A hydraulic debarker is a machine removing

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

from wooden logs by the use of water under a pressure of or greater. Hydraulic debarking can reduce soil and rock content of bark, but may increase the water content. Debarking water may be recycled after effective settling, but suspended solids may increase wear on high-pressure pumps. Hydraulic debarking has declined where water quality problems have arisen.

History

Bark on mature

redwood Sequoioideae, commonly referred to as redwoods, is a subfamily of Pinophyta, coniferous trees within the family (biology), family Cupressaceae, that range in the Northern Hemisphere, northern hemisphere. It includes the List of superlative tree ...

trees of coastal

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

can vary from in thickness. Redwood bark is thick, stringy and tough; and can cause

sawmill A sawmill (saw mill, saw-mill) or lumber mill is a facility where logging, logs are cut into lumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes ...

machinery to malfunction. Men called peelers removed bark from fallen trees in the woods through the early 20th century, but the process was dangerous and labor intensive. In the mid-20th century hydraulic barkers were built at several large sawmills including the Union Lumber Company at

Fort Bragg, California Fort Bragg is a city along the North Coast (California), North Coast of California in Mendocino County, California, Mendocino County. The city is west of Willits, California, Willits, at an elevation of . Its population was 6,983 at the 2020 ...

, the Northern Redwood Company at Korbel, and the Pacific Lumber Company at Scotia, California. The last was featured in a popular sawmill tour.

Operation

Although less expensive mechanical debarkers were adequate for smaller logs harvested from young trees on redwood tree farms, hydraulic barkers remained in operation until all

old growth An old-growth forest or primary forest is a forest that has developed over a long period of time without disturbance. Due to this, old-growth forests exhibit unique ecological features. The Food and Agriculture Organization of the United Natio ...

trees had been harvested from company timberlands. The

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...

published hydraulic barking category effluent limitations in the 1970s. Wastewater discharged from debarking could average no more than 2.5 pounds of

biochemical oxygen demand Biochemical oxygen demand (also known as BOD or biological oxygen demand) is an analytical parameter representing the amount of dissolved oxygen (DO) consumed by aerobic bacteria growing on the organic material present in a water sample at a s ...

(BOD) and 12 pounds of

total suspended solids Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water qu ...

(TSS) per thousand board feet of lumber produced (0.5 kg BOD and 2.3 kg TSS per cubic meter of lumber). Daily waste discharge rates could be three times as high as 30-day averages, but pH was required to remain between 6 and 9.40CFR429.21(b)
Accessed 2012-09-13

References

* Carranco, Lynwood ''Redwood Lumber Industry'' Golden West Books, San Marino, California (1982)

Notes

{{Forestry tools Sawmill technology Forestry equipment