The inverted pressure balance lubricated plug valve is a type of quarter-turn valve that uses a cylindrical or tapered plug to control flow. It is designed with a pressure-balanced plug mechanism that equalizes pressure inside the valve plug cavity, making operation easier even under high-pressure conditions.
It is called inverted because the pressure balance holes/channels are located in such a way (often in the upper plug area) that pressure is equalized from the body cavity to the plug ends, reducing torque requirements.
Additionally, the valve requires sealant (lubricant injection) to achieve tight shutoff and reduce wear between plug and body.
The inverted pressure balance lubricated plug valve is a heavy-duty, quarter-turn isolation valve with reduced torque requirements due to its pressure-balanced plug design. It is widely used in oil, gas, chemical, and power industries for high-pressure and high-temperature services. Regular lubrication and sealant injection are key for reliable performance and long life.
 

Description

1.Structure Of inverted pressure balance lubricated plug valve

Body: Cast or forged steel, with flanged, welded, or threaded ends.
Plug: Cylindrical or tapered, with a through port or rectangular opening for fluid passage.
Stem: Connected to the plug, transmits operator torque.
Pressure balance holes: Allow body pressure to equalize across plug ends to reduce operating torque.
Sealant injection system: Channels for lubricant/sealant injected via a grease fitting.
Gland/Bonnet: Provides stem sealing and access for lubrication.
Seating surfaces: Metal-to-metal contact, enhanced by sealant.
Typical construction drawings show the plug inside the valve body, with lubricant passages distributed to seating surfaces.

2. Standards Of inverted pressure balance lubricated plug valve

Design and manufacturing typically conform to:
API 599 – Lubricated Plug Valves
API 6D – Pipeline Valves (for transmission pipelines)
ASME B16.34 – Valve design and pressure-temperature ratings
ASME B16.10 – Face-to-face dimensions
ASME B16.5 / B16.47 – Flanged ends
ISO 14313 – Equivalent to API 6D for pipelines
Fire-safe standards (API 607 / ISO 10497) if required

3. Features Of inverted pressure balance lubricated plug valve

Pressure-balanced plug reduces torque, even at high differential pressures.
Inverted design prevents plug from seizing under pressure.
Positive sealing with injected sealant (resists leakage).
Quarter-turn operation for fast open/close.
Versatile service – handles gas, liquids, slurries, and corrosive media.
Robust construction suitable for high-pressure and high-temperature service.
Long service life with proper lubrication.

4. Applications Of inverted pressure balance lubricated plug valve

Inverted pressure balance lubricated plug valves are widely used in:
Oil & gas pipelines (isolation and block service)
Refineries & petrochemical plants
Chemical and fertilizer industries
High-pressure steam service
Slurry and abrasive service (with appropriate trim)
Gas distribution systems
Corrosive service (with alloy or lined body materials)

5. Operation Of inverted pressure balance lubricated plug valve

Operated by lever, gear operator, or actuator.
Quarter-turn (90° rotation) moves valve from fully open to fully closed.
Lubricant injection is required periodically via sealant fittings before operation in critical service.
Pressure balance system ensures reduced torque and smooth operation.
Open/close direction is indicated on stem cap or handle.

6. Maintenance Manual Of inverted pressure balance lubricated plug valve

Routine Maintenance

Lubrication
Inject proper valve sealant/lubricant through grease fittings before cycling.
Use manufacturer-recommended sealant compatible with the process medium.
Operation check
Cycle valve periodically to prevent sticking.
Ensure smooth operation; if torque is unusually high, check lubrication.
Leak check
Inspect body and stem for external leakage.
If minor leakage occurs at seat, inject additional sealant.
Stem packing
Adjust gland follower to control stem leakage.
Replace packing if leakage persists.

Overhaul / Major Maintenance

Disassemble valve by removing bonnet/stem assembly.
Inspect plug and body seat surfaces for scoring, wear, or corrosion.
Re-polish or lap plug if needed to restore surface finish.
Replace seals, packing, and O-rings as per OEM recommendation.
Reassemble and test under hydrostatic and seat leakage test conditions (per API 598).

 

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