Small Farmer's Journal

Facebook  YouTube

Small Farmer's Journal
PO Box 1627
Sisters, Oregon 97759
800-876-2893
541-549-2064
agrarian@smallfarmersjournal.com
Mon - Thu, 8am - 4pm PDT

Lightning Protection for the Farm

Lightning Protection for the Farm

U.S. Department of Agriculture, 1959
by Harry L. Garver, agricultural engineer, Agricultural Engineering Research Division, Agricultural Research Service

Lightning is a particularly dangerous threat on the farm.

Every year over 400 persons are killed and over 1,000 are injured by lightning in the United States. Nearly all of these fatalities and injuries occur in rural districts.

Lightning is a major cause of farm fires. In Iowa from 1930 to 1947, fires started by lightning caused an average annual property loss of over $160,000.

Livestock and trees are also major victims of lightning damage.

Lightning protection can save the farmer money in two ways: By preventing loss of life and property, and by reducing the cost of his fire insurance.

THE NATURE OF LIGHTNING

Lightning is electricity that has both high amperage (rate of flow) and high voltage (pressure).

High voltage enables lightning to travel great distances through the air. High amperage is the main reason for lightning’s destructive power.

Experiments have proved that a charge of electricity must have a thousand times the voltage of household current to travel, or jump, just 1 foot through the air. Lightning, therefore, which usually travels over 2,000 feet between cloud and earth, must have extremely high voltage. But high voltage without large amperage is relatively harmless. The amperage of lightning discharges between clouds and the earth sometimes reaches 200,000 amperes or more.

Lightning follows the line of least resistance. The air through which lightning must pass between clouds and the earth is an insulating material of high resistance. Materials used in building construction have less electrical resistance than air. When such materials lie between the clouds and the earth, lightning naturally goes along the line of low resistance that they provide.

Lightning-protection systems for buildings give lightning ready-made lines of low resistance. They do this by providing unbroken bodies of material that have lower resistance than any other in the immediate neighborhood. A protection system routes lightning along a known, controlled course between the air and the moist earth. Well-installed and maintained, a lightning-protection system will route lightning with over 90-percent effectiveness.

Lightning Protection for the Farm

PROTECTION FOR BUILDINGS

Lightning-protection systems for buildings consist of three parts—air terminals (“rods” or “points”), conductors, and ground connections (fig. 1).

All materials used in lightning-protection systems should comply with the specifications of the Code for Protection Against Lightning published by the National Bureau of Standards.

Lightning Protection for the Farm

AIR TERMINALS

Air terminals are rods or tubes of metal (fig. 2) that are installed at every projecting high point of a building, such as roof peaks, chimneys, dormers, ventilators, gables, flagpoles, towers, and water tanks.

Terminals are manufactured in various lengths, but usually measure between 10 and 24 inches from tip to base. When terminals are made of copper tubing, they should be at least 5/8 inch in diameter and have a wall thickness over 0.032 inch.

Space the terminals along roof ridges, railings, and parapets according to the length of the terminals. (Recommended spacing also applies to metal-covered roofs.) If they are less than 24 inches long, space them less than 20 feet apart. If they are between 24 and 60 inches long, space them no more than 25 feet apart. There should be a terminal within 2 feet of each gable end of any roof.

Lightning Protection for the Farm

Short terminals — usually 10 inches long — are satisfactory for projecting parts of a building. They are usually clamped directly to the conductor cable. Longer terminals have bases that are attached to the building, and the conductors are clamped to the bases. Air terminals over 18 inches long are usually supported by metal tripods (fig. 3). Wind, snow, and ice seldom damage well-erected air terminals. Do not mount ornaments and weather vanes on air terminals. They may weaken terminal mountings.

Lightning Protection for the Farm

Air terminals on chimneys must be coated with lead to prevent corrosion from smoke fumes. They should project 10 to 24 inches above the top of the chimney (fig. 4).

Silos and towers with peaked tops need 1 or more air terminals; those with flat tops need 2 or more.

CONDUCTORS

Conductors are the parts of lightning-protection systems that connect air terminals with grounds. They are made of any good electricity-conducting material that will stand exposure to weather. Aluminum or copper is now used in most installations, instead of the once-common galvanized steel. Aluminum and galvanized steel corrode and lose strength in salt air. Do not use these materials for conductors where salt air is common.

The conducting capacity of a conductor depends on its weight. The minimum acceptable weight, per thousand feet, is: Copper, 187.5 pounds; aluminum, 95 pounds; and galvanized steel, 320 pounds.

Lightning Protection for the Farm

The cable form is now more popular than the rod. Cable is easier to install, because it is flexible, and it has fewer joints to interfere with the conducting of electricity (fig. 5).

Lightning Protection for the Farm

Install conductors to join air terminals in straight lines, along the face of the gables to the eaves and then down to ground connections (fig. 6). Avoid unnecessary bends. Do not use bends with curves of under 8- inch radius.

When copper or aluminum cable is used, make necessary joints with strong fittings that will permanently connect the parts without soldering.

Lightning Protection for the Farm

Fasten conductors with single- or double-nail strap fasteners. On masonry use brass screws set in masonry anchors (fig. 7). To make a neat and durable installation, space fasteners about 3 feet apart.

Metal roofs or building walls can serve as part of the conductor system only if there are no breaks in their construction that would prevent them from being electrical conductors.

Branch conductors, usually made of conductor material of smaller diameter, should connect all structural metal parts of the building with the main conductor system. Use branch conductors to interconnect roof vent pipes that are within 6 feet of any conductor, and also to interconnect stanchions, litter tracks, haytracks, guy wires, door tracks, and stationary farm apparatus to the main conductor system.

GROUND CONNECTIONS

Ground connections are of vital importance to the operation of the lightning-protection system. Make the ground connection properly; it is the key to the efficiency of the whole system.

At least two ground connections are usually needed for every lightning-protection system. They should be spaced as far apart as possible. They should also extend below and away from building foundations to prevent damage to walls from lightning discharge.

Lightning Protection for the Farm

Ground connections are made in one of four ways: By driving a copper-clad or galvanized steel rod at least 10 feet into the ground, or by stranding copper conductor cable and burying it in a trench, or by clamping copper conductor cable to a buried sheet metal plate (fig. 8), or to a water pipe. The chief requirement is to get the lightning-protection system into good and permanent connection with moist earth. Never try to ground a conductor by putting a short length of it into the earth; this does not give enough electrical contact.

Determine the character of the soil in which the ground is to be made. Test moisture conditions at various locations around the building, taking into consideration the dryness or wetness of the season at the time. Select the more moist locations for making ground connections.

Avoid soil or chemical substances that will corrode the ground connection. Heavily galvanized steel resists corrosion for long periods in soil. Copper and copper-clad steel resist corrosion indefinitely in soil that is relatively free from ammonia.

Do not use aluminum for ground connections; it corrodes in soil.

Do not paint ground connections. Painting reduces their electrical conductivity.

If it is not practical to reach permanently moist earth, increase the area of the ground connection by extending the metal horizontally under the soil, or by using several grounds extending radially away from the point of entry into the ground. Other alternatives are to increase the number of ground connections or to run a ground entirely around the building with all conductors connected to it.

Lightning Protection for the Farm

Where soil conditions do not permit driving or digging to a sufficient depth, make a ground by burying a copper cable in a trench running away from the building (fig. 9). For a depth of 5 feet make the trench 15 feet long; for a depth of 4 feet make it 20. Make shallower trenches proportionately longer.

Cover the trench floor with a 5-inch layer of pea-sized charcoal, which will help the grounding ability of the cable. Untwist the cable and spread the strands over the charcoal. Cover the strands with another 5 inches of charcoal and fill the trench in with soil. The ground may be improved still more by splicing another cable to the conductor cable near the point of entry into the ground, and then spreading these additional strands in the same or another trench.

Lightning Protection for the Farm

Connections to water piping where it enters a building generally makes the best ground available. Make connections to water pipes with a strong clamp (fig. 10). Individual deep-well casings are excellent for ground connections.

Connect aluminum conductor cable to copper or steel ground connections with clamps designed for the purpose; otherwise connections are likely to corrode. Make these conductor-to-ground joints within a foot of the ground level.

Use a wooden housing to protect conductors and ground connections from damage by livestock.

After the ground connection is installed and connected with the whole system, have it tested for electrical resistance. Any competent lightning-protection system installer has an instrument for testing grounds. The meter readings should be very low on the scale for a ground connection in good condition: under 5 ohms is excellent; between 5 and 25 ohms is very good; and between 25 and 50 ohms is good.

PROTECTION FOR LIVESTOCK

Livestock are usually killed instantly when they are near a fence that receives a lightning discharge. An ungrounded or improperly grounded wire fence can carry some of the electric current from the lightning discharge along its wires as far as 2 miles. Wire fences that are attached to trees or buildings are most likely to receive and carry lightning discharges, but any ungrounded wire fence with wooden posts, or steel posts set in concrete, is a hazard to livestock.

Ground wire fences to avoid this hazard. Use posts of galvanized steel at intervals of about 150 feet along the fence.

Lightning Protection for the Farm

Another way to ground wire fences is to use pieces of 1/2- or 3/4- inch galvanized steel rod or pipe. Drive these pieces about 5 feet into the earth alongside the wooden fenceposts at about 150-foot intervals. Allow a few inches of pipe or rod to extend above each post. Fasten these pipes or rods to the posts with pipe straps so that they touch all the fence wires (fig. 11).

PROTECTION FOR TREES

Trees are often ruined or severely damaged by lightning. This is hazardous because the lightning discharge is transmitted to nearby areas. Also, if the tree is sufficiently damaged it may fall on a building.

Trees that especially need protection are those that are higher than nearby farm buildings. Other trees that should be protected are those under which livestock usually shelter in a storm and those that are individually valuable.

Protect a tree by installing one or more 10-inch air terminals at the highest secure part of the tree and grounding them through conductors. Very large trees may need two conductors and several air terminals.

Mount the conductors with long-shanked screw fasteners to keep the conductors from contact with the tree when a lightning discharge is being carried in the system.

Where there is a small group of trees, only a few of the tallest need to be protected. If a grove of trees is available for the livestock, remove isolated trees from the pasture, or fence them off to prevent the stock from sheltering under them in a storm.

Lightning Protection for the Farm

To make a ground connection, dig a trench and bury the unraveled end of the conductor cable in it. Make the trench shallow near the tree to prevent damage to the roots. Make it slant downward away from the base of the tree so as to reach moist soil (fig. 12).

To protect the exposed part of the conductor from damage by the livestock, cover it with a wooden casing.

INSTALLATION

Generally, it will be necessary to have an expert plan and install a lightning-protection system. Few persons have the equipment and skill to install and to test their own lightning-protection systems. The farmer should know, however, what the proper materials are and the methods used in the installation.

Follow the work carefully, especially the ground-connection installation. All ground connections should be tested with special equipment to make sure that they are adequate for lightning-protection requirements.

Reputable contractors guarantee their work; many of them will inspect the installation periodically.

Use materials approved by Underwriters’ Laboratories, Inc. All such materials are clearly labeled.

Follow installation methods described in detail in the Code for Protection Against Lightning, published by the National Bureau of Standards, or in Installation Requirements for Master Labeled Lightning Protection Systems, published by Underwriters’ Laboratories, Inc.

Lightning Protection for the Farm

INSPECTION AND MAINTENANCE

Make a periodic inspection of your lightning-protection system to be sure it is in working order.

Look for bent, loose, or missing air terminals, broken conductor cables, and loose connecting clamps. If new construction has been added since the lightning-protection system was installed, check to see that it has been interconnected with the system.

PERSONAL SAFETY

Do not go outdoors or stay outdoors during thunderstorms unless absolutely necessary. If you are caught outdoors, seek shelter in a cave. You may also take shelter in a deep valley or at the foot of a steep cliff, but guard against being caught by flash floods following the storm.

If a shelter is not available, lie down in any low spot in the ground.

Do not stay near isolated trees, wire fences, or small sheds in exposed locations. Keep off hilltops and open pastures or fields.

If you are in a truck or an automobile, stay inside.

If you are indoors, and the building does not have a lightning-protection installation, keep away from fireplaces, stoves, and other metal objects.

Spotlight On: Equipment & Facilities

Horse Powered Snow Fencing and Sleigh Fencing

Horse Powered Snow Fencing and Sleigh Fencing

by:
from issue:

We were planning on having our cattle out in a sheltered field for the winter but a busy fall and early snows meant our usual fencing tool was going to be ineffective. Through the grazing season we use a reel barrow which allows us to carry posts and pay out or take in wire with a wheel barrow like device which works really well. But not on snow. This was the motivation for turning our sleigh into a “snow fencer” or a “sleigh barrow”.

Step Ahead Horse Progress Days 2016

Step Ahead: 23rd Annual Horse Progress Days 2016

by:
from issue:

I had only been to Horse Progress Days once before, at Mount Hope, Ohio in 2008. It had been an eye-opener, showing how strong and in touch with sustainable farming values the Amish are, and how innovative and sensible their efforts could be. So at the 23rd annual event in Howe, Indiana, I was there partly looking for signs of continuity, and partly for signs of change. Right off I spotted an Amish man with a Blue Tooth in his ear, talking as he walked along.

Wheel Hoe

The Wheel Hoe: A Tool For Shallow Tillage

When we bought this little farm I soon realized I needed a wheel hoe. The size of the horse and tractor dictated space wasting wide rows in crop production and, to some degree, so does my two wheeled tractor.

McCormick-Deering Ensilage Cutter No 12B

McCormick-Deering Ensilage Cutter No. 12B

from issue:

IMPORTANT TO McCORMICK DEERING OWNERS: This pamphlet has been prepared and is furnished for the purpose of giving the user as much information as possible pertaining to the care and operation of this machine. The owner is urged to read and study this instruction pamphlet and if ordinary care is exercised, he will be assured of satisfactory service.

Building a Community, Building a Barn

Building a Community, Building a Barn

by:
from issue:

One of the most striking aspects of this development is the strength and confidence that comes from this communal way of living. While it is impressive to build a barn in a day it seems even more impressive to imagine building four barns or six, and all the rest of the needs of a community. For these young Amish families the vision of a shared agricultural community is strong, and clear.

Illusive Herd of Threshasaurus Sighted

Illusive Herd of Threshasaurus Sighted

by:
from issue:

The Threshasaurus’s large size and curious nature may appear antagonistic, but they are mostly curious and largely non-threatening. Be careful when approaching, however, as they do have sharp teeth and many fast moving, exposed pulleys.

Multi-Purpose Tool Carrier Equi Idea Multi-V

Multi-Purpose Tool Carrier: EQUI IDEA Multi-V

Building on the experiences with a tool carrier named Multi, consisting of a reversible plow interchangeable with a 5-tine cultivator, the Italian horse drawn equipment manufacturer EQUI IDEA launched in 2012 a new multi-purpose tool carrier named Multi-V. The “V” in its name refers to the first field of use, organic vineyards of Northern Italy. Later on, by designing more tools, other applications were successfully added, such as vegetable gardens and tree nurseries.

Work Bridle Styles

Work Bridle Styles

Here are fourteen work bridle styles taken from a 1920’s era harness catalog. Regional variants came with different names and configurations, so much so that we have elected to identify these images by letter instead of name so you may reference these pictures directly when ordering harness or talking about repairs or fit concerns with trainers or harness makers. In one region some were know as pigeon wing and others referred to them as batwing or mule bridles.

Geiss New-Made Hay Loader

Gies’ New-Made Hayloader

by:
from issue:

I was sitting on a 5 gallon bucket staring at the hayloader. I had a significant amount of time and money invested. My wife, the great motivating influence in my life, walked up and asked what I was thinking. I was thinking about dropping the whole project and I told her so. She told me that it had better work since I had spent so much money and time on it already. She doesn’t talk that way very often so I figured I had better come up with a solution.

Haying With Horses

Haying With Horses

If the reader is considering the construction of a barn we encourage you to give more than passing thought to allowing the structure of the gable to be open enough to accommodate the hanging of a trolley track. It is difficult or impossible to retrofit a truss-built barn, which may have many supports crisscrossing the inside gable, to receive hay jags. At least allowing for the option in a new construction design will leave the option for loose hay systems in the future.

Hay Making with a Single Horse Part 1

Hay Making with a Single Horse Part 1

by:
from issue:

For the last ten years, I have made hay mostly with a single horse. This has not necessarily been out of choice, as at one time I had hoped to be farming on a larger scale with more horses. Anyway, it does little good to dwell on ‘what if ’. The reality is that I am able to make hay, and through making and modifying machinery, I probably have a better understanding of hay making and the mechanics of draught.

Homemade Ground-Drive PTO Forecart

Homemade Ground-Drive PTO Forecart

by:
from issue:

As we start, consider a few things when building a pto cart. Are big drive tires necessary? Is a lot of weight needed? Imagine the cart in use. Try to see it working where you normally go and where you almost never go. Will it be safe and easy to mount or dismount? Can you access the controls of the implement conveniently? Is it easy to hook and unhook? Where is the balance point? I’m sure you will think of other details as you daydream about it.

LittleField Notes Spring 2013

LittleField Notes: Spring 2013

by:
from issue:

If we agree that quality of plowing is subject to different criteria at different times and in different fields, then perhaps the most important thing to consider is control. How effectively can I plow to attain my desired field condition based on my choice of plow? The old time plow manufacturers understood this. At one time there were specific moldboards available for every imaginable soil type and condition.

Homemade Cheese Press

Homemade Cheese Press

by:
from issue:

On the Gies farmstead we occasionally wallow in goat milk. From it we make our own butter, yogurt and cheese as well as drink some. This has prompted me to build a little cheese press to help with the extra milk. The press is made from inexpensive 1/2 inch thick plastic cutting boards used for the top and bottom plates and pressure disks, white pvc pipe, and a plastic floor drain cap.

Homemade Beet Grinder

Homemade Beet Grinder

by:
from issue:

This is my small beet grinder I built about 6 years ago. It has done nearly daily duty for that time. The beet fodder is added to my goat and rabbit rations which are largely homemade. Adding the pulp to the grain rations has aided me in having goat milk throughout the winter months. My beets are the Colossal Red Mangels. Many grow up to 2 feet long. I cut off enough for a day’s feed and grind it up each morning. Beets oxidize like cut apples. Fresh is best!

Building an Inexpensive Pole Barn

Building an Inexpensive Pole Barn

by:
from issue:

The inside of the barn can be partitioned into stalls of whatever size we need, using portable panels secured to the upright posts that support the roof. We have a lot of flexibility in use for this barn, making several large aisles or a number of smaller stalls. We can take the panels out or move them to the side for cleaning the barn with a tractor, or for using the barn the rest of the year for machinery.

Fjordworks Plowing the Market Garden Part 2

Fjordworks: Plowing the Market Garden Part 2

Within the context of the market garden, the principal aim for utilizing the moldboard is to initiate the process of creating a friable zone for the root systems of direct-seeded or transplanted cash crops to establish themselves in, where they will have sufficient access to all the plant nutrients, air, and moisture they require to bear successful fruits. To this end, it is critical for good plant growth to render the soil into a fine-textured crumbly condition and to ensure there is no compaction within the root zone.

McCormick Deering/International No 7 vs no 9

McCormick Deering/International: No. 7 versus No. 9

McCormick Deering/International’s first enclosed gear model was the No. 7, an extremely successful and highly popular mower of excellent design.

Small Farmer's Journal

Small Farmer's Journal
PO Box 1627
Sisters, Oregon 97759
800-876-2893
541-549-2064
agrarian@smallfarmersjournal.com
Mon - Thu, 8am - 4pm PDT