INTENSIFIES 



725 



Inlet from Supply 

 Mams 





If w is the weight of the outer ram, we now have 



A , w F ,, 

 P = p -1 Ibs. per square inch. 



With a single intensifier the supply of high pressure water cannot be 

 made continuous, and delivery only takes place on the in stroke. At the 

 end of this stroke water is admitted to the ram cylinder from the supply 

 mains, while the water below the piston is allowed to escape. This type 

 of intensifier is often fitted to testing 

 machines deriving their pressure 

 supply from towns' mains at a com- 

 paratively low pressure. 



Where a continuous supply of high 

 pressure water is required, this may 

 be obtained by using two intensifies 

 placed side by side, each automatic- 

 ally working the valves of the other. 



When applied to the working of a 

 hydraulic press, the water escaping 

 from beneath the piston during the 

 down stroke may be utilised to bring 

 the press platform up to its work, 

 and to perform the first part of the 

 compression. 1 



ART. 195. FRICTION OF LEATHER 

 COLLARS FOR BAMS. 



Stationary 

 Cylinder 



Stationary 

 Ram 



Pressure Water 



Outlet 



FIG. 348. Hydraulic Pressure Intensifier. 



One or other of the types of packing 

 illustrated in Fig. 349 is commonly 

 used for hydraulic rams or plungers. 

 The material used is leather, and, 



since the pressure of the water itself forces the packing against the ram, 

 this pressure, and the friction produced, become proportional to the pres- 

 sure intensity of the water. A very complete series of experiments carried 

 out by Mr. John Hicks on rams J inch, 4 inches, and 8 inches diameter, 

 and with pressures up to 6,400 Ibs. per square inch, indicate that 



(1) For pressures above 400 Ibs. per square inch, friction is directly pro- 

 portional to pressure intensity. 



1 For further details of valve arrangements, etc., the reader may refer to Elaine's 

 " Hydraulic Machinery," p. 345. 



