US1281017A - Method of setting and operating safety-valves. - Google Patents

Description

o. s. J ACOBUS. METHOD OF SETTING AND OPERATING SAFETY VALVES.

APPLICATION FILED APR- 7. I917.

1,281,017. I Patented Oct. 8, 1918" W A TTORNEYS.

DAVID S. JACOIB'US, OF JERSEY CITY, NEW JERSEY, .ASSIGNOR TO THE BABGOCK & WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A'CORPORATION OF NEW JERSEY.

METHOD OF SETTING AND OPERATING SAFETY-VALVES.

Specification of Letters Patent.

Patented Oct. 8, 1918.

Application filed April 7, 1917. Serial No. 160,370.

To all whom it may concern.

Be it known that I, DAVID S. JACOBUS, a citizen of the United States, residing at J ersey City, in the county of Hudson and State of New Jersey, have invented certaln new and useful Improvements in Methods of Setting and Operating Safety-Valves, of which the following is a specification,

It is well known that a safety valve must have relieving capacity at least equal to the boiler evaporation at the pressure at which the valve is set to blow off, as otherwise the boiler pressure will continue to rise with consequent danger of explosion, and modern boiler practice, by which boilers are being run at higher and higher capacities, necessitates the use of an increasing number of safety valves upon a given boiler. Thus, in a 1000 H. P. boiler, eight or ten safety valves of four and a half inches in diameter may be required. In the present forms of spring pop safety valves the valve will not shut at the same pressure at which it opens,

and the pressure must fall below the pressure at which the valve opens before it will close. For example, if a valve is set to open at 200 pounds steam pressure per square inch, it may not close until the pressure falls to 194 pounds per square inch. The difference in pressure between that at which the valve opens and at which it' closes is called the blow-down pressure. In applying safety valves to a boiler the most important requirement is that the pressure shall not rise over a certain fixed amount, and in addition to this in order to avoid undue losses through the blowing away of steam, the valve or valves must be so a ranged as to prevent an undue amount of blow down pressure. The purpose of the present invention is to provide a method of setting and operating safety valves to materially reduce the number required, for a given boiler, below that called for by present day practice.

Most large sized spring pop safety valves give a freeo ening for the passage of steam of an area about one-tenth to one-sixth the area of the steam connection to which they are attached. Should a greater opening be provided the blow down pressure becomes too great. It is a comparatively easy matter to construct a valve having a high capacity with more than the usual amount of blow down pressure, but the difiicult part of the problem has been to construct such a valve with a high capacity, which means a high 11ft, wlthout exceeding the usual specified blow down pressure of about six to' eight that it becomes worn or is thrown out of adjustment. It is necessary therefore with spring pop safety valves, as now constructed, to restrict the amount of blow down pressure to prevent undue waste in efficiency when the valve blows. But restricting the amount of blow down pressure limits the capacity of the valve to the extent above indicated when the valve is given a free area or lift of only about one-tenth to one-sixth the area of the steam connection. By the present invention it is, however, possible to provide a greater blow down pressure of say ten to fifteen pounds, and the valves may be made to open so as to have a considerably greater lift than is possible with the usual valves having a blow down pressure of six to eight pounds, so that a less number of safet valves may be safely. and economically use upon a given boiler, than is possible with valves as now constructed and set.

The invention will be understood from the following description taken in connection with the accompanying drawings in.

which Figure 1 illustrates an arrangement of three safety valves upon a single steam drum, and Fig. 2 an arrangement wherein the valves are mounted upon Y fittings.

In Fig. 1 the letters A, B and C designate safety valves set on a single steam drum D of a boiler. To illustrate the principle of my invention it may be assumed that the valve A is set to blow at 200 pounds steam pressure, the valve B at 204 pounds steam pressure, and the valve C at 208 pounds steam ressure. It may also be assumed that the vali e A has a blow down pressure of six pounds, that is on blowing at 200 pounds pressure per square inch it will close at 194 pounds per square inch. The valve B may.

blow down pressure of fourteen of ten'pouznds, and the valve C a blow down pressure of fourteen pounds, so that if the three valves are all made to blow they will all close at or about the same pressure, namely, 194. pounds per square 1nch. In thls way the valves B and C may readlly have progressively greater rellevlng capacities than the valve A by reason of the fact that a greater blowdown pressure is "allowed them; If the valve A has a lift of 0.13 inch, the valve-B may'have a lift of say 0.20 nch termines the minimum pressure to which the boiler must be blown down, a greater relieving capacity can be obtamed with a glven number of valves constructed and arranged as described with correspondingly; improved results, so that with a glven boiler a less number of safety valves will be required, with however the same results as with a larger number of the usual construction and setting as now employed.

A modified form of setting is shown in Fig. 2 in which the valves E, F, Gr and H are-mounted on Y fittings I and J above the "steam drum K. These valves may be set in series arranged for difl'erent amounts of blow down and varying capacities. lln cominon with the arrangement'shown in Fig. 1,

a greaterrelieving capacity may be obtained for a given number of valves for a glven amount of blow down pressure. If desired,

corresponding valves on each Y fitting may be set for the same amount of blow down pressure, that is, one of the valves on a given Y fitting may have a blow down pressure of say six pounds, and the other a blow down pressure of say ten pounds. This will enable the construction of the two valves for each Y fitting so that their combined capacity will be greater than the combined capacity of two valves each having a blow down pressure of six pounds. The idea suggested might be carried still furtherby installing the valves in groups of three or more.

The above specification describes valves of the same areafor which the variation in relieving capacity is secured through providing different amounts of lift. If desired, Valves of varying diameters may be employed.

Several valves may also be inserted in the same casing and used in place of two valves on a Y fitting. I

If desired, the valve which is set at the highest pressure on a boiler and which is the last to blow, could be made a special or emergency valve that would give a relatively high lift with a blow-down ressure that would be so great that this va ve would not close as soon as the others. A hand lever attachment could be placed on this special valve whichcould be used for closing the valve by hand after the pressure is reduced ,to that at which the other valves close. A

valve of the sort to be closed by hand could be made to give the, full area of the opening of the steam pipe which leads to it and should the other valves on the boiler fail to discharge enough steam to prevent the pressure rising to a point where the special valve will open, the opening of the special valve would surely prevent any further increase of pressure through its relatively large relieving capacity.

' Where valves are set in series in the way proposed, the valves which are at the highest pressure are only called on to act in an extreme emergency, and in modern practice such valves may practically never open, or open say only once in one or two years, this arising through the fact that there must be some unusual occurrence which requires the steam to be shut off from the entire plant,

and this with the boilers running at their maximum capacity in order that the safety valves may be called on to release the maximum capacity. As such occurrences are rare it can readily be seen that the valves which are set the highest in the series are seldom called on to act, or possibly may never be called on to act. It would therefore be no hardship as far as operating the steam plant is concerned to close the valves which are set at the highest pressure by hand should an occurrence arise that caused such special or emergency valves to open.

Safety valves are provided with hand levers for opening the valves by hand in order to make sure that-the valve does not.

become stuck to its seat. This is done daily 1n many plants in order to make sure that the safety valves are. in proper adjustment. The same levers that are used for opening the valves as described could be employed for closing the special or emergency valve.

What ll claim and desire to secure by Letters Patent of the United States is: 1. The herein described method consistmg 1n arranging safety valves upon a boiler so that they shall have progressively increasing lifts with increasing blow-down pressures and correspondingly increased relievmg capacities.

2. The herein described method consisting in arranging safety valves upon a boiler with progressively increasing lifts and correspondingly increased relieving capacities, and with progressively increasing blow down pressures.

3. The method of controlling the pressure of a steam boiler which consists in providing the same with a plurality of safety valves, and regulating said valves to open at different steam pressures and to close at substantially the same steam pressure.

4. The method of controlling the pressure of a steam boiler which consists in providing the same with a series of safety valves, and regulating said valves so that they shall have progressively increasing blow off capacities, and correspondingly increasing blow down pressures. v

5. A steam boiler having at least two safety valves, one of said valves having a greater lift and a'greater blow down pressure than the other, with correspondingly increased relieving capacity.

6. A boiler having at least two safety valves, one of said valves being set to open at a difi'erent'steam pressure from'the other valves, and both valves being arranged to blow down to substantially the same steam pressure.

7. A boiler having a lurality of safety valves with progressive y increasing lifts and greater blow-down pressures and correspondingly increased relieving capacities.

.8. A boiler having a plurality of. safety valves .with progressively increasing lifts and correspondingly increased relieving capacities, said valves being arranged with progressively increasing blow-down pressures.

9. A boiler having a plurality of safety valves arranged to open at progressively increasing steam pressures and correspond ingly increasing blow-down pressures.

10. A boiler having a plurality of safety valves including one of relatively high steam relieving capacity tobe used as an emergency valve, s'aid special valve being arranged to blow in case the other valves cannot fully discharge the steam generated, and means for closing said special valve by hand after blowing.

11. A boiler having a plurality of safety valves with progressively increasing lifts and correspondingly increased relieving capacities, the last valve to blow having means by which it may be closed by hand after it has opened and the steam pressure has fallen the desired amount.

In testimony whereof I have hereunto signed my name in the presence of two sub scribing witnesses.

DAVID S. JACOBUS. Witnesses:

EDITH CAMP, JOHN A. W. DIXON.

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