Semi-automatic High-Pressure Installation. 157 



apparatus are made tight in a simple way which we have 

 used extensively for some years, and have found to be 

 entirely satisfactory. For example, A and B (fig. 4) are 



two tube-ends which have to be 

 joined together. One of them, A, 

 is recessed, and the recess is rilled 

 by a ring of derma tine* 0, which 

 before the joint is assembled stands 

 a little proud of the tube. It is now 

 only necessary to bring the tubes 

 firmly together, and a fluid-tight 

 joint results. 



In the figure the tube-ends are 

 held together by an ordinary union, 

 but the same form of joint is equally 

 serviceable when, instead of this, 

 the tubes are provided with flanges 

 which are bolted together ; and it 

 is equally applicable to large and 

 to small bores. It can, of course, 

 be used where one of the pieces to 

 be coupled has a bore smaller than 

 the other or is a blank. u Red " 

 dermatine is rather harder than 

 u black," and is correspondingly 

 easier to machine ; it stands oil or 

 water. 



The advantages of this joint 

 are: — It is fluid-tight from the 

 outset, before any pressure has been applied, and remains 

 tight up to any pressure which the couplings are strong 

 enough to stand. It can be taken apart and remade f 

 a great number of times without renewing the dermatine 

 ring, and is extremely simple to make, requiring only 

 ordinary workshop accuracy. On the other hand, where two 

 pieces have to be coupled fluid-tight and in accurate relation 

 to one another, this result is readily secured, as the pieces 

 are in direct contact. If under working conditions the tubes 

 or couplings are subjected to mechanical strain, the joint 

 itself is unaffected. 



* Gutta-percha also makes an excellent temporary joint, and is to 

 be preferred to dermatine should it be necessary to use very thin (in the 

 radial direction) rings. It is not acted upon by castor oil. 



t This is essential, as the apparatus must be cleaned out at intervals, 

 because the castor oil gets contaminated by small metallic particles 

 (possibly scale), and also appears to have a slow action on the steel. 



