US2277075A - Apparatus for the control of hydrocarbons - Google Patents

Description

March 24, 1942. D H 2,277,075

APPARATUS FOR THE CONTROL OF HYDRQCARBONS Filed Feb. 11, 1938 4 Sheets-Sheet 1 INVELNI'UR:

, EDWARD TDAHL i) W Lucuala'L E. T. DAHL March 24, 1942.

APPARATUS FOR THE CONTROL OF HYDROCARBONS 4 Sheets-Sheet 2 Filed Feb. 11, 1938 RR R March 24, 1942.- E. T. DAHL 2,277,075

AEPARATUS FOR THE CONTROL OF HYDROCARBONS Filed Feb. 11, 1938 4 Sheets-Sheet 3 m2? 260 Amy/ :2 g IN \/E'.N+ u R:

L Mun A1712 T DAHL E. T; DAHL I March 24, 1942.

APPARATUS FOR THE CONTROL OF HYDROCARBONS Filed Feb. 11, 1938 4 Sheets-Sheet 4 :N ELN+ n R:

' EDWARD T DA L ii/ C QMM bug. 4w

Patented Mar. 24, 1942 APPARATUS FOR THE CONTROL OF HYDROCARBONS Edward T. Dahl, Abington, Mass., assignor to Mason-Neilan Regulator Company,

Boston,

Mass, a voluntary trust of Massachusetts Application February 11, 1938, Serial No. 189,950

Claims.

My invention relates to pipe still heaters and reaction chambers of the type commonly employed for treating liquid hydrocarbons, as for example, by cracking to convert higher boiling point constituents to lower boiling point constit- I uents, wherein the liquid hydrocarbons flowing continuously through the still are maintained at a relatively high temperature and pressure, and are discharged to the reaction chamber at a considerably lower pressure in which a separation of constituent fraction occurs. For example, it is not infrequent to encounter temperatures even in excess of 1000 F. and pressures of 1000 pounds per square inch. Stills of this type are well known to those skilled in the art, and include a furnace with tubular heating coils, or passes, through which the hydrocarbons flow at a substantially uniform velocity and at a temperature and pressure as required by the com stituents, the requisite conditions of flow and temperature being maintained by automatic controllers suitable for the purpose.

As is well known to those familiar with the cracking process, the condition of temperature and pressure must be maintained within certain definite limits to avoid undesirable flashing or improper break-up of components. Alow pressure may create excessive vapor formation in the pipe still, and the tubes may become overheated and burn out due to insuificient heat exchange, since the specific heat of vapor is considerably lower than that of the liquid. Also, a rapid reduction of pressure below a certain limit may cause sudden flashing of one or more liquid components, altering the product and possibly resulting in an immediate destructive pressure and even an explosion. On the other hand, if the pressure exceeds the maximum limit, the quality of the product may be impaired and the structural limit of safety be exceeded. It is theretore particularlly important that the hydrocarbcn pressure in the still piping be maintained within required limits.

While attempts have been made for many years to control the pressure as required for satisfactory and safe operation, in some instances by automatic means with hand operated by-pass valves for emergency use, and customarily by manual control means, such attempts have not been satisfactory, and a primary object of my invent-ion is to provide an arrangement and construction in combination with pipe still heater and associated apparatus by which the difficulties heretofore experienced in the treatment of high boiling point hydrocarbons, or materials having similar characteristics, are entirely eliminated.

The primary reason for unsatisfactory results in the past has been due to the fact that there is a break-up of the molecular structure of the hydrocarbons in the apparatus with pronounced coking, which has necessitated frequent shutdowns for cleaning. From observation and tests I find that coking arises from an accumulation .of tarry particles on the wall of a transfer line or valve, from a break-up of components due to improper temperature or pressure, and also that the rate of coking is substantially in inverse ratio to the rate of flow. For this reason, points of-little or no circulation, such as dead. ends in by-pass lines, pockets, and obstructed areas, become coked more rapidly than other parts of the apparatus where higher velocities are 'encountered. This has not been taken into consideration in the past and therefore conventional forms of valves have been used, both automatic and hand operated, which have proven to be totally unsuitable for the purpose. Where automatic valves have been used, it has been necessary to provide by-pass lines with hand valves for emergency use when the automatic valves become coked. Such lines afford only limited protection, since they form dead end pockets with little or no circulation where much. more rapid coking may occur than at any other point in the line of flow, and furthermore these lines are an added expense. For this reason shutdowns for cleaning purposes have been much more frequent than would otherwise be necessary. While it is recognized that automatic control is far preferable to manual control from the point of safety, convenience, and uniformity of product, it has not been practical to use automatic control to any extent for the reasons stated above.

Therefore, realizing the importance of high velocity and of uninterrupted flow for the prevention of coking, I provide a. single line of undivided flow, using a valve body in said line designed without pockets, obstructions, or abrupt changes in the direction of flow in which maximum velocity commensurate with conditions may be maintained, and combined with that valve, mechanism for automatic operation and mechanism for manual operation for actuating the same valve plug, thus providing a single point of regulation for both automatic and man ual control. My arrangement, therefore, not only affords a dependable automatic control for maximum periods of operation, but also provides dependable manual operation both for controlling the product and for emergency use.

A further object of my invention is to provide means for limiting the automatically controlled range of flow within a predetermined sector, or band of the entire range of flow, and for preventing a complete interruption of flow, or an excessive flow, which may happen due to the failure of any of the control mechanism, as for example, failure of the power device operating fluid supply, or the pressure controller. This consists of combining with the automatic and manual mechanism, limiting devices or stops,

which may be set for limitation of the valve plug travel. These stops are adjustable and may be used to limit the valve plug movement so that it is possible to have the valve operate over that section of characteristic flow curve which is best suited for maximum efficiency and safety of plant operation. I provide two forms of mechanism, in one of which the limiting stops are adjacent the hand control, readily accessibl to the operator, and in the other the stops are associated with indicators to facilitate adjustment.

Still another object of my invention is to secure identical flow characteristics by using the same valve plug for manual and automatic control. This is not possible where a by-pass is used for even though an expensive type of hand valve with a special plug is provided, owing to lack of circulation and rapid coking before the valve is opened, the characteristics may be altered.

The above and other features of the invention will be more clearly described and its object better understood from the following description and accompanying drawings in which drawings like numbers refer to like parts throughout.

In the drawings Fig. 1 is a diagrammatic view of a pipe still heater and a reaction chamber showing the novel combination and arrangement herein described.

Fig. 2 is a sectional view of a combined automatic and manual operated valve embodied in my invention.

Fig. 3 is a fragmentary view partly in section on the line 3-3 of Fig.2.

Fig. 4 is a view partly in section of a valve similar to that shown in Fig. 2, but having a modified form of operating mechanism.

Fig. 5 is a fragmentary view showing an indicating device applied to the construction illustrated in Fig. 4.

Fig. 6 is a bottom plan view of the mechanism shown in Fig. 5.

Having reference to the drawings, and. particularly to Fig. 1, a pipe still heater, indicated at I0, is provided with the usual coils or passes and burners l2, which may be oil or gas fired, or instead of which an electrical heating element may be used, it being understood that any well known medium may be employed. As herein shown, the burners are oil operated, and are connected to a suitable source of supply by a line |3 having a diaphragm operated valve M connected by a pipe |5 to a suitable control instrument l6 governing the operating pressure from an air line H, which is responsive to the burner line pressure by means of a connection 20, and to the still temperature by a thermal connection same being arranged to maintaina rate of flow to the burners in accordance with the still demand to maintain the level of temperature required.

At 2| is indicated a hydrocarbon feed line through which the oil is fed to the coils I I from any suitabl source as by a pump, herein shown as a steam driven feed pump 22, for affording the requisite oil pressure for the cracking process. As is now customary in the art I provide a substantially constant rate of flow of hydrocarbons through the still in order to avoid changing loads which tend to create temperature fluctuation, and for this purpose I employ a rate of flow controller 23 having connections adjacent to an orifice plate 24, said controller, as herein shown, being of the air operated type and for this purpose supplied by line 25. A diaphragm operated valve 26 controls a steam line 21 to the pump 22, said valve being governed by the controller 23 through an operating pressure line 28.

The still piping discharges into a reaction chamber 29, of any usual construction, through a line 3|, and in this line, preferably adjacent the reaction chamber, I provide an angle valve 30 having a diaphragm chamber 32 operated through a line 33 by a suitable controller 34. The controller 34 is responsive to the still pressure through a line 35, by which it is connected with the discharge line 3|, and governs pressure in the diaphragm chamber 32, the required operating pressure being supplied to the controller by a line 35. It will be understood that controller 34 is adapted to maintain a set pressure in still tubing H by controlling valve 30 to regulate the flow of hydrocarbons through discharge line 3|.

The valve 30 is shown in Fig. 2 and comprises an angle valve body 48 preferably connected at the inlet side to the discharge line 3|, by a cone-shaped reducer 3|, as by flanges 41 and 41', and at the outlet to the vaporization chamber 29 as by a flange 48. The body is shaped to form an inlet passage 49 extending from the flange 41 to a restricted port 50, the walls of the passage having smooth surfaces. At the approach to the port 50 the passage gradually expands, as shown at 49', to allow for the displacement of the extension 5| of a valve plug 5|, and to avoid undue restriction to the flow at this point, for excessive velocity around the stem of the plug may cause abrasion and turbulence.

The inlet passage 49 is formed to afford a path of streamlined flow for the hydrocarbons throughout its length and is adapted to maintain a velocity within a range in which the flow is sufliciently rapid along all parts of the wall surface to prevent the deposit of carbon, and yet is below the critical velocity beyond which difficulties arise from erosion. With this con struction a much higher fluid velocity is permissible without creating erosion than is possible with a valve of usual construction. Furthermore the valve plug 5| acts in the nature of a straightening vane to streamline the flow to the nozzle and allows a proportionately higher velocity without erosion to the valve plug extension and surrounding surfaces due to absence of abrupt changes in the direction of flow, pockets and obstructions, common to valves heretofore used in connection with pipe still apparatus.

The restricted port 59 is preferably formed by a Venturi-shaped member 52, adapted to be threaded into the valve body, as shown at 53. The valve plug 5| is of cylindrical construction,

and is shaped to cooperate with the port 50 to afford the control characteristics desired and to form a gradually constricting free flowing passage. The diameter of the plug'5l is preferably less than that of the port, sufficient clearance being allowed for a minimum circulation required to prevent carbon deposit at the control point when the valve is closed. I also employ this construction as an additional factor of safety for if the valve plug fractures and becomes inoperative it will be passed through the port by the upstream pressure and thus prevent a build up of back pressure as would otherwise occur. It will be noted that my construction affords a substantially uniform velocity through the valve inlet passage, thereby retarding the formation of carbon deposit, and that the velocity increases at the port 50 thus providing a maximum scouring action at the point of control. It will also be noted that by the use of the venturi principle a high velocity is maintained beyond the nozzle which gradually decreases to the valve outlet. I have found that carbon builds up more rapidly at the down stream side of a port than at other parts of the valve, in valves of usual construction, due to a sudden expansion of the fluid, eddy pockets and corresponding drop in velocity.

The valve plug I makes a reasonably snug working fit in a passage 58 in a sleeve 59, which has a driving fit with the body, as indicated at 68, the outer end of the sleeve being formed with a flange 6I, received in a recess in a flange portion 62 of the body 46. I preferably provide an air cooled intermediate, to prevent the high temperature to which the valve body is subjected I from radiating to the operating mechanism, comprising a finned structure 63, affording a large cooling area, and having a flange 64, for connecting same to the valve body by bolts 65, which makes a tight joint with the sleeve guide 59. Longitudinally of the air cooled intermediate 63 is a central passage varying in diameter as shown, and adapted to make a guiding fit with a valve stem 66 at 61. At 68 is shown a passage threaded at its outer end to receive a flushing oil line 69, maintained at a pressure higher than that in the pipe still tubing by a suitable pump not shown. The inner end of the passage 68 opens into an enlarged portion III which forms a clearance around the stem 66 by which the pasvalve plug 51 with which the stem 65 makes a threaded connection, and is further secured thereto by a pin I2. Adjacent the guide portion 61 of the stem passage is an enlarged passage I3 in which suitable packing is compressed by a gland I4. I employ two packing rings and I6, the former engaging a shoulder IT at the inner end of passage I3, and the latter being engaged by the gland I4, said packing rings being separated by a perforated lantern gland I8 which affords a storage space for grease to lubricate the stem and packing.

The flushing connection 69 admits cold flushing oil, from a source not shown, to the valve stem 66 and thence to the valve plug extension 5 I eventually seeping through to the valve body.

The flushing oil is preferably a decarbonated finished product adapted to prevent the formation of carbon, and as it flows around the valve stem and plug it helps to cool the parts, and thus prevents carbon deposit which would otherwise accumulate due to lack of circulation. I thus providemeans for preventing formation of carbon on working part surfaces where rapid circulation does not occur, and thereby insure a positive valve operation.

The automatic operating mechanism includes a power device, herein shown as a diaphragm responsive to the instrument 34, and carried by a yoke 8| having a portion 82 through which extends a cylindrical projection 83 from the intermediate structure 63, said projection being threaded to receive a clamping nut 84 by which the parts are secured together. Integral with the yoke BI is a tubular spring chamber 85 having a flange 86 to which the diaphragm chamber 32 may be bolted as shown. The diaphragm 88 is actuated by the fluid pressure from the controller 34 against a spring 81 through a diaphragm button 88 and a stem 89. The inner end of stem 89 is connected by a coupling 90 to the valve stem 66, as by threading. The spring 8'! may be mounted between spring buttons 9| and 92, the former being adapted to move with the stem 89, and the latter being carried by a guide support 93 threaded into the inner end of the spring chamber 85. As suitable guides for the stem 89 I preferably provide bearings 94, 95 and 95, as shown.

In operation, the valve plug 5| is automatically positioned by the pressure responsive instrument 34 to maintain a back pressure on the still piping as required. I

The manual operating mechanism includes a hand-wheel I86, which may be replaced if desired by a chain wheel or other mechanism for remote operation, said handwheel being secured to the outer end of a shaft III! by a nut I08 as shown. The shaft Ill! is mounted in combined radial and thrust bearings I89 carried in recesses in a bracket III). The bracket III] is shaped, as shown, for strength and is secured 'to posts II2 extending from the intermediate structure 63. Extending from the bracket I III are arms I I3 which support a shaft II4 which in turn carries levers H5 and H6 (Figs. 2 and 3). These levers constitute means for transmitting rotary motion, applied to the handwheel, to reciprocating motion to the valve stem, and also operate as limiting stops for automatic valve operation as will be described.

Lever H5 is in the shape of a fork and comprises a lateral end section III, carrying two adjustable set screw stops H8 and H9, and spaced arms I29 extending inwardly from said section, said arms being provided intermediate their ends with bosses I22 through which the pivot shaft H4 is received and to which it is secured by set screws H5 (see particularly Fig. 3). The arms I29 have rollers I23 rotatably mounted therein and adaptedto ride in transverse slots I24 in the side of the stem coupling 99.

Lever H6 is operatively connected with the hand-wheel shaft I01 by a block I25 threaded to the shaft, as indicated, and comprises a base I26 loosely mounted on the shaft IIIl between the arms I20 of the lever H5, and a bifurcated arm I26 extending from said base. The bifurcations of said arm carry rollers I21 in operative engagement with slots I28 in the block I25, said slots being arranged transversely of the axis of the handwheel shaft. Lever H6 is operatively connected with valve stem lever 5 by the adjustable stops I I8 and I I9. The ends of the stops project from the end section II! of the lever H5 and are adapted to engage contact faces I29 a shaft on the base' I25 of the lever H6. It will thus be noted that the stops H8 and H9 may be'adjusted to prevent any relative movement between the levers, or may be adjusted to allow as much relative movement as required thereby permitting the valve stem to be moved by the diaphragm 80 within fixed limits. Furthermore, it will be noted that the stops I I8 and H9 may be adjusted to permit the diaphragm 80 to move the valve plug I'between full open and closed positions if desired. These stops are in practice adjusted by the still operator to provide an automatic operating range having maximum and minimum limits, thus aifording a safe range of operation which cannot be exceeded by failure of the automatic operating mechanism. Furthermore, the entire range of movement permitted to the valve plug by the limiting stops may be varied within the entire range of valve movement between full open and closed positions adjusting the lever I I6, through the handwheel I06, and. thereby setting the minimum valve opening.

If manual operation is desired, the valve stem may be urged inwardly to move the plug to clos- -ing position against spring 81 by rotating the handwheel in a clockwise direction, or the valve plug may be moved to an open position against the fiuid pressure in the diaphragm by turning the handwheel in the reverse direction.

In the reaction chamber, indicated at 29 in Fig. l, where a separation of constituent fractions occurs, the liquids must be drawn off as they accumulate, and even more difficulty has been encountered due to the extremely rapid formation of coke. I-Iere also it has been customary to maintain the required liquid level by a hand valve of usual construction because automatic valves with hand-controlled by-pass lines have been found unsatisfactory. While the pressure drop between the reaction chamber and the discharge line, is usually less than the pressure drop liquid level in the reaction chamber is maintained by a suitable float I32, which controls fluid operating pressure from a supply line I33 through a line I33 to the diaphragm chamber I34 of the valve I30 by a pilot I35 of any usual construction. Thus a constant level is provided and rapid coking avoided at another point in the apparatus which in the past has required frequent shut-downs for cleaning purposes.

I have found by many tests that my improved arrangement has lengthened the operating period from three to four times. It has made it possible to provide a better product and at the same time eliminated the use of by-pass valves where automatic control has been attempted, or the constant attention of an operator where manual control has been used. I

In Fig. 4 I have shown a diaphragm operated valve, similar to that shown in Fig. 2, having a modified type of hand and stop mechanism. This comprises a handwheel I40, mounted on I4I journalled in bearings I42, and threaded along its central portion for a correspondingly threaded cross head I43 provided with pins I43 engaging slots I44 in opposite walls of a casing I 45. The casing I 45 is provided with an end wall plate I detachably secured thereto, and said casing is mounted between the air cooled intermediate I46 and the spring chamber I41 being secured to flanges on said members. An angle lever I50 is pivoted at I5I in the walls of the casing I45. The forked arm I52 of the lever I50 engages the pins I43 as shown. The diaphragm stem I53 and valve stem I54 are connected by a coupling I55, into which they are threaded, which moves with the stems and makes a loose fit through a cross head I56. The coupling I 55 is provided with a flange I51 at its outer end, and is threaded externally to receive an adjustable stop nut I58 and lock nut I59, the flange I51 and stop nut I58 being adapted to contact the cross head I56 should the stem movement imparted by the diaphragm exceed that for which the device is set. The cross head I56 is provided with pins I56 that are adapted to engage oppositely disposed slots I60 located in the side walls of the casing I45 at each side of the coupling I55 and parallel therewith. The other arm I52 of the lever I50 is also forked and is adapted to engage the pins I56 of the cross head I56 as shown.

Thus the extent of range of the automatic movement depends on the distance between the stops and this distance may be adjusted as desired from a setting where the diaphragm imparts no movement to the valve plug to a setting wherein it may move the plug from closed to open position. Hand operation is obtained by turning the wheel I40 and either moving the cross head I56 against the stop I58 to close the valve, or against the stop I51 to open the valve. To position the range of automatic movement within the entire rangeof valve movement the cross head I56 may be set by the wheel I40 to give the selected range desired. Thus I pro- (III vide means for automatic operation within a range in which it is practical to operate, means for varying the extent of that range, means of affording manual operation between full open and closed positions, and means for adjusting the automatic range at any point desired within the manual range.

In connection with the construction illustrated in Figs. 5 and 6 I have shown an effectivemeans for indicating the range of automatic operation at which the device may be set, for indicating the exact setting of said range within the entire range of operation, and for indicating the position of the valve plug within these ranges. As is well known to those skilled in the art, the total valve travel between full open and closed positions is not great. Small increments of valve movement afiord relatively large variations in flow, and in the operation of pipe still apparatus it is very important that the permitted minimum and maximum valve openings be strictly adhered to, in setting the range of automatic control, to insure a practical and safe range of motor operation.

The indicating device is shown in Figs, 5 and 6 and includes three pointers X, Y and A, the first two of which indicate the limits of movement which may be imparted to the valve plug by the diaphragm, or like power device, the last pointer being used to show the exact opening of the valve plug. Pointers X and Y are pivotally mounted between ears I10 on a pin I1I, said ears being formed on one end of a supporting member I12 pivoted at its opposite end on a pin I13 extending outwardly from one side wall of the casing I45. Integral with the supporting member I12 is an arm I14 having a slot I longitudinally thereof, and in this slot is an adjustable pivot I16, connected to one end of a link I11, the other end of which is pivoted at I18 to one pin I58 of the cross head I58. Thus the supporting member I12 assumes a radial position about its pivot I13 in accordance with the position of the cross head. The pointers X and Y are formed with shoulders I19 at the pivoted end, which extend over opposite sides of a web portion I88 of the supporting member I12 and the free ends of the pointers are provided with fingers I8I projecting toward each other so that they move in one plane (see particularly Fig. 6). Yielding means, preferably in the form of a coil spring I82, surrounding the pivot I1I, the ends of which engage the pointers X and Y, as shown, and urge the indicating fingers I8I of the pointers apart and the shoulders I19 against the web I80. Adjustment screws I83 in the shoulders I19 are provided by which the pointer fingers I8I may be spaced as desired.

The pointer A is also pivoted at I13, being secured at the outer end of the pivot pin in a plane parallel with the pointers just as described. This pointer is likewise provided with a slot I84 by which it is connected through an adjustable pivot I85 and link I86 to the flange stop I51 on the coupling I55 by means of a pivot pin I81 secured to the flange and extending outwardly through a slot I68 in the casing. It will thus be understood that the pointer A assumes a radial position around the pivot I13 in accordance with the position of the coupling I55, which in turn moves with the valve plug.

As a suitable protection to the indicating mechanism just described I provide a hat-shaped cover I88 secured to the casing by screws I89, a part of one side of the raised portion of which is formed radially about the pivot I13 On which the pointers are mounted. The arc-shaped side has a rectangular opening and within the cover and over the opening a scale plate I9I, having onset sides I92 is secured, as by screws I93. In the plate I9I are slots I94 and I95, the former being in the plane of movement of pointers X and Y, and the latter in the plane of movement of pointer A. The slots extend through the oilset sides I92 of the scale plate and the pointers project into the slots and may be moved out of the slots at the sides under the cover I88. Suitable markings may be applied to the scale plate I9I, as shown, to indicate valve openings and set limits of valve movement.

By the arrangement just described a small increment of valve or cross head movement is magnified at the pointer ends so that a close setting and an exact reading may be obtained. To facilitate production and provide a device adapted to various sizes of valves with correspondingly varying valve travels, the slots I15 and I84 in the supporting member arm I14 and pointer A respectively herein above described, provide an adjustable setting for the links I11 and I86. Thus the throw imparted by the links I11 and I85 may be varied and adjusted so that the pointer A will move between closed and open positions, as shown in the scale, for a corresponding valve travel of valves of various sizes, and similarly the pointers X and Y may be adjusted.

In the operation of the still unit it may frequently be necessary to change the volume of hydrocarbons passing through the still, or a new run may be made in which the liquid components are changed. This may require a change in the 5 scope of the range of automatic'valve travel or a change in normal valve opening, in accordance with the conditions. The operator first determines the normal valve opening maintained by the controller 24 to afiford the pressure or liquid level desired under the predetermined rate of flow. This will be apparent from the position of apointer A in the scale. The handwheel I40 is then rotated counter-clockwise and the cross head I56 moved outwardly until it contacts the flange stop I51 on the coupling I55. With the cross head in this position and the valve still at the normal opening, the pointer Y is adjusted to a position coinciding with that of the pointer A indicating the amount of valve opening. After this adjustment has once been made further adjustment of this pointer is normally not required in later valve settings. The cross head is then moved inwardly until pointer Y indicates on the scale the minimum valve opening allowable for minimum operating conditions and pointer X is moved to a position on the scale to show a maximum allowable flow, at which position pointers X and Y are equidistant from pointer A. Adjustable stop lock nut I59 is loosened and the stop I58 adjusted until its distance from the cross head is exactly equal to the distance between the cross head and the flan e stop I51. This may be checked by rotating the handwheel clockwise bringing the cross head in contact with the stop I58 which should place indicator pointer A at pointer X. The lock nut I59 is then made fast and the valve set for the flow range required. It will thus be understood that this indicating mechanism greatly facilitates setting the valve to the exact range required, and applies equally in the maintainence of liquid level in the reaction chamber as well as to pressure in the still as will be understood by those skilled in the art. While I have illustrated and described the best embodiment of my invention known to me, it will be understood that changes may be made without departing from the spirit of my invention as set forth in the appended claims.

Having thus described my invention, I claim: 1. A control valve having a passage for the flow of a controlled medium and a valve plug for controlling the flow through said passage, a power device capable of actuating said plug throughout its total range of movement, means connected to said plug and movable therewith, a pivotally mounted angle lever having a free end in the range of movement of said means for restricting the movement effected by said power device to a portion only of the total range of movement of said plug, and a hand device in operative connection with the other end of said lever for varying the position of its free end within the path of movement of said means to adjust the range of plug movement eifected by the power device within its total range of movement. 2. A control valve having a passage for the flow of a controlled medium and a valve plug for controlling the flow through said passage, a power device capable of actuating said plug throughout its total range of movement, means connected to said plug and movable therewith, a pivotally mounted angle lever having a free end in the range of movement of said means for restricting the movement effected by said power device to a portion only of the total range of movement of said plug, a block pivotally connected to the other end of said lever, a rotatable shaft having a fixed mounting on which said block is threaded, and a handwheel connected to said shaft for varying the position of the free end of said lever within the path of movement of said means to adjust the range of block movement efiected by the power device within its total range of block movement.

3. A control valve having a passage for the flow of a controlled medium, and a valve plug for controlling the flow through the passage, a power device capable of actuating said plug throughout its total range of movement, means connected to said plug and movable therewith, second means in the range of movement of said first means for restricting the movement efi'ected by said power device to a portion only of the total range of movement of said plug, said first and second means being relatively adjustable to vary the magnitude of said restricted movement, mechanism for manually varying the position of said second means within the path of movement of said first means to adjust the range of plug movement effected by the power device within its total range of movement, an indicator arm operatively connected with said first means to indicate the position of said plug, and a pair of indicators operatively connected to said second means to indicate the limits of the restricted range of plug movement.

4. In a control valve for governing fluid flow having a body for the passage of fluid and a valve plug governing flow through said passage, the combination with a stem connected to said valve plug and a pressure operated device connected to said stem for moving said valve plug between full open and closed positions, of a hand operated device, said stem and hand operated device constituting a power operated member and a hand operated member respectively, stops movable with one of said members and a stop movable with the other of said members selectively engageable with the aforesaid stops, said stops affording means for moving said valve plug between full open and closed positions by said hand operated device, and the positions of at least two of said stops being adjustable to limit the range of plug movement normally effected by one of the said devices to a selected rangeof variable magnitude, the movement of the other stop serving also to vary the position of said range, between full open and closed positions, independently of its magnitude. l

5. In a control valve for governing fluid flow having a body for the passage of fluid and a valve plug governing flow through said passage, the combination with a stem connected to said valve plug and a power device operatively connected with said stem for actuating said valve between full open and closed positions, of a hand operated device, stops movable with said stem and a stop movable with said hand operated device selectively engageable with the aforesaid stops affording means for moving said valve plug between full open and closed positions by said hand operated device, and the positions of said first named stops being adjustable to limit the range of plug movement normally effected by said power device to a selected range of variable magnitude, the movement of the other stop serving also to vary the position of said range, between full open and closed positions, independently of its magnitude.

EDWARD T. DAHL.

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