internal triggering delay but it reacts faster than any industrial vehicle could go.

Q.		Can I use Limit ALERT on my 36V electric forklift truck?
A.		Yes. The Limit ALERT power supply was specially designed to accommodate any supply voltage from 12VDC to 48VDC. This means that you can use Limit ALERT on any vehicle, electric or internal combustion, with a power system in that range. Furthermore, the Limit ALERT power supply can handle the large (200 volt and higher) voltage spikes that many electric vehicles have present on their electrical bus.

Q.		We have a situation that isn’t quite suited for either Worker ALERT or Limit ALERT. Can the units be modified to work in our application?
A.		Yes. In our manuals and on our website (www.alertsafetyproducts.com), we suggest quite a few alternative applications where one or the other of the products will work off-the-shelf (e.g., sounding the vehicle horn at an intersection). If those don’t meet your needs, contact us.

Standards and Regulation Questions

Q.		What is the OSHA regulation that requires an operator to honk the vehicle horn at an intersection?
A.		OSHA Standard 29 CFR 1910.178(n)(4) states: “The driver shall be required to slow down and sound the horn at cross aisles and other locations where vision is obstructed.” By wiring Limit ALERT’s relay in parallel with the vehicle’s horn button, Limit ALERT can be used to help drivers comply with this regulation, thus reducing the risk of injury and/or equipment damage. Please note: it does not relieve the driver of the responsibility to comply with this Standard, but it does help reduce your risk.

Q.		Do we need to get the manufacturer’s approval to mount Limit ALERT on our vehicles? How about mounting reflectors on a vehicle for Worker ALERT?
A.		There are two considerations in this regard: OSHA and the manufacturer’s warranty. We will address these separately in A1 and A2 below.
A1.		OSHA Standard 29 CFR 1910.178(a)(4) requires a judgement call on the user’s part. It states that "Modifications and additions which affect the capacity and safe operation shall not be performed by the customer or user without manufacturer’s prior written approval. Capacity, operation, and maintenance instruction plates, tags, or decals shall be changed accordingly." We feel that Limit ALERT Base Units and Worker ALERT reflectors do not “affect the capacity and safe operation” of a vehicle. However, since the user (or the user’s designated service company) performs these installations, it is the user’s responsibility to make sure that installation and operation are done in compliance with this standard. (See the following question about what to do if you think you need the manufacturer’s approval but cannot obtain it.)
A2.		The following points address the manufacturer’s warranty (as well as OSHA standards): Limit ALERT only requires a power connection (2 wires, 12VDC-48VDC). It consumes about 1 Watt of power (a very small amount of power for any vehicle) and has an internal fuse. If it is felt that tapping into the vehicle’s power supply would void a warranty, Limit ALERT can be run for weeks on two 6V lantern batteries or for months on a 12v car battery. Both Limit ALERT and the reflectors for Worker ALERT are applied with adhesive tape and do not require any holes to be drilled. Limit ALERT can honk the vehicle’s horn automatically. This requires wiring Limit ALERT’s relay in parallel with the vehicle’s standard horn button. This function enhances “safe operation” since it alerts pedestrians and other operators that this vehicle is nearby and it alerts the driver that he is entering an area where he must use caution. Thus, it can help the operator to comply with OSHA Standard 29 CFR 1910.178(n)(4). (See the previous question and answer.) Limit ALERT has a “latched” mode that flashes the alert LED, activates the pulsating audible alarm, and holds the internal relay closed until they are reset by turning the Limit ALERT power switch to OFF. This closed relay contacts can be used to stop the vehicle by wiring them in series with the vehicle’s seat switch or foot switch (often called the “deadman’s switch”). We view this as an enhancement to “safe operation”, since it is performing the same function as when an operator stands up (or removes his foot from the foot switch) while the vehicle is in motion. Here again, it is the user’s judgement as to whether the vehicle can be stopped safely in this manner given the load it may be carrying, the location, and other factors that only the user can evaluate. Certain ALERT products (Worker ALERT, Dock ALERT, etc) require that reflectors (or a reflective strip) be placed on the vehicle to trigger the ALERT photo-detector, which is mounted on a wall, column, or other fixed location. If the vehicle is leased, the leasing company may want to be consulted before any such additions are made to their machine. However, it is highly unlikely that such action would void a manufacturer’s warranty. Furthermore, we view this as an enhancement to “safe operation”, since reflectors enhance the vehicle’s inherent visibility.

Q.		If we cannot obtain a “manufacturer’s prior written approval” (OSHA Standard 29 CFR 1910.178(a)(4)) to add a piece of equipment to a vehicle, what recourse do we have?
A.		According to OSHA’s own interpretation dated 04/11/1997: “…if no response or a negative response is received from the manufacturer, OSHA will accept a written approval of the modification/addition from a Qualified Registered Professional Engineer. A Qualified Registered Professional Engineer must perform a safety analysis and address any safety and/or structural issues contained in the manufacturer's negative response prior to granting approval. Machine data plates must be changed accordingly.”