Learn about fundamental of pipes that used in process piping of oil and gas industries.
In this video, you will learn about fundamental of pipe that used in process piping of oil and gas industries. You will learn different types of pipe and common material and ASTM grades. You will also learn about NPS & Schedule number that used to define pipe size and thickness. You will also learn about double random & single random pipe length, and what is the difference between small bore and large bore pipe.
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OK, What is Pipe?
The pipe is a straight pressure tight cylindrical hollow, used in the piping system to transport liquid, gas and sometimes solids.
Different types of pipes are used in different design conditions, considering technical and commercial parameters. For small & medium sizes requirement, seamless pipes are more popular whereas for larger diameter, welded pipes are more economical.
Pipes are mainly classified into two main categories seamless and welded. Welded pipes are further classified based on the method of welding. There are two ways to weld pipe 1st is with filler metal and 2nd is without filler metal. SAW process is with filler metal welding whereas ERW and HFW are no filler welding methods to weld the pipe. EFW pipe can be welded with or without filler material. SAW pipes are further classified as straight seam and spiral seam pipe. Straight seam pipes are also known as L-SAW or long seam SAW pipes. Medium diameter straight SAW pipe has single seam whereas large diameter pipe has a two weld seam.
ASME B31.3 provides the list of material that can be used in Process Piping. ASME B31.3 covers Carbon steel, Low alloy steel, Stainless steel, Exotic material, such as Titanium, Copper, Nickel and its alloy and Non-metal such as PVC, HDPE, GRE/GRP etc.
Here in this table, you can see that carbon steel material is used up to 425-degree centigrade and above that low alloy steel is used. For corrosive services, stainless steel materials are used. For low-temperature service, LTCS materials are used. Non-metallic material such as GRE GRP pipes are used in sea water and other low pressure but corrosive services.
With the increase in technological advance lined and clade materials are getting popular in Process industries. When combining two materials, we can get the advantage of the two materials at low cost.
Lined pipe has a Mechanical bonding between pipe and line material.
By applying lined material to carbon steel pipe we can get the benefit of anti-corrosion property of lined material and strength of carbon steel
Commonly used lined material are PTFE, Rubber, Glass, and FRP (Fiber reinforced plastic)
Clade Pipe – as against to mechanical bond between pipe & lined material, Clad pipe has Meteorological bond between pipe and cladding material
The cladding is done by an explosive bonding process or by welding of clad material on the pipe which is also known as overly.
High strength carbon steel material is clad with high corrosion resistant stainless still material to achieve cost benefits
Ok, now let’s discussed pipe size. Pipe size is defined in either in NPS, NB or ND
NPS – Nominal Pipe Size
All American standard used NPS designation to define pipe size. This is a modern derivation of earlier IPS – Iron Pipe Size. NPS is not an OD or ID of the pipe it is in-between the outer and the inner diameter of the pipe but not exactly in the middle of it. For example, NPS 2 size pipe outside diameter is 60 mm or 2.375 inches. NPS 12 and the smaller pipe has outside diameter greater than the designated size and for NPS 14 and above size pipe outside diameter is the same as the designated size in inches. That mean 16” pipe OD is 16”.
NB – Nominal Bore
This is the European equivalent of NPS. In this standard pipe sizes are mentioned in millimeter
DN – Diameter nominal
This is the German equivalent of NPS. In this standard also, pipe sizes are mentioned in millimeter
Here you can see the Pipe cross-section clarifying ID/OD & NPS. Pipe outside diameter is standardized hence ID will change with changed in Pipe thickness.
In the project, you will come across the terms such as small Bore & large bore. Do you know what is Small Bore and Large Bore Pipe?
In general, Pipes having size range ½” – 1 ½ ” are termed as small bore. Pipes having size range 2” & above are termed as big bore. This may slight vary depend on the company to company but at most it is same. As some company refers up to 2 1/2” small bore and above that large bore.
- Standard dimension of carbon and alloy steel pipe in the range of 1/8” to 80” covers in ASME B36.10.
- Standard dimension of stainless steel pipe in the range of 1/8” to 30” covers ASME B36.19
Pipe length is mentioned in either meter or in feet. During production pipes are not manufactured in same lengths and during construction of process plant, you required various lengths of pipe. To address this issue pipe standard has defined pipe lengths, in single random and double random categories.
Single random pipe comes in
4.8 m to 6.7 m in lengths with 5% of lengths in between 3.7 to 4.8 m
Double random pipe has a
minimum average of 10.7 m and a minimum length of 4.8 m with 5 % of lengths in between 4.8 m to 10.7 m, Maximum size is by default restricted due to transport constraint. You cannot transport very long pipe via regular mean. However, you can order Fixed length pipe, but it will cost you more
Based on your construction requirements you can choose the pipe lengths.
Pipe Thickness are expressed in Schedule number (common schedule nos. are 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160). If you want thicker pipe than Sch 160, you have to mention in your specification or in PO.
Pipe Thickness are also expressed as STD, extra strong-XS, double extra strong-XXS. If you refer ASME B16.10 which gives a standard dimension for carbon steel pipe, you will find the corresponding schedule no. to this standard schedule no. Higher the schedule no. higher the thickness of the pipe and lower the Insider Diameter.
What is Schedule No?
A schedule number is an approximate value of the equation = 1000 P/S
P is the service pressure in (psi)
S is the allowable stress in (psi)
As said earlier, the outside diameter of each pipe size is standardized. Therefore, inside diameter depends on the schedule number of pipe
ASME B36.10 provides standard dimension requirements for Welded & Seamless wrought iron pipes.
The thickness of ss pipe is also expressed in Schedule number. However, there are only four schedule nos. are mentioned in ASME B36.19 that is (5S, 10S, 40S, 80S)
Schedule no with S suffix is used for SS pipe as per ASME B36.19,
So, please remember schedule no. 10 and 10S are not same and have a different thickness & material.
Pipe can be a
Plain end – plain end pipes are used with socket type weld fittings
Beveled end – this kind of end used when butt type weld fittings are used
Threaded end pipe used with threaded connections in piping system
There is Special end such as socket & spigot with O-ring type gaskets are also available
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