What it means
Steel pipe is manufactured in sections called joints, and the length of each joint varies a little from one to the next. Rather than demanding exact lengths, buyers order pipe by length range, called random length.
Single random length is the shorter range, around 20 feet, and double random length is the longer range, roughly twice as long, in the region of 35 to 40 feet. The advantage of longer joints is fewer joints for the same total distance.
Each joint has to be connected to the next, either by welding on a pipeline or by threaded couplings in a well, and each connection takes labour and equipment time and is a possible point of failure. Halving the number of connections can save a meaningful amount on a large project.
The disadvantage is handling. Longer pipe is heavier to move, harder to transport on trucks and trains, and may need larger equipment on site.
Some rigs and sites cannot accommodate very long joints, so engineers have to check that the pipe will fit the equipment before ordering. For buyers, the specification is part of the purchasing contract and affects the price per foot or per tonne.
Suppliers sometimes charge a premium for double random length because it needs more selection and handling at the mill. Project managers should compare the premium with the savings on installation labour and inspection.
Accountants and project controllers see the effect in the cost of a pipeline or well. The pipe itself is capitalised as part of the asset, along with installation costs, and a lower installation cost reduces the total amount added to the balance sheet.
Estimating the number of joints and connections is therefore a routine step in building the project budget.
In practice
Real-world examples.
Example
A pipeline contractor chooses double random length for a long, flat route where trucks can deliver long joints. The number of welds falls by half, which shortens the schedule by several weeks. The project manager reports the saving to the client.
Example
A procurement officer compares two quotes for casing pipe. One is for single random length at a lower price per foot, and the other is for double random length at a slightly higher price. She calculates that the saving on connections outweighs the higher price and recommends the longer pipe.
Example
An engineer working in mountainous terrain finds that the access road has tight bends that long trucks cannot take. She specifies single random length even though it costs more to join. The extra connection cost is accepted in the budget.
Formula
Calculation
Number of joints = Total length required / Average length per joint
Connection cost = Number of connections x Cost per connection
Worked example: a pipeline needs 12,000 feet of pipe. Single random length joints average 20 feet, double random length joints average 40 feet, and each field connection costs $400. Assume one connection per joint, to keep the arithmetic simple.
Step 1: Single random joints = 12,000 / 20 = 600, so connection cost = 600 x $400 = $240,000
Step 2: Double random joints = 12,000 / 40 = 300, so connection cost = 300 x $400 = $120,000
Step 3: Saving on connections = $240,000 - $120,000 = $120,000
If double random length pipe costs $30,000 more in total to buy, the net saving is $120,000 - $30,000 = $90,000.Case study
Seen in the real world.
Northfield Pipeline Services is an illustrative, fictional contractor that bid for a 30-mile gathering line. The estimator priced the job with single random length pipe, which required 7,920 joints of 20 feet for the 158,400 feet of pipe.
Before submitting the bid, the project controller asked for a second estimate using double random length joints. This reduced the number of joints to 3,960, and with each connection costing $350, the saving was 3,960 x $350 = $1,386,000 on connections alone.
The longer pipe cost $400,000 more and needed two additional trailers, costing $60,000. The net saving was still $1,386,000 - $400,000 - $60,000 = $926,000, which allowed Northfield to submit a more competitive bid. The illustrative lesson is that pipe length is a small specification with a large effect on cost.
Watch out
Common mistakes.
- Assuming every joint is exactly the same length, when random length means a range that varies from joint to joint.
- Choosing the longest pipe without checking site access, when transport and handling may rule it out.
- Comparing only the price per foot, when installation costs often decide the true total.
Questions
People also ask.
What does double random length mean?
It means the pipe is supplied in joints of roughly twice the length of single random length, typically in the range of about 35 to 40 feet.
Why do buyers order random lengths?
Mills produce joints with natural variation, and ordering by range is cheaper than demanding one exact length.
Does DRL always save money?
Not always, because higher purchase prices, transport limits and handling needs can reduce or cancel the savings.
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