An anti-two-block system is used to prevent or warn the operator of a two-block condition on a crane. Two-blocking is the dangerous condition where the lower hook block is raised until it contacts any part of the boom tip hardware. The term comes from block and tackle terminology, describing when the blocks (or pulleys), upper and lower, come into contact with each other.
Two-blocking may occur while winching up, while telescoping the boom out, or when booming down (unless the winch is mounted on the boom). Continuing any of these actions will cause the lower hook block to be drawn over the top sheave or cause the wire rope to break – either of which will cause the load to fall out of control to the ground.
Why have an A2B system?
Required by jobsite rules. Get work on more jobsites with an A2B system.
Required by OSHA for manbasket work, lockouts also required.
Owner recognizes a cost savings due to reduced damage, downtime and repairs.
Owner wants accident protection for men and equipment.
Owner wants to meet current industry safety standards.
Why use a radio or wireless A2B system?
Eliminates cable reel cable problems and downtime.
Much easier, faster installation.
Lower purchase price and operating costs
Why buy a LIFTek A2B system?
Guaranteed lowest total cost: purchase price + operating cost = total cost
Most rugged stainless steel construction – OEM’s agree
Longest battery life, 5 year battery warranty on the L25, with 8 year design life.
Fail-safe design – if the unit is damaged or stops working – it alarms within 30 seconds
“Portable” design, easily swapped or stowed, No DIP switches to set.
Designed for rugged boom truck service – use on any crane.
Fastest service – 99% same day turnaround on warranty or repair work
Pay for themselves in reduced downtime and repairs expense of cable reel systems
Made in U.S.A. – no shipping hassles
Always in stock for same day shipment
Free technical support for the life of the product
Works with any existing lockout hardware or use our low cost kits
Why is the transmitter battery so important in an A2B system?
The battery used in an A2B boom switch is critical to the reliability and operating cost of the entire system. LIFTek uses a high capacity lithium primary cell which costs about $45 to replace once every 5 to 8 years. This replacement cost may seem high initially, but using a battery of this type is actually far less expensive than using alkaline batteries.
The true cost of batteries is not just the cost of the cells (example: about $26 for AA alkaline batteries over the same time period), but the time and aggravation spent changing them when they get low every 6 to 12 months. Alkaline batteries have to be changed 8 to 16 times during the 5 to 8 year life of a LIFTek lithium cell. In rental fleets, sending someone out to change batteries for a customer can cost $50 or more every time. Downtime costs over the life of the system can really add up.
Also, the LIFTek battery has welded leads and gold contacts which do not corrode like other battery contacts in this low current application. In addition, the LIFTek cell has a 10 yr shelf life, and is much more reliable at low temperatures.
Why does LIFTek use an external antenna on the boom switch?
LIFTek uses an external antenna on the boom switch so that the boom switch enclosure can be made of steel (powder coated 304 stainless steel in fact). Internal antenna designs require that the switch enclosure be made of a plastic (non-metallic) material which leaves the entire switch weaker and more vulnerable to impact. The external antenna is coated stainless steel cable, which is very tough and because of its size, provides a very reliable and uniform radiation pattern.