Hi
Our today’s topic
Pipe thickness selection calculation of water pipelines

Why we should do pipe thickness calculation?
Many a times, water flows inside pipe at high internal pressure and temperature. The high internal pressure may cause the bursting of the pipe if the pipe thickness is not sufficient. Pipe should be thick enough to withstand that high pressure at that temperature.
From experience we can also assume a pipe thickness. But to optimize the cost and avoid being over-conservative, we should do minimum pipe thickness calculation.
Codes or Standards to be followed (for Straight Pipe under internal pressure) –
ASME B31 is the most recognized standard for piping in the engineering world. They have published piping standards for different services. (For determining wall thickness and stiffening requirements for straight pipe under external pressure, the procedures outlined in UG-28, UG-29, and UG-30 of Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code to be followed)
ASME B31.1– Power Piping
Piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems (more conservative) include but are not limited to steam, water, oil, gas, and air services
ASME B31.3– Process Piping
For piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals
ASME B31.4– Pipeline Transportation Systems for Liquids and Slurries
Piping transporting products that are predominately liquid between plants and terminals and within terminals, pumping, regulating, and metering stations like Hydrocarbons, LPG, CO2, Anhydrous Ammonia, Alcohol etc.
ASME B31.5– Refrigeration Piping and Heat Transfer Components
Piping for refrigerants and secondary coolants
ASME B31.8– Gas Transmission and Distribution Piping Systems
Piping transporting products that are predominately gas between sources and terminals, including compressor, regulating, and metering stations; and gas gathering pipelines
ASME B31.9– Building Services Piping
For piping typically found in industrial, institutional, commercial, and public buildings, and in multi-unit residences, which does not require the range of sizes, pressures, and temperatures covered in B31.1
ASME B31.12– Hydrogen Piping and Pipelines
For piping in gaseous and liquid hydrogen service, and pipelines in gaseous hydrogen service
ASME B36.10M– Dimensional Standard
Standard of dimensions of welded and seamless wrought steel pipe for high or low temperatures and pressures.
In our discussion, we shall use ASME B31.1 & B36.10M. (Actually, in all standards, methodology are same; difference is in factor of safety)

When computing the design pressure for a pipe of a definite minimum wall thickness by this equation, the value of P obtained may be rounded out to the next higher unit of 10.

The terminologies used in the formula are –
tm = minimum required wall thickness, in. (mm)
(This minimum thickness shall be increased by an amount sufficient to provide the manufacturing tolerance allowed in the applicable pipe specification or required by the process. The next heavier commercial wall thickness shall then be selected from thickness schedules such as contained in ASME B36.10M or from manufacturers’ schedules for other than standard thickness.)
P = internal design pressure, psig [kPa (gauge)]
So, the shutoff head = Pump rated head x 1.1
It is the minimum shut-off head. Actual shut-off head will be provided by the pump supplier.
From the minimum value, to get the design pressure for calculation before buying the pump, we use to multiply with 1.5 to be in safe side.
So, the design pressure = Static head pressure at pump suction + Pump rated head x 1.1 x 1.5
Do = outside diameter of pipe, in. (mm)
d = inside diameter of pipe, in. (mm)
S = maximum allowable stress in material at the design temperature, psi (MPa)
(The value of SE or SF shall not exceed that given in Mandatory Appendix A of ASME B31.1 for the respective material and design temperature. )
E = weld joint efficiency (for welded pipe)
F = casting factor (for casting pipe)
A = additional thickness, in. (mm)
(To compensate for material removed in threading, grooving, etc., required to make a mechanical joint, for mechanical strength of the pipe, for corrosion and/or erosion)
y = coefficient
Let us solve a real problem to understand this in a better way
Problem –
Let’s assume there is a tank on the ground floor of a building filled with water.
We have an empty tank on the rooftop of the building at 40m height. We need to transfer the water from the ground tank to the rooftop tank through carbon steel pipe. Temperature of water is 30°C.
The pump flow capacity is 100m3/hr and head is 5kg/cm2. The discharge pipe size is 150NB and the pipe material is ASTM A53 grade A,

свернуть