FIELD OF THE INVENTION
The present invention relates to hydraulic testing of emergency stop valve and control valve.
More particularly the present invention relates to a fixture for hydraulic testing of emergency stop valve (ESV) and control valve (CV) of steam turbine used in power plant.
BACKGROUND OF THE INVENTION
Steam turbine is a heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft to drive an electrical generator and to generate electricity.
In a typical larger power stations, the steam turbines are split into three separate stages, the first being the High Pressure (HP), the second the Intermediate Pressure (IP) and the third the Low Pressure (LP) stage, where high, intermediate and low describe the pressure of the steam. The high pressure (HP) turbine is the first main engine turbine to receive steam from the main steam system. It is designed to efficiently extract work out of high pressure steam.
After the steam has passed through the HP stage, it is returned to the boiler to be re-heated to its original temperature although the pressure remains greatly reduced. The reheated steam then passes through the IP stage and finally to the LP stage of the turbine. A steam turbine consists of three main components viz. Outer casing, inner casing and bladed rotor.

Emergency Stop Valve & Control Valve (ESV & CV) are connected to the HP inlet assembly. Through ESV & CV, steam from the boiler is made to enter to HP turbine blades through main steam line.
Emergency stop valves (ESV) are quick closing valves between turbine and steam generator and these valves resides inside a main body or casing known as ESV & CV casing. One Emergency Stop Valve and one HP Control Valve are combined in a common body with their valve spindles arranged at right angles to each other. The stop valve can rapidly interrupt the supply of steam from steam generator to the turbine. The HP control valve controls the steam flow to the turbine according to the prevailing load. In the event of a disturbance in the system or on trip-out, both emergency stop valve and control valve close rapidly.
ESV & CV must be tested before supplying to the site for correct operation and therefore before doing ESV & CV assembly, hydraulic testing of ESV & CV casing is required. The purpose of doing hydraulic testing is to ensure the soundness of casing material. If casing material is not sound then during ESV & CV operations at thermal power plant, casing may burst/crack resultingserious consequences.
For performing the hydraulic testing (refer fig.3):
- Stop & control sides of ESV & CV are closed by respective valve covers fitted with plugs.
- Breech nut side is closed with the help of a fixture.
Pipelines for inlet and outlet for water (testing fluid) with pressure gauges are fitted to the ESV & CV casing. Water is filled in ESV & CV casing and required pressure is established in casing. Finally, casing is checked at required pressure.

The fixture which was foreseen for this purpose was to be used at breech nut side to seal it for any leakage during hydraulic testing. At face B, there is a provision of putting O-ring (a seal in the form of a ring with a circular cross section, typically made of rubber and used especially in swiveling joints) but groove available for this was of smaller size. O-ring was fitted in the groove and fixture was assembled with the breech nut. After that pressure in water pipeline was increased slowly and it was observed that water was found leaking through Breech nut side at much below the required pressure. For investigation the fixture was removed and found that O-ring got cut/damaged at various places.
Second time the same process as above was repeated and found the same problem with the O-ring. The same bottleneck was found for the failure of subsequent hydraulic testing of the casing repeatedly.
For hydraulic testing, ESV & CV casing is placed such that its stop side is in vertically top position as in this position breech nut side rests horizontally (refer fig.3). Earlier, the fixture was foreseen to be assembled in vertical position of breech nut side, and for the same, the sealing fixture on breech nut side was assembled with breech nut and then whole ESV & CV casing was to be overturned to abovementioned position for getting hydraulic testing done. If hydraulic test fails, then we have to overturn the whole casing such that breech nut side is up, dissemble the fixture from breech nut, replace damaged O-ring with new one, assemble the fixture in breech nut and then get overturned the casing to get hydraulic test done.
These processes were repeated 4-5 times and it was huge loss of time and energy.
Since assembly of ESV & CV couldn’t be started without hydraulic testing, delivery of ESV & CV also was not possible.

Also there was no provision of press-out bolts in the fixture which inhibited difficulty in disassembling the fixture from breech nut as fixture gets locked inside inlet insert’s annular space.
Also there was no provision to hold fixture in upright position.
Thus to eliminate the problems in prior art, there was a need of a new fixture for hydraulic testing of ESV & CV casting.
OBJECTS OF THE INVENTION
An object of the present invention is to develop a fixture which can perform successfully the hydraulic testing of casing of an emergency stop valve and control valve of steam turbine used in power plants.
Another object of the present invention is to develop a fixture that can perform the hydraulic testing of Emergency stop Valve (ESV) and Control valve (CV) by avoiding any leakage of emergency stop valve (ESV) and control valve (CV) casing.
A further object of the invention is to develop a fixture for hydraulic testing of emergency stop valve and control valve which can be used repeatedly and for multiple turbine ratings.
BRIEF DESCRIPTIONOF ACCOMPANING DRAWINGS
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which

Figure 1 is the perspective sectional side view of developed fixture for hydraulic testing of ESV & CV casing constructed in accordance with the present invention;
Figure 2 is perspective front view of developed fixture for hydraulic testing of ESV & CV casing constructed in accordance with the present invention;
Figure 3 is a photographic view of the placement and orientation of ESV & CV casing during hydraulic testing set up;
Figure 4is a photographic view of developed fixture for hydraulic testing of ESV & CV casing;
Figure 5 is an illustrated photographic view for solution through developed fixture;
Figure 6 is a photographic view of developed fixture being lifted through crane;
Figure 7 is an illustrated photographic view for developed fixture and breech nut assembly;
DETAILED DESCRIPTION OF THE INVENTION
Assembly and description of the developed fixture (F) is as per below:
. Minor plate (10) have atop a flat part Face B (1);
. Circular inner groove (5) is provided in the vicinity of Face B (1); in which one O-ring
(3) will be inserted for sealing water leakage from Face B; • Major plate (9) contains Plurality of holes for press-out bolts (8) and plurality of holes
for tightening bolts (7) on the periphery of pitch circle diameter;

. Minor (10) also have a flat part Face A (2);
• Circular outer groove (6) is provided on Face A (2) in which two O-rings (3) will be inserted for sealing water leakage from O-ring (3) Face A (2);
• Major plate (9) also have on its top a threaded hole for assembling with it a lifting bolt (4) for lifting the entire fixture;
• Major plate (9) and minor plate (10) are connected to each other through a pipe (11) welded in between them horizontally;
Assembly of the fixture with the breech nut will be done as per below:
Step 1. Fixture (F) will be lifted using lifting bolt (4) and will be brought near breech nut side of the ESV & CV casing;
Step 2. Two matching bolts are to be inserted in holes made for tightening the fixture with breech nut and temporary flexible threaded connection is made between matching bolts and breech nut. Matching bolts are used only for guiding tightening bolts. After tightening by bolts one by one, the matching bolts are removed;
Step 3. Matching bolts are tightened such that it will guide and push the fixture (F) towards the breech nut;
Step 4. Minor plates (10) extruded part containing atop Face B (1) is to be inserted in the HP inlet insert of the breech nut in such a way that the single O-ring (3) in the inner groove (5) located in the vicinity of Face B (1);
Step 5. Height difference between inner groove (5) and outer groove (6) is kept in such a way that the two O-rings (3) in the outer groove (6) on minor plate (10) at its Face A (2) will automatically rests at the seal plane of the breech nut when step 4 is performed;

Step 6. Tighten the fixture (F) firmly on the breech nut with the help of tightening bolts
using the holes for tightening bolts (7);
Step 7. Check for any possible leakage from the sealing plane between breech nut and
fixture (F) and proceed for hydraulic testing if there is no leakage;
Step 8. After hydraulic testing a completed, unscrew the tightening bolts first and then
pull the fixture out by unscrewing press out bolts.
Regarding the earlier problem encountered during fixing of O-rings which were getting damaged after each hydraulic test, one O-ring (3) was placed in the vicinity of Face B(1) on groove (5).
The reason behind putting this one O-ring (3) in the vicinity of Face B(1) is as per below:
Breech nut consists of HP inlet insert or the hollow part at center (refer fig 7). During hydraulic test, water flow direction is from casing’s inlet insert inner diameter (which resembles as pipe) to outside through inlet insert face. If we put O-ring on this face B(1), water leakage will be eliminated.
It was envisaged that, since this one O-ring (3) in the groove (5) in the vicinity of Face B(1) was not available in prior art, all the hydraulic pressure was sustained by one single O-ring (3) in the outer groove (6) on Face A (2).
Fixture (F) was developed such that:
1) The Face B (1) of fixture (F) goes inside the inlet insert face of the breech nut. O-ring (3) placed in the groove (5) undercutting Face A(2) of minor plate (10) blocks the path of water flow just outside of inlet insert’s annular space thus eliminating the chances of water leakage.

2) Outer groove’s (6) depth and width at Face A(2) to accommodate two number of O-rings (3) instead of single O-ring in outer groove (6) as used in prior art. If water leaks through Face B(1) then two number of O-rings on Face A(2) will block the water leakage.
As there is enormous required hydraulic test pressure, two number of O-rings at Face A (2) are used as precaution.
One lifting hole (4) is made on circumferential surface to hold the fixture in vertical position. (Refer fig.6).
Plurality of press-out bolts (8) were provided in the developed fixture (F) to make easy arrangement for removal of the developed fixture (F) correctly from breech nut.
Plurality of holes (7) for tightening developed fixture (F) on breech nut (12) before hydraulic testing were provided in the developed fixture to make easy arrangement.
With the development of the fixture (F), the hydraulic test of ESV & CV could be completed successfully.
It is further important to note that in addition to provide sealing for hydraulic testing, the same fixture (F) is adaptable for different ratings of steam turbines having combined ESC & CV arrangement, providing an even further versatile scope of use.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur by those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

GAINS:
(A) TANGIBLE GAINS:
1) Reduction in Man power engagement time
3 person (1 crane operator + 2 Riggers) = 9hrs per casing For 12 nos. casing, man hour saving = 108 hrs
2) Reduction in Crane engagement time
Heavy crane engagement time saved for overturning of ESV&CV casing= 3 hrs per casing. 12 nos. ESV&CV casing assembled which account for total saving of crane hours = 36 hrs.
3) Elimination of rework
Savingby rework in leakage of hydraulic testing for one casing =5hrs per leakage multiplied by as many leakages.
Man power use for rework (3 fitter + 1 crane operator + 2 riggers) = 6 for each leakage. Man hour saving = 5 x 6 hours for each leakage.
4) Elimination of holding cost of the job
Cost incurred due to delay is eliminated.
(B) INTANGIBLE GAINS:
1. On time delivery of ESV CV with successful hydraulic testing.
2. Quality Improvement because of ascertaining hydraulic testing.
3. Increased Customer satisfaction for better performing turbine components.
4. Reduction in handling time of job and lesser holding/inventory cost.
5. Despatch schedule complied as per plan.

We claim
1. A fixture (F) for hydraulic testing of emergency stop valve (ESV) and control valve
(CV) comprising:
a major plate (9) having a circular base for fixing the fixture (F) with the breech nut (12) during testing;
a pipe (11) connecting the major plate (9) to a minor plate (10) by welding joint;
the minor plate (10) having a projected portion (1) at the central region with surface level 1(B) and a stepped down surface (2) with surface level 2(A), the surface 2having plurality of grooves (5,6) with variable depth for accommodating O-ring (3), the height of the surfaces 1 (B) and 2 (A) of the minor plate (10) are so maintained that when the fixture(F) is fixed to the breech nut (12) abutting the surfaces (13) of major plate (9) and (18) of breech nut (12), the projected portion (1) passes through the inlet insert (14) and the face (19) of the inlet insert (14) abuts over the O-ring seal on groove (5), near the region (15) when the surface (16) of the breech nut (12) abuts near the region (17) of groove (6) ensuring double protection leakage proof at groove region (5,6) between face (19) of inlet insert (14) and the faces 2(A) near groove (5) and between surface (16) of breech nut (12) and face2 (A) near groove (6) of the fixture.
2. The fixture as claimed in claim 1, where the grooves (5) and (6) are provided with
single and double O-rings (3) respectively.

3. The fixture as claimed in claim 1, wherein the major plate (9) is provided with plurality of holes (7) arranged in a circular periphery for fixing the major plate (9) with breech nut (12) with surface (13) of major plate (9) inside the breech nut (12).
4. The fixture as claimed in claim 1, wherein the major plate (9) is provided with plurality of holes (8) for press out bolts for taking out the fixture from the breech nut (12) during dismantling of fixture.
5. The fixture as claimed in claim 1, wherein the fixture is provided with lifting bolt (4) on the major plate (9) for transportation of the fixture with the help of crane.
6. A method of working with the fixture for hydraulic testing of emergency stop valve (ESV) and control valve (CV) comprising:
- lifting the fixture (F) by holding on the lifting bolt (4) for bringing it near the
inside surface (18) of the breech nut;
- inserting the matching bolts through the holes (7) for making temporary flexible
threaded connection;
- tightening the matching bolts such that it will guide and push the fixture (F)
towards breech nut (12);
- ensuring that the surface (19) of the insert (14) abuts with the single O-ring (3)
in the inner groove (5) located in the vicinity of face 1(B) when the plane (16) of
the breech but (12) abuts with the double O-rings (3) in the outer groove (6) at
plane 2 (A);

- taking out the matching bolts one by one while tightening by bolts at the same time;
- performing the testing operation of emergency stop valve and control valve casing;

- taking out the bolts once the testing operation is completed;
- inserting the press-out bolts through holes (8) for taking out the fixture when the fixture base is separated from the breech nut (12).