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_ Lee Sand Blast Machine An Economical and Effective Method of Remov- ing Scale and Barnacles from Ships' Bottoms HE use of the sand blast has become quite widely recognized in recent years as one of the most economical and effective meth- ods of removing scale and barnacles from ships' bottoms. Since the pub- lication of the original article on this subject, in THE Marine Review of January, 1911, it has been adopted with uniformly satisfactory results by ship yards all over this country. In this article there was set forth a description of a "Kelly" sand blast machine which had been used _ suc- cessfully in cleaning scale from the hull of the new steam yacht Emrose. Since then, several important changes in design have greatly improved and augmented the capacity of the ma- chine, and it is now referred to by the manufacturer, Arthur E. Lee, 30 -Church street, New York, as the "Lee multiple nozzle, positive, con- tinuous feed, sand blast apparatus." Most important of the new features is the addition of three more nozzles, making it possible to operate four sand blast streams simultaneously from the same machine, as shown in Fig. 2. One machine thus does the work for which four formerly were required, while for operating the ma- chine itself and the four nozzles, the labor of five men only is required, where formerly eight would have been employed. This increase in the capacity was made possible largely by the special type of sand feeding device peculiar to this machine. This device consists of a revolving wheel, located horizontally at the bottom of the sand chamber, the periphery of the wheel being grooved, or slotted, much in the same manner as an 'ordinary gear wheel. As the wheel tevolves, the sand falls into the grooves, being carried around until "it comes into the path of a current 'of compressed air, which catches it Up and conveys it to the entrance of the hose leading to the sand blast Nozzle. The addition of the three hose connections, therefore, simply entailed the passage of three ad- 'ditional compressed air currents through the grooves of the _ feed wheel. Another change which is embodied im the improved design makes it un- Recessary to halt the operation of the Machine temporarily while replenish- 'Img the supply of the abrasive. The = sand chamber, which formerly was a unit, has been divided into two compartments, as shown in Fig. 3; each of these compartments may be made air-tight by means of a cone- valve entrance. The sand charging operation is conducted as follows: The sand is shoveled into the top compartment and the top cone-valve closed by means of an external lever, after which compressed air at the regular working pressure is duced into the top compartment. Next, the lower cone-valve drops automatically, permitting the sand to intro- o hose. Then too, it is advisable to use perfectly dry sand, although com- paratively damp sand may be used without clogging the hose. The flow of sand from the sand chamber to the sand blast nozzle may be regu- lated automatically by changing the speed of the air motor which operates the feed wheel. The capacity of the sand containor, five cubic feet, is sufficient to enable the machine to operate with all four nozzles on one charge for 2714 minutes. For one nozzle, used independently, one charge will last one hour and 50 minutes. FIG. 1--LEE PORTABLE SAND BLAST MACHINE AS PROVIDED WITH CONNECTIONS FOR OPERATING FOUR SAND BLAST STREAMS flow from the upper into the lower compartment, and the lower cone- valve then is hoisted back into place and held there by means of a second external lever, until the air in the upper compartment has been ex- hausted into the atmosphere, by means of a three-way cock, when the pressure in the lower compartment automatically holds the cone-valve in. its seat. By means of this double air-locking device, the supply of sand may be renewed constantly without interfering with the regular opera- tion of the machine. The sand which is charged into the container must be sieved through a 10-mesh screen in order to free it from lumps or stones which might obstruct the free passage through the The machine consumes compressed air at the rate of 60 cubic feet of free air per minute for each of the four nozzles, and 25 cubic feet in addition for the air motor. The pressure required at the nozzles for the most efficient operation is 80 to 90 Ibs. per square inch, but for the propulsion of the sand from the ma- chine to the nozzle, 30 to 40 pounds pressure is sufficient. can be throttled down as desired by means of an ordinary air valve which is furnished. The air used for carry- ing the abrasive from the machine to the nozzles is passed through a slotted baffle plate, or separator, at the intake, which arrests the moisture. The water of condensation which thus accumulates may be removed by The pressure .