0
Coupling Glass Tubing to Other Materials
0
0
T H O M A S R. TAITl AND JAMES T. MITCHELL Werfern Division, The Dow Chemical Co., Piffsburg, Colif.
c
ONNECTING glass tubing to pipe or tubing of other mate-
rials such as saran, copper, or steel is usually very awkward. The problem is more difficult when pressure, temperature, or other considerations prevent the use of rubber tubing connections. The joints ordinarily used must be improvised on the spot and are usually different for each combination of materials. I n order t o overcome these difficulties a standardized joint has been developed that will permit easy joining of glass tubing to A stock of interchangeable any other type of pipe or tubing. parts may be prepared beforehand and may be assembled into the proper joint for any combination of materials t o be joined, without resorting t o makeshift methods. The resulting joint is able to stand moderate temperature and pressure. Various joints using these fittings are shown in Figure 1. The jointse!a very simple t o put together; finger pressure is usually sufficient to tighten them. They have been found very useful in making connections between the heterogeneous pieces of equip1
Present address, Western Scientific Apparatus, Berkeley, Calif.
Figure 1.
Joints Using Versatile Coupling
A. Glasr to saran tubing 6. Glass to copper tubing C. Glasr to copper fitting D. Glass to pipe (via saran halt-union) E. Glass to glarr F. Glass to saran fitting
B D
THESE PORTIONS REMOVED BY FACING
lq
7 E
C
@
I
Figure 2.
I4
Parts of Joint
A. Glass tublng end E. Sann split nut
C. Proposed spllt nut D. Washer E. Coupling
239
ment so often encountered i n r e s e a r c h work. A particular use a t this laboratory has been for water jackets on condensers and similar applications. The joints have been used on vacuum and on pressure of about 70 pounds per square inch gage, with no leaks. The glass-to-glass connection is especially good in cases where contamination from rubber or groundjoint lubricant is to be avoided. The necessary parts of the joint are made as follows:
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
240 Table 1. Tubing ~~~h Size, A B
SARAN
C
Joint Dimensions
Dimensions of Coupling P a r t s (Figure 2 ) , Inches D E F G H I J KThread
SPLIT
,---WASHER
NUT7
BlNG
G L A S S TUBING END
Figure 3.
NUT
ARED TUBING
The tubing to be attached should be well flared and a lubricant such as silicone stopcock grease should be applied to the threads. JVhen metallic tubing is used, a washer (Figure 2 0 ) made of some resilient material, suitable for use with the fluid or gas to be used in the apparahs, should be placed between the flared t,ubing and the glass tube end. The cushioning effect of the split nut minimizes the danger of t'he tubing nut damaging the glass. Figure 3 is a cross section of a glass-to-tubing joint. The position of the washer used Lvith met'allic tubing is shown; with saran tubing this washer would not be necessary. For connections other than to saran or metallic tubing a coupling is necessary. This coupling, shown in Figure 2B, is easily made, from plastic rod for instance, and does not normally come in contact with the inaterial handled. The internal running thread is the same size and pitch as t'he standard flared-tubing fittings.
Assembled Joint, Glass to Metallic Tubing
SARAN
Another special part is shown in Figure 2B. This saran split nut is made by drilling out, facing a t each end, and splitting a commercially available saran tubing union. The dotted lines in the figure show the extent of the facing operation, which at one end consists of removing the entire threaded portion. Splitting along 8-8is done with a single-edge razor blade, with the fitting on a mandrel. If the split nuts were to be molded commercially for this purpose it would be better to incorporate a tongue and groove lock, as shown in Figure 2C. When the split nut is placed over the tube end, a fitting similar to a standard flared-fitting half-union is formed. Any tubing nut-saran, copper, or other-can be screwed to the fitting.
SPLIT N U T 7
r
COUPLIN G SARAN HALF UNION
-
The end of a glass tube is shaped so that it is similar t o the male end of a flare-type copper tubing fitting. The resulting form is shown in Figure 2 A . The shaping is done with glassforming pliers that have been machined t o give the desired form when they are pressed over the hot, rotating glass tubing. Heavy-walled tubing is the most suitable and the dimensions given in Table I should be used. After forming the tube end, the inner coiner a t Jf should be rounded nith a sharp flame. The glass portion of the joint (Figure 2 8 ) may be purchased from the Braun-Knecht-Heimann Co., 1400 16th St., San Francisco, Calif.
Vol 45, No 1
Figure 4.
Assembled Joint, Glass to Saran Half-Union
Figure 4 shows a glass-to-tubing fitting joint using the coupling. K i t h a Teflon washer, any material for which glass is suitable can be handled. The tubing fitting can either be joined to tubing or, if it is a half-union, can screKv into standard pipe fittings. A glassto-glass joint is accomplished by coupling two glass-saran bodies in a coupling in a manner similar to that shown in Figure 4. -4xvasher is also necessary in this joint, Table I gives the dimensions of all the parts of the vaiious joints. I n the first column are standard tubing sizes in inches. These dimensions are the same for the glass tubing and the saran or metallic tubing to which it is connected. It has proved vise t o make the internal diameter of the split nut, E , a little larger than the external diameter, A , of the glass tubing. RECEIX E D for review February 21, 1952.
ACCEPTEDJ u l y 8, 1952.
0
0 0 0
Effect of ultitesting on Refinery Production Costs
0
M. R. M O R R O W
AND
C. T. SHEWELL
Refining Deparfment, Humble Oil & Refining
D
URING Torld War I1 the need for immense volumes of
material for the Armed Forces required that literally billions of items such as rifle shells be manufactured to rather close tolerances. It would have been a physical impossibility, because of the lack of man power, to inspect each of these billions of shells, and, hence, industry was forced by the situation to accept statistical quality control of their product in order to meet military demands. Statistical quality control in this sense meant examining only a small fraction of the total production, and, from the results of these samples, to dram conclusions concerning the quality of the entire product. I n effect, the petroleum industry has alivays relied on such statistical samples
Co., Bayfown, rex.
amounting to a few milliliters to 5 or 10 gallons from t:inliagc of 1000 to 100,000 barrels. These small samples, assumed to be representative of the material in the tank, are tested one or more times by a given test method and the contents of thc tank are sold by the refiner and accepted by the consumer on the basis of the tests on these small samples. A4fter the same mar, the Committee on Analytical Research of the Smerican Petroleum Institute was organized for the specific purpose of devising new tests and improving old tests which n-ere used by refiners in their internal operations to make their processing more efficient. I n such a program, the criteria employed in evaluating test methods include the ability of the
