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Turbine Bypass Valve Challenges

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2 90 ELBLOW

90 Elbow

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มีให้เลือกตั้งแต่ 1/8" - 4"

10 TEE

Tee

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6 NIPPLE

Nipple

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มีให้เลือกตั้งแต่ 1/8" - 4"

14 STREET ELBOW

Street Elbow

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มีให้เลือกตั้งแต่ 1/8" - 4"

3 COUPLING

Coupling

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12 ROUND CAP

Round Cap

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9 REDUCE SOCKET

Reduce Socket

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5 HEX BUSHING

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13 SQUARE PLUG

Square Plug

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15 UNION

Union

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มีให้เลือกตั้งแต่ 1/8" - 4"

8 REDUCE NIPPLE

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ลดเกบียว เกรดอุตสาหกรรม
มีให้เลือกตั้งแต่ 1/8" - 4"

4 CROSS

Cross

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มีให้เลือกตั้งแต่ 1/8" - 4"

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17 BALL VALVE 1PC

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18 BALL VALVE 2PC

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19 BALL VALVE 3PC

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20 BALL VALVE 3WAY

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26 NEEDLE VALVE

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21 GATE VALVE

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22 GLOBE VALVE

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มีให้เลือกตั้งแต่ 1/8" - 4"

24 Y STRAINER VALVE

Y Strainer

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มีให้เลือกตั้งแต่ 1/8" - 4"

23 SWING CHECK VALVE

Swing Check Valve

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มีให้เลือกตั้งแต่ 1/8" - 4"

25 SPRING CHECK VALVE

Spring Check Valve

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1 Brass Adapter

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2 Brass Bushing

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มีให้เลือกตั้งแต่ 1/8" - 4"

3 Brass 90 Elbow

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มีให้เลือกตั้งแต่ 1/8" - 4"

4 Brass Hose Nipple

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มีให้เลือกตั้งแต่ 1/8" - 4"

5 Brass Nipple

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มีให้เลือกตั้งแต่ 1/8" - 4"

6 Brass Reduce Nipple

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มีให้เลือกตั้งแต่ 1/8" - 4"

7 Brass Tee

Brass Tee

Tee way 3 ทางเกรดอุตสาหกรรม
มีให้เลือกตั้งแต่ 1/8" - 4"

8 Brass Union

Brass Union

Tee way 3 ทางเกรดอุตสาหกรรม
มีให้เลือกตั้งแต่ 1/8" - 4"

9 Brass Ball Valve 1pc

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มีให้เลือกตั้งแต่ 1/8" - 4"

10 Brass Ball Valve 2pc

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Tee way 3 ทางเกรดอุตสาหกรรม
มีให้เลือกตั้งแต่ 1/8" - 4"

11 Brass Ball Valve 3pc

Brass Ball Valve 3 pc

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มีให้เลือกตั้งแต่ 1/8" - 4"

12 Brass Ball Valve 3way

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มีให้เลือกตั้งแต่ 1/8" - 4"

Turbine bypass valves are some of the tough purposes in a power plant. Keeping these valves working efficiently and avoiding unexpected failures is critical for plant operation.
When engineers are requested to list essentially the most difficult control valve applications, turbine bypass valves are invariably mentioned. Frequent thermal cycles, excessive strain drops, and the need for tight shutoff push these valves to the restrict. Unfortunately, many crops tend to ignore these valves till they fail, creating unplanned outages, misplaced manufacturing, and high costs for reactive maintenance. This article provides instructed methods of inspection to anticipate and mitigate points beforehand, and it presents upgrade options ought to a valve must be repaired or changed.
Strictly Severe Service
Severe service control valves are utilized in essentially the most troublesome installations inside course of plants. These installations generally include cavitating, erosive, corrosive, noisy, excessive strain, high temperature, high stress drop, or excessive velocity media. Turbine bypass valves are uncovered to many of these process conditions; but, they need to reply flawlessly and stay leak free when closed.
As their title suggests, turbine bypass valves are used to bypass steam turbines throughout plant startup and shutdown, as properly as when a turbine trips off-line (Figure 1). In regular operation the valves are completely closed, forcing all the steam via a turbine. During startup, bypass valves divert steam away from the turbine till the properties and conditions of the steam are acceptable for sending it to the turbine. เกจวัดแรงดัน4บาร์ of happens in reverse at shutdown. Using bypass valves at startup and shutdown helps to guard the turbine by diverting potentially moist steam, and by guaranteeing solely applicable steam conditions and flows make their way to the turbine itself.
1. Depending on the facility plant design, a number of turbine bypass valves could also be employed to immediately shunt steam round a turbine ought to it trip offline. Courtesy: Emerson
Should a turbine trip, the steam must proceed flowing to keep away from gear injury because of overpressure and high temperature, so the turbine bypass valve immediately opens to maintain move via the system.
As it operates, a turbine uses steam to perform work, decreasing outlet steam temperature and pressure. When a turbine bypass valve opens, it’ll drop the stress, but the exit steam will remain fairly superheated, doubtlessly destroying downstream tools. To keep away from that state of affairs, turbine bypass valves either incorporate a water injection system within the valve physique, or make use of a separate water injection desuperheater simply downstream, in either case to decrease the exit steam temperature.
As a result, turbine bypass valves face an ideal storm of extreme service conditions. While the plant is in operation, these valves must remain tightly closed to avoid wasting power. When a turbine trip occurs, the bypass valves should respond instantly, exposing them to rapid temperature modifications and requiring them to move very excessive flows at high strain drops, creating high noise and potentially extreme vibration.
Getting Ahead of the Game
Given the punishing service, the reality is that just about every turbine bypass valve will in the end fail ultimately. Unfortunately, many of those valves are put in in difficult-to-access places, are usually welded in place, and tend to be closely insulated. As a outcome, they’re often ignored until problems begin to surface. Steam leakage by way of the valve is normally the primary symptom noticed, but far more significant and potentially dangerous damage can occur.
The excessive strain drops invariably generate excessive noise and excessive vibration. Over time these vibrations, coupled with frequent temperature changes, fatigue the steel in the valve, water connections, and the piping itself (Figure 2). Such metal fatigue can lead to catastrophic failure beneath strain.
2. Over time, the high vibrations and thermal shock skilled by turbine bypass valves will fatigue the steel and create cracks in each the valve itself and the encircling piping. Courtesy: Emerson
To keep away from this drawback, every turbine bypass valve and its related piping should be routinely inspected. Some kind of non-destructive examination must be periodically employed to detect metal fatigue issues that might be creating however are not yet visually apparent. If a plant lacks the data or tools to perform these inspections, the valve vendor or authorized representative could also be utilized to carry out turbine bypass well being examine services (Figure 3).
3. A routine turbine bypass valve well being check and full inspection is strongly suggested. Metal fatigue can develop in various welds situated on the valve itself, and within the inlet, outlet, and water supply piping (circled areas). Courtesy: Emerson
Fabrication welds on the physique and water manifold, buyer connection welds, diffuser welds, and surrounding piping may be inspected to identify any growing problems before the equipment is compromised. Water injection nozzles and desuperheaters must be appropriately inspected and maintained to keep away from problems related to quenching and cracking.
There are additionally threats to trim components, such as seat floor erosion. One frequent expression of such erosion, specifically on the plug, is also known as “gear toothing.” This occurs more generally in circulate down valves, the place the steam accelerates by way of the cage holes after which strikes the trim/seat area directly, inflicting extreme wear and lowering service life. Over time, this high-velocity steam, which may include water throughout startup conditions and magnetite throughout any situation, will erode and harm the valve seat and trim (Figure 4).
4. Flow down valve physique designs are prone to trim injury as the moist, erosive steam passes through the cage and impacts the seat. Courtesy: Emerson
Common upkeep objects like soft items and spray nozzles can usually get replaced relatively easily and at minimal cost. Trim components that need to be changed because of heavy wear, such as gear toothing, can be quite costly, especially if their supply needs to be expedited. The worst-case state of affairs for a turbine bypass valve is metallic fatigue developing within the valve physique or diffuser, with excessive restore procedures, or even a full valve substitute, required.
Upgrade Opportunities
Many of the turbine bypass valves presently in service had been put in through the heyday of combined cycle plant development from 1998 to 2004. Most of these valves and piping systems are displaying their age and infrequently have vital indicators of metallic fatigue. Others have plenty of life left in them however could benefit from upgrades in know-how. Technology and practices have improved, and upgrading to the latest sealing know-how could inject new life into the valve.
Another example of a expertise improve is when there have been repeated failures with a welded diffuser. In this occasion, a detachable two-in-one seat diffuser will scale back required maintenance.
If a turbine bypass valve should be replaced, plant personnel are strongly inspired to look beyond a direct substitute and consider potential improvements. A significantly important item to contemplate when looking at replacement and improvement opportunities is valve orientation.
Downward Flowing Valves with Horizontal Actuators. Historically, most turbine bypass valves employed a move down trim design paired with a horizontal actuator (Figure 5, left). This arrangement is ideal for locations with low overhead clearance, and it locations the actuator nearer to the deck or floor for straightforward access, however it creates numerous long-term operational problems. Gravity tends to result in elevated and uneven wear on trim parts, and the side-mounted actuator is vulnerable to response issues.
5. Downward flowing valves with horizontal actuators (left) had been the main choice a quantity of a long time in the past for turbine bypass valves. New move up valve designs (right) may be put in without piping modifications in most cases, offering extended service life and improved efficiency. Courtesy: Emerson
Downward Flowing Valves with Vertical Actuators. A superior choice for circulate down is vertical mounting of the actuator. This association ends in reduced and extra even put on, longer runs between upkeep outages, and improved actuator response. The problem with this orientation is that replacement opportunities are typically for horizontally mounted actuators, and the two designs aren’t readily interchangeable with out vital piping modifications.
Upward Flowing Turbine Bypass Valves. When adequate overhead area is on the market with existing horizontal actuator circulate down designs, a circulate up design can easily meet the existing face-to-face requirements of the old valve, while lowering a variety of the put on frequent to circulate down designs with a horizontal actuator, corresponding to gear toothing. Because the trim simply switches from move right down to flow up, this change can be made with out modifications to present piping.
Flow up valves (Figure 5, right) significantly extend seat and trim service life because the steam is transferring relatively slowly because it passes over the plug and seat (Figure 6). As the steam moves through the small holes of the cage, it accelerates significantly, but that power dissipates into the large physique cavity of the valve instead of striking the seating floor.
6. Downward flowing valves topic the seat to erosive high-velocity steam. Upward flowing steam velocities are much lower as a result of they move over the seat and accelerate later because the steam strikes by way of the small trim holes, significantly extending trim service life. Courtesy: Emerson
Notice how the circulate up trim (Figure 7) is certainly displaying erosion, however when in comparability with the circulate down trim proven above (Figure 4 right), the seating floor on the seat ring and plug stay comparatively undamaged, permitting the valve to shut off completely, the required mode in regular operation.
7. These footage of circulate up trim clearly present the erosive influence of high-velocity steam, however not like the flow down trim harm shown beforehand, this valve has no damage to the seating surface and may still shut off tightly. Courtesy: Emerson
The circulate up valve fashion design nonetheless provides the identical management responsiveness and move capacity, but the model new flow association dramatically extends the operating lifetime of the seals, seat, and valve internals.
Consult an Expert
Turbine bypass valves are highly specialised pieces of engineered gear that should be carefully specified, put in, and maintained. It is therefore wise to be proactive by reaching out to trusted specialists prior to purchase as they can help with valve sizing and specifications based mostly on particular working situations.
For existing installations where unplanned turbine bypass valve failures are bedeviling your facility, or if it has been a while for the explanation that plant turbine bypass valves have been absolutely inspected, it would be sensible to consult your turbine bypass valve vendor for help and assist.
Many of these vendors provide full inspection and health examine companies to identify areas the place metallic fatigue and stress cracking are creating. Ideally the valve could be repaired, but when a valve alternative is warranted, the seller can even provide guidance in evaluating bypass valve design kinds and selecting the best choice for the precise application.
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