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Tundish
Tundish
Tundish
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The word tundish originates from a shallow wooden dish with an outlet channel, fitting into the bunghole of a tun or cask and forming a kind of funnel for filling it. These were originally used in brewing.

In general, any tundish will accept flow and store a small amount of material, while dispensing material elsewhere, similar to a funnel. In contrast to a funnel, the purpose is generally to regulate flow, and achieve a more steady output with intermittent inputs, and the tundish typically will take on a different shape.

Plumbing

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The term tundish is still used today in plumbing, where a funnel or hopper is filled by an outlet pipe above it. This is often provided for intermittent overflows, or where an air gap is required, to avoid possible back-contamination.[1]

Metal casting

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In metal casting, a tundish is a broad, open container with one or more holes in the bottom. It is used to feed molten metal into an ingot mould to avoid splashing and give a smoother flow. The tundish allows a reservoir of metal to feed the casting machine while ladles are switched, thus acting as a buffer of hot metal, as well as smoothing out flow, regulating metal feed to the moulds and cleaning the metal. Metallic remains left inside a tundish are known as tundish skulls[2] and need to be removed, typically by mechanical means (scraping, cutting). A casting tundish is lined with refractory bricks specific to the liquid metal which is being cast. A tundish preheater may improve performance by heating the refractory before pouring metal, and may allow removal of molten oxide and skull material while preheating.[3]

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Tundish

View on Grokipedia
from Grokipedia
A tundish is an intermediate vessel that receives and temporarily holds a small amount of or molten during transfer to another , functioning similarly to a with added buffering capacity. The term has distinct applications in and . In , a tundish is a refractory-lined intermediate vessel used in the process to receive molten from a teeming ladle and distribute it evenly to one or more molds, acting as a buffer to ensure steady flow and metal quality. In the steel production workflow, the tundish bridges the discontinuous ladle metallurgy stage with the continuous solidification in molds, enabling sequence casting where multiple ladles can be processed without interrupting the caster. It regulates the flow rate to maintain constant casting speeds, typically between 0.5 and 3 meters per minute, while minimizing turbulence that could entrain slag or cause defects in the final product. By holding a reservoir of molten steel—often 20 to 50 tons depending on caster design—the tundish allows time for ladle changes, reducing downtime and improving overall plant efficiency in modern steel mills. In plumbing, a tundish is a fitting installed on overflow or discharge pipes from hot water systems, such as cylinders or boilers, to provide an air gap that prevents backflow contamination and allows visual monitoring of leaks or discharges for safety compliance.

Etymology and History

Etymology

The term "tundish" derives from "tunne disch" or "tundish," a compound formed from "tunne" (from tunne, denoting a large cask or barrel used for storing liquids such as wine, ale, or ) and "dish" (from disc, referring to a shallow plate or container). This etymological root reflects its initial function as a simple, shallow wooden vessel designed to channel liquids efficiently. In its early usage, the tundish served as a funnel-like device for filling tuns, especially in contexts, where it helped prevent spills and overflows during the transfer of fermenting liquids into large casks. The design emphasized controlled pouring to maintain the integrity of the contents, underscoring the practical needs of medieval liquid handling. The earliest recorded instance of "tundish" appears around 1388–89 in the Abingdon Accounts, an English medieval financial record, describing it as an implement for precise liquid dispensation. Over centuries, the term has persisted and adapted to contemporary industrial applications in fields like and .

Historical Development

The tundish originated in the late as a "tun-dish," a shallow wooden dish with an outlet channel designed to fit into the bung hole of a large cask (tun) in the industry, enabling controlled filling without overflow or spillage. This simple device addressed practical needs in ale and production, where precise pouring prevented waste and contamination during cask filling. By the 19th century, with the expansion of industrial processes during the , tundishes were used in various liquid handling applications in factories and early infrastructure. Their adaptation for modern systems, such as overflow indicators, occurred in the . In the mid-20th century, the tundish found a transformative role in with the adoption of for production, a key milestone beginning in the late and , with the first commercial machines installed in the United States in 1949, Europe in 1950, and Japan in the late . Early concepts of tundish-like reservoirs appeared in patents as far back as 1857 (Bessemer), with practical use in non-ferrous by before applications. This innovation replaced traditional by using the tundish to regulate molten flow from the ladle to the mold, improving efficiency and steel quality. By the 1970s, material advancements reflected the device's dual applications: in , tundishes shifted to constructions for resistance and ease of installation amid the rise of systems, while metallurgical versions evolved to refractory-lined designs, including vibratable plastics and low-cement castables, to better withstand extreme temperatures and extend service life.

Applications in Plumbing

Design and Function

In plumbing systems for hot cylinders and drainage, a tundish is a conical or funnel-shaped device featuring an overflow at the top and an outlet pipe connection at the bottom, with the body typically 100-150 mm in diameter to accommodate visible flow. The incorporates a tapered structure that directs discharge downward while maintaining an unobstructed air gap between the inlet and outlet, ensuring safe drainage without direct pipe connection. This shape, adapted from historical funnels, facilitates efficient management in confined spaces. The primary function of the tundish is to establish an air gap that prevents back-siphonage, thereby protecting potable systems from cross-contamination by or sewer contents during negative pressure events. By breaking the continuous path, it acts as a type AA , complying with requirements under Building Regulations Part G3 for unvented hot systems. Additionally, the tundish aligns with BS EN 806 specifications for installations conveying for human consumption, emphasizing design elements that support hygienic integrity. A key feature is the integrated visual inspection window, often a transparent or clear section in the body, which allows users to monitor any discharge from pressure relief valves and detect or system faults early. This visibility ensures timely intervention, as even minor drips can indicate issues like a failing expansion vessel or , enhancing overall without requiring disassembly.

Installation and Standards

In plumbing systems for unvented hot water storage, the tundish is positioned below the hot water cylinder's and above the discharge pipe to create a visible overflow path. Per Building Regulations Approved Document G3, it must be installed vertically in the same compartment as the storage system, as close as possible to and lower than the safety device, with a maximum of 600 mm of pipework between the valve outlet and tundish . The discharge pipe from the tundish requires a minimum 300 mm vertical drop before any bend or horizontal section to ensure safe drainage. Installation begins by isolating the water supply and draining the system, followed by connecting the tundish to the relief valve outlet using compatible pipework—typically copper or plastic—with compression joints for secure, leak-free fittings. A minimum air gap must be maintained between the tundish outlet and discharge pipe, generally at least 20 mm or twice the internal diameter of the discharge pipe, whichever is greater, in compliance with the Water Supply (Water Fittings) Regulations 1999. This air gap functions to prevent backflow and potential contamination of the potable supply. The entire setup must incorporate metal or heat-resistant discharge piping with a continuous fall of at least 1:200 thereafter, terminating in a safe, visible location away from electrical devices or walkways. Only G3-qualified engineers may perform the installation to adhere to these requirements. Maintenance involves annual visual inspections during routine boiler or cylinder servicing to detect blockages, leaks, residue from discharges, or accumulation, which can impair visibility and function. is cleaned by accessing the through the tundish and wiping without full disassembly. Replacement is advised if discoloration, , or structural damage appears, as these indicate degradation; while no fixed lifespan is specified, tundishes typically last several years under normal conditions but should be swapped during system overhauls if wear is evident. Key standards governing tundish use include UK Building Regulations Part G (, hot water safety, and water efficiency) and the associated BS EN 12897:2006 for unvented hot water storage system specifications. Internationally, equivalents emphasize prevention, such as ASSE 1011 for hose connection vacuum breakers that incorporate air gaps to mitigate siphonage risks in similar low-pressure applications.

Applications in Metallurgy

Role in Continuous Casting

In the of production, the tundish serves as an essential intermediate vessel positioned between the ladle and the mold, acting as a buffer to hold a of molten typically ranging from 20 to 50 tons. This capacity enables a steady and uninterrupted flow of liquid steel into the casting mold, even during ladle exchanges, which occur periodically to maintain production continuity. By bridging the batch-wise ladle operation with the continuous withdrawal of solidified steel, the tundish prevents disruptions that could otherwise lead to interruptions or quality inconsistencies. The tundish plays a critical metallurgical by facilitating homogenization of the molten , maintaining it at approximately 1500–1550°C to ensure uniform thermal conditions throughout the sequence. This stabilization is vital for quality, as it minimizes thermal gradients that could cause uneven solidification. Additionally, the tundish promotes the removal of non-metallic inclusions through extended and optimized flow patterns, allowing lighter inclusions to float and separate, thereby reducing defects such as slivers or entrainments in the final product. Flow control devices like weirs and within the tundish enhance this process by increasing and mixing zones while reducing dead volumes. To achieve high-quality casts, the tundish precisely controls the pouring rate of molten to align with the mold's withdrawal speed, which typically ranges from 1 to 3 meters per minute, ensuring a consistent liquid level in the mold. This synchronization prevents excessive at the meniscus, which could introduce air or and result in surface defects like cracks or oscillations marks. By smoothing out flow variations from the ladle, the tundish maintains stable casting conditions, contributing to the overall efficiency and yield of the operation. A key enhancement in tundish operations is the application of electromagnetic stirring (EMS), which induces gentle horizontal flows to promote uniformity in composition and temperature across the vessel. This stirring increases the mixing zone volume and average flow speeds, accelerating the collision, coalescence, and flotation of inclusions for improved cleanliness. EMS transforms outlet regions into active mixing areas, reducing dead zones and achieving faster homogenization compared to unassisted flows, ultimately enhancing the quality of the cast . The , adopted widely since the mid-20th century alongside the growth of , exemplifies how metallurgical refinements optimize the process.

Design Features and Materials

The tundish in is designed as an open-top vessel, typically measuring 2 to 5 meters in length for and bloom casters, with a outer shell that provides and a inner lining for thermal and chemical protection. This structure includes an inlet section for receiving molten from the ladle via a shroud, and an outlet section equipped with 2 to 8 nozzles or slide gates depending on the caster type, which direct the flow into the molds. To optimize molten distribution and , internal flow control devices such as weirs, dams, or baffles are incorporated, promoting and aiding in the separation of inclusions while minimizing turbulence. The primary materials for the tundish lining are high-alumina or magnesia-based refractories, selected for their ability to endure temperatures above 1600°C, resist erosion from molten and , and maintain . These refractories, often with MgO content ranging from 70% to 90% balanced by SiO2, are applied as bricks, castables, or gunnables in multiple layers: a permanent working layer for direct contact with the melt, an insulation layer to reduce heat loss, and a safety backing for backup. The nozzles and submerged entry shrouds are typically composed of alumina-graphite or fused silica composites to prevent and ensure precise flow control. Key design features include preheating systems using plasma torches or gas burners to sustain the superheat of the molten , compensating for drops during transfer and enabling longer casting sequences. gas shrouding around the submerged entry nozzles and ladle shrouds is standard to create an inert atmosphere, preventing reoxidation and pickup in the . Post-casting, solidified metal residues known as tundish skulls form along the walls and bottom due to cooling; these are managed through mechanical deskulling processes, such as pneumatic hammers or hydraulic breakers, followed by of the recovered metal. This buffering capacity ensures a steady, continuous flow to the molds, supporting efficient sequence casting.

References

  1. https://www.ispatguru.com/tundish-and-its-role-in-continuous-casting/
  2. https://ccc.illinois.edu/PDF%20Files/Reports00/d.reports00/MSTS_fluidv99.9991_noq.pdf
  3. https://www.sinometalcarbon.com/news/the-tundish-a-crucial-component-in-modern-steelmaking.html
  4. https://inspectapedia.com/plumbing/Tundish.php
  5. https://www.etymonline.com/word/tundish
  6. https://www.oed.com/dictionary/tundish_n
  7. https://www.merriam-webster.com/dictionary/tundish
  8. https://www.etymonline.com/word/tun
  9. https://www.ispatguru.com/historical-aspects-of-the-continuous-casting-and-related-technologies-for-steel/
  10. https://www.metallurgical-research.org/articles/metal/pdf/1999/10/metal19999611p1389.pdf
  11. https://lakeviewpuller.com/2021/08/10/house-plumbing-systems-through-the-years/
  12. https://www.saimm.co.za/download/PresidentialAddress2008.pdf
  13. https://www.reliancevalves.com/gb/en/products/heating-system-components/tundishes
  14. https://www.viessmann.co.uk/en/heating-advice/boilers/what-is-a-tundish.html
  15. https://assets.publishing.service.gov.uk/media/66f6c6ce3b919067bb4828cc/ADG_with_2024_amendments.pdf
  16. https://www.reliancevalves.com/gb/en/products/heating-system-components/tundishes/dry-trap-tundish
  17. https://knowledge.bsigroup.com/products/specifications-for-installations-inside-buildings-conveying-water-for-human-consumption-general
  18. https://www.legislation.gov.uk/uksi/1999/1148/schedule/2/made
  19. https://www.ispatguru.com/basics-of-continuous-casting-of-steel/
  20. https://scholarsmine.mst.edu/matsci_eng_facwork/603/
  21. https://new.abb.com/metals/insights/improvement-of-steel-cleanliness-with-electromagnetic-stirring-in-tundish
  22. https://archive.nptel.ac.in/content/storage2/courses/113104059/lecture39/39_3.htm
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC9865547/
  24. https://www.ispatguru.com/refractory-lining-of-a-continuous-casting-tundish/1000/
  25. http://www.ispc-conference.org/ispcdocs/ispc13/content/13/13-1596.pdf
  26. https://www.metallurgical-research.org/articles/metal/full_html/2021/06/metal210233/metal210233.html
  27. https://basstechintl.com/blog/chemical/five-interesting-facts-tundish-refractories/
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