Design feature comparisons
Velan ball valves offer a number of advantages for delayed coker service, for example:
The above comparison table is intended to highlight some of the advantages ofVelan coker ball valves and is not intended to downgrade competitors designs.
Valve range
NPS3-18(DN 80-450)ASME
Classes: 300-600-900
Materials
Valves are generally supplied in: A217 Gr.C5 and C12 A351 Gr.CF8M and CF8C As well as WCB for lowertemperature applications.
Lantern ring
A lantern ring with steam block andextra deep stuffing box minimizesthe risk of leakage occurring througlthe packing chamber.
Sturdy one-piece baland stem
The sturdy one-piece balland stem provides optimalstrength and is well suited toapplications where fouling dueto coke fines are a concern. The one-piece design avoidsthe problems generally associ-ated with the more conven-tionaltwo-piece ball and stemwhich is highly susceptible tosolids buildup in the ball-stemjoint and a resulting increasein operating torques.
Automation
The electric, hydraulic orpneumatic actuator is selected infunction of coker service. A largetorque safety factor ensuresthe valve will cycle under themoststringent conditions. Whenselecting actuators, specialattention is paid to the cokerdeck environment.
The stem coupling
The stem coupling is designed to perform three mainfunctions: Protect against "overtorquing"" of the stem. Protect the actuator components. Protect against an unintentional switch into bypass.
Steam purges
Steam purges to bellows and body areaensure the valve cavities are keptfree ofcoke buildup.
Scraper fype seats
Unique seatdesign scrapes cokebuildup from the surfaceof the ball during eachcycle. Seats are hard-facedto ensure a long.trouble-free service life
Strong bellows
Strong bellows offera unigue seatloadincdesign thatmaintainsthe floating seats inconstant contact witlthe ball and ensures apositive seal
lsolation ball valves
Valve range
NPS2-18(DN 50-450)ASME Classes:150-300-600-900NPS20-36(DN 500-900)ASME Classes: 150-300
Materials
Valves are generally supplied in: A217 Gr.C5 and C12 A351 Gr.CF8M and CF8CAs well as WCB for lowertemperature applications
Lantern ring
A lantern ring with steam block and extradeep stuffing box minimizes the risk of leakageoccurring through the packing chamber.Live-loading is available upon request.
Scraper type seats
Unique seat designscrapes coke buildup from thesurface of the ball during eachcycle. Seats are hardfacedto ensure a long, trouble-freeservice life.
Strong bellows
Strong bellows offer a uniqueseatloading design that maintainsthe floating seats in constantcontact with the ball and ensuresa positive seal.
Steam purges
Steam purges to bellows andbody area ensure the valve cavi-ties are kept free of coke buildup.
Full bore
Valves are full bore, HighCv and light weight. High quality castingsRT & MTinspected perASME B16.34.
Sturdy one-piece ball and stem
The sturdy one-piece ball and stemprovides optimal strength and is wellsuited to applications where fouling dueto coke fines are a concern. The one-piece design avoids theproblems generally associated with themore conventional two-piece ball andstem, which is highly susceptible tosol ids buildup in the ball-stem joint and aresulting increase in operating torques.
The stem coupling
The stem coupling is designed to perform twomain functions: Protect against "overtorquing" of the stem. Protect the actuator components.
The valves shownin the adiacentphotograph were installed aspart of a de-bottleneck projectaimed, among other things, atincreasing the units' liguid vield.As this was an existing structureit was importantto minimizepiping changes. Because theexisting valves were 70% plugvalves the engineering firmevaluated full bore plug valves.but found the units weights to be substantially higher.
Rather thanevaluate the structural changesrequired in order to accepttheseheavier, larger units the end useropted to use our lighter full boreball valves. As a bonus, the ballvalves provided a better sealthan was possible with the previous valves. Two years later thesame end user installed NPS 24(DN 600) Velan overhead ball valves.
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