underfiring

Noun

underfiring (uncountable)

1. Intentional operation of a boiler, furnace, oven, etc., at a low level.
   • The designer believes that by this combination of a combustion-chamber with the underfiring grate the combustion of the fuel is improved.1890, Daniel Kinnear Clark, “Systematic Trials of Furnaces and Boilers (continued)”, in The Steam Engine: A Treatise on Steam Engines and Boilers. […], half-volume I, London; Glasgow: Blackie & Son...
   • Underfiring of steam boilers, though not approved in this country, is very largely practised in America, […]1892 July 15, “American Engineering Notes. [New Type of Steam Boilers.]”, in The Electrical Review, volume XXXI, number 764, London: H. Alabaster, Gatehouse & Co. […], →OCLC, page 68, column 2

   Antonyms:

   overfiring

2. The state of not burning fuel at the desired level, and thus not providing heat efficiently.
   • In natural gas-fired boilers, gas pressure is critical to proper burner operation and efficient combustion. Variations in gas pressure may cause over- or underfiring of the boiler. […] Underfiring may cause flame instability and poor combustion efficiency due to high levels of excess air.1999, James E. Piper, “Boiler Systems”, in Operations and Maintenance for Energy Management, Abingdon, Oxfordshire; New York, N.Y.: Routledge, published 2015, →ISBN
   • Gas-burner maintenance should include these measures: […] Adjust gas input if combustion testing indicates overfiring or underfiring.2008, John Krigger, Chris Dorsi, “Heating Systems”, in The Homeowner’s Handbook to Energy Efficiency: A Guide to Big and Small Improvements, Helena, Mont.: Saturn Resource Management, →ISBN, page...

   Antonyms:

   overfiring

3. (also, attributive) Heating from below.
   • [W]hile there were fully as many under-firing as tube-firing boilers, at work, the majority of explosions took place in boilers of the latter class, and they almost invariably commenced with the collapse of the fire flue.1856 May, William Kemble Hall, “On the Causes of Explosions of Steam Boilers”, in John F[ries] Frazer, editor, Journal of the Franklin Institute of the State of Pennsylvania, for the Promotion of the...
   • In an underjet coke oven, a distribution system for delivering a combustion-medium into the underfiring system of said coke oven, comprising: a header-pipe having a plurality of outlets therealong; pipe-connections at a region so remote from the active combustion zone of the underfiring system of...1944 June 26, W[alter] C[larence] Rueckel, Ceramic Nozzle for Regenerative Underjet Coke Ovens, US Patent 2470112 (PDF version), column 8

   Antonyms:

   overfiring

4. The state of being insufficiently fired or underfired.
   • Hence it is, I must suppose, that while more effects could be produced with rose if one could only be sure of the fire, yet carmine is the more serviceable, as one is at so much less risk of loss from overfiring, which is more common than underfiring.1884 January, Aurelio de Vega, “Overglaze Painting on Porcelain. VII.—The Colours—Blacks, Blues, Browns, Carmines.”, in Amateur Work, Illustrated: Help and Guidance for Self-helpers, volume III...
   • The brick color which you describe as the result of your carmine after firing is generally due to underfiring and a second fire, stronger, will remedy this, but if this is caused by the painting either laid on too thick or spoiled by other colors, there is no remedy.1892 December, A. R. C., “Answers to Correspondents”, in The China Decorator: A Monthly Journal Devoted Exclusively to this Art, volume XII, number 1, New York, N.Y.: The China Decorator Publishing...

   Antonyms:

   overfiring