Tubular products are termed ‘tube’ or ‘pipe’. Tube is customarily specified by its outside diameter and wall thickness, expressed either BWG (Birmingham wire guage) or in inches or in thousands. Pipe is customarily identified by ‘nominal pipe size’ with wall thickness defined by ‘schedule number’.
Piping materials
Carbon steel pipe is strong ,ductile, weldable, machineable, reasonably durable and is nearly always cheaper than pipe made from other materials. If carbon steel pipe can meet the requirements of pressure, temperature, corrosion resistance and hygiene, it is the natural choice.
Methods for joining pipe
Piping components
Elbows, Tees, Flanges, Gaskets, Nipples, Unions, Valves, Reducers, Steam traps, Bellows
Types of elbows
Long radius elbows:- normally used elbows are long radius with centerline radius of curvature equal to 1½ times the nominal pipe size for ¾ inch and large sizes.
Short radius elbows:- SR elbows with centerline radius of curvature equal to the nominal pipe size Reducing
Elbows :- this elbows have centerline radius of curvature 1½ times the nominal size of the pipe to be attached to the larger end.
Bends :- Are made from straight pipe. Common bending radii are 3 and 5 times the pipe size. 3R bends are available from stock. Larger radius can be custom made.
Returns :- It changes direction of flow through 180 degrees, and is used to construct heating coils, vents and tanks etc.
Piping Design
Piping arrangements:-
Clearing and Access:-
Route piping to obtain adequate clearness for maintaining and removing equipment.
Locate within reach or make accessible, all equipment subjected to periodic operation or inspection, with special reference to check valves, pressure relief valves, traps, strainers and instruments.
Take care to not obstruct access ways i.e. doorways, truck-ways, walkways, lifting wells etc.
Elevations of lines are usually changed when changing horizontal directions where lines are grouped together or are in a congested area, so as not block spaces where future lines may have to be routed.
Keep field welds and other joints at least 3 inches from supporting steel, building siding or other obstruction. Allow room for the joint to be made
Allow room for loops and other pipe arrangements to cope with expansion by early consultation with staff concerned with pipe stressing. Notify the structural group of any additional steel required to support such loops.
Stresses On Piping
Thermal Stresses:- change in temperature of piping due either to changes in temperature of the environment or of the conveyed fluid, cause changes in temperature in length of the piping. This expansion or contraction in turn causes strain in piping, supports and attached equipment.
Settlement Strains:- foundation of large tanks and heavy equipment may settle or tilt slightly in the course of time. Connected piping and equipment not on a common foundation will be stressed by the displacement.
Flexibility in piping
To reduce strains in piping caused by substantial thermal movement, flexible and expansion joints may be used. However, the use of these joints may be minimised by arranging piping in a flexible manner. Pipe can flex in a direction perpendicular to its length: thus, the longer an offset, or the deeper a loop, the more flexibility is gained.
Pipe Racks
A ‘pipeway’ is the space allocated for routing several parallel adjacent lines. A ‘piperack’ is a structure in the pipeway for carrying pipes and is usually fabricated from steel, or concrete and steel. Piperacks for only two or three pipes are made from T-shaped member, termed ‘Tee-head supports’.
Piperacks are expensive, but are necessary for arranging the main process and service lines around the plant site. They are made use of in secondary ways, principally to provide location for ancillary equipment.
Pumps, utility stations, manifolds, fire-fighting and first-aid stations can be located under the piperack. Lighting and other fixtures can be fitted to stanchions. Air-cooled heat exchanger can be supported above the piperack.
The smallest size of pipe run on a piperack without additional support is usually 2inch. It may be more economic to change proposed small lines to 2inch pipe, or to suspend them from 4inch or larger lines, instead of providing additional support.
Valves in piping design
Valves are used for these purposes:-
Which size valve to use:-
Nearly all valves will be line size- one exception is control valves, which are usually one or two sizes smaller than line size, never larger.
At control stations and pumps it has been almost traditional to use line-size isolating valves. However, some companies are now using isolating valves at control stations the same size as the control valve, and at pumps are using ‘pump size’ isolating valves at suction and discharge. The choice is usually an economic one made by a project engineer.
Where to place valves
Operating access to valves
Valves Operating Heights
Access to valve in hazardous valves
If there is no P&ID
In this article, you will learn the PLC cooking timer example for kitchen automation using…
Learn an example PLC program to control a pump based on level sensors using ladder…
In the PLC timer application for security camera recording, when motion is detected then camera…
In this example, we will learn batch mixing with PLC ladder logic program using timer…
This PLC example on manufacturing line assembly is an intermediate-level PLC program prepared for the…
In this article, you will learn the PLC programming example with pushbutton and motor control…
View Comments
Thanks mr. Reddy for building such a nice, simple and informative website.
Thank you for your sharing.