What is Cryogenic Piping? | Materials and Pipe Supports for Cryogenic Services

Written by Adarsh in Piping Design Basics,Piping Supports

Cryogenic piping refers to the piping network that operates below -29⁰C. This temperature represents the demarcation of embrittlement for carbon steel materials. However, various literature considers the piping systems operating below -150⁰C (-300⁰F) as cryogenic piping systems in the true sense. Industrial processing and transportation of propane, butane (LPG), methane (LNG), ethylene, nitrogen, ammonia, oxygen, etc. require the extensive use of a cryogenic piping system. These piping systems must be designed with special care to work in such low temperatures. In this article, we will explore more details about cryogenic piping.

Properties of Common Cryogenic Materials

Cryogenic materials are odorless, tasteless, and colorless when vaporized. Cryogenic liquids need to be carefully handled as they may cause skin burns and frostbite. Table-1 below lists the liquid temperatures and the liquid-to-gas expansion ratio of some of the common cryogenic materials:

Cryogenic Material	Liquid Temperature (⁰C)	Liquid-to-gas volume expansion ratio
Oxygen	-183	1: 860
Nitrogen	-196	1: 696
Methane	-162	1: 579
Helium	-269	1: 757
Argon	-186	1: 847
Hydrogen	-253	1: 851
Fluorine	-187	1: 888

Table-1: Properties of Common Cryogenic Materials

Why is Cryogenic Piping Challenging?

As the temperature gets extremely low during the operating condition, the material of the pipe faces different types of corrosion and deterioration issues as the chemical and physical properties of the material change. Normal piping systems can’t hold the processing gas in the form of liquid. Also, as can be seen from Table 1, cryogenic liquids generate a large volume of gases when vaporized. So, if they vaporize inside a sealed container, the container can burst due to the enormous pressure. As a result, this cryogenic piping requires a special type of materials, supports, and valves different than that of normal piping systems which makes the design of cryogenic piping systems highly critical and challenging. Some of the cryogenic piping system requirements are:

Sufficient flexibility as with lower temperatures the material contracts creating huge thermal stresses which must be compensated using proper flexibility.
All cryogenic lines are insulated to avoid heat gain from the environment and for safety. All these increase the weight of the pipe making the cryogenic systems more rigid.
Specially designed long-stem, extended bonnet valves are used as Cryogenic Valves.
The use of costly materials increases the project cost. So, every chance of optimization shall be used to minimize the project cost.

Cryogenic Piping Materials

With a decrease in temperature, materials become brittle, and impact test requirement as per code arises. Various parameters need to be considered for selecting cryogenic piping materials like

Suitability for different fabrication techniques
Corrosion resistance
Resistance to oxidation and sulfidation
Strength & ductility
Suitable for the cleaning process
Toughness, resistance to abrasion, erosion, galling, and sizing.
Physical property characteristics
Rigidity
Impact Resistance, etc

Materials that have established themselves as suitable cryogenic piping materials are provided in Table 2 below:

Ferrous Materials
Cryogenic Piping Material	Lowest Temperature (⁰C) for Application
SA-333 Grade 1	-46
SA-333 Grade 7	-73
SA-333 Grade 3	-101
SA-333 Grade 8	-196
Austenitic Stainless Steel (Grade 304, 304L, 321, 347)	-254
Austenitic Stainless Steel (Grade 316, 316L, 316 Ti, 316 Nb)	-196
Non-Ferrous Cryogenic Pipe Materials
Aluminum Alloy (1100, 3003, 5052, 5083, 6061, 5086)	-254
Copper Alloy (C10200/C12200), Copper Nickel Alloy (70600, C71500)	-198
Monel 400	-198

Table-2: Common Cryogenic piping materials

Several non-metallic materials like Grafoil, Mineral wool, Fiberglass, Polyurethane, Styrofoam, Perlite, Viton, Glass reinforced Teflon, etc serve as various components in cryogenic piping applications.

Cryogenic Piping Standards and Cryogenic Piping Design Guide

ASME B31.3 is the main governing standard for designing cryogenic piping systems. The usual cryogenic piping design considerations are:

Pipe Sizing is done using normal pressure drop criteria. A drop in pressure can create flashing of part of the liquid which may result in a two-phase flow. So, if a similar situation arises, the two-phase flow must be considered for sizing. However, for oxygen gas piping, the fluid velocity is also considered during pipe sizing.
As the ambient temperature is hotter than the cryogenic liquid temperatures, there will be continuous heat leaks to the cryogenic pipeline and piping system which must be considered during the design.
Extended stem valves are used to keep the operator at ambient temperature.

Cryogenic Piping Insulation

All frequent-use cryogenic piping and pipeline systems are insulated using any one of the following cryogenic insulation types:

Expanded foams (For example, Foam glass, polyurethane)
Powder Insulation (Example, Perlite)
Vacuum Insulation
Evacuated powder & fibrous insulation
Opacified powder insulation

The main aim of the cryogenic piping insulation system is to create a vapor barrier to keep atmospheric moisture from leaking into the insulation space. This moisture permeates insulation and then condenses. Which significantly increases the corrosion changes in the lines. Also, build-up of water or ice may occur which in turn, results in lowered performance. Whenever the insulation has been compromised, the thermal efficiency is lost and energy consumption increases. So, high energy consumption can be reduced by using adequate insulation materials. the vapor barrier system must keep atmospheric moisture from entering the insulation space and freezing against the cryogenic lines.

Whenever a cold system is required, the entire system shall be fully insulated including the piping components, piping/tubing of instead instruments, drains, equipment nozzle, and supports. Cryogenic insulation is applied in multiple layers.

Cryogenic Piping Supports

As a matter of their extremely low temperature, extremely superior insulation properties, durability, and stable function are required for cryogenic pipe supporting devices. While designing the cryogenic supports we have to consider structural characteristics, design load, other requirements, and economical aspects for each shoe, guide, stop, and trunnion. We must clarify the behavior of cryogenic piping including pipe support, during normal operation they should also take warm-up and cool-down conditions into account. There are problems encountered in the system such as higher displacement due to the thermal expansion and contraction, pipe insulation, embrittlement of materials, icing around or between the supports, and rapid changes of phase due to large heat fluxes.

Cryogenic Pipe Supports shall meet the following requirements.

Lighter weight
High reliability in water & resistance to oil and corrosion
High weather tightness
They must have physical strength against compression, bending, and shearing
Suitable for mass production
Low water absorption
Heat and flame resistance
Must incorporate a molded heavy-density layer bonded with stainless steel.

Cold insulation supports are usually made from:

High-Density polyurethane foam
Phenolic foam insulation
Polyisocyanurate or PIR

Supports shall meet the design requirements in respect of compressive strength under sustained load, thermal conductivity, coefficient of friction, service temperature, and flammability. Even considering the unexpected thermal bowing and fluctuations of flow rate pipe, the support span for cryogenic piping shall be much shorter than that of hot insulated piping, support shall be immediately adjacent to any change in direction of piping.

Cryogenic supports will be equipped with advanced temperature-resistant technology that protects pipes in extreme cold. Cold climates are critical for pipe supports they aren’t built to withstand the elements. Worse yet, pipes are fragile in frigid environments, and ice formation can wear down both pipes and supports, also must be designed to support pipes in temperatures as low as -320°F. They will encapsulate the fragile insulation used in these piping systems.

To stop the thermal transfer from the interior of pipes to surrounding structures they must be nonconductive. Foam-insulated cores are given to some shoes to naturally keep pipes from sudden temperature changes of heat transfer. By keeping heat inside pipes, can save energy and stop the ice formation that can destroy pipes. A cold shoe is a support used for cryogenic applications where the heat transferred to the surface is not relevant and can be used for temperatures right down to -300˚ Fahrenheit.

Cryogenic Piping Stress Analysis

Cryogenic pipelines are a special case where the operating temperature used is extremely lower than the installed ambient temperatures. There should be a degree of rigor that is relevant for the safety of operations and potential hazards and therefore accurate flexibility analysis is very important to manage thermal forces, stresses, and displacements. Some of the Cryogenic piping stress analysis considerations are provided below:

Cryogenic piping systems may have a thermal-bowing effect. So it must be considered. Click here to know more about the use of pipe thermal bowing effect.
If it’s vacuum-insulated piping the two pipes having different displacements are to be considered and connected. The main pipe which is at cryogenic temperature contracts and the jacketed pipe usually at a temperature bit above ambient expands.
Equipment nozzle loads are usually qualified using Finite Element Analysis or FEA.
Expansion bellow or Flexible hoses may be required in the analysis.
Cryogenic pipe systems behave completely opposite to high-temperature piping systems. Due to the contraction of the cryogenic piping system, the supports that are usually lifted off in high-temperature piping carry the load in cryogenic-temperature piping.

LNG Piping and Cold Box Piping systems are typical examples of cryogenic piping systems.

What is Material Selection Diagram? Its Purpose, Development, and Example

Written by Partha Pratim Panja in Engineering Materials,Process

What is a material selection diagram?

A material selection diagram often called MSD in engineering terminology is basically an engineering drawing that shows the basic scheme of a process along with the information for material selection & specification of all the equipment, and lines associated with the process as well as utilities & offsite.

What is the purpose of the material selection diagram?

As we know, in a project, the cost of the materials contributes a major part to the overall project cost. So selection of proper material is a very important parameter. Besides, the important parameter of a project like the overall design, stability, and sustainability also depends on material selection.

As MSD summarizes the related information that is required for material selection of the equipment & piping in process industries so MSD is a necessary document for developing piping material specification (PMS). The piping material specification is an important document by material engineers and it is used for assigning line class/ specification to each line on the P&IDs.

How to develop a material selection diagram?

In the simplest form, an MSD is a drawing that consists of a marked-up or overlaid version of a PFD (process flow diagram). So to develop an MSD you need to have the following documents,

a) Basic Engineering Design Data (BEDD)
b) Simplified Process Flow Diagram (PFD),
c) Material selection information developed by the process team,
d) PFD marked up with proper operating pressure, temperature, design temperature, and pressure.

The content, format, use, and updating philosophy of a material selection diagram must be in agreement with the client and contractor/fabricator/licensor in the preliminary phase of the project.

Besides the above, all main documents and some other suitable standards like API, NACE, corrosion curves, and company standards shall be used as necessary documents for developing MSD

Who develops the material selection diagram?

In general, MSD is prepared by a material engineer or metallurgist in collaboration process engineer. The material engineer responsible for developing MSD must be familiar with the corrosion mechanism of the material, particularly the type of unit being designed.

Information to be shown on MSD

Material of construction used for the equipment & its component, piping network (as per material legend), normally recognized by name or by tag. (See Table: 1),
Chemical injection, corrosion inhibition points,
Corrosion allowances,
Corrosion-resistance cladding of alloy with minimum thickness & side of the components,
Linings/coating for specific internal corrosion consideration,
Prefabricated equipment as “Manufacturer’s Standard”,
A special section of materials, prevention of corrosion, testing requirements in the form of notes (e.g. thermal stabilization, stress-relief [SR] requirements, maximum hardness requirements, velocity limits, etc. The equipment components whose material of construction to be shown are as below,

TYPE OF EQUIPMENT OR PIPING	COMPONENTS	Mandatory/Optional (M/O)
Heat Exchanger (Plate and Frame)	Plates Frame Gaskets	M O O
Heat Exchanger (Shell and Tube)	Shell Channels Baffles/Cages Tubes Tube sheet	M M O M M
Tank	Shell (includes fixed roof and bottom) Floating roof Linings Seals	M O M O
Towers	Shell Trays/ Packing Distributors	M M O
Centrifugal Pumps	API material Class(if applicable) Casing Impeller	O O O
Drums	Shell Boot (if present) Internals	M M O
Piping	Pipe Control Valve Valve trim	M O O
Reactors	Shell Internals	M O
Heater	Radiant tubes Convection tubes Hangers	M M O
Air Cooler	Headers Tubes Plugs (if different)	M M O

Table: 1 List of Equipment Components

MOC for supplementary components like special gaskets, seals, etc should be identified on MSD. Additional components like bolting, impingement plates, and vessel trims may be included based on factors such as whether the materials are covered in other sites, projects, or company work practices.

Material Designations

Materials should be designated by standard formats e.g. CS or UNS (unified numbering system), 316 SS. Another specification is ASTM (e.g. A516, A351), DIN (Deutsches Institut fur Normung), etc. Generally, using specific material specifications (e.g., ASTM, ASME, and DIN) is acceptable in agreement with the client and contractor. There is a legend that should be used in each MSD. A typical example of a legend is tabulated in Table: 2.

MSD	UNS Designation	Full Designation
CI		Cast iron
DI		Ductile iron
CS	K02504, K02401, K03006	Carbon steel
LTCS		Low-temperature Carbon steel
1-1/4 Cr	K11562, K11756	1 ¼ Cr- ½ Mo
2-1/4 Cr	K21590	2 ¼ Cr-1 Mo
5 Cr	K21590	5 Cr- ½ Mo
9 Cr	K81590	9 Cr-1 Mo
12 Cr	S40500 (405 SS), S41000 (410 SS), or S41008 (410S SS	12-13 Cr steel
304L	S30403	304L SS
316L	S31603	316L SS
321	S32100	321 SS
347	S34700	347 SS
310	S31000	310 SS
2205	S32205/S31803	22% Cr Duplex SS
Alloy 20	N08020	Alloy 20
6% Mo	S31254, N08367, N08926	Super austenitic SS with 6% Mo
800	N08800 (alloy 800), N08810 (alloy 800H), or N08811 (800HT)	Alloy 800
825	N08825	Alloy 825
625	N06625	Alloy 625
276	N10276	Alloy 276
400	N04400	Alloy 400
Adm	C44300, C44400, C44500	Admiralty brass
NRB	C46400, C46500, C46700	Naval rolled brass
70/30	C71500	70/30 Cu-Ni
90/10	C70600	90/10 Cu-Ni
Ti-2	R50400	Titanium grade 2
Ti-12	R53400	Titanium grade 12

Table: 2 Material Designations

Format of Notes & Contents

General Notes: These are the notes which are applicable to the whole process unit & must be labeled with a discrete letter on all MSDs. These should be repeated in a similar order using the same letter on all MSDs.

Specific Notes: These notes are specific to the specific equipment, piping component, or location on the MSD. This note should be identified with a discrete identifying letter and generally follow the general notes on the corresponding MSD page (if MSD is more than one page).

The below table (Table: 3) is the list of commonly used nomenclature that is generally used in the process industry,

Nomenclature	Actual Meaning
B	Baffles
C	Casing
CA	Corrosion allowance
CH	Channel
H	Header
IMP	Impeller
INJ	Injection point (e.g. wash water, chemical)
INT	Internals
PWHT	Post-weld heat treatment for service or material. (Design code requirements for PWHT based on thickness must also be met, but are not typically identified on the MSD.)
SH	Shell
SR	Stress relief
T	Tubes
TS	Tube sheets

Table: 3 List of Nomenclature

Requirements of special materials shall be shown in MSD, normally in the specific note region. The typical example of special requirements is as follows,

-Alloy 20 or alloy 825 drains in SS reactor,
-Higher content (>2.5%) of molybdenum for type 316L SS in cold, used in seawater, naphthenic acid service,
-Maximum limit of strength on CS used in LPG sphere,
-Welds & thermal stabilization of base materials for type 321 SS or 347 SS that is operated more than 427ᵒC,
-Seals & gaskets used for MTBE (methyl tert-butyl ether) service, etc.

Corrosion Allowance

Corrosion allowance is a driving parameter for material selection for construction, especially for the equipment which is operated at high pressure. So defining the CA plays a very important role. A certain acceptable CA shall be shown on the MSD for every component excluding pump casing or when the client defines only a minimum CA for a specific material that must be written as a general note.

Process data to be shown on MSD

The process data used for materials selection must be indicated on the MSD. These process data may vary unit-wise. Examples of some typical process data (as applicable), including contaminants & corrosive agents which have the potential ability to affect materials selection, include:

– Operating temperature
– Operating pressure;
– Hydrogen partial pressure
– MDMT
– H₂S, CO₂ concentration, or partial pressures
– Sulfur, Free water, Ammonia, Chloride concentrations
– Water dew point
– Phase (Liquid, vapor, or mixed phase)
– Amine type, strength, and acid gas loading
– Total acid number (TAN) or neutralization number
– pH
– Critical corrosion velocity limits
– Short-term operating conditions that could affect materials selection.

The source of the process data e.g. pH, hydrogen partial pressure, H₂S concentration, etc, may be found in heat & mass balance. These data can be represented in a separate sheet. If so, the page number & revision of information shall be shown in MSD.

Guideline on completing Material Selection Diagram

MOC & CA should be decided on the basis of predicted corrosion rate or material degradation rate under influence of all process variables e.g. stream composition, velocity, temperature & pressure, and the design life of the specified component.

-Most cases the maximum normal operating condition is used to decide the materials. Design temperatures & pressures are not usually used to calculate predicted corrosion & degradation mechanism.
-In some environments, huge corrosion or degradation of materials can occur when normal operating condition is exceeded. So the effect of short-term conditions on MOC needs to be considered. Examples are Alternate operations (presulfiding, catalyst regeneration), No flow (power failure, steam-out, cleaning, etc), Start-up & shut down, Upsets & emergency conditions, start of run (SOR) & end of run (EOR) conditions.

Material Selection Diagram Sample

The below figures (Fig. 1, Fig. 2, and Fig. 3) show a sample of the material selection diagram examples:

**Fig. 3: Typical Material Selection Diagram**

Underground Piping Insulation

Written by Adarsh in Engineering Materials,Piping Design Basics

In refineries, chemical, and petrochemical industries we frequently find that pipes are insulated. All of these pipes are aboveground. So, sometimes a question arises in mind “does the underground pipe need to be insulated?”. Underground or buried pipes sometimes require insulation and sometimes do not. In this article, we will explore more regarding underground piping insulation.

Examples of Underground Piping Systems

Underground pipes are laid below the grade line. Common examples of underground pipes are:

– Cooling water (with line sizes normally ≥18″ NB)
– Fire-Water
– Contaminated Rainwater Sewer from the process catchment area. (CRWS)
– Oily Water Sewer (OWS)
– Liquid Effluent that runs to the Effluent Treatment Plant.
– Closed Blow Down system (CBD)
– Sanitary system
– Storm Water
– Equipment drainage to slop tank
-Fuel oil piping
-Water, Crude, Gas, or Oil Pipelines

The following materials are used commonly for the construction of piping systems & their advantages over the fabrication of underground pipe are listed below:

Carbon steel—closed-drain systems, cooling water, and fire water
Stainless steel—closed drains—chemical and corrosive service
Cast iron—used for oil-water drains and stormwater (hub and spigot fittings)
Ductile iron—used in Process water (its stress value is higher than that of cast iron) (hub and spigot fittings)
Concrete pipe—surface drainage, and for 15″ and bigger pipes
Fiberglass-reinforced plastic pipes— These mostly are used for low-temperature, corrosive service, and pressure systems.
PVC—corrosive service
Vitrified clay pipe- These gravity drain systems can’t be used under roads or even when subjected to significant loads (the maximum operating temperature for them will be 200°F/93°C)
Glass Pipe—used main for floor drains in process plants, usually acid service

Most of the above-mentioned lines are normally low-temperature lines. They do not carry fluids that are either cryogenic or have very high temperatures similar to above-ground piping systems. So, in principle, buried or underground pipes do not need to be insulated similarly to aboveground piping systems.

However, moisture and corrosion are constantly threatening the underground piping. Even though corrosion-resistant coatings are applied on the pipe surfaces, still the exposure to water and chemicals in the soil creates many problems in the buried system. Insulating the underground pipe with the correct materials can provide an additional measure of protection for them. This is one of the main reasons for insulating underground piping. Also, sometimes chilled district cooling systems and steam networks are laid underground which needs insulation.

Purposes of Underground Piping Insulation

The major benefits that an insulated underground piping system provides are:

It keeps the system safe. A properly insulated underground piping can prevent condensation, energy loss, vapor leaks, and temperature regulation.
Underground piping insulation preserves the pipes by restricting direct contact from moisture and corrosion. It increases the operating life span of buried pipes.
As the buried insulation faces the soil and corrosive environment, the main pipe does not suffer major problems. Hence, the maintenance and repair action reduces. The underground insulation gets damaged but they are cheaper as compared to the primary pipe. So, there is a huge saving in the budget over the complete span of the pipe.
Reduces heat loss from pipes.
Prevents the freezing of the liquid it carries through the pipe.
Prevents direct contact with unlike metals that would cause electrolyte action.
Prevents contact with concrete and other materials that can damage the parent pipe surface.

Underground Pipe Insulation Materials

The leading product under underground use is the Armaflex Tuff coat as it has high water vapor diffusion resistance and low thermal conductivity. Armaflex class o nitrate foam – this insulation is the industry-leading underground insulation. That consists of an additional wrap-around self-seal plastic coating.

Mineral powder insulation, perlite insulating concrete, gilsulate, and cellular glass insulation are some of the other examples of excellent insulating materials for underground piping systems.

In general, all underground piping insulation materials should possess the following properties:

Good mechanical strength for direct burial.
High corrosion resistance (Resistance against soil moisture and soil acids)
Long-term insulation efficiency

Factors affecting the selection of Underground Piping Insulation System

The design and selection of an ideal underground pipe insulation system depend on factors like:

Type of piping or pipeline system: hot or chilled water, steam, or other
Operating temperature of the fluid that the main pipe will carry
Pipe OD and length
Depth of pipe cover
Soil type, bearing strength, electrical potential
Location of water tab
Road Crossing and Traffic load, etc

Some piping systems in the ground are required to be double-walled or secondarily contained. There will be a primary pipe and there will be a secondary pipe over the primary pipe and the purpose of that is to if the primary pipe systems fail, they are a backup plan or another layer of pipe to contain it.

Sometimes, underground pipe jacketing is also widely used in place of buried insulated piping.

Can pipe insulation be buried?

Placing the insulated piping and pipeline systems underground is one of the most practical methods of underground piping system installation. The need for costly tunnels is eliminated by this process which in turn, speeds up the buried piping installation.

What is a Pre-insulated underground pipe?

Pre-insulated underground piping systems provide a better solution by avoiding the challenges of installing insulation. There are various options available for pre-insulated underground pipe systems. They are strong and durable and can work over a variety of temperature ranges.

What is a Fire Hydrant? Its Types, Working, Components, and Color Coding

Written by Anup Kumar Dey in Health & Safety

A fire hydrant is a visible connection point placed in defined locations for firefighters to tap into a water supply. All buildings, parking areas, roadsides, mines, industrial areas, etc. must have fire hydrants with a connection to a water service network. They are designed to provide the water required by firefighters instantly to fight and extinguish a fire. Till the 18th century, underground fire hydrants were used. However, from the 19th century onwards, above-ground pillar-type fire hydrants become popular and mostly used. A fire hydrant is basically a pipe with the control of a valve through which water flows from a water main in order to put out a fire.

Purpose and Uses of Fire Hydrants

The primary purpose of fire hydrants is to supply water for suppressing fire. However, they can be used for several secondary purposes like:

Line Flushing: Due to their high flow capability and easy operation, fire hydrants can be used to flush main distribution system lines.
Testing System: To test the hydraulic capacity of the distribution system, fire hydrants can be used.
Other Common uses: Fire hydrants are also frequently used as a water source for commercial construction work, sewer cleaning, street construction, street cleaning, etc.

Working of a Fire Hydrant

Fire hydrants with a variety of valves and connection points are seen in many places. In the event of a fire breakout, firefighters locate the fire hydrants, connect their hoses and then pump a large volume of pressurized water to put out the fire. A special pentagonal wrench is used to remove the valve cover of the hydrant. Then after attaching the hoses, the firefighters open the valve for the water to flow.

They usually have a connection point to hook up a fire hose and a nut or bolt to turn on which will start the flow. Every fire hydrant is essentially just an attachment to the main water line. Underneath that connects the hydrant valve through a pipe called a riser. However, normal hydrants don’t change the water pressure or flow in any way. They function as valves so firefighters can utilize the already present pressure in the water pipes. While all of this may sound simple the internal mechanics of a fire hydrant are a little more complex and can vary by region.

Types of Fire Hydrants

There are two types of Fire Hydrants; Wet hydrants and Dry hydrants.

Wet Hydrant

Wet hydrants are widely used in places where there is no problem of freezing. In such types of fire hydrant systems, the water in the main supplies the hydrant close to the surface. So, in cold weather conditions, it is susceptible to freezing.

Dry Hydrant

A dry hydrant system stores the water below the ground. The Earth’s temperature is usually higher than the cold environment temperature in cold regions. So, the possibility of freezing can be prevented by this arrangement. When the dry hydrant system is required to be used, firefighters open a valve on top of the hydrant and engage their hose in it. This causes the drain valve to open inside the hydrant. This allows the water to come through which the firefighters use against the fire.

Difference between Wet barrel Hydrant and Dry barrel Hydrant

The main differences between a wet hydrant and a dry hydrant are mentioned below:

Wet Hydrant or Wet Barrel Hydrant	Dry Hydrant or Dry Barrel Hydrant
Wet Hydrants are used where water-freezing issues are not present	Dry barrel hydrants are used in cold regions where the temperature routine drops below water freezing temperature.
In the wet hydrant design, the water is placed aboveground	The water in the dry barrel design is kept below ground to avoid freezing.
A wet Hydrant is easier to construct and cheap.	On the other hand, dry barrel hydrants are costlier and difficult to construct.
Maintenance of wet barrel hydrants is easier due to easy access.	Maintenance is comparatively difficult.

Table 1: Wet Barrel Hydrant vs Dry Barrel Hydrant

Components of a Fire Hydrant System

The main components that constitute a fire hydrant system are:

Fire Fighting Pumps & Accessories
Piping
Panels
Landing Valves
Hoses
Couplings
Hose Reel
Branch Pipes & Nozzles
Fire Brigade Connections
Wiring & Instrumentations
Maintenance Valves

Color Coding of Fire Hydrants

Following NFPA standards, all fire hydrants are color-coded. These colors indicate the expected flow during the operation. Usually, the top caps of the fire hydrants are painted. The following table provides the common colors according to the flow.

Color-Coding	Flow	Meaning
Light Blue/Blue	>1500 GPM	Very good flow, suitable for industrial applications.
Green	1000-1500 GPM	good for residential purposes
Orange	500-999 GPM	marginally adequate
Red	<500 GPM	Low flow, inadequate

Table 2: NFPA color coding of fire hydrants

Codes and Standards of Fire Hydrants

The codes and standards that are used as guidelines for designing fire hydrant systems are:

NFPA 1
NFPA 25
NFPA 291
AWWA
A112.21.3M
BS EN 14384
BS 750
DIN 3222
DIN EN 14339
AS 2419
FP-009
IS 3844
IS 13039

Fire Fighting System Online Courses

To learn more details about fire fighting systems, their operation, application, etc you can join the following online in-depth video courses:

Basic Fire Fighting
Fire Safety: Become A Fire Safety Expert
Fire Safety Master Course: The Untold Secrets Of Fire Safety
Design Fire-Fighting Systems
Become A Fire Protection Design Engineer – Basic to Advanced

Hydraulic Calculation Guidelines

Written by Partha Pratim Panja in Process

1. What is the purpose of hydraulic calculation?

A hydraulic calculation is performed for the pump, compressor, control valve, and piping system. These are the most commonly used equipment & instruments in the process industries. The main objective of hydraulic calculation is to provide criteria & minimum requirements for the selection of pumps, compressors, and control valves to develop the process datasheet. As to procuring pumps, compressors & control valves, it is necessary to convey all the process information to the respective vendors in form of a process datasheet. If specific instructions are given in the project specifications that should have precedence over the requirements given in these guidelines.

The hydraulic calculation can be done at the different stages of a project e.g. at a preliminary stage, at the detail engineering stage also after issuing isometric drawings.

2. Steps for Hydraulic calculation

For hydraulic calculation, a Hydraulic circuit needs to be built prior to hydraulic calculation. Also, you need to gather the required data (refer to 2.1) prior to doing hydraulic calculation you need to follow the below steps:

Step-1, Select the loop whose hydraulic calculation needs to do.
Step-2, Mark up the hydraulic loop in PFD and then in P&ID.
Step-3, Draw the hydraulic loop in respective software (as the different companies use different software).
Step-4, Every element across which pressure drops like flow meter, strainer, heat exchanger, dryer, control valve, F.O., etc should be shown in the hydraulic circuit to calculate endpoint pressure in each and every segment.
Step-5, Put the flow rate, physical properties, nominal diameter, roughness factor, equivalent length, etc in each pipe segment.
Step-6, Run the model.
Step-7, Check & evaluate the result of the hydraulic calculation.

2.1 What are data required for hydraulic calculation?

The data to be used for the hydraulic calculation, such as the flow rate, temperature, pressure, and so on should be clarified as follows. The design data will be obtained from, but not limited to, the following documents;

Process Flow Diagram (PFD)
Basic Engineering Design Data (BEDD)
Piping & Instrument Diagram (P&ID)
Heat & Material Balance (H & MB)
Plot plan
Equipment datasheet
Piping material specification

Input Data for hydraulic calculation

The following is a summary of input data to be prepared before the hydraulic design.

(1) Operational data required in the hydraulic calculation

– Service for identification
– The fluid name for identification
– From-To for identification
– Flow rate(s) of liquid and/or vapor
– Temperature
– Pressure
– Physical properties

For Liquid service: Density, Viscosity, Vapor pressure, Critical pressure, SpGr @15°C

For Vapor service: Density, Viscosity, Molecular weight, Specific Heat Ratio (Cp/Cv)

Compressibility Factor (Z)

Two-phase flow: Densities and Viscosity for both liquid and vapor

(2) Construction data in the hydraulic calculation

– Line Class
– Elevation at the inlet and outlet of the piping system.
– Distance between source and destination.
– Instruments, types, and quantities
-Different Valves & fittings, types, and quantities.
– Control valve(s)
– Pump(s), compressor(s) and blower(s)

(3) Design requirement in the hydraulic calculation

– Pump NPSH_available
– Over design % – specification of the design flow rate, if any
– Turndown % – specification of the minimum flow rate, if any

3. Hydraulic Calculation & Formulas

3.1 General:

(1) As we know, pumps’ & compressors’ capacity, power & requirements of head depend on the frictional pressure drop imparted by the associated piping system. So in a hydraulic calculation, the whole loop needs to be developed as per P&ID. Pressure losses through the pipeline should be carefully calculated. As the main parameters that are used to check are pressure drops & velocity. If it has been observed in a hydraulic calculation that the pressure drop & velocity exceed the limiting criteria given in the project criteria then line size can be increased & it is subjected to the client’s approval. The basic principle to fix the line sizes should be based on an economical point of view, i.e., minimizing the sum of operational costs and investment.

3.1.1 Basic Principle for Line Sizing used in Hydraulic Calculation:

(1) The basic principle to fix the line sizes during performing hydraulic calculations should be based on an economical point of view, i.e., minimizing the sum of operational costs and investment.
(2) However, line sizes should not exceed the limitations given in project specifications
(3) In some instances, the process requirements will take precedence over the economical aspects; for example, in the case of pump suction lines where the NPSH is the main concern.
(4) In revamping or modification projects of the existing plant, the fluid velocity is more likely to be increased than in new installation projects.

3.1.2 Pressure drop Calculation formula used in Hydraulic Calculation:

(1) Frictional pressure drop shall be calculated using the Darcy-Weisbach equation as follows:

Here,

ΔP= Frictional Pressure drop
f= Moody’s friction factor
L_e= Equivalent length
S2= Unit conversion factor.

(2) For laminar flow (Reynolds number below 2000) the friction factor can be calculated as f=64/Re, Here f=friction factor.

(3) For turbulent flow (Reynolds number above 4000 the friction factor can be calculated using an equation developed by Colebrook correlation as given below:

Where, ɛ=pipe inside roughness, unless otherwise specified the roughness of commercial steel pipe can be taken as 0.0457 mm.

The following are typical fluids in this category.

– General hydrocarbon
– Chemically treated water such as cooling water, boiler feed water, etc.

(4) Hazen and William’s empirical formula shall be applied in a hydraulic calculation, taking Hazen and Williams as

Where

h_f= Frictional head loss, m
L_e= Equivalent length, m
C = Friction factor
Q = Flow rate, m³/Sec
D = Pipe inside diameter, m
S₃ = Unit conversion factor, 0.002125

The formula can be used for any liquid having a viscosity in the range of 1.13 centistokes which is the case for water at 15 °C. Friction factor C = 100, for the following service;

– Seawater, flowing in an untreated inner surface pipe
– Oxygen-contained and chemically untreated water such as drinking water, industrial water, etc, flowing in an untreated inner surface pipe

(5) Compressible Gas flow formulae used in the hydraulic calculation

For Low-pressure drop service: For estimating pressure drop in short runs of gas piping, Darcy-Weisbach’s formula described above is applicable and accurate, assuming pressure drop through the line is not more than 10% of the total pressure (GPSA Engineering Databook, Section 10).

For High-Pressure drop service, in ordinary gas piping, the flow is closer to adiabatic than truly isothermal. The pressure drop of adiabatic flow can be calculated using the following equations:

Equations for pressure drop of adiabatic flow — **Equations for a pressure drop of adiabatic flow**

Here,

P = Pressure (N/m2)
T = Temperature (°K)
N = Pipe resistance factor
u = Velocity (m/s)
a = Sonic velocity (m/s)
M = Mach number = u/a
Y = Mach number factor
f = Moody friction factor based on average viscosity
D = Pipe diameter (m)
L = Pipe length (m)
k = C_p/C_v, specific heat ratio (-)
R = gas constant= 847.9/molecular weight ((kgf/m2) ・m3/kg-mol・°K)
Subscript 1= Inlet & 2=Outlet. i= 1 or 2

Calculation procedure

Step-1: Assume downstream conditions (P2, M2, T2)
Step-2: Calculate M1 by equation (3) as a trial and error method.
Step-3: Calculate T1 by equation (4) with M1 from Step 2.
Step-4: Calculate pressure drop by equation (5) with M1, T1 from Step-2, 3.
Step-4: If P1 calculated is equal to the given inlet pressure, the calculation can be terminated. If not so, return to Step-1 with new assumed conditions.

3.2 Standard Pipe Data:

3.3 Limitation of Line Size:

The lines should be sized within the limitations tabulated below (see Table 1)

Fluid	Erosional Velocity	Sonic Velocity	Noise Velocity	Minimum Velocity	Flow pattern	Special requirement
Liquid-General	Yes					Yes
Liquid-at boiling point	Yes					Yes
Gas or vapor		Yes	Yes
Gas/Liquid	Yes				Yes
Steam condensate	Yes				Yes
Slurry	Yes			Yes		Yes
Steam		Yes	Yes

Table-1: (Limiting parameter)

3.3.1 Erosional Velocity formula used in Hydraulic calculation:

(1) The velocity above which erosion may occur in gas/liquid two-phase flow can be determined using the following empirical equation. V_e= C_e/√ρ_m, where, V_e =Erosional velocity, ρ_m=Homogeneous density, C_e = Empirical constant normal in the range of 180-240.

(2) Water piping: The maximum velocity should be less than the values given below,

Mortar or concrete 3.0 m/s
Mortar lining seal coat with paint 5.0 m/s
Steel cast iron or PVC 6.0 m/s

(3) Amine Solution:

The velocity in the Amine process should be less than the following;

Carbon steel
- Liquid 3 m/s
- Vapor 30 m/s
Stainless steel
- Liquid 9 m/s
- Vapor 36 m/s

3.3.2 Sonic Velocity formula used in Hydraulic calculation:

(1) The maximum velocity shall be less than 50% of the sonic velocity for continuous gas or vapor services.

(2) For intermittent services, such as pressure relief valve discharge piping, 80% of sonic velocity may be acceptable. Care should be taken over the back pressure limitations.

(3) The sonic velocity can be calculated as follows.

**Equation of Sonic Velocity Calculation**

Where,

V_sonic= Sonic velocity (m/s)
g_c = Gravity conversion factor (kgf・m/kgf・s2)
k = Specific heat ratio = Cp/Cv
R = Gas constant = 847.9 (kgf/m²)(m³)/(kg-mole)(°K)
T = Temperature (°K)
M = Molecular weight

(4) When pressure drops across the valve is relatively high, e.g. steam injection, nitrogen header, and so on, check the sonic velocity for valve downstream piping.

3.3.3 Slurry Line:

(1) Cycle oil The minimum and maximum velocities for cycle oil containing catalyst fines shall be as follows;

Minimum velocity 1.1 m/s
Maximum velocity 2.1 m/s

(2) Other services

If practical, flow velocity should not be less than 0.9 m/s to minimize the deposition of solids. [API RP-14E 2.3a – 1991]. The maximum velocity should be lower than the erosional velocity, which will depend on the fluids and processes. Therefore the erosional velocity will be provided by the process licenser.

3.3.4 Two-Phase Flow Pattern:

(1) The estimation method of pressure drop and flow pattern for gas/liquid two-phase flow in the hydraulic calculation is based on the following:

Pressure drop: HTFS method
Flow pattern: TULSA university method

(2) Flow patterns

The flow pattern is determined using the method developed by TULSA university which is based on the Taitel and Dukler method. Also, this method is applied in HTFS Handbook TM2 (Aug. 1986).

(3) The flow pattern map with the definition of coordination is as follows:

Flow pattern in two phase flow — **Flow pattern in two-phase flow**

The flow pattern is defined as follows:

Bubble flow: The gas phase is distributed as discrete bubbles in a liquid continuum. The bubbles tend to flow in the upper part of the pipe.
Stratified flow: The separation of the liquid & gas phase is complete; the liquid is flowing at the bottom of the pipe and the gas at the top.
Wavy flow: As the gas velocity is further increased in stratified flow, surface waves begin to build upon the liquid layer.
Slug flow (Intermittent flow): As the gas velocity is further increased in the wavy flow region, the waves become big enough to reach the top of the pipe. These waves are propagated by gas at high velocity, often have a frothy nature, and are referred to as “slugs”.
Annular flow: As the gas velocity increases still further, the slugs no longer occur and the flow becomes essentially annular but with a thicker film at the bottom of the pipe than at the top.

3.3.5 Guideline for Line Sizing in Hydraulic calculation:

The final line size shall be determined in the hydraulic Calculation. In order to minimize rigorous analysis, the following guidelines are useful for practical line sizing. Tables 2 to 4 show the practical pressure drops and practical velocities for each service.

Service	ΔP₁₀₀( kgf/cm2/100m)	V_practical(m/s)	Remarks
Pump Suction -Boiling point liquid -Subcooled Liquid	0.05 0.08
Pump Discharge -Carbon steel -Stainless Steel	0.15 1.5
Column draw-off	0.05	1.0
Liquid to reboiler	0.05
Liquid to CV at BP	0.05
Gravity flow -general service		1.0

Table-2: Pressure drops and practical velocities for Liquid Service

Service	ΔP₁₀₀(kgf/cm2/100m)	V_practical(m/s)	Remarks
Atmospheric / Vacuum 10 kgf/cm2G and below 100 kgf/cm2G and below Over 100 kgf/cm2G	0.01 – 0.07 0.07 – 0.20 0.20 – 0.70 0.7% of P_op
Reboiler return -Kettle type -Thermosyphon type -Furnace type	0.02 – 0.05 0.02 – 0.05 0.18
Compressor suction -Reciprocating -Centrifugal	0.0-0.5	12 Economic velocity

Table-3: Pressure drops and practical velocities for Gas and Vapor Service

Service	ΔP₁₀₀(kgf/cm2/100m)	V_practical(m/s)	Remarks
Instrument, plant air Atmospheric Up to 3.5 kgf/cm2G Up to 7.0 kgf/cm2G Up to 10 kgf/cm2G	0.05 0.07 0.11 0.13
Saturate steam -Below 7 kgf/cm2G -Above 7 kgf/cm2G	0.20 0.45	40 – 60 30 – 50
Superheat steam -10 kgf/cm2G and below -100 kgf/cm2G and below	0.07 – 0.20 0.20 – 0.70	Max. 75
Steam condensate: Upstream of steam trap or control valve	0.05
Steam condensate: Downstream of steam trap or control valve	0.2-0.7	25
Cooling Water	0.3	1-4
Sea Water		1-4

Table-4: Pressure drops and practical velocities for Utility Service

3.4 Equivalent Length of piping

3.4.1 Estimation of Equivalent Length for Hydraulic Calculation:

(1) Equivalent length of piping: Equivalent length should be taken from the piping layout if it is not available, the length should be taken from the plot plan, and the equivalent length (Le) of the piping will be estimated based on the straight length (Ls) as follows:

Process area: 3.0 times Straight length (can be changed as per project specification)
Lines on the pipe rack: 1.5 times of straight length for temperature greater than 100ᵒC & 1.2 times of straight length for temperature lower than 100ᵒC (can be changed as per project specification).

It is advisable to count the number of elbows, tees, and valves and evaluate the equivalent length, assuming piping layout for large-size or high-pressure piping.

(2) Pump suction line: When the piping layout is not available, the equivalent length of the pump suction line should be assumed as 50 m minimum for process pumps and utility pumps.

(3) Expansion loop: Thermal expansion loops are normally set for lengthy and high-temperature service lines such as an HP steam line and flare line. Since expansion loops increase equivalent length considerably, confirm the Piping Section for the expected numbers of pressure balance is tight under selected pipe size.

3.5 Pressure Drop Data

3.5.1 Pressure Drop of Instruments for Hydraulic Calculation:

(1) If the estimated pressure drop is available for the instrument, use it in the hydraulic calculation. If not, use the allowable pressure drop.

(2) If pressure drop data for an instrument is not available, data (for low viscosity service) may be assumed as follows:

Flow orifice 0.2 kgf/cm2
Venturi tube 0.02 kgf/cm2
Rotameter 0.2 kgf/cm2
Positive displacement meter 0.6 kgf/cm2 (strainer included)
Turbine meter 0.5 kgf/cm2 (strainer included)

(3) For high viscosity service (μ > 1cP) or non-Newtonian fluid, the pressure drop shall be calculated or evaluated from the available sources such as vendor information.

3.5.2 Pressure Drop of Piping Components for Hydraulic Calculation:

(1) Pump Suction Strainers

The pressure drop of a permanent strainer should be taken as follows.

0.5 m for dirty service
0.3 m for clean service

3.5.3 Pressure Drop of Equipment for Hydraulic Calculation:

If estimated pressure drop data for the equipment are not available, the pressure drop for low viscosity service may be assumed as follows:

Heat exchangers 0.3 – 0.7 kg/cm2
Air coolers
- 0.3 – 0.5 kg/cm2 for clean service
- 1.0 – 1.5 kg/cm2 for fouled service
Filters 0.7 kg/cm2

3.5.4 Pressure Drop of Control Valve Hydraulic Calculation:

Normally the following criteria for the control valve are used during hydraulic calculation.

(1)A control valve DP shall be determined as greater values of the following,

-Minimum 0.7 kg/cm² on pump loop
-8 % of pump discharge
– [(1.1135 x (maximum flow/normal flow))²-1] x ΔP_friction, where the ratio of maximum flow rate to normal flow rate is overdesign factor
– 33% of ΔP_friction

3.6 Hydraulic Circuit & Calculation Sheet

The below figure shows a hydraulic circuit,

(2)The following data sheets should be prepared as a result of the hydraulic calculation.

– Hydraulic flow diagram
– Pressure balance
– Flow pattern for two-phase flow

(2) The data sheet shall include the following information.

-Line sizes, Source equipment (its pressure and elevation), Pump suction and discharge pressure, equipment in the pump discharge line, their inlet pressures and pressure drops, inlet and outlet pressure of control valve, Destination, its pressure, and elevation.

(3) The following parameters should be evaluated based on the hydraulic calculation results.

– Design pressure, operating pressure, line classes, nozzle size of equipment, equipment elevation, etc.

The below figure represents an example of a hydraulic balance sheet,

pumps & line calculation sheet — **Pumps & line calculation sheet**

4. Hydraulic Calculation Software Programs:

In the earlier days, hydraulic calculation has been performed in excel-based calculation sheets. But nowadays, various software has been developed for error-free hydraulic calculations. These software programs also save man-hours and perform the calculation faster. Common Hydraulic calculation software programs that are used widely among the EPC industries are:

HRS System,
Hcalc,
Mensura Genius,
AFT Fathom,
Hytos,
Hydratec,
Fluidflow
PASS/Hydrosystem,
Pipenet,
Flomaster,
Flownex, etc

Online Video Courses on Process Hydraulics and Hydraulic Calculations

The following online video courses are extremely useful to learn and get an in-depth knowledge of Process Hydraulics and Hydraulic Calculation:

Fluid Flow | Flow through Pipes| Effects of Fluid Properties on the Piping System

Written by Adarsh in Mechanical,Piping Design Basics,Process

What is meant by Fluid Flow?

Fluid flow describes how fluid behaves when in motion. It is a vital engineering perspective and studied in hydraulics and fluid mechanics. The theory of fluid flow is very important for effectively sizing piping and equipment.

What is a Fluid?

Any substance which can flow is called fluid. Liquids, gases, or a mixture of both of them are collectively called fluids. They contain a finite mass, occupy a space, and are tangible. They are substances that are either made up of different molecules or particles. They are flowing when the particles of the substance have a change in the relative position concerning time. The properties acquired by the fluids are

It does have a mass of its own.
It doesn’t have shapes.
It occupies the shape of the vessel or pipe where it is flowing.
It can flow under its weight.

Mechanics is the study of force and its effects. The forces that act on the fluid are

Surface force
Body force ( gravitational force)

Fluid Flow inside Pipeline

Flow-through pipes or fluid flow is a type of flow within a closed conduit with a certain pressure. Another type of flow is an open channel flow. These fluid flows are applied to transport chemicals, petroleum products, gas products, sewage flows, household water supply, etc. in different piping and pipeline systems.

The flow of all Real fluids is termed viscous flow (as they possess a viscosity) These properties of viscosity are characterized by the shear stresses or the frictional forces between the fluid layers and fluid to a solid surface, the same as the physical parameters of the pipe & the external force’s affecting the piping system by displacement and loads. The fluid’s flowing and flow parameters affect the piping system in many ways.

How does Fluid flow in Pipes?

Whenever the fluid is flowing, there will be an energy that causes the fluid to flow. There are three different types of energy within the flowing fluid – flow energy (pressure head), kinetic energy, and potential energy. There are basically two causes that make a fluid flow through a pipe.

Tilting the pipe’s so that the flow becomes downhill, in this scenario where the gravitational energy transforms itself into kinetic energy.
The second way is to make a pressure difference created through different types of pumps By applying the pressure at one end of the pipe greater than the pressure at the other end. Pumps use impellers, which are connected to the motor to accelerate the fluids into the discharge line. Which makes the flow rate inside the system. The pump doesn’t decide what pressure and flow rate it will deliver to the piping system connected it to.

Pipe Flow Calculations

Flow rates through pipes

The flow rate (discharge) is termed as the volume of the fluid which passes per unit of time, through the pipes. ie, area of pipe*velocity at which fluid flows through the pipe (unit-m³/s).

Types of Fluids

The two types of flow through a pipe can be classified as laminar or turbulent flow. The non-dimensional number, Reynolds number (Re), is used to determine the type of flow-through pipes.

Laminar flow: When the fluid moves slowly in layers in a pipe, without much mixing among the layers. usually occurs when the velocity is low / the fluid is very viscous. The maximum flow will be at the center of the pipes and the minimum flow at the pipe walls. (Refer to the Fig. 1 below)

Turbulent Flow: When the velocity of the flow exceeds some threshold value for a given fluid in a pipe, ie. when the velocity is high. flow becomes turbulent, the fluid becomes irregularly fluctuating with time. The velocity at the center of the pipe is approximately equal to the average flow velocity.

Usually, in piping analysis, the flow assurance activities can be founded using the surge analysis software- like the AFT impulse, AFT Fathom, Bentley water hammer, etc. To know the flow rates, pressure, and velocity in piping systems AFT Fathom is commonly used.

Impact of Fluid Properties on Flow through Pipes

The properties of the fluid have a great effect on the piping system where it is flowing.

Considering the density (mass/unit volume), whenever the fluid density is more the mass will also be high making the system compact and dense.

As the viscosity of the fluid increases, we have to adjust the performance of the pumps to equal it up for the additional shear resistance. Usually, there will small reduction in inflow, a more significant reduction in head or pressure, and a sudden increase in power draw.

According to Bernoulli’s principle, as the pressure gets increases the velocity decreases as the pressure and velocity of the fluid are inversely proportional to keep the algebraic sum of the potential, kinetic energy, and pressure constant.

Some of the parameters within the system affect the fluid properties like density, velocity, and viscosity which affect the fluid flow in the piping system.

Like the temperature change will change the viscosity and density of the fluid.
The length and the inner diameter. In the case of turbulent flow the internal roughness of the Pipes.
Position of supply and discharge containers relative to pump position.
Addition of rises and falls within the pipe layout.
The number and different types of bends in the system.
The number of valves and other pipe fittings in the system.
Entrance and exit conditions of the pipework.

Another important property of the fluid is the specific gravity (relative density) [density of fluid/density of standard fluid]

When we change the specific gravity of the fluid being pumped, the outlet pressure changes in proportion to the change in density. ( lighter fluids create less pressure)

The pressure drop will become unaffected, the hold-up will be increasing due to the effect of surface tension.

Losses in Flow through Pipes

Whenever the fluid flows inside the pipe there will be losses of energy. The losses while flowing through pipes can be classified into:

Major Losses and
Minor Losses

Major losses: This is due to the pipe wall friction; They are frictional resistance forces and are proportional to the volume, depending upon the density of the fluid, nature of the surface, nature of the fluids, and solid wall in contact, and are independent of pressure. Major losses can be calculated by the Darcy Weisbach equation & Chezys formula as given below:

Minor losses: energy losses due to eddy formations in the fluid, caused by the sudden increase (contraction) and sudden decrease (enlargement)of fluid velocity. Due to pipe bends, pipe fittings, and even obstacles.

Gas Flow through Piping System

Gases flow through the piping system in inclined, horizontal & vertical orientations and narrow passages such as chokes for flow control. As per the Joule-Thomson effect when an ideal gas passes by at constant pressure the temperature remains constant, but a pressure drop occurs at some points as the inner energy is transformed into kinetic energy, so as this temperature falls.

Velocity at which the gas flow through a pipe = volumetric flow _actual/ area of the pipe.

The gas velocity can be derived from the formula for selecting the recommended pipe schedule for the gas flow as per the standards for better gas pipe sizing. The factors to consider for pipe sizing are design flow rate, design temperature, and minimum operating pressure.

Pipes in Series

Pipes are said to be in series When pipes of different diameters are connected from one end to another end to form a pipeline. The total loss of energy (or head) will be the sum of losses in each pipe and the local losses at the connection. The volume flow rate will be constant & head loss is the sum of parts.

The discharge passing through the pipe is the same

Q=A₁V₁=A₂V₂=A₃V₃

The sum of the total head loss in the pipe is equal to the difference in liquid surface levels.

Pipes in Parallel

The pipes are said to be parallel; if the main pipe gets divided into two or more branches, Which again joined together downstream to form a single pipe. Which is connected so that the flow gets divided and comes back together again. In this case,

The Rate of fluid flow (main pipes) = the sum of the Rate of flow(through branch pipes).

Pressure loss across all the branches for the pipe parallel is the same. Q = Q₁ +Q₂.

Online Course on the Flow of fluids through piping systems, valves, and pumps

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