An example of internal corrosion that has
decayed through the fence top rail
More and more lately, I have been getting calls from people pricing materials for the fencing of corrals, arenas, working pens etc. with a lot of confusion going on. They want to make sure they are comparing apples to apples and from the sound of it, there are a lot of apples and oranges out there. I get a lot of questions about gauges, schedules (relating to wall thickness) and about used vs. new vs. reject vs. secondary vs. surplus. Questions like: what is the difference between schedule 30 and schedule 40? How come as a "schedule" gets bigger, the pipe gets thicker, but as a "gauge" gets bigger, the pipe gets thinner? Is used pipe OK to use? What's the difference between "new" pipe, "new reject" pipe" and "new secondary" pipe?
When using used pipe, you never know where the corrosion will break out. This fence was holding up pretty well except for the one rail
Let me tell you up front, I'm biased and I don't have a lot of good things to say about used pipe. Now I'm not saying all used pipe is a bad buy, I'm just saying that MOST used pipe is a bad buy. Let me count the ways. First of all, the used oilfield pipe available for the fence market is pipe that is deemed no longer fit to be used in the oil patch. With the high oil prices and the pipe shortages, believe me, they (the oil operators) are wearing it out before they sell it off as structural.
Here's what happens: Let's talk about salt water and oil production. Most of the existing wells in Oklahoma, Kansas and Texas are classified as stripper wells. These are wells that produce a lot of fluid on a daily basis but take it from my oil patch pipe days; the oil operators consider them selves lucky if they get a 10% "cut" in their production. This means that if the well produces 10 barrels of oil a day, it also produces 90 barrels of SALTWATER per day. Do I need to explain the effects of saltwater on steel? Don't think so! Furthermore, periodically, acid is dumped down the wells to help the flow of fluids into the well bore. Hmmm, That can't be good on the pipe. I think you're getting it.
Last but not least, let's just touch on rod wear, the most destructive effect on oil field pipe. Bet you thought the hole that is drilled to make an oil well goes straight down. right? Wrong! That is what I thought when I first started selling oil country tubulars in the early 80's. Well let me tell you, oil and gas wells are spiral! Without going into the dynamics of drilling into rock several thousand feet, you're just going to have to take my word for it cause I hate to type. But if you really want to know, hey, I love to talk, so call 877-851-2365.
What were we talking about? Oh yeah. Rod wear. Inside the oilfield pipe, which a lot of folks call drill stem, are the sucker rods. Now very quickly, a brief lesson on oil production and artificial lift. The pumping unit sits on the surface. Attached to the horse head on the pumping unit is the bridle. Attached to the bridle is the polish rod. Attached to the polish rod are the sucker rods. Wayyyyy down the hole is the rod pump. Well, to pump this fluid (saltwater & oil) out of the hole, the horse head, the polish rod, the sucker rods and the pump have to go up & down, 60 minutes per hour, 24 hours per day, 365 days per year. OK, stop and think. All these rods, going down all this pipe, IN A SPIRAL HOLE, are rubbing against something and that something is YOUR USED PIPE. By the way, did I mention that sucker rods are harder than the hubs of H E double hockey sticks. Getting my drift on rod wear?
To spell it out, these super hard rods, rubbing constantly against YOUR pipe, causes some very thin spots inside the pipe. Thus pipe that was nice and thick when it was new, has salt-water corrosion, acid corrosion and very thin spots due to "rod wear". Does this sound like pipe that will last a lifetime? Don't think so. How does an oil operator determine their pipe is no longer fit to re-use in their well? Usually there are 3 ways. The first is the easiest. They know their pipe has holes in it because their well is leaking down the backside or will not hold pressure, so they pull it out and get rid of it (hopefully not in your fence). The second way is by pulling the pipe out of the well and hydro-testing it. Here a service called "pipe testers" fill each individual piece of pipe with water then pressure up on it to see if it will hold the pressure or "pop". This is where the splits we have all seen come from. Is all pipe without splits OK? Not necessarily. The third way to test is by electronic-magnetic inspection (known as an EMI). Here each piece of pipe is run through a high tech inspection unit that determines if there are thin places in the pipe.
There are four grades of EMI'd pipe. Most generally they use these specs: White band - Means pipe has a maximum of 12% body wall loss (this is new specs according to the API, we will cover this later). Yellow band - Means the pipe has a maximum of 15 % body wall loss. Blue band - Means the body wall loss is somewhere between 16 & 30%. Finally, Red band - Means the pipe has a body wall loss of over 30%. This is the pipe usually that is turned over for structural use. All the white, yellow & blue are reused in oil wells. Does that mean you should stay away from pipe with red bands painted on it? Well, probably yes, but many times the inspection companies simply do not paint the red band so you don't really know.
Now not all oil field tubing is like this. How can you tell? If you can look 30 feet down a 2" or 2 ½" hole and see the internal condition of the pipe, you don't need it any way. You're too busy flying around in a red cape and jumping tall buildings in a single bound. Seriously, however, if you know the pipe came from a flowing gas well (they don't use rods or produce salt-water) it is probably all right. Trouble is, unless you buy it right at the wellhead, it is hard to know. Enough bashing of used pipe. Let's move on.
Pipe that has not been subject to corrosion will last a lifetime or more. My place was built in 1957 and a couple of years ago we tore out some of the fence to expand the lot. New pipe posts that had been set in concrete 45 years previous were pulled out of the ground. We busted off the concrete at the bottom of each post and they were all reusable. New pipe is definitely the safest way to go in building your fence but there are different types of new pipe. New is new and if your pipe vendor is honest and knowledgeable, he can help you determine what is best for you.
Since there are no guidelines for identifying the specifications for fencing pipe and everybody makes up their own definitions, I'm going to tell you what ours is;
Good: Good pipe in our book is normally a dead length (vs. random lengths), has no holes, no un-welded seams and is straight. Secondary or Seconds: Secondary pipe per our interpretation is like good pipe but is probably random length or has some minor cosmetic flaw. Reject: Reject pipe is kind of a catchall term where the pipe could have one or more separate defects. Some of those are un-welded seams, windows (where small samples of the pipe were cut out for testing), bows and varying wall thicknesses. Since every mill has their own criteria for what they reject, the quality will vary from mill to mill.
Here at GoBob we try hard to visually inspect the pipe and pass on
to you the best possible description of it before you buy. All of this pipe is usable if it meets your needs. Keep this in mind. Seconds and reject are usually a good buy for fencing pipe (if you know what you are getting) but it is the hardest to find. You and I are hoping the mills screw up and produce a lot of reject while they are doing their best not to. That's why our supplier is always looking for alternatives, which brings up another good point. Don't be stuck on the most popular pipe sizes. They are highest in demand and lowest in supply. You can usually make a good buy if a slightly oddball size is available. What does it matter if it will do the job? I sincerely doubt your neighbor will be out there with a tape measure to make sure you used a 2 3/8" instead of a 2 ¼" or 2 ½". So ask your pipe vendor if any off sizes are available.
APPLES TO ORANGES?
The biggest confusion my customers have is in regard to wall thickness. The wall thickness on pipe makes all the difference in the world. Most importantly it determines the price per foot, but it also determines what job the pipe will perform. We will get into that in a minute. It has come to our attention that the use of "schedules" is probably the most abused term in the structural pipe business. Here you are, calling around, trying to compare apples to apples and you happen to ask, "What is the wall thickness on that 2 3/8" schedule 40?" and the pipe dealer you're talking to says, "I don't know".
I actually had one guy tell me that he called a pipe dealer for prices, a gal answered the phone and gave him prices on 2 3/8" schedule 30 and on schedule 40. When he asked her what the difference was she said she did not know but that she would ask her supervisor. When she came back on the phone, her answer was, "Well, schedule 30 is a little less than 1/8" and schedule 40 is a little more."
How does that make you feel? Let's talk about this just for little bit. There are three main organizations that maintain standards and specifications for pipe. The American National Standards Institute (ANSI), the America Society for Testing Materials (ASTM) and the American Petroleum Institute (API). The ASTM and ANSI cover most structural pipe while the API covers oil field pipe. Now there is a multitude of specs that these organizations maintain that don't pertain to us so all I'm going to talk about is wall thickness. As a general rule, the tolerances for pipe body wall are plus -0-, minus 12%. For example; the specified wall thickness on schedule 40 with a 2 3/8" OD (2" nominal) is .154 inches (which means 154 thousands). Per the tolerance, the thickness of the pipe can be no more than .154 inches but it can be as little as .1355 inches (this is the minus 12%).
The problem is this. Since all scrap is bought by the mills by the pound, all the mills sell the dealers by the pound which in turn sell it by the foot to you, it behooves them to buy the pipe as thin as possible. Since .1355 wall weighs less per foot than .154, you may not be getting as good a deal as you thought if you buy it from a dealer at the lower end of the tolerance versus a dealer with pipe at the higher end of the tolerance.
THAT'S why it is important to know the wall thickness of the pipe you are being quoted. Worst yet, I know for a fact a lot of pipe has been sold that is under tolerance. In our example, if one dealer is selling .130" wall and calling it schedule 40 and the other dealer is selling pipe with a .140" wall at a higher price (which he should be), then first dealer is either cheating or just ignorant. This is a big problem and nobody can fix it. So what do you do? If your pipe dealer does not know the wall thickness, how can you tell?
I think using schedules in fence pipe is a lost cause. Besides, what you really want to know is this: Will the pipe you're buying going to do the job you want it to do. And just as important, don't spend more money than you need to. If a thinner wall will do the job, why spend more on thicker pipe? It is all going to look the same when it is welded up. Here is what we have done to make it easier to buy the pipe you need. We classify pipe by it's "Strength Rating", STR for short and give you a wall thickness range for each STR and pipe size. We also list the recommended uses for each STR. Have I lost you? It's really simple as I think you will see. Listed below are the STR's and recommended usage for 2 3/8" OD pipe. By the way "OD" stands for the "Outside Diameter"
2 3/8"OD STR 30 Wall thickness range - .063 to .074
Suitable for constructing light to medium duty gates and portable panels. Also may be used for rail material in very low pressure areas of your fence or just for decorative fence with no livestock. Too light for posts
2 3/8" OD STR 40 Wall thickness range - .076 to .089
Suitable for gates. OK for top rail and rails in low pressure fence (such as horse fencing). May be used in low pressure cattle fence if vertical stays are installed between posts. Too light for posts.
2 3/8"OD STR 50 Wall thickness range - .091 to .112
A little heavy for gates. Too heavy for portable panels. Can be used for top rails in a lot of applications if the top rail is set over five feet tall, especially horse fence. OK for lower rails in medium pressure areas like large pens. OK for post in very low or no pressure areas. Too light for corral posts.
2 3/8"OD STR 60 Wall thickness range - .113 to .122
Too heavy for gates & portable panels. Makes good top rail in livestock pens with top rail set over five feet, especially for horses. OK for lower rails in all pens and straight alleys. OK for posts in large pens or perimeter fencing, low to medium pressure. Too light for posts in heavy crowding areas.
2 3/8"OD STR 70 Wall thickness range - .123 to .129
Suitable for top rail in cattle pens with a recommended setting at five feet or more. OK for lower rails in medium pressure areas such as smaller pens. OK for posts in large pens and perimeters with medium pressure. Too light for posts in heavy crowding areas.
2 3/8"OD STR 80 Wall thickness range - .130 to .136
Suitable for top rail and lower rails in all applications. OK for posts in large pens, perimeters and small pens. Too light for posts in heavy crowding areas.
2 3/8"OD STR 90 Wall thickness range - .140 to .154
Suitable for top rails and lower rails all applications, including the heaviest crowding areas. May be used for posts in the heavy crowding areas if reinforced with extra posts in the corners.
2 3/8"OD STR 100 Wall thickness range - .190 to .218
Over kill for top rail and lower rails. Don't waste your money (for rails). Excellent for posts in the heaviest of crowding areas. Use these as posts as an alternative to 2 7/8" for a lot less money.
Well, I could tell you a lot more but I'm tired of typing and sharing all my wonderful knowledge for free. Just kidding on the sharing knowledge part, but the two finger "hunt and peck" typing is the truth. It is, however, a lot easier for me to talk. And I love to talk about pipe, steel. horses and cattle. There's other folks that like to talk, so if I'm already on the phone, bend their ears. Hope this helps ya!
Bob Studebaker and all the folks at GoBob Pipe.
Click Here to see what the papers have to
say about GoBob Continuous Fence!