Full bore ball valve is a valve that the hole diameter of its ball is the same size with the pipe size. Reduced bore ballvalves is a valve that the hole diameter of its ball is not the same size with the pipe size. In minimum the reduced ballvalves ball diameter are one size lower than the pipe size i.e. 4 inch pipe and ball diameter is 3 inch (usually symbolizedas 4 x 3 inch ball valves). From its definition we can quickly know that the full bore will have less pressure drop andreduced bore will have more pressure drop since reduced bore is just like a restriction orifice that narrowing at the middlepart. So when full bore or reduced bore ball valves will be used?
As default for offshore platform application where weight and cost is matter, the reduced bore ball valves should be used.Reduced bore ball valves is lighter in weight compare to full bore ball valves. Also, the reduced bore ball valves might beused in application where the pressure drop through the valves is not significantly effect the services (at most applicationthe pressure drop through reduced bore ball valve is very low).
For actuated ball valves that used to isolate vessel or any fluid services, reduced ball valve usually used for productionseparator, suction scrubber, glycol generator etc. While full bore actuated ball valves usually used for blow down,piggable line, production manifold, pipeline etc. Actually for blow down or any similar application, we can also use areduced bore since the pressure drop usually isn’t significant. But usually it comes from the project specificationthat requires it to be full bore. It differs with piggable line that must be in form of full bore to allow the pig going through thevalves at pigging activity.
Below is the illustration of full bore ball valve and reduced bore ball valve from Valbart.
CAST TRUNNION BALL VALVE
The trunnion ball valve is used to cut off or connect the media in various of Class150~Class2500. The valves made of different materials are suitable for various media such as water, steam, oil, liquefied gas, natural gas, coal gas, nitric acid, oxidizer, urea and etc. The driving modes include manual operation and electric operation. The connection ends can be flange or butt welding.
STRUCTURAL FEATURES 1. Double Block And Bleed(DBB)
When the valve is closed and the middle cavity is emptied through the discharge valve, the upstream and downstream seats will independently block the fluid at the inlet and outlet to realize double block function. Another function of the discharge device is that the valve seat can be checked if there is any leakage during the test. In addition, the deposits inside the body can be washed and discharged through the discharge device to reduce damage to the seat by impurities in the medium.
2. Low Operating Torque
The trunnion pipeline ball valve adopts the trunnion ball structure and floating valve seat, so as to achieve lower torque under operating pressure. It uses self-lubricating PTFE and sliding bearing to reduce the friction coefficient to the lowest in conjunction with the high intensity and high fineness stem. 3. Emergency Sealing Device
The ball valves with the diameter more than or equal to 6″(DN150) are all designed with sealant injection device on stem and seat. When the seat ring or stem O ring is damaged due to accident, the corresponding sealant can be injected by the sealant injection device to avoid medium leakage on seat ring and stem. If necessary, the auxiliary sealing system can be used for washing and lubricating the seat to maintain its cleanliness.
4. Fireproof Structure Design
In case of fire during the use of valve, the seat ring, stem O ring and middle flange O ring made of PTFE, rubber or other non-metal materials will be decomposed or damaged under high temperature. Under pressure of the medium the ball valve will push the seat retainer rapidly towards the ball to make the metal seal ring contact the ball and form the auxiliary metal to metal sealing structure, which can effectively control valve leakage. The fireproof structure design of trunnion pipeline ball valve conforms to requirements in API 607,API 6FA,BS 7655 and other standards.
Body Material:WCB,WC6,LCB,WC9,CF8,CF8M,CF3 and CF3M
Metal Seats: Tungsten Carbide(TC), Stellited, Ni60.
Design: API6D, BS1414/ASME B 16.34
Face to Face: ASME B 16.10
End Flange:ASME/ANSI B 16.5,
BW End: ASME B 16.25
Anti-static NACE MR-01-75.
Double block and bleed design(DBB)
Double stem sealing.
The ball can maintain pressure sealing of pipeline when it is closed or fully opened.
Shorter upper sleeve reducces bearing load and operation torue
Limit device ensures the accurate opening and closing position of the valve.
The ball and stem are separated so as to reduce stem load.
The stem adopts anti-blow-out design.
The sealing surface is inserted into te metal seat by polymer or plastic
The metalbacked self-lubricating PTFE bearing and PTFE thrust washers
Reduce the opening torque and prolong the service life of the valve.
Stem leakage can be prevented through the emergency grease fitting.
Drive actuators offered for the knife gate valve include handwheel with rising or non-rising stem, or alternatively double or single-acting pneumatic cylinders, Bevel Gear, electric actuators. Pneumatic Accessories:
Cylinder & Solenoid (FESTO,AirTAC,HERION,ASCO,UNIWO,SMC)/ Positioner(YTC,ABB, SIEMENS,AZBIL)/Filter/ Limit switch(OUMRON,FESTO,IFM,P+F) Electrical Motor Actuator:
Actuator Make – Rotork, Auma, ACT, Antrieb etc.