PIPE VS TUBING (WRONG PERCEPTION)

This subject looks familiar since mostly people also know and understand as well that pipe is a kind of tube. But im interested to share my experience, there is some misundertanding in this world, in people opinion, between the differences of pipe and tube. This is normally used by site person during inspection. The story began when my friend showed me about his training notebook, it mention the differences between pipe and tube as below tabel.

PIPE	TUBE
Nominal dimension or measured diameter is ID(inside diameter)	Nominal dimension or measured diameter is OD(outside diameter)
Outside diameter depend on wall thickness of pipe called "schedule"	Inside diameter depend on wall thickness of Tube called "gauge"

 

example : pipe 1/2" have ID 1/2" but tube 1/2" have OD 1/2"………………..correct or not????

 If you find the same case with me, you cant judge it as a mistake. Above tabel is not fully wrong. Please look it more deeply. I make some correction as below.

PIPE	TUBE
Nominal dimension (NPS-nominal pipe size), measured diameter is ID (inside diameter) only for sch STD size 12" and above.	Nominal dimension or measured diameter is OD(outside diameter)
Inside diameter depend on wall thickness of pipe called "schedule", OD based on ASME NPS standard but for size 14" and above just measure inch to mm size, e.g. 14"having OD 355.56mm. OD pipe always same.	inside diameter depend on wall thickness of tube called "gauge"

 

Above tabel can be used when you do inspection so no need to bring thick handbook right!!

Pipe Inspection Before Assembly

Identifying the condition of pipe is the most important thing before you do further action such as cutting, welding or another purpose. Once material received, you have to inspect its condition, if there is any defect out of spec tolerance, we have to confirm manufacture prior to replacing. For pipe, first of all, please do visual checking as below:

1.       Check stamp on the body of material whether it’s comply with our requirement or not, normally it consists of material grade (ASTM no), size, schedule & heat number.

2.       Check dimension of pipe consist of pipe length, thickness & OD pipe

3.       Check outside & inside surface of pipe whether there is a defect or not.

4.       Check the certification of pipe, this may explain about material arrangement, PMI test result, etc.

For surface checking, several defects commonly find on inside or outside of pipe body.

-          Pipe Bending

This defect happened normally due to transportation or handling not using proper tools. This defect can’t be acceptable, measure how long the damage and cut it off.

-          Pipe Pitted/unsmooth pipe

This defect happened because of finishing surface from manufacture or it possible because of wrong handling. The defect coming from finishing surface such as pitted (inside or outside of pipe body), the pitted must be measured how deep it is and compare with allowable thickness, if still achieve the minimum thickness required by ASME/ANSI, it is acceptable.

Another defect due to finishing surface is unsmooth pipe, normally this is because of manufacture doesn’t do machining on the surface or final finishing. Come back with what spec you required when ordering, if doesn’t required smooth surface so it can be acceptable. but I remind you, every small defect pipe will have effect on running fluid.

Unsmooth pipe due to material handling can be scratch normally outside body pipe. Measure how deep it is and check with allowable thickness, if still achieve, it can be accepted.

-          Rusty pipe

Rusty pipe normally happened once CS or LTCS pipe received but if you find rusty pipe on stainless steel class pipe, this is not acceptable. You need to remove the rusty before its spread throughout the body. Cleaning can be done using chemical cleaning spray such as WD40 or others.

Valve n Pipe Connection

Butt Weld Connection
The buttwelding ends are prepared by beveling each end of the valve to match a similar bevel on the pipe. The two ends are then butted to the pipeline and joined with a full penetration weld.
This type of joint is used on all valve styles and the end preparation must be different for each schedule of pipe. These are generally furnished for control valves in sizes 2-1/2-inch and larger.
Care must be exercised when welding valve bodies in the pipeline to prevent excessive heat transmitted to valve trim parts. Trims with low-temperature composition materials must be removed before welding.
ANSI/ASME B16.25

Socket Weld Connection
The socket welding ends are prepared by boring in each end of the valve a socket with an inside diameter slightly larger than the pipe outside diameter. The pipe slips into the socket where it butts against a shoulder and then joins to the valve with a fillet weld.
Socket welding ends in a given size are dimensionally the same regardless of pipe schedule. They are usually furnished in sizes through 2-inch
Flange Connection
Standards for Flanges: DIN, ANSI, AS, BS, JIS
Raised Face Flanges (RF):
RF flanges seal with a flat gasket designed for installation between the raised faces of two mating flanges (both with raised faces). The raised faces have a prescribed texture to increase their gripping and retaining force on this flat gasket. Some users of raised face flanges specify the use of spiral wound gaskets.
Ring Type Joint Flanges (RTJ) or Ring Joint Facing Flanges (R-JF):
RTJ flanges have grooves cut into their faces which accept steel Ring Gaskets. RTJ flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or "Coining") the gasket to make Intimate Contact inside the grooves, creating a metal to metal seal.
An RTJ flange may have a raised face with a ring groove machined into it. This raised face does not serve as any part of the sealing means. For RTJ flanges that seal with BX ring gaskets, the raised faces of the connected and tightened flanges may contact each other. In this case the compressed gasket will not bear additional load beyond the bolt tension, vibration and movement cannot further crush the gasket and lessen the connecting tension.
EN 1092-1:
Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN designated - Part 1: Steel flanges
This European standard specifies requirements for circular steel flanges in PN designations PN 2,5 to PN 400 and nominal sizes from DN 10 to DN 4000. This standard specifies the flange types and their facings, dimensions, tolerances, threading, bolt sizes, flange face surface finish, marking, materials, pressure/ temperature ratings and flange masses.
EN 1092-2:
Flanges and Their Joints - Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated - Part 2: Cast Iron Flanges
The document specifies requirements for circular flanges made from ductile, grey and malleable cast iron for DN 10 to DN 4000 and PN 2,5 to PN 63. It also specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of jointing faces, marking, testing, quality assurance and materials together with associated pressure/temperature (p/T) ratings.
EN 1092-3:
Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN designated - Part 3: Copper alloy flanges
This document specifies requirements for circular copper alloy flanges in PN designations from PN 6 to PN 40 and nominal sizes from DN 10 to DN 1800.
EN 1092-4:
Flanges and Their Joints - Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated - Part 4: Aluminium Alloy Flanges
This standard specifies requirements for PN designated circular flanges for pipes, valves, fittings and accessories made from aluminium alloy in the range of DN 15 to DN 600 and PN 10 to PN 63. This standard specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of faces, marking and materials together with associated P/T ratings. The flanges are intended to be used for pipework as well as for pressure vessels.
EN 1759-1:
Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, Class designated - Part 1: Steel flanges, NPS 1/2 to 24
This European Standard specifies steel flanges, Class designated. The standard lists dimensions, tolerances, materials, P/T ratings and technical delivery conditions.
EN 1759-2:
Flanges and Their Joints - Circular Flanges for Pipes, Valves, Fittings and Accessories, PN Designated - Part 2: Cast Iron Flanges
The document specifies requirements for circular flanges made from ductile, grey and malleable cast iron for DN 10 to DN 4000 and PN 2,5 to PN 63. It also specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of jointing faces, marking, testing, quality assurance and materials together with associated pressure/temperature (p/T) ratings.
EN 1759-3:
Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, Class designated - Part 3: Copper alloy flanges
The document specifies requirements for circular copper alloy flanges in Class designations Class 150 and Class 300 and nominal sizes from DN 10 to DN 900 (NPS 1/2 bis NPS 36).
EN 1759-4:
Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, Class designated - Part 4: Aluminium alloy flanges
This standard specifies requirements for Class designated circular flanges for pipes, valves, fittings and accessories made from aluminium alloy in the range of DN 15 to DN 600 (NPS 1/2 to NPS 24) and Class 150 to Class 300. This Standard specifies the types of flanges and their facings, dimensions and tolerances, bolt sizes, surface finish of faces, marking and materials together with associated p/T ratings.



Clamping Connection

Lug Connection
In a lugged connection the valve is fastened directly to the pipe flange by connecting the pipe flange with bolts to the valve body also drilled with threads

Thread Connection
Thread connection is usually used on 2" (50 mm) valves or under, and is not recommended for elevated temperature service. This connection is also used in low maintenance or non-critical applications.
Threads are according NPT (National Pipe Threads) as American Standard which is the most used in the oil industry or BSP (British Standard), the most common in Europe.
BSP thread can be taper (ISO 7/1 standard or the DIN 2999 and JIS B0203 equivalents) and parallel (ISO 228/1 or DIN ISO 228/1, BSP PL, JIS B0202 equivalents)


Wafer Connection
In a wafer connection the valve is installed between the pipe flanges and tightened to its place with the bolts for the pipe flanges.
In some wafer types there are some centering holes on the body to ensure valve's correct position between the flanges.
Wafer type body is the lightest body version for mounting between piping flanges. Therefore a wafer valve use to be cheaper than other valves. Also it is fast mounting.
But wafer connection is not an option when one side is removed and is wanted to keep the sealing with the other side.
Neither it is used with hazardous fluids such as hydrocarbons and chemicals. In case of fire bolts could dilated and displace the flanges resulting in leakage.
Valves with waffer connection are quite usual in butterfly and gate valves