Claims:1. A blow down valve comprising:
a stem (05) in a form of cylindrical rod having tapering surface at upper end and threading at lower end placed in the middle of the blow down valve;
a yoke bush (08) placed at the top of the stem (05);
a yoke (04M) having an internal thread at top and bottom attached with the yoke bush (08) at the top;
a bonnet (14N) having an external thread at top and bottom attached the yoke (04M) at the top ;
a valve body (01M) having an internal thread attached with the bottom of bonnet (14N) ;
a packing cartridge (03) placed inside the bonnet to ensure the leak free joint between the bonnet (14N) and stem (05);
a gland follower (06) placed above the packing cartridge (03);
a gland flange (07) placed over the gland follower and clamped by means of stud and nut;
a stellite seat ring (13) fitted horizontally over the middle of the stem above the valve body (01M);
a spiral wound gasket (15N) inserted inside the valve body (01M) to make the leak free joint between the bonnet (14N) and the valve body (01M);
a dial (09) in the form of a truncated hollow cone fitted at the top of the stem (05);
a handle (10) fitted with the stem (05) for closing and opening the stem (05);
a lock nut (11) that locks the handle (10) with the stem (05); and
an indicator (12) in a form of scale fitted with the stem.

2. The blow down valve as claimed in claim 1, wherein the yoke bush (08) is made of brass.

3. The blow down valve as claimed in claim 1, wherein the packing cartridge (03) is a set of Hollow cylindrical shaped rings made up of grafoil material. , Description:TECHNICAL FIELD
[001] The present invention generally relates to blow down valves for high temperature and high pressure applications such as in steam generator applications. More particularly, the present invention leads to an advanced blow down valve having zero welding between body and yoke and having a bonnet in the valve assembly.
BACKGROUND
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Normally, a conventional designed blow down valve that are used in turbine extraction lines where high pressure drop is involved suffered from severe erosion and rapid wearing out. The size of the valve ranging from 1” to 2-1/2” and also depends upon the pipeline where these valves are used for high temperature and high pressure (1500 and 2500 Class rating) applications. Materials used for the valves are SA105 grade material (carbon steel), F22 grade material (low alloy steel), and F91 grade material (high alloy steel).
[004] In the existing method, machining of the valve body consists of following steps, boring is done in the middle of valve body. A step is formed at the top to match with corresponding yoke for welding and step boring is carried out at the bottom. A stellite seat ring is welded in the middle of the valve body and an inlet passage hole is made from the side of the valve body which connects to middle bore of the valve body followed by step boring operation for socket inclusion.
[005] The machining of the yoke (04) consists of following steps, boring is done in the middle of yoke. The threading operation is carried out at the top of yoke and a step is formed at the bottom for matching with corresponding valve body.
[006] In addition, the body-yoke welding process consists of following steps, the valve body and the yoke are pre heated in the furnace, where pre heating is done at 220 degrees Celsius for F91 grade material, 200 degrees Celsius for F22 grade material, whereas carbon steel bodies are not required to pre heat.
[007] After pre heating, the valve body and the yoke are moved to welding shop where the valve body is welded with yoke by means of conventional Tungsten Inert Gas (TIG) welding for root and subsequently followed by Manual Arc Welding (MAW) process. After completion of welding process, valve body assembly is post heated at 750 to 770 degree Celsius for F91 grade material, 700 to 750 degree Celsius for F22 grade material, whereas carbon steel bodies do not require post weld heat treatment.
[008] The welding process is very stringent for F91 & F22 grade materials because of pre-heat, post heat and stress relieving requirements. After the heat treatment is over, the assembly is taken out for both visual examination and Radio-graphic Testing (RT). If the defect is found in the body-yoke welding, then the repairing takes more time for gouging, grinding, welding and again testing. Sometimes it has been found that, some cracking occurs in the stellite seat ring of the valve body. Stelliting means stallite deposition on seat area or A ring made up of stallite is fixed in seating area of valve. This is done before body-yoke welding process. It is ir-repairable and the whole body-yoke assembly is thrown as scrap which leads to loss of material and time.
[009] Moreover, in valve assembly, lapping operation is carried out in the valve body for required finish (0.8µ). Here, Blue matching inspection is conducted in the matching areas of stem (05) and valve body.
[010] If mis-matching is found in the inspection, it leads to valve leakage during the hydro testing. Hence, it is required to extend the lapping time substantially. Sometimes, a whole day per valve also takes for lapping process. This leads to increase the cycle time of valve. Then the stem and gland flange are placed in the middle of the valve body and packing cartridge is inserted properly. Gland follower is placed over the packing cartridge and clamped by means of stud and nut.
[011] After that yoke bush is screwed with yoke then dial and indicator are mounted in the valve assembly. Handle is fitted at the top of stem and locked by means of lock nut .Then the valve assembly is moved to hydro testing.
[012] While hydro testing of valve, it is found that seat leakage. So, valve assembly is dismantled for rectifying the problems. This leakage is occurred due to ‘center-out problem’. That means concentricity of valve body and yoke is disrupted at the time of body-yoke welding process. This problem cannot be rectified. Hence, whole body yoke assembly is subjected to scrap which leads to heavy loss of material.
[013] Moreover, in existing manufacturing method, before and after body-yoke welding, the assembly with stellite welding is sent to furnace for heat treatment. Sometimes, the stellite in the body cracks, which is not repairable with existing configuration. Thus it results in rejection of the total body-yoke Assembly.
[014] In addition to that, in existing manufacturing method, concentricity of valve body and yoke is disrupted during the welding process. This leads to mis-matching of valve body & stem and seat leakage problem.
[015] Hence, there is a need to find out an efficient method of making the valve body and yoke as one assembly, without involvement of welding and there is also another need to make repairable stelliting on the seat area of the valve body. Hence, these problems are also to be addressed while developing an efficient method of manufacturing Blow down valve for the above applications.
[016] These and other objects and advantages will become more apparent when reference is made to the following description and accompanying drawings.
OBJECTS OF THE DISCLOSURE
[017] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[018] It is therefore, an object of the invention is to propose an efficient blow down valve having zero welding between the valve body and the yoke.
[019] Another object of the invention is to propose an efficient method of making access for repairing stelliting.
[020] The further object of the invention is to propose an efficient structure of valve body and yoke.
[021] A still further object of the invention is to introduce a bonnet that facilitates in an efficient working of the blow down valve.
SUMMARY OF THE INVENTION
[022] This summary is provided to introduce concepts related to the structure of the blow down valve for high temperature and high pressure applications such as in steam generator applications. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[023] In an embodiment, the present disclosure provides a blow down valve comprising a stem in a form of cylindrical rod having tapering surface at upper end and threading at lower end placed in the middle of the blow down valve, a yoke bush placed at the top of the stem, a yoke having an internal thread at top and bottom attached with the yoke bush at the top,a bonnet having an external thread at top and bottom attached the yoke at the top,a valve body having an internal thread attached with the bottom of bonnet,a packing cartridge placed inside the bonnet to ensure the leak free joint between the bonnet and stem,a gland follower placed above the packing cartridge,a gland flange placed over the gland follower and clamped by means of stud and nut, a stellite seat ring fitted horizontally over the middle of the stem above the valve body ,a spiral wound gasket inserted inside the valve body to make the leak free joint between the bonnet and the valve body ,a dial in the form of a truncated hollow cone fitted at the top of the stem ,a handle fitted with the stem for closing and opening the stem ,a lock nut that locks the handle with the stem ,and an indicator in a form of scale fitted with the stem.
[024] The blow down valve as claimed in claim 1, wherein the yoke bush is made of brass.
[025] The blow down valve as claimed in claim 1, wherein the packing cartridge is a set of hollow cylindrical shaped rings made up of grafoil material.
[026] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[027] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[028] Figure 1 shows the sectional views of existing valve body.
[029] Figure 2 shows the sectional view of existing yoke.
[030] Figure 3 shows the sectional views of existing Blow down valve assembly with all the part assembled.
[031] Figure 4 shows the sectional views of proposed valve body.
[032] Figure 5 shows the sectional view of proposed yoke.
[033] Figure 6a shows the sectional views of the conventional blow down valve assembly with all the part assembled.
[034] Figure 6b shows the sectional views of proposed blow down valve assembly with all the part assembled.
[035] Figure 7 shows the sectional view of the proposed bonnet.
DETAILED DESCRIPTION
[036] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[037] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[038] Referring to the figure 1 that shows the conventional method of machining of valve body (01) which consists of following steps, boring is done in the middle of valve body (01). A step is formed at the top to match with corresponding yoke (04) for welding and step boring is carried out at the bottom. Stellite seat ring (13) is welded in the middle of the valve body (01). An inlet passage hole is made from the side of the valve body (01) which connects to middle bore of the valve body (01) followed by step boring operation for socket inclusion.
[039] Referring to the figure 2 also shows conventional method of machining of yoke (04) that consists of following steps, boring is done in the middle of yoke (04). The threading operation is carried out at the top of yoke (04) and a step is formed at the bottom for matching with corresponding valve body (01).
[040] Referring to the figure 3, also shows conventional method of joining body-yoke by welding consists of following steps, valve body (01) and yoke (04) are pre heated in the furnace, where pre heating is done at 220 degrees Celsius for F91 grade material, 200 degrees Celsius for F22 grade material, whereas carbon steel bodies are not required to pre heat. After pre heating, valve body (01) and yoke (04) are moved to welding shop where the valve body (01) is welded with yoke (04) by means of conventional Tungsten Inert Gas (TIG) welding for root and subsequently followed by Manual Arc Welding (MAW) process.
[041] After completion of welding process, valve body assembly is post heated at 750 to 770 degree Celsius for F91 grade material, 700 to 750 degree Celsius for F22 grade material, whereas carbon steel bodies do not require post weld heat treatment. The welding process is very stringent for F91&F22 grade materials because of pre-heat, post heat and stress relieving requirements. After the heat treatment is over, the assembly is taken out for both visual examination and Radio-graphic Testing (RT).
[042] If the defect is found in the body-yoke welding (02), then the repairing takes more time for gouging, grinding, welding and again testing. Sometimes it has been found that, some cracking occurs in the stellite seat ring (13) of the valve body (01). It is ir-repairable and the whole body-yoke assembly is thrown as scrap which leads to loss of material and time.
[043] Moreover, in valve assembly, lapping operation is carried out in the valve body (01) required for finishing (0.8µ). Here, Blue matching inspection is conducted in the matching areas of stem (05) and valve body (01). If mis-matching is found in the inspection, it leads to valve leakage during the hydro testing. Hence, it is required to extend the lapping time substantially. Sometimes, a whole day per valve also takes for lapping process. This leads to increase the cycle time of valve.
[044] Then the stem (05) and gland flange (07) are placed in the middle of the valve body (01) and packing cartridge (03) is inserted properly. Gland follower (06) is placed over the packing cartridge (03) and clamped by means of stud and nut. After that yoke bush (08) is screwed with yoke (04) then dial (09) and indicator (12) are mounted in the valve assembly. Handle (10) is fitted at the top of Stem (05) and locked by means of lock nut (11). Then the valve assembly is moved to hydro testing.
[045] While hydro testing of valve, it is found that leakage occurs in seat. So, valve assembly is dismantled for rectifying the problems. This leakage is occurred due to ‘center-out problem’. That means concentricity of valve body (01) and yoke (04) is disrupted at the time of body-yoke welding process. This problem cannot be rectified. Hence, whole body yoke assembly is subjected to scrap which leads to heavy loss of material.
[046] Hence, there is a need to find out an efficient method of making the valve body (01) and yoke (04) as one assembly, without involvement of welding and there is also another need to make repairable stelliting on the seat area of the valve body (01). Hence, these problems are also to be addressed while developing an advanced method of manufacturing blow down valve for the above applications.
[047] Accordingly, as shown in the figure 4 & 6b, the valve body having advanced structure is proposed, the machining of the valve body (01M) consists of following steps, boring is done in the middle of the valve body (01M). A step boring and internal threading operation is done at the top to engage with a bonnet (14N). A step boring is carried out at the bottom. Stellite seat ring (13) is welded in the middle of the valve body (01M). An inlet passage hole is made from the side of valve body (01M) followed by step boring for socket inclusion.
[048] Referring figure.5, the yoke having advanced structure is proposed, the machining of yoke (04M) consists of following steps, boring is done in the middle of yoke (04M). An Internal threading operation is carried out at the top of yoke (04M) to engage the yoke bush (08). After that an internal threading operation is done at the bottom of yoke (04M) to engage the bonnet (14N).
[049] Referring figure.7, machining of bonnet (14N) consists of the following process, boring is done in the middle of the bonnet (14N) and step boring is done in both side top and bottom of the bonnet (14N). An external threading operation is carried out at the top and bottom of the bonnet (14N) to screw with yoke (04M) and valve body (01M) respectively. Hexagonal machining is done in the outer circumferential area of bonnet (14N).
[050] Referring figure.6a & 6b, in valve assembly, lapping operation of valve body (01M) is done for required finish (0.8µ) then spiral wound gasket (15N) is inserted in the valve body after that stem (05) is inserted into the bonnet (14N) and screwed with valve body (01M). Then gland flange (07) is placed in the middle of the valve body (01M) and packing cartridge (03) is inserted into the bonnet (14N) properly. Gland follower (06) is placed over the packing cartridge (03). After that yoke (04M) is screwed with bonnet (14N) and clamped by means of stud and nut, then dial (09) and indicator (12) are mounted in the valve assembly. Handle (10) is fitted at the top of stem (05) and locked by means of lock nut (11). Then the valve assembly is moved to hydro testing. While hydro testing of valve, it is found that no seat leakage occurred in the proposed type blow down valve and valve is completed with final inspection.
[051] Accordingly, the valve body is made with internal thread and the yoke is also made with the internal thread depends upon the valve size. The bonnet is used as connecting piece between the yoke and the valve body. Thus it eliminates the welding process and subsequent operations in the welding. Thereby, substantial saving in time and money.
[052] Accordingly, the valve body is made with internal thread and the yoke is also made with the internal thread depends upon the valve size. The bonnet is used as connecting piece between yoke and valve body. Based on the experiments carried out, the optimum size for the bonnet is obtained to connect the valve body and yoke. Now without welding, we got body and yoke assembly having strength equal to welding of Body and Yoke. Thereby, the whole welding process is eliminated and the drawbacks said in the background are also eliminated. In the proposed method, since the body-yoke is not welded, the seat crack can be easily repaired and the rejection of the body is eliminated. Thereby, substantial saving in time and money.
[053] These are completely addressed in proposed blow down valve. Now, this proposed method of manufacturing of blow down valve leads to increase the productivity by reducing the rework and rejection rate.
[054] In addition to that, Mis-matching of valve body and stem, ‘center out problem’ and seat leakage problem are completely addressed in proposed blow down valve.
[055] Thus, with the system and the method described in the present disclosure, various technical problems of the state of the art are resolved. Also, although a number of exemplary method options are described herein, those skilled in the art can appreciate that the proposed blow down valve, without deviating from the scope of the subject matter of the present disclosure.
[056] Further, it will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope.
[057] Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.
[058] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

REFERENCE NUMERALS

01-VALVE BODY 01M- VALVE BODY
02-BODY-YOKE WELDING 04M- YOKE
03-PACKING CARTRIDGE 14N-BONNET

04-YOKE 15N-SPIRAL WOUND GASKET
05-STEM
06- GLAND FOLLOWER
07- GLAND FLANGE
08-YOKE BUSH
09-DIAL
10-HANDLE
11-LOCK NUT
12-INDICATOR
13-STELLITE SEAT RING