RU2757469C1 - Control valve for steam turbines with zero steam leakage along the stem at fully open - Google Patents

Abstract

FIELD: power engineering.SUBSTANCE: invention relates to the field of power engineering. The control valve for steam turbines contains a valve box, a valve box cover, a spool, a diffuser seat, a valve stem, an axle box. The valve stem from the side of the axle box is equipped with a rigidly fixed locking disc, on the surface of which an annular protrusion with a rounded surface is made on the side of the contacting axle box, and an annular saddle in the form of a corresponding annular recess is made on the contacting surface of the latter. The valve is equipped with spherical washers located between the cylindrical heads of the half-couplings, constituting a flexible coupling connecting the end of the valve stem to the actuator stem.EFFECT: elimination of steam leakage along the stem when the valve is fully opened.1 cl, 1 dwg

Description

The invention relates to the field of power engineering and is designed to improve the efficiency of high-pressure cylinders of steam turbines with nozzle steam distribution.

A feature of steam turbines with nozzle steam distribution is that steam is supplied to them using a number of control valves (most often four) with their sequential opening (AV Shcheglyaev "Steam Turbines"). In the case of a four-valve steam distribution, the rated turbine load is achieved with three valves fully open and a fourth valve partially open. At 50% turbine unloading, the first two valves remain fully open. For power turbines with a capacity of 200-300 MW, losses from steam leakage along the control valve rods reach 1.5%. Accordingly, if steam leakage along the three valve rods is prevented, the efficiency of the HPC of these turbines can be increased by 0.8-1%.

Currently, to solve this problem, some turbines in Russia use liquid metal seals made in accordance with patent RU No. 832187 (F16J 15/14, 06/25/1974) (There are no seals on the control valve stems on steam turbines of foreign companies). The main disadvantages of liquid metal rod seals are their relative complexity and loss of density when the rods vibrate.

The technical problem solved by the proposed device consists in increasing the efficiency of high-pressure cylinders by eliminating the leakage of steam along the stem when the valve is fully opened.

The technical problem posed is solved by the fact that in a known control valve, mainly for steam turbines, containing a valve box, a valve box cover, a spool, a diffuser seat, a valve stem, an axle box, according to the invention, the valve stem on the side of the axle box is provided with a rigidly fixed locking disc, on the surface of which an annular protrusion with a rounded surface is made on the side of the axle box in contact with it, and an annular saddle is made on the contacting surface of the latter in the form of a corresponding annular recess, while the valve is equipped with spherical washers located between the cylindrical heads of the half-couplings constituting a flexible coupling connecting the end part of the stem valve with actuator stem.

The figure shows the design of the proposed control valve with a device for eliminating steam leakage along the stem when the valve is fully open and the assembly for connecting the valve stem to the actuator stem. The following designations are adopted:

1 - valve box;

2 - valve box cover;

3 - spool;

4 - diffuser seat;

5 - valve stem;

6 - axle box;

7 - locking disc;

8 - ring valve;

9 - annular seat of the shut-off valve;

10 - rod of the drive mechanism;

11 - valve stem coupling half;

12 - half-coupling of the drive mechanism stem;

13 - connecting bolts with a cylindrical head;

14 - spherical washer.

The mechanism for preventing steam leakage along the valve stem works as follows:

When the valve opening mechanism is turned on, its stem 5 raises the spool 3. At the same time, the shut-off disk 7, rigidly connected to the stem 5, approaches the end surface of the axle box 6 and when the spool 3 is fully lifted, the annular valve 8 (Fig., A), located on the shut-off disk , enters the annular saddle 9, made on the end surface of the axle box 6, completely blocking the steam access to the gap between the axle box 6 and the rod 5.

To eliminate a possible mismatch between the full stroke of the spool 1 and the full stroke of the stem 10 (Fig., B) of the drive mechanism, both of these stems 5 and 10 are connected by a flexible coupling consisting of a valve stem half coupling 11, a drive mechanism stem half coupling 12, four special connecting cylinder head bolts and ball washers 14.

This design allows additional axial movement of the rod of the actuator 10 within the elastic deformation of the spherical washer 14 (in this case, within 3 mm) after the annular valve 8 is seated on its annular seat 9.

The flexible coupling connecting the rods 5 and 10 is arranged as follows. At the end of the valve stem 5 by means of a threaded connection, the coupling half 11 is attached, and at the end of the stem 10, the coupling half of the drive mechanism is installed on the thread. Both half-couplings are interconnected by four fastening bolts 13, under the cylindrical heads of which spherical washers are laid, which provide the possibility of additional axial displacement of the rod 10 relative to the stationary rod 5, located on the stop of the axle box seat 8, by 3 mm.

Thus, a control valve is proposed, mainly for steam turbines, containing a spool, a seat, a valve stem, a journal box, a valve body, a valve box cover, characterized in that a locking disc with an annular valve is installed on the valve stem on the side of the journal box, and on the end part of the journal box a reciprocal annular saddle is made.

In addition, the valve stem is connected to the stem of the valve drive system by a flexible coupling, which provides the possibility of axial movement of the stem of the valve drive mechanism, after the stop valve lands on its seat in the axle box, within 3 mm.

Claims (1)

A control valve, mainly for steam turbines, with zero steam leakage along its stem when the valve is fully open, containing a valve box, a valve box cover, a spool, a diffuser seat, a valve stem, an axle box, characterized in that the valve stem on the side of the axle box is provided with a rigidly fixed a locking disc, on the surface of which an annular protrusion with a rounded surface is made on the side of the axle box in contact with it, and an annular seat is made on the contacting surface of the latter in the form of a corresponding annular recess, while the valve is equipped with spherical washers located between the cylindrical heads of the half-couplings constituting a flexible coupling, connecting the end of the valve stem to the actuator stem.

Images