Basic Info.
Nominal Pressure
150~2500lb
Channel
Straight Through Type
Structure
Floating Ball Valve
Application
Industrial Usage, Water Industrial Usage, Household Usage
Painting
Manufacture′s Std
Product Warranty
12~18 Months
Transport Package
Sea Worthy Plywood Cases
Specification
CE, ISO, API
Product Description
Double Block & Bleed ball Valve with Tiny Size
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.
5. Anti-static Structure
The ball valve is provided with the anti-static structure and adopts the static electricity
discharge device to directly form a static channel between the ball and body or form
a static channel between the ball and body through the stem, so as to discharge the
static electricity produced dut to friction during the opening and closing of ball and seat
through the pipeline, avoiding fire or explosion that may be caused by static spark and
ensuring system safety.
6. Reliable seat sealing structure
The seat sealing is realized through two floating seat retainers. They can float axially
to block the fluid, including ball sealing and body sealing. The low pressure sealing
of valve seat is realized by spring pre-tightening. In addition, the piston effect of valve
seat is desinde reasonably, which realizes high pressure sealing by the pressure of
the medium itself. The following two kinds of ball sealing can be realized.
7. Single Sealing (automatic Pressure Relief In Middle Cavity Of Valve)
Generally, the single sealing structure is used, that is, there is only the upstream sealing.
As the independent spring loaded upstream and downstream sealing seats are used, the
over-pressure inside valve cavity can overcome the pre-tightening effect of the spring, so
as to make the seat release from the ball and realize automatic pressure relief towards
the downstream part.
The upstream side: When the seat moves axially along the valve, the pressure P exerted
on the upstream part(inlet) produces a reverse force on A1. As A2 is higher than A1,
A2-A1=B1, the force on B1 will push the seat to the ball and realize tight sealing of the
upstream part.
8. Double Sealing (double Piston)
The trunnion pipeline ball valve can be designed with the double sealing structure before
and after the ball for some special service conditions and user requirements. It has double
piston effect. Under normal condition, the valve generally adopts primary sealing. When the
primary seat sealing is damaged and causes leakage. The secondary seat can play the
function of sealing and enhance the sealing reliability.
The seat adopts the combined structure. The primary seal is metal to metal seal. The
secondary seal is fluorine rubber O ring that can ensure the ball valve reach the bubble
level sealinge. When the pressure differential is very low, the sealing seat will press the
ball through the spring action to realize primary sealing. When the pressure differential
rises, the sealing force of seat and body will increase accordingly so as to tightly seal
the seat and ball and ensure good sealing performance.
Primary sealing: Upstream. When the pressure differential is lower or there is no pressure
differential, the floating seat will move axially along the valve under the spring action and
push the seat towards the ball to keep tight sealing. When the pipeline pressure P increases,
the force exerted on the area A2 of valve seat is higher than the force exerted on the area
A1, A2-A1=B1. Therefore, the force on B1 will push the seat towards the ball and realize
tight sealing of the upstream part.
Secondary sealing: Downstream. When the pressure differential is lower or there is no
pressure differential, the floating seat will move axially along the valve under the spring
action and push the seat towards the ball to keep tight sealing. When the valve cavity
pressure P increases, the force exerted on the area A4 of valve seat is higher than the
force exerted on the area A3,A4-A3=B1. Therefore, the force on B1 will push the seat
towards the ball and realize tight sealing of the upstream part.
9. Safety Relief Device
As the ball valve is designed with the advanced primary and secondary sealing that has
double piston effect, and the middle cavity cannot realize automatic pressure relief, the
safety relief valve must be installed on the body in order to prevent the danger of
over-pressure damage inside the valve cavity that may occur due to thermal expansion
of medium. The connection of the safety relief valve is generally NPT1/2. Another point
to be noted is that the medium of the safety relief valve is directly discharged into the
atmosphere. In case direct discharging into the atmosphere is not allowed, we suggest
that the ball valve with a special structure of automatic pressure relief towards upper
stream should be used. Refer to the following for details. Please indicate it in the order
if you don not need the safety relief valve or if you would like to use the ball valve with
the special structure of automatic pressure relief towards upper stream.
10. Secial Structure Of Automatic Pressure Relief Towards Upper Stream
As the ball valve is designed with the advanced primary and secondary sealing that has
double piston effect, and the middle cavity cannot realize automatic pressure relief, the
ball valve with the special structure is recommended to meet the requirement of automatic
pressure relief and ensure no pollution to the environment. In the structure, the upper
stream adopts primary sealing and the lower stream adopts primary and secondary sealing.
When the ball valve is closed, the pressure in the valve cavity can realize automatic
pressure relief to the upper stream, so as to avoid the danger caused by cavity pressure.
When the primary seat is damaged and leaks, the secondary seat can also play the function
of sealing. But special attention shall be paid to the flow direction of the ball valve. During
the installation, note the upstream and downstream directions. Refer to the following drawings
for sealing principle of the valve with the special structure.
11. Blow-out Proof Stem
The stem sdopts the blow-out proof structure. The stem is designed with the footstep at
its bottom so that with the positioning of upper end cover and screw, the stem will not be
blown out by the medium even in case of abnormal pressure in the valve cavity.
12. Corrosion Resistance And Sulfide Stress Resistance
Certain corrosion allowance is left for the body wall thickness. The carbon steel stem, fixed
shaft, ball, seat and seat ring are subjected to chemical nickel plating according to ASTM
B733 and B656. In addition, various corrosion resistant materials are available for users to
select.
According to customer requirements, the valve materials can be selected according to NACE
MR 0175/ISO 15156 or NACE MR 0103, and strict quality control and quality inspection should
be carried out during the manufacturing so as to fully meet he requirements in the standards
and meet the service conditions in sulfurization environment.
13. Extension Stem
As for the embedded valves, the extension stem can be supplied if ground operation is needed.
The extension stem is composed of stem, sealant injection valve, and drainage valve that can
be extended to the top for the convenience of operation. Users should indicate the extension
stem requirements and length when placing orders.
For ball valves driven through electric, pneumatic and pneumatic -hydraulic operations , the
extension stem length should be from the centre of pipeline to top flange.