Types of GI Pipes & their classification

GI Pipes are one of the most widely used industrial products in India in 2023. They have a great demand in the field of construction and industry. It is due to their high corrosion resistance as they have minimal carbon content and are zinc-protected. According to the thickness of the sheet used to make the pipe, GI pipes are available in three grades.

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Galvanised Iron pipes undergo a certain process to build resistance. This is because the zinc coating provides complete rust prevention. Depending on the customer’s needs, these pipes are available in numerous sizes and specifications.

Here are the various types of GI Pipes available in the Indian market

GI Pipes can be classified into various types in India based on the types of Industrial usage. These pipes are categorised into light, medium and heavy. 

Class A GI Pipes

Class A are the light gauge pipes with a yellow colour strip for identification. They are cheaper than other classes of GI Pipes.

Class B GI Pipes

Class B are medium gauge pipes with a blue colour strip for identification. They are Costlier than Class A and cheaper than class C.

Class C GI Pipes

Class C is heavy gauge pipes with a red colour strip for identification. They are costlier than other classes of GI Pipes.

Additional Classifications of GI Pipes

Beyond the basic classifications, industries sometimes require further specifications such as:

GI Pipes for Water Supply

These are designed to ensure clean and safe drinking water. They are treated to be free from any contaminants and are often used in municipal water systems.

GI Pipes for Industrial Use

These pipes are designed to handle different types of industrial fluids, including chemicals and gases. Their corrosion-resistant properties make them ideal for harsh environments.

GI Pipes for Sewage Systems

Often used for wastewater and sewage systems, these pipes are built to handle high pressure and resist corrosion from various waste materials.

Applications of GI Pipes in India 2023

1. Water supply to residential areas
2. Wastewater conveying
3. Sewerage
4. Chemical transportation
5. Air duct
6. Compressed Airline

Features of Galvanized Iron Pipes

1. GI Pipes are very durable and possess higher longevity.
2. They are best suited for rigorous fabrication.
3. GI Pipes are known for higher corrosion resistance.
4. GI Pipes are easy to cut and retain the finish for a longer time.
5. Galvanized Pipes are suitable for usage in extreme temperatures.

Benefits of using GI Pipes

1. GI Pipes have a long life span. The minimum lifespan is around 30 years under extreme conditions.
2. Under normal conditions or when they are less exposed to the atmosphere the Galvanised Iron Pipes can last up to 40 to 50 years if maintained well.
3. Pure iron is completely carbon-free and exceedingly ductile. Zinc is a durable metal that prolongs the life of steel and iron. This is a great combination for external usage, due to its high restiveness.
4. Most GI Pipes are ISO Certified.

Ensuring safety while using GI Pipes

1. While installing a GI Pipe, that passes through a wall, a provision for expansion must be made.
2. These pipes must be treated with anti-corrosion paints whenever necessary and should be treated with lime.
3. GI Pipes must be in a layer of sand when placed underground.

Manufacturing of GI Pipes

Depending on their diameters, the wall thickness of its sheet varies. This pipe is prepared before being immersed in a zinc solution. The pipe is prevented from rusting in this way. GI Pipes are manufactured in a way that they are simple to thread, cut and bend and may be combined easily. They can have a life span of a minimum of twenty-five years, even when used in coastal areas.

Finding the right GI Pipes according to the need

Industries, home water supply lines and other construction applications frequently use G I pipes. They are acquired in various sizes and wall thicknesses according to the requirements. GI Pipes are so adaptable that it is simple to find them everywhere in commercial and residential places.

Due to their best reasonable cost and long life, they are typically manufactured and galvanised to prevent corrosion and soil attack and they are the most popular. The GI Pipes in industries use a variety of pipe manufacturing techniques.

Explore wide range of GI Pipes at L&T-SuFin

L&T SuFin is a renowned website for ordering GI Pipes and other industrial products. They provide customers with logistics and some financial support according to the type of product ordered. Check out the L&T SuFin website to get your required GI Pipes. Do read more blogs from L&T SuFin to get yourself informed about any industrial knowledge.

Learning Objectives

• Understand the challenges of low- and high-rise piping systems.
• Learn about three piping system types: HVAC (hydronic piping), plumbing (domestic water, and waste and vent piping), and specialty piping for chemicals and fluids (saltwater systems and hazardous chemicals).

Pipe and piping systems are found within many elements of buildings. Numerous people have seen a P-trap below a sink or refrigerant lines routing to and from their residential split system. Fewer have seen the main utility piping routing from a central plant or the chemical treatment systems within a pool equipment room. Each of these applications requires a specific type of pipe to meet the requirements of the codes, physical limitations, specifications, and best design practices.

There is no simple piping solution to meet all applications. Provided that specific design criteria are followed and the right questions are asked of the owner and operational staff, these systems can meet all of the physical and code requirements. In addition, they can maintain the proper cost and lead times to create a successfully implemented building system.

HVAC piping

HVAC piping encompasses many different fluids, pressures, and temperatures. This piping can be located above or below ground and route through the interior or exterior of a building. These factors must be taken into consideration when specifying HVAC piping within a project. The term “hydronic” refers to the use of water as a heat transfer medium for cooling and heating. In each application, the water is supplied at a set flow rate and temperature. Typical space heat transfer is completed using an air-water coil designed to return the water at a defined temperature. This results in a specified quantity of heat delivered or removed from the space. Hydronic chilled and heating water are the dominant systems used to condition large commercial facilities.

For most low-rise building applications, the expected system working pressure is typically less than 150 pounds per square inch gauge (psig). Hydronic systems (both chilled and heating water) are closed-loop systems. This means that the total dynamic head of the pumps takes into account the friction losses within the piping system, associated coils, valves, and accessories. The static height of the system does not affect the pumping capacities, but it does affect the required working pressure of the system. A 150 psig working pressure rating for chillers, boilers, pumps, piping, and accessories is common for equipment and component manufacturers. This pressure rating should be maintained within system designs whenever possible. Many buildings that are considered as low- or medium-rise will fall into the 150 psig working pressure category.

Maintaining the piping system and equipment below the standard pressure of 150 psig becomes more difficult when designing high-rise buildings. A static piping height above approximately 350 ft (with no pump pressure added to the system) will exceed the standard working pressure rating for these systems (1 psig = 2.31 ft of head). This system would most likely employ a pressure break (in the form of heat exchangers) to isolate the higher pressure requirements of the tower from the rest of the connected piping and equipment. This system design would allow standard pressure chillers to be designed and installed, while specifying higher pressure piping and accessories within the tower component.

When specifying piping for a large campus project, designers/engineers must be intentional when editing the associated specifications sections (ARCOM MasterSpec sections 23 21 13.23 and 23 21 13.13, respectively, for above- and below-grade hydronic piping) to be certain that the piping specified for the tower and podium are reflective of their individual requirements (or collective requirements if heat exchangers are not used to isolate the pressure zones).

Another component of the closed-loop systems is water treatment and purging of any oxygen from the water. Most hydronic systems are fitted with water treatment systems composed of various chemicals and inhibitors to maintain the water flowing through the pipes at optimal pH (approximately 9.0) and microbiological levels to resist bio-film buildup and corrosion within the piping. Stabilizing water within the system and removing any air helps provide the full life expectancy of the piping, associated pumps, coils, and valves. Any air left within the piping can cause cavitation at the chilled and heating water pumps and reduce heat transfer within chillers, boilers, or hydronic coils.

Hydronic systems can use the following piping types:

Copper

Drawn-temper tubing, which complies with ASTM B88 and B88M with types L, B, K, M, or C, with ASME B16.22 wrought-copper fittings and unions joined with lead-free solder or brazing for underground applications.

Drawn-temper tubing, which complies with ASTM B88 and B88M with types L, B, K (normally only used below grade), or A, with ASME B16.22 wrought-copper fittings and unions joined with lead-free solder or brazing for aboveground applications. Pressure-seal fittings are allowed for this tubing as well.

Type K copper is manufactured with the highest tubing thickness and allows for working pressures from 1534 psig at 100 F for ½-in. piping, to 635 psig for 12 in. The working pressures of types L and M are less than K, but are still more than suitable for HVAC applications (pressures range from 1242 psig at 100F for ½-in. and 435 psig for 12-in. for type L, and 850 psig and 395 psig for type M, respectively. These values are taken from Tables 3a, 3b, and 3c of “The Copper Tube Handbook,” published by the Copper Development Assn.

These working pressures are taken for straight lengths of piping, which are not typically the pressure-limiting areas of the system. Fittings and unions, where two pieces of pipe are joined, are more likely to cause leaks or fail under the working pressures of some systems. The typical joining types for copper piping are soldering, brazing, or pressure seals. These joining types should be made with lead-free materials and be rated for the expected system pressures.

Each joining type is capable of maintaining a leak-free system when the joint is sealed properly, but these systems respond differently when a joint is not fully sealed or crimped. Solder and brazed connections will more likely fail and leak when the system is first filled and tested and the building is not yet occupied. In this scenario, the contractor and inspector can quickly identify where a joint has not been sealed, and remedy this problem before the system is fully operational and occupants and interior finish items are damaged. Pressure-seal joints can replicate this scenario as well, provided that they are specified with a leak detection ring or assembly. This allows water to leak out of the fitting if it is not fully pressed to identify problem areas in the same manner as solder or brazing. If the pressure-seal fittings are not specified with this item, they can sometimes hold pressure during the construction tests and may only fail after a period of operational time, thereby causing significantly more damage to the occupied space and potentially harming the occupants, especially if this piping is carrying heating hot water.

Sizing guidelines for copper piping are determined based upon code requirements, the recommendations of the manufacturer, and best practices. For chilled water applications (where the supply water temperature is typically 42 to 45 F), the recommended velocity limitations of copper pipe systems is 8 fps to maintain low system noise and reduce the possibility of erosion/corrosion. For heating water systems (where the supply water temperature is typically 140 to 180 F for space heating applications and up to 205 F when used to produce domestic hot water in a hybrid system), the recommended velocity limitations for copper pipe is much less. “The Copper Tube Handbook” lists these velocities at 2 to 3 fps when supply water temperatures are above 140 F.

Copper piping is typically available in certain sizes, the maximum of which is 12 in. This limits the use of copper within main campus utility piping systems, because these building designs typically require piping sizes in excess of 12 in. routing from the central plant to the associated heat exchange devices. Copper piping is more typically found within hydronic systems for sizes 3 in. and smaller. For sizes larger than 3 in., grooved steel piping is more commonly used. This is due to cost differences between the steel and copper, the differences in labor requirements of grooved piping compared to solder or brazed piping (where pressure fittings are not allowed or recommended by the owner or engineer), as well as recommended water velocities and temperatures within each of these piping materials.

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Steel

Black or galvanized steel piping, which complies with ASTM A 53/A 53M with malleable-iron (ASME B16.3), or wrought-steel (ASTM A 234/A 234M) fittings and malleable-iron (ASME B16.39) unions. Both class 150 and class 300 flanges, fittings, and unions may be used with threaded or flanged fittings. This piping may be joined by welding with welding filler metals which comply with AWS D10.12/D10.12M.

Grooved mechanical-joint fittings and couplings, which complies with ASTM A 536 for grade 65-45-12 ductile iron, ASTM A 47/A 47M for grade 32510 malleable iron, and ASTM A 53/A 53M for types F, E, or S, Grade B fabricated steel; or ASTM A106, Grade B steel fittings with grooves or shoulders constructed to accept grooved-end couplings.

Steel piping is more commonly used for larger piping sizes in hydronic systems as stated above. This system type allows for a variety of pressure, temperature, and sizing requirements to meet the demands of chilled and heating water systems. The class designation indicated for the flanges, fittings, and unions references the psig working pressure of saturated steam for the associated element. A class 150 fitting is intended to operate at a working pressure of 150 psig at 366 F, while a class 300 fitting will provide a working pressure of 300 psig at 550 F. A class 150 fitting will provide a water working pressure of 300 psig up to 150 F, while a class 300 fitting will provide a water working pressure up to 2000 psig at 150 F. Additional fitting classes are available for specific piping types. Class 125 or 250 is available for cast-iron pipe flanges and flanged fittings in compliance with ASME 16.1 as an example.

Grooved pipe and coupling systems use a cut or formed groove located on the ends of the piping, fittings, valves, etc., which is attached by a flexible or rigid coupling system between each length of pipe or fitting. These couplings contain two or more pieces that are bolted together and have a gasket within the waterway of the coupling. These systems work with class 150 and 300 flange types and with ethylene propylene diene monomer (EPDM) gasket materials, and are able to operate with 230 to 250 F fluid temperatures (depending upon the piping size). The grooved piping information has been taken from Victaulic guide specifications and literature.

Schedule 40 and 80 steel piping is acceptable for HVAC applications. The piping schedule refers to the piping wall thickness, which increases as the schedule number increases. With the increase in piping wall thickness, there is also an increase in the working pressure allowed for straight pipe. Schedule 40 piping allows for working pressures from 1694psig for ½-in. piping, to 696psig for 12 in. (both from -20 to 650 F). Schedule 80 piping allows for working pressures from 3036psig for ½ in. and 1305psig for 12in., respectively (both from -20 to 650 F). These values are taken from the Watson McDaniel engineering data section.

Plastic

CPVC plastic piping, which complies with ASTM F 441/F 441M for both schedule 40 and schedule 80 with socket-type fittings (ASTM F 438 for schedule 40 and ASTM F 439 for schedule 80) and solvent cements (ASTM F493).

PVC plastic piping, which complies with ASTM D 1785 for schedule 40 and schedule 80 with socket-type fittings (ASM