Selection of valve is very important in the petroleum industry. An incorrect selection of valve may cause a loss of income, pollution of environment, and an increase of maintenance costs. 3Z double block-and-bleed valve was designed to withstand frequent cycling and provide a tight seal shutoff, and used in metering stations, tank farms, marine loading docks, air port and blending plants.
3Z double block-and-bleed valve is designed that the seals do not come into contact with the valve body while operating. The seals come into contact with the body at the last moment of closing. This design eliminates abrasion of the seals and extends seal life without leakage.
When the valve is closed, the elastomeric seals on the slips are compressed between the slips and valve body for tight sealing. As for being fire-safe, slips are seated by metal-to-metal with valve body. This results in both an elastomeric and metal-to-metal tight sealing.
3Z DBB valve is possible to inspect and replace the sealing slips on the pipe line. Bolted bottom cover can be disassembled to replace the sealing slips on the pipe line.
The bleeding system is designed to relieve any excess rise of pressure in the body cavity, due to thermal expansion of the liquid when the valve is closed. The relief valve is set to open at 25 psi or above and bleeds excess pressure to the upstream side.
Note : The system performs a function when the valve is closed and the isolation valve is opened
3Z double block-and-bleed plug valves are designed to operate by hand wheel, gear or actuator. 3Z valves can supply variable operators as per customer`s requirements.
3Z DBB valves with approach sensor are available as per customer`s requirement.
3Z DBB valve with long stem and pneumatic operator has been installed in loading arm of LNG terminal, in the Middle East. The 3Z special long stem is available as per customer`s requirement.
are designed for the rigid requirements of bi-directional meter proving which especially requires the valve to be cycled hundreds of times per day and has a short cycling time around 10 seconds during valve operation.
3Z 4-way diverter valves supply special low differential pressure device systems with pressure gauge to proof seal integrity and to make low differential pressure (2~5psi) between the upstream and the body cavity for the purpose of flow diverting at short cycling time required by meter proving systems.