US2317837A - Method and means for treating ferrous objects - Google Patents

Description

April 27, 1943. R. WEBSTER 2,317,837

METHOD AND MEANS FOR TREATING FERROUS OBJECTS I Eiled July 25, 1941 2 Sheets-Sheet 1 jag- .1 V

HIGH 1 PRESSURE I; PUMP ii April 27, 1943. WEBSTER 2,317,837

METHOD AND MEANS FOR TREATING FERROUS OBJECTS Filed July 25, 1941 2 Sheets- Sheet 2 HIGH 5 PRESSURE PUMP Patented Apr. 27, 1943 METHOD AND MEANS FOR TREATING FERROUS OBJECTS Ronald Webster, Evanston, 111., assignor to The -Hydro-Blast Corporation, Chicago, 11]., a cor- I poration of Illinois Application July 25, 1941. SerialNo. 403,954

2 claims The present invention relates to a method and means for treating ferrous objects and is more particularly concerned with a method for sand blasting ferrous objects such as castings or forgings by means of a liquid stream having sand entrained therein, and for inhibiting rust formation upon such ferrous objects after they are sand blasted, and forsuitaole apparatus for performing the above method. I

When ferrous objects are treated by a wet sand blasting process, such as that shown and described in Patent No. 2,200,587 issued to Leslie L.-Tirrell on May 14, 1940, for Method and apparatus for sand blasting," such objects are quickly. cleaned of scale or other surface deposits, with the result that a very highly reactivesurface is present upon the ferrous object so treated. Such a surface in the presence of water willrust extremely rapidly. In fact, a rust deposit noticeable to an unaided eye will appear in a matter of just a few minutes.

The present invention provides a method and apparatus for preventing this rusting.

I am aware that rust inhibiting chemical solutions in the broad sense are not new with me, but I have found that the use ofthese known solutions in the heretofore approved manner is not effective in preventing the formation of rust upon wet sand blasted surfaces. For instance. a surface treated with the sand blasting gun of the type above described and then treated with a dichromate inhibiting solution 'either with a spray to provide a novel device having'the above objectives and which enables the proportion of inhibiting substance incorporatedin the sand propelling stream to be kept substantially constant under varying conditions.

An additional object of the present'invention is to provide a novel wet sand blasting system having the'above objectives and which addihibiting wet sand blasting stream.

gun or with a brush will develop rust particles in spite of such treatment. This effect may possibly be brought about by the formation of microscopic rust particles upon the surface before it is possible to complete the sand blasting operation and apply the inhibiting solution, or it may be that the sand particles moving at high velocity form relatively deep pockets into which a dichromate or other inhibiting solution cannot be forced by ordinary means. .I therefore. provide an arrangement which applies the inhibiting solution to the surface being sand blasted simultaneously with the sand blasting operation. Such an arrangement I have found effectively prevents the formation of rust. r

It is therefore the principal object of the present inventionto provide a method and means for preventing. th'eformation of rust upon ferrous objects treated by liquid propelled sand grains. Another object of the present invention is to provide a means for incorporating a rust inhibiting substance in a wet sand blasting jet.

Still another object of the present invention is In the drawings, in which similar characters of reference refer to similar parts throughout the several views l Fig. l is a somewhat diagrammatic representation of a device for forming an inhibiting solution of constant proportions and for feeding this solution to a sand blasting gun;

Fig. 2 is a diagrammatic representation illustrating the device shown in Fig. 1 as used in connection with asand blasting device of the type shown in the before-mentioned Tirrell patent;

Fig. 3 is a diagrammatic representation similar to that shown in Fig. 2 showing an .altemative arrangement for using the device illustrated in Fig. 1 in connection with the sand blasting system shown in the before-mentioned Tirrell patent; and p Fig. 4 ma "diagrammatic representation of a somewhat different inhibiting" arrangement, adapted for use with a sand blasting arrangement such as that shown in the before-mentioned Tirrell patent, I

valve I4, which may be of any well-known construction. Thus water under pressure in the pipe I2 flows into the'tank Ill when the liquid level therein drops below a. predetermined point, and after sufficient water) has entered the tank through the pipe l2 to refill the tank to a predetermined level, the float valve closes until the water level again drops, whereupon it recycles.

above the bottom thereof upon blocks I8. A quantity of potassium dichromate- 'crystals is placed inthe basket l6 and dissolve in the .water until a saturated solution has been reached. The purpose of; the basket is to expedite the formation of the inhibitor solution by providing a greater area of contact between the water in the tank and the dichromate crystals than would be afforded if these crystalswere merely placed upon the bottom of the tank where they would have a tendency to clump together and expose only their upper surfaces. Since the solubility of potassium dichromate varies considerably depending upon the temperature of the water in which, it is dissolved -a coil 20 surrounds the basket l6 and is connected to cause cold water at a substantially, constant temperature to flow therethrcugh from the pipe 22 and into'pipe 24. This supply of cold water should preferably be below atmospheric temperature and for this purpose I have found that an ordinary commercial water supply line is adequate, inasmuch as under normal circumstances the temperature of this water is comparatively constant and is con.-

siderably belowthe temperature of the atmosphere within the room in which the inhibitor is 7 located. The how of water through the coil 20 V is'controlled by means of valves 26 and-2B. The

valve 26 is positioned between the water pipe 22 andthe coil 20 while the valve 28 is similarly connected between the coil 20 and the outlet pipe 24..

To the left of thetank I I havearranged a pump 30 driven by an electric motor 32. This pump can be of any well-known type, providing 22 previously mentioned. Water from the main line, therefore, can be used to fill the tank [0 and also can pass through the cooling coil 20. The pipe 24 connected to the exhaust side of the cooling coil is connected at its opposite end to the water supply pipe 52 at the point somewhat beyond the connection between the supply line 52 and the before-mentioned branch pipe 54, while a valve 5l'is positioned in the main line 52 between the connections to the branch pipes 54 andv 24.. .Thus, by regulating the valves 51, 26 and 28, the quantity of water flowing through the cooling coil can be determined.

it will pump a comparatively small amount of I liquid at a pressure somewhat above the city water supply line pressure. The inlet side of this pump is connected by means of a pipe 34 to an inlet opening enclosed within a strainer 36 positioned within the tank Ill. The exhaust side of the pump is connected by meansyof a pipe 38 and a valve 40 toa pipe 42. The op-v tioned'within the tankflfl. 'Thus, with the pump posite-end of this pipe 42 is open, and is posi operating, the inhibiting solution flows through the screen 36 and pipe. to the pump 30, and] i is returned to the tank from the pump by way of the pipe 38, valve 40 and pipe 42. This recirculation of the inhibiting'fluid and the resulting agitation insures the rapid formation of a saturated solution of dichromate and waterwithin the tank ID. The action of the pump 30 increases the temperature oI-ythe water flowing therethrough somewhat, and would normally cause a gradual rise in temperature within the tank I, were it not for the cooling coil 20 the flow through which is so adjusted that the 'tem-' perature of the water inthe tank is maintained comparatively constant and below that of the room within which the tank is housed. v The reason for maintaining this low temperaturewill 1 be indicated presently.

The pipe 38 connected'to the exhaust side of the pump 30 also connects by way of a needle valve 44 with a pipe 46leading to the point at which the inhibiting solution is to be introduced into the water supply line. In order to facilitate control of'the system, the pipe 46 is equipped with a suitable pressure gauge 48.

Because of the possibility that the float valve l4 may at some time fail in operation, an overflow pipe 50 leading to a drain is provided to prevent the inhibiting solution from overflowing the'tank and spilling upon the floor upon which the tank rests. V I g .Referring to Fig. 2 of the drawings, a mam water line is indicated. by the numeral 52; 1 Branch pipes connected to this line extend downwardly and are connected with the pipes l2 and Ata point beyond the connection between the pipe 24 and the line 52, the main water line 52 is connected to theinhibitor outlet pipe 46, while a check valve. 56 in the main line52 between the branch pipes 24 and 46 prevents the return flow a pipe 10 and a valve 12 with the outlet side of the valve 58.

The outlet side of the high pressure pump 62 is connected to the sand blasting gun 14 by means of a pipe 16 and hose' 18 and furnishes water under high pressure to this sand blasting gun.

'A tank 80 containing wet sand is connected to a pipe '82 whichisin turnconnected by a hose 84 with the sand inlet fitting 86 of the gun 14. For a detailed description of the gun l4 and the sand tank 80, reference is made to the before-mentioned Tirrell patent, The high pressure pump 62 can be-of any desirable design that will properly operate the gun I4. Preferably it should pump water at a rate of approximately thirty gallons a, minute at a pressure of approximately twelve "hundred pounds per square inch.

. .With the arrangement thus described, the pump 30 recirculates the inhibiting solution through the tank I0 and rapidly forms a saturated solution of potassium dichromate and water at a temperature controlled by the coil 20. As required', a portion of this fluid is diverted through the needle valve 44 into the main line 52, where the mixture of water and: inhibiting solution properly proportioned passes onwardly to the water-heater 64, from which it returns to the main line and continues to the high pressure pump 62. By regulating the valves 68, I2 and 58,-the temperature of the water reaching the high pressure pump 62.can be determined. From the pump 62, water under high pressure mixed with the inhibiting solution, passes to the gun 14, where it picks up abrasive particles and projects them against the work to be treated.

The needle valve 44 should be so regulated that the water forced to the gun 14 has mixed therein approximately one pound of potassiurr dichromate to four thousand gallons of water the-operator. -By the use of the water heater 64, however, the temperature of the .watercan beincreased to whatever is the 'operators comfort.

The coil 20 is advisable because, as has been previously mentioned, the recirculation of themhibiting fluid by the pump 30 .raises the temperature of the fluid and thusincreases the concentration of, potassium dichromate in the solution. If the solution is permitted to becomewarmed appreciably above room temperature and then the pump 30 is stopped, the pump and the sev-- desirable to insure Therefore, when the pump is stopped, the

fluid within the pump and the various connecting fittings and the valve 44 will not precipitate dichromate crystals, since the fluid in the system is below atmospheric temperature. That is, the tendency is for the fluid to become warmer rather than colder when the apparatus stands idle.

In Fig. 3 I have shown an arrangement which differs somewhat from that shown in Fig; 2, principally in that the temperature of the Water is raised by the water heater 64 prior to the entrance of the water into the inhibiting solution forming apparatus. In this arrangement the heater branch pipes 66 and 10 are'connected across the valve 58 which is located in the supply line'52 in a .position ahead of the inhibitor. After passing through the heater, a portion of the water is diverted through the branch pipe i2 to the tank Ill. Inasmuch as the water in a position adjacent the inhibitor is heated and may be above atmospheric temperature, water is diverted from the main line As in the previous embodiment, inhibitingfiuid is drawn from the tank 10 through the pipe 34 to the inlet side of the 'pump 30, from where it passes through the pipe 38 back to the tank H] by way of the return pipe 42. Similarly also, a portion of this liquid is diverted through a needle valve to the main line 52 at a point beyond the check valve 56.

With this alternative arrangement, the system can be started somewhat more quickly than with the one previously shown. This is because hot water passing to the tank [0 will more quickly dissolve the crystals in the basket l6 than will cold; water. The solution, therefore, can be brought u to saturation more quickly with the apparatus shown in Fig. 3 .than is possible with that shown in Fig. 2. During the interval of The system, therefore, is always main- ,tained in condition for immediate use.

is provided within the .tank I0.

time while a saturated solution is being formed, one or both of the valves 26 and 28 may be closed to prevent cold water from-flowing throughthe coil 20. The limitation of the system shown in Fig.3 over that shown in Fig. 2 is that the heat brought into the tank II] with the incoming water must. be absorbed by the cold water coil 20 in order to keep the-concentration of the:

solution from becoming excessively high. This limitation is not great in practice, however, because the heat reabsorbed by the .coil 20 is not lost, but is taken back into the system, since this coil on its outletside connects to the 'main water line leading to the high pi cssure pump 62.

In Fig. 4, I have shown an alternative arrange nient f which is satisfactory for some installations, although it does notprovlde the nicety of control present inthe previously described embodiments. It is, however, more economical to construct. In this system, no cooling coil The tank is otherwise arranged as shown in Fig. 1. Inthis embodiment, water from the main line v52 passes through a check valve 56 and through a water heater 64 to the high pressure pump 62,.all in a manner similar to that provided in thescheme 'shownin Fig. 2. In a position ahead of the check valve 56, a portion ofthe water is diverted to the branch conduit l2 and thence into the tank to maintain the water level therein. The inhibiting solution removed from the tank passes in the manner previously described through the pipe 34 to the inlet side of the inhibitor pump 30. Instead of the inhibiting solution being recirculated by the pump 30- back to the tank [0, this solution, by means of a by-pass 88, is recirculated to the inlet side of the pump. Thus the inhibiting solution is continuously being recirculated from the exhaust to the inlet side of the pump, while, as needed, a

portion of this fluid is .withdrawn from the pump circuit through a branch pipe and needle valve 44, to the main line at a position beyond the check valve 56. As the fluid slowly passes through the needle valve 44 to the main line,

this fluid is replaced in the pump 30 by additional fluid being drawn from the tank l0. v

Since in this arrangement no cooling coil is provided to maintain the temperature within the tank 10, and since additionally the water is not recirculated through this tank, the result is that the solution will not. come up to a saturated condition as rapidly as it will in the previously described embodiments. Additionally', as water is periodicallysupplied to the tanklll to replace the fluid withdrawn, the concentration of the solution within the tank II] will be periodically lowered. In fact, with this arrangement, a saturated solution will seldom 'be reached excepting when the apparatus is permitted to stand idle for a period of time since the entering water has a tendency to maintain the solution somewhat below the saturation point. It will be appreciated also that atmospheric temperature will afiect the tank temperature and therefore. the

concentration of the solution passed to the main. line 50. This system, therefore, needs more atparticularly critical. Under these conditions,

therefore, theinhibitor canbe operated with little through the pipe 34.v V

attention providing it is adjusted to insure a sufil cient concentration of potassium dichromate in the water reaching the guninasmuch as ordiplied to a sand blasting gun, it will be appreciated I that other inhibiting chemicals may readily be used in the place of potassium dichromate. The

reason for the choice ofpotassium dichromate is that this chemical in its comrnerical state is comparatively inexpensiveand can be allowed to remain upon the surface of the'castings or forgings even though they are subsequently painted,

whereas certain other inhibitors which leave an oily .fihn must be removed in order to secure adequate adhesion of a paint film.

From the above description of my invention as illustrated in three separate alternative embodiments, it will be appreciated that the. method and apparatus described adequately fulfill the objectives set out for this invention at an earlier portion of this speciflcation.

V supply line, a high pressure pump connected to said line,'a sand blasting gun connected to said high pressure pump, said sand blasting gun having means therein to incorporate abrasive particles in the high pressure water stream passing therethrough, means to dissolve a'corrosion inhibiting chemical in water to form a substantially saturated solution, heat exchange means to control the temperature of said solution and to maintain the temperature of said solution below atmospheric temperature, pump means for withdrawing said saturated inhibiting solution and for forcing said inhibiting solution into said supply line, and heat exchange'means adapted forelevating the temperature of the mixed water and inhibiting fluid to approximately the body surface temperature of the operator.

2. A sand blasting device comprising, a water supply line, a tank, means for dissolving a rust "inhibiting chemical in said tank, means to circulate water away from and back into-said tank, means to by-pass a portion of the water so circulated to the water supply line, means to maintain the temperaturewithin said tank substantially constant and at a temperature, below atmospheric temperature, means to heat the water in said supply line to substantially the body surface temperature of the operator, a high pressure pump, means connecting said high pres- What I claim is new and useful and desire to secure by Letters Patent of the United States is: I 1. A sandblasting system comprising a water sure pump to said supply line, a sand blasting gun, and means connecting said sand blasting gun to said high pressure pump and means to supply abrasive material to said gun. t

' RONALD WEBSTER.

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