Vacuum Gate Valve – Product Maintenance & Installation Manual

Vacuum Gate Valve

Product Maintenance & Installation Manual

Sangong Flow Control Co.,Limited



This Vacuum valve is used for vacuum and minus pressure system and cooling water system of thermal power plant, as well as minus pressure cooling water systems of chemical, medicine industries, used as cut off and stop device.


  1. Nominal Pressure (Bar) and Nominal Size (mm)

Nominal Pressure

10.0 ~ 25.0

40.0 ~ 64.0


Nominal Size

50 ~ 900

50 ~ 400

80 ~ 400

  1. Suitable Medium: Water, Steam, Air, Oil.
  2. Working Temperature: ≤400℃


Working Principle and Structure

  1. Working Principle: The wedge moves up and down in the body which follows the stem movement, to reach open and close.
  2. Structure:

A Structure Type: Parallel Duo Wedge and Outside Screw and Yoke

B Actuated Type: Manual and Electric, connection type: Flange type and Butt Weld Type.

C Floating sealing structure consists of gate valve, guiding yoke and spring, which can redeem sealing if seat wears out.

D For the manual operated vacuum gate valve, it adjusts the centric of wedge by limit nut on the stem which to reach sealing between the wedge and seat; for electric vacuum gate valve, it adjusts the center of wedge by the limit nut under the guiding yoke.

E Perfect connection of stem and guiding yoke, the movement of stem leads the guiding yoke to move in its path, to make sure duo plates open and close at same time.

F The stuffing box is in vacuum sealing design. Nickel filled flexible graphite packing reinforces the combination structure composed of PTFE packing and grease sealing ring, mean while, it adds high vacuum seal silicon grease which improves the sealing effect of packing and stem, to reach the isolation of system and atmosphere.

Gate Valve is operated by electric actuator. Electric actuator can spot operated as well as long distance operation. Structure of electric actuator’s detail is as Manual of Electric Actuator.


Maintenance, Installation and Usage

  1. 1.      Maintenance

1)     The vale should be in house with dry, ventilation environment, and prevented from rain, dampness and rusty.

2)     Valve must be closed during stock and transportation, and make sure followings:

  1. Wedge surface must be painted rust-proof oil and covered with oilpaper.
  2. Valve inlet and outlet must be filled with foam plate and cover with plug to prevent dust, rust and keep clean and protect the flange facing.
  3. After greasing the echelon screw part of stem, it must be protected and be dust-proof for the outside part.

3)     It must take periodical inspection if valves are in long stock time. It needs to check if there is dust and rust on stem outside surface, echelon screw part, and the integrate flanges each three months, and also must check the protection of flange facing and welding end. Re-paint rust proof oil and make protection again after removing the rust and cleaning.

4)     It is recommended to inject lubricant oil in rotation area when using, and add grease on stem echelon screw part. It needs to inject 7051-High Vacuum Seal Silicon Grease after every four year’s service.

5)     Maintenance of electric actuator is as per Manual of Electric Actuator.

  1. 2.      Installation and Usage

1)     The manual operated vacuum gate valve which size below DN450 can be installed in vertical or horizontal. For size DN450 and above, manual vacuum gate valve and electric vacuum gate valve, the valve should be installed vertical in the horizontal pipeline. Normally the valve is in fully open or close position when service, but also can at any open position if necessary.

2)     Please pay attention of followings before installation:

  1. Take away the plug and foam plate on both sides of valve, clean inside and remove the oil;
  2. Take away the oilpaper of the wedge, remove the oil on wedge.
  3. Take away the oilpaper on the screw stem, re-paint lubricate grease on it.

3)     Valve must be installed in correct flow direction.

4)     Valve is open and close by handwheel in uniform force. When it is getting position, it must achieve position of open and close slowly.

5)     Valve is opened in clockwise and closed in anticlockwise.

6)     Valve can not be hung at handwheel and electric actuator.

7)     Inject 7051-High Vacuum Seal Silicon Grease at screw plug hole on the stuffing box, to ensure the isolation of system and atmosphere.

8)     Before the assembly of eclectic actuated valve on the pipeline, it must check the operation indicator of electric actuator and valve wedge position, to make sure compliance of the two.

9)     It can not have solid particle in medium in case of damaging the seal facing.

10) Each valve is tested and inspected before departure from workshop. Installation party and company can install the valves directly in the pipeline.


Main Spare Part and Material

Part Name




Seal facing

Stem Nut





25 WCB



Nickel Filled flexible graphite ring

St.Steel-Flexible Graphite gasket

May Occurred Malfunction and Solution

Possible Malfunction



Leakage occurred at sealing of seat and wedge

1. Dirty and dusty on seat facing

1. Remove the dirty and dusty

2. Sealing facing is scraped, damaged or in corrosion

2. Grinding or welding and machine seal facing to reach sealing request

Leakage at stem packing

1. Packing gland was not tight enough

1. Fasten the packing bolts uniformly

2. Packing damaged

2. Add or change packing

3. Surface of stem at stuffing box is in corrosion

3. Repair surface of stem or replace

4. Inject high vacuum sealing silicon grease

Leakage at connection of body and bonnet

1. Bolts is not fastened uniformly

1. Fasten bolts in uniform pressure

2. Middle flange facing damaged

2. Repair the flange facing

3. Gasket worn out or damaged

3. Replace gasket

Shaft movement is not smart

1. Over tight of packing gland

1. Relax the packing gland

2. Skew of packing gland

2.  Adjust the packing gland

3. Sundries at rotation position

3. Remove sundries and add lubrication oil

4. Stem and screw on stem nut damaged

4. Repair damaged part or replacement

Possible malfunction and solution for electric actuator, please read Manual of Electric Actuator.

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