Tow Engineer

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Line angles affect how much tension is on the lines as well as the snatch blocks, chains, straps and anchors. The larger the angle between the incoming and outgoing lines to the snatch block, the more line tension on each side of the line will increase and tension on the snatch block will decrease. When the lines are parallel, the force multiplication is concentrated on the snatch block and line tension is reduced.

The reason the line tension increases with wider line angles is that you are starting to produce lateral forces; when the line angle reaches 120 degrees, you are no longer reducing line tension.

Sheave Friction

All snatch block sheaves create friction when the rope moves around the sheave. Even the most efficient snatch blocks operate at about 98 percent. This means that if the fall line has 100 lbs. of tension when it enters the first snatch block, the outgoing line will have 102 lbs. of tension on it.

The snatch blocks we use in the towing industry are generally about 90-percent efficient, so the line tension on the exiting line would be 110 lbs. This is not enough to be concerned with when only using a few snatch blocks. However, when dealing with heavy loads and many snatch blocks, friction may become a factor.

Snatch blocks in theory are simple, but real-life applications require a thorough understanding of the basics to use them effectively and safely.

Editor’s note: In the May 2012 issue, Abejuela covered pulley systems (snatch blocks) and how they can be used to multiply or redirect force.

Terry Abejuela has 30 years of light-duty towing-and-recovery experience; he ' s also been a light-duty level 1 instructor for the California Tow Truck Association since 1998.

Stay Safe When You Get Wet by Matthew Bartlett

As towing operators, we endure weather, accidents, rescues, fires, breakdowns, everyday roadside emergencies and more on any given day.

One thing that we frequently run into that not a lot of us give a second thought to is submerged vehicles. Whether they are in a “live” flood or in a body of water like a pond, lake or river, water-related emergencies have a lot of extra dangers from “regular” casualties.

Towers should train for water rescues and learn about the hidden dangers in order to utilize the proper equipment and methods. Learning more about these recoveries, the industry as a whole can begin to invoice the correct amounts for the specialized recovery work, citing the education and equipment it takes to complete these types of recoveries legally and safely.

As an industry, we have all become accustomed to the OSHA and ANSI regulations on working beside the roadway, but how many people knew there were several regulations about working near the water?

The most important thing towers should realize is in the Public Safety and Commercial Diving world is that all water is considered “contaminated. minated Water is,

“The presence of substances, materials, energy and organisms that renders the water platform unsuitable for use. ” Which nowadays is pretty much any untreated drinking water.

Contamination

There are numerous OSHAregulations that stipulate safety procedures when working in or around contaminated waters. There are four categories of water contamination: • Category 1 is the highest level which involves human remains, animal remains, oils and petroleum-based products. • Category 2 is an above-normal contamination of chemical or biological contaminants. • Category 3 is baseline contamination where water quality is “normal. ” • Category 4 is no contamination, such as drinking water or in a swimming pool.

In most cases, towers deal with vehicles, and the contaminants of those vehicles make the water Category 1.

Floods

When we are dealing with vehicles in a flooded area, we usually are dealing with vehicles that are in fast-moving water known as “swift” water, which is a different kind of danger that many towers tend to ignore. Dealing with vehicles in swift water takes a whole different kind of training and only specially trained personnel should work in swift waters. There are several documented cases where towers have lost their lives attempting to deal with a vehicle in swift water.

If the vehicle is in a river or a flooded road or in any way in moving water, you should not enter the water unless you have the training and equipment and back-up personnel to do so. Time and time again we see in publications great recoveries that were completed in a great effective way out of rivers or flooded areas. However not very often do you see safety lines, Class 5 life jackets, throw ropes or any other “ water safety ” item in the photos. Not to say there are not some or all of these on some jobs, but we all have been at that job where the police want the car gone and we just do what we do as quick as possible.

The equipment we are talking about here is very inexpensive and can save someone’s life and save company owners the financial end of an injury or wrongful death. There are some cases in the public safety world where