t 7-'#/h 
 
 / 
 
 MDDC - 7&4 
 
 UNITED STATES 
 ATOMIC ENERGY COMMISSION 
 OAK RIDGE 
 
 TENNESSEE 
 
 MERCURY SLUG FLOWMETER 
 by 
 K. L. Yudowitch 
 
 Carbide and Carbon Chemicals Corporation 
 
 Published for use within the Atomic Energy Commission. Inquiries for additional copies 
 and any questions regarding reproduction by recipients of this document may be referred 
 to the Documents Distribution Subsection, Publication Section, Technical Information Branch, 
 Atomic Energy Commission, P. O. Box E, Oak Ridge, Tennessee. 
 
 Inasmuch as a declassified document may differ materially from the original classified 
 document by reason of deletions necessary to accomplish declassification, this copy does 
 not constitute authority for declassification of classified copies of a similar document which 
 may bear the same title and authors. 
 
 
 Date of Manuscript: Unknown 
 Document Declassified: March 24, 1947 
 This document consists of 2 pages. 
 
MDDC-794 
 - 1 - 
 MERCURY SLUG FLOWMETER 
 
 Incidental to other researches at the Manhattan Project, the author developed with J. F. 
 Bacon and other associates^ meter to measure small gas flows at various pressures. The 
 requirements of an operating pressure drop of less than 3 mm. of mercury and independence 
 from physical properties of the gas made capillary flowmeters, rotameters, and circuit- 
 terminating flowmeters undesirable. 
 
 Various designs of absolute displacement meters were investigated. The design which 
 was adopted was suggested by a meter described by Appleby and Avery*. In operation, the 
 mercury slug traverses the spiral path as indicated. The spiral was made by winding six 
 mm. pyrex tubing in a plane and allowing it to set on a slightly convex carbon block. This 
 fixes the spiral outlet one to two mm. above the inlet. 
 
 In filling the meter with mercury, it is essential that sufficient mercury be used that a 
 new slug close the spiral entrance before the original slug completely leaves the spiral. 
 
 The length of the slug and, therefore, the volume swept out per cycle was found to vary 
 somewhat with flow-rate. This requires volume calibration over the range of flow-rates to 
 be encountered. In all cases the slug length decreased gradually as the flow-rate was in- 
 Teased; the greatest variation encountered being a 15 per cent volume increase over the 
 total useable range. At rates greater than about 250 cc/min, the slug breaks into several 
 sections, causing erratic behavior; at rates less than about 25 cc/min, the volume swept 
 out per cycle increases erratically. Timing and counting of the cycles may be done manu- 
 ally or by means of a relay activated the the passage of the slug past the contacts shown 
 in the illustration. 
 
 The advantages of this meter are: 
 
 (1) It operates on a low pressure drop. 
 
 (2) It operates over a broad pressure range (2 to 76 cm). 
 
 (3) Its operation is independent of the physical properties of the gas being measured. 
 
 (4) It gives an integrated or average flow-rate, rather than an instantaneous rate. 
 
 These meters have held their calibrations to within from one to 10 per cent over a period 
 of several months of regular use. Most variations were probably due to mercury contami- 
 nation. 
 
 ♦Appleby, W. J. and Avery, W. H. 
 

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 3 1262 08910 9861 
 
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