North American Oil & Gas Pipelines

JUN 2018

North American Oil & Gas Pipelines covers the news shaping the business of oil and gas pipeline construction and maintenance in North America, including pipeline installation methods, integrity management innovations and managerial strategies.

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32 North American Oil & Gas Pipelines | JUNE 2 018 aggressiveness that can provide a big productivity boost on the job. Also, the use of sharpened knives naturally results in a finer particle size. Rotor Redesigns As knives are gaining popularity in recent years, manu- facturers have responded with newer mulching head rotor designs that better accommodate the performance of knives. Because the knives are so much more aggressive than car- bide teeth, some of the newer rotors are larger in diameter and often include some type of limiter to keep the knives from biting into too much material at one time. These limit- ers are intended to feed the proper amount of material into the knives for maximum efficiency, as well as produce ideal particle sizes. The two main types of limiters found on today's mulch- ing heads are rings and depth gauges. Ring-style mulching heads have metallic rings fixed around the rotor between ev- ery tooth. They keep trees, branches and any other material from entering the machine deeper than the rings. Depth gauges are a different approach to controlling the amount of material being fed into the mulching head. The depth gauges, which are welded onto the rotor in front of the cutting teeth, function similarly to raker teeth on chain saws. Although they do help prevent the teeth from taking in too much material at one time, the depth gauges offer added flexibility, allowing operators to bite into material more ag- gressively when needed. Rings vs. Depth Gauges Ring-style limiters have been on the market for a longer amount of time. Depth gauges, however, were recently in- troduced to help improve on some of the shortcomings that vegetation management professionals have experienced with ring limiters. For instance, some find mulching heads with rings to be overly limiting. After a tree or branch is knocked down and the operator backs over it for mulching, the rings can hinder the ability to pick the material off the ground for proper cutting. On the other hand, depth gauges improve the ability to bite into material and pick it off the ground for mulching. Additionally, ring-style rotors tend to create excess drag, since the rings are always rubbing on the material being mulched. This may cause the rotor to slow slightly or draw extra horsepower from the power unit. However, depth gauges are not in constant contact with the material being mulched, helping to alleviate these issues. Carbide Tooth Compatibility Even though knives have increased in popularity on mulching heads, many customers still desire the ability to switch to carbide teeth as conditions require, such as opera- tion in rocky terrain. While all styles of rotors allow users to switch between knives and carbide teeth, not all rotors per- form equally with different teeth. One common experience with ring-style rotors is that they do not seem as compatible with carbide teeth. The limiting design of rings, combined with the reduced aggressiveness of carbide teeth, tends to limit performance of the mulching head. This occurrence is especially noticeable when mulch- ing material off the ground. Carbide teeth generally do not pick up the material as well. Depth gauges are engineered to address this issue. Many us- ers find that this newer style of rotor improves performance and picks up material better when using carbide teeth. This is a major advantage of depth gauges, since most of the work with a mulching head is done back dragging over material on the ground. In the end, purchase decisions for mulching heads will largely come down to personal preference. However, the in- troduction of depth gauges offers a fresh alternative to maxi- mize the use of both sharpened knives and carbide teeth. It's a great new option that vegetation management profession- als can really sink their teeth into. Bill Schafer is product development supervisor at Loftness, a manufacturer of vegetation management equipment, based in Hector, Minnesota.

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