US 1231280 A
Description (OCR text may contain errors)
J. F. METTEN. SAFETY VALVE.
APPLICATION FILED NOV 16. 1916- ]Patented June 26, 1917.
3 SHEETS-SHEET! L m zm J. F. METTEN.
Patented June 26, 1917.
3 SHEETS-SHEET 2.
J. F. METTEN.
SAFETY VALVE. ATI-ON FILED NOV 16 Patented June 26, 1917.
3 SHEETS-SHEET 3.
JOHN F. METTEN, OF PHILADELPHIA, PENNSYLVANIA.
Specification of Letters Patent.
Patented June 26, 191?.
Application filed November 16, 1916. Serial No. 131,649.
' especial reference to means whereby an ejector is combined with the pilot valve in such manner as to control the movement of the main valve more positively and accurately than in prior constructions, and also to enable the pressure which actuates the pilotv valve to be more constant.
The invention is of especial applicability to safety valves for steam boilers, etc., whereby some serious disadvantages of spring loaded valves are overcome. All marine boilers-and the majority of stationary boilers are now fitted with spring loaded safety valves. These valves are of the type in which the main valve is held to its seat against the boiler pressure bya heavy spring, so adjusted that when the pressure reaches a predetermined amount, the resultant load against the inner side of the valve is suflicient to overcome the spring, thereby opening the valve and permitting the steam to escape until the pressure falls-to a point where the spring closes the valve. As the boiler ressures approach the blow-01f point, the di erence between the spring load and the steam load becomes so slight that at times there is not sufficient load to hold the valve tightly to its seat unless the latter is in perfect condition. For this reason, safety valves are apt to leak at the ranges of pressure approaching their bloW-oif point.
Again, the heavy springs have a very rapid rise in compressionload as their length is reduced, so that the lift of the valve is extremely limited and the relieving capacity is correspondingly curtailed. Various arrangeinents ofpopping rings have been proposed so that when the valve lifts, the kinetic energy of the escaping steam will augment the load due to static pressure of the steam under the seat, thus augmenting the lift from' to The amount of .additional lift that can be secured bythese means is very limited, as the valve does not seat until the pressure falls considerably below the blowoff point, if the popping ring effect is excessive. These conditions have} so limited the size and capacity of this type of valve, that from four to six safety valves are often necessary on large boilers to obtain the necessary relieving capacity and obtain satisfactory conditions as to tightness, reliable operation, and maintenance of the desired constant boiler pressure.
According to this invention, the valve is actuated by differential pressure on a piston or diaphragm subjected on one side to the fluid pressure, and on the other side to the same pressure when the valve is to be in one position, and to a reduced pressure when it is to be moved to another position. The broad feature of the invention resides in the provision of an ejector supplied by approximately constant steam pressure for controlling the piston, and a pilot valve which controls the ejector. When combined with a safety valve for a boiler, herein illustrated as a'preferred embodiment of the invention, a number of advantages are realized, which,
so .far as I am aware, have not heretofore been obtained.
In the accompanying drawings,
Figure 1 is a vertical sectional view of a safety valve embodying the invention;
Fig. 2 is a side view, partly in section;
Fig. 3 is a plan view;
Fig. 4 is a section on the line 44 of Fig. 1;
Fig. 5 is a section on the line 55 of Fig. 1, and I Fig. 6 is a plan view of the main valve.
I 1 is a main casting having a pilot valve 2 and a main valve 3. v This casting has a lower main passage 4 which is bolted to the boiler, and which branches as at 6 around the partition 7 and merges in the valve chamber 8. In the upper portion 9 of the partition is provided a valve seat 10 upon which the valve 3 seats, this valve having the customary guiding ribs 11. The valve body 3 is attached to a stem 12 by means of a nut 13, and on'the valve stem 12 is a controlling piston 14, working in a cylinder 15. The lower side of piston 14 is subject to the pressure in chamber 8, and the diameter of piston 14 is proportioned: to the efi'ective diameterof the valve 3 so that the valve 3 will be lifted when the effective pressure on top of the iston 14 is reduced a certain amount. 16 1s a bafiie or guide vane, it being seen that the main escape of steam is from the passage 4 through the passages 6 to chamber 8, thence through the valve and out at the passage 17, the outflowing steam being deflected by the baflie-16 to avoid inter ference with the free escape of steam through the pilot valve escape passage 37.
The cylinder 15 is connected by a pipe 18 to a chamber 19 formed in the auxiliary pilot valve casting 20. This chamber 19 is connected by passage 21 and pipe 22 to the main body of steam pressure within the,
boiler at suflicient distance from the chamber 4 so that the pipe 22 will carry the main boiler pressure. With the large escape area provided by the high lift of the main valve, there is a decided fall of pressure at the en tering side, as in the chamber 4, so that without the pipe 22 connected to a distant point, there would be an objectionable fall of pressure in the pipe 21. By connecting this pipe 22 to a distant point, it will be seen that the pressure therein which actuates the pilot valve is not afi'ected by the fall of pressure which occurs in the passage 4 whenever the main valve 3 is open. The steam pressure from'pipe'22 through passage 21, chamber 19 and pipe 18 to the cylinder 15 balances the piston 14, sothat the main valve 3 is normally held seated by the unbalanced pressure thereon in chamber 8. The effective area of piston, 14 is sufficiently in excess of the elfectiye area of the main valve 3 to insure that when the pressure on the top side of'piston 14 ,is decreased a predetermined amount the pressure' on the other side overbalances the opposin pressure on the valve 3 and opens the va ve.
Mounted in the assage 25 connected to the chamber 19. 1s the pilot valve 2. Mounted on the stem 26 of the pilot valve is a piston 27 and bearing on the piston 27 is the spring 28. The tension of the spring 28 is adjusted by means of a hollow nut 29 threaded in the yoke 30 and having the turning head 31, 32 beinga lock nut. The stem 26 of the pilot valve is extended into a spindle 33 which slides through the hollow nut 29 in the turning head 31 and engages with a lever 34 pivoted at 35. The engagement is effected by means of nut 36 threaded on the upper end of the spindle 33. By lifting the lever 34 it will be seen that the pilot valve 2 can be lifted manually against the pressure of spring 28, as when it is desired to blow-off, as Well as automaticallywhen 'the pressure on under side of pilot valve overcomes spring 28. s
The pilot valve 2 is normally held seated against the pressure in chamber 19 by spring 28, and disposed in the conical passage 25 "and carried by the pilot valve 2 is a cone 38, which is enlarged at its lower end below the pipe 18, but which does not entirely close the passage. Below the. lower enlarged portion of cone 38 are guiding lugs 39. Surroundin the cone 38 and projecting into the conical passage 25 is a nozzle 40, the nozzle 40, as seen in Flg. 1, pro ecting into the passage 25 above the lower end of the pilot valve seat 42. I
Whenever the pressure on the pilot valve overcomes the spring'28, the constant-pressure steam in pipe 22 passes around the cone 38 and out through the valve 2 and passage 37 into the exhaust chamber 17. The steam passing at high velocity through the conical passage 25 acts on the principle of an e ector to reduce the pressure in chamber 19- pressure in pipe 21 because the pipe 22 is connected to the boiler at some distance from the chamber 4. The ejector pressure is thus substantially constant and not sub-' ject to the fluctuations which would occur if the pipe 21 were directly connected to the chamber 4. Inasmuch as the pilot valve piston 27 is subjected to the escape pressure resulting from the steam passing through the pilot valve 2 when open, the lift of the pilot valve is augmented to provide a free escape from the ejector. By providing means for varying the area of passage 37 the back pressure on the piston 27 can be varied to suit the amount of blow-down desired. It results by this construction that when the pilot valve once opens suflieiently to cause the main valve 3 to open, both valves will stay open until the main boiler pressure has fallen to the desired extent,
seats the main. valve because the area of piston 14 is somewhat larger than the effective area of the main valve 3.
By this invention, the capacity of a given size of valve is greatly increased by reason of causing it to be controlled by the main boiler pressure instead of the local pressure in the inlet chamber, and the opening of the main valve can be such as to fully utilize the valve diameter. In prior valves provided with popping rings such wide open- 4 ing has not been possible. For instance, a
four inch safety valve of this type will give a .clear discharge opening equal to the area of the seat by a. one inch lift, which would equal in capacity. five ordinary valves provided with popping rings cach t-having ap 1 grf'eximately three-sixteenths of}; an inch nozzle and pilot valve seat 42, so that the valve can be sembled.
This application is in part a continuation of my application filed December 22, 1915,
Serial No. 68,157.
Having thus described my invention; Idequickly assembled or disasclare that what I claim as new and desire to secure by Letters Patent, is:-
1. In combination, a safety valve for a steam boiler, a pressure operated pilot valve, a nozzle controlled thereby, a pressure operated element associated with said safety valve and having a chamber on one side connected by a conduit in said nozzle, the other side of said element being exposed to the boiler pressure, and a fluid pressure supply connection to said nozzle from a comparatively remote point within the boiler.
2. The combination with a fluid pressure actuated pilot valve, of means cooperating with the valve when open to produce an ejector action, a main steam boiler safety valve having a face normally subject to boiler pressure tending to hold said safety valve closed, and a conduit by which the pressure fluid may be removed from said face to the ejector.
3. The combination with a tube having a .pilot valve, of a casing having a conical wall in advance of said valve, and controlled thereby, a conical extension in said tube and 'carried by said valve, and cooperating with the wall of said casing to produce an annular jet when said valve-is opened, and
mechanism controlled by the operation of said annular jet.
4. The combination with a main valve opening inwardly and held to its seat by fluid pressure, of a loaded pilot valve controlling said main valve and adapted to be lifted by predetermined fluid pressure, means forming an outlet chamber in advance of said pilot valve, a nozzle within said chamber controlled by said pilot valve, a piston connected to said main valve. a cylinder for said piston, means connecting said chamber and said cylinder, and means whereby said valves discharge through a common outlet.
5. In a safety valve, the combination of a body having a passage for connection to a source of fluid pressure, a main valve. seat and a cylinder opening from said passage, said cylinder being larger in diameter than said seat, a main valve comprising a valve head cooperating with said seat and a piston sliding on said cylinder, an auxiliary valve, an ejector nozzle controlled thereby, and a passage from said ejector nozzle to the rear side of said piston whereby when the ejector is operative, said piston overcomes the seating pressure on the main valve, and when said ejector is inoperative, said piston is overbalanced by the seating pressure on the valve, said passage, being freely connected through the ejector nozzle to receive full boiler pressure under normal conditions.
6. A safety valve comprising a main valve held normally seated by boiler pressure, a pilot valve for controlling the main valve, yielding mechanical means normally holding said pilot valve seated an ejector nozzle discharging into the main valve exhaust and controlled by said pilot valve, a source of supply for said ejector independent of the inlet side of the main valve, an ejector chamber adjacent said nozzle, and a connection from said chamber to one side of said main valve.
' 7. The combination with a steam boiler, of i a main valve and a pilot controlling "valve therefor, of an ejector nozzle between the boiler and said pilot valve, means for supplying pressure to said nozzle, a chamber surrounding said nozzle and having an annular passage extending through said pilot valve seat, and a controlling pipe connection from said nozzle chamber to said main valve.
8. The combination with a main valve and pressure controlled means for actuating said valve, of a pilot valve controlling said main valve and adapted to be opened by predetermined pressure, an outlet chamber in advance of said pilot valve openin into the exhaust passage of said main va ve, and a baflie between said pilot valve exhaust and the main valve exhaust.
9. The combination with a main valve and pressure controlled means for actuating said valve, of a pilot valve controlling said main valve and adapted to be opened by predetermined pressure, an outlet chamber in advance of said pilot valve opening into the exhaust passage of said main valve, abaflie between said pilot valve exhaust and the main valve exhaust, and means supplying pressure to said pilot valve independently of the fall in pressure on the inlet 'side of the main valve when the latter is open.
10. In combination, a steam boilersafety valve, a pilot valve therefor subject to boiler pressure tending to open it, a mechanical means opposing such steam pressure, and a member associated with the pilot valve and subject to the impact of steam escaping from the pilot valve opening when said valve is open, said member being positioned so that the impact of the steam thereon is in oppomotive fluid inlet connected to the boiler and a motive fluid inlet connected to said chamber, a pilot valve seated over the injector nozzle, and mechanical means tending to hold said pilot valve to its seat. a
12. In combination, a steam boiler safet valve, means mechanically connected therewith having a face subject to boiler pressure tending to hold the valve closed, a chamber around said face, an ejector adapted to exhaust motive fluid from said chamber, and a pilot valve controlling said ejector.
13. In combination, a steam boiler safety valve, means mechanically connected therewith having a face subject to boiler pressure tending to hold the valve closed, a chamber around said face, an ejector adapted to receive motive fluid from the boiler and there,
by to exhaust fluid from said chamber, a pilot valve controlling said ejector on the discharge side thereof, and yielding mechanical means tending to hold said pilot valve to its seat against the boiler pressure.
14. In combination, a steam boiler safety valve, means mechanically connected therewith having a face subject to boiler pressure tending to hold the valve closed, a chamber around said face, an ejector adapted to exhaust fluid from saidchamber, a valve seated over the ejector against boiler pressure, there being a freeconnection between the boiler and said chamber through said ejector, and yielding mechanical means tending to hold said pilot valve to its seat against boiler pressure. y
In testimony whereof I aflix my signature, in presence of two witnesses.
JOHN F. MEITEN;
FRANCIS L. CRAMP, J H. MCMASTER.