Parallel Slide Gate Valve
Parallel Slide · DN40–DN400 · PN16 · Steam Duty
The parallel slide gate valve uses two parallel discs spring-loaded against the seats, giving tight sealing without wedge jamming at thermal cycling.
Preferred for high-pressure steam mains and turbine extraction lines.
Key Features
Tight Isolation
Wedge-to-seat geometry gives reliable shutoff with minimal leakage.
Low Pressure Loss
Straight-through bore keeps pressure drop near zero in open position.
Rising / Non-Rising Stem
OS&Y rising stem shows open/closed at a glance; NRS suits buried service.
Resilient or Metal Seat
EPDM/NBR for water; SS316/Stellite for steam and slurry.
Bi-Directional
Wedge disc seals in both flow directions for flexible installation.
Actuator Ready
Top flange accepts gearbox, pneumatic or electric actuators.
Technical Specifications
| Parameter | Specification |
|---|---|
| Body Material | WCB / SS304 / SS316 / Ductile Iron GGG50 |
| Wedge / Disc | Solid Wedge / Flexible Wedge / Parallel Slide |
| Seat Material | Resilient (EPDM / NBR) / Metal (SS316 / Stellite) |
| Size Range | DN40 – DN1200 (1.5" – 48") |
| Pressure Rating | PN10 / PN16 (ANSI 150 / 300) |
| End Connection | Flanged (ISO 7005-2 / ASME B16.5) / Butt-Weld |
| Stem Type | Rising Stem (OS&Y) / Non-Rising Stem |
| Operation | Handwheel / Gearbox / Pneumatic / Electric |
| Temperature | Resilient: -10→+80°C ; Metal: -40→+425°C |
| Leakage | Tight shutoff, bubble-tight with resilient seat |
| Standards | Design reference: API 600 / GB/T 12234 / EN 1171 — no API monogram held (API 609 applies to butterfly valves, not gate valves) |
| Certification | ISO 9001:2015, MTC available |
How to Specify a How to Specify a Parallel Slide Gate Valve
A parallel slide gate valve exists because a wedge sticks. It is the classic choice for high-temperature steam and for lines that cycle thermally.
Choose it where a wedge would stick
Two parallel discs with a spreading spring means the seats are not wedged into the body. On a line that heats and cools, that is the difference between a valve you can operate and one you cannot.
The spring and disc gap are the maintenance items
Wear shows as a slower, less definite closure rather than a sudden failure. On a critical steam isolation valve, plan for the discs and spring as service parts.
Not for dirty media
The parallel disc faces are vulnerable to a particle trapped between them. Parallel slide is a clean-service design; slurry belongs on a knife gate.
Confirm the temperature and pressure class
This is a high-energy design. State both, and state the flange standard, before a quotation is meaningful.
Orientation is by design, not convenience
Many parallel slide valves have a defined pressure side. Confirm it with us before installation rather than assuming symmetry.
Installation & Maintenance
Fit it where the pipe can move
A parallel slide valve on a hot line expects some thermal movement. Rigidly anchoring both sides works against the design intent.
Follow the pressure-side marking
Fitting the valve the wrong way round loads the discs incorrectly and shortens seat life.
Operate it through the full travel after heat-up
The first hot cycle is when a parallel slide valve proves itself. Stroke it once hot and record the effort.
Keep the stem and yoke clean
On an OS&Y valve, dust and rust on the rising stem thread travel straight into the stem nut.
Common Specification Mistakes
Using it on dirty service
A trapped particle prevents the discs from seating.
Treating it as interchangeable with a wedge gate
They fail differently and are maintained differently.
Ignoring the defined pressure side
Installing it backwards is silent and progressive.
Frequently Asked Questions
When should I use a rising-stem (OS&Y) gate valve?
Use OS&Y where you need visual confirmation of open/closed position — typical for fire protection and above-ground piping. Non-rising stem suits buried or space-limited installs.
Resilient seated or metal seated?
Resilient (EPDM/NBR) seats give bubble-tight shutoff for clean water up to +80°C. Metal seats handle steam, slurry and temperatures up to +425°C.
Why choose a knife gate valve?
Knife gate valves have a sharpened disc that cuts through slurry, pulp and viscous media — ideal for mining, wastewater and bulk solids.
Applications & Use Cases
Water & Wastewater
Resilient-seated gate valves for mains, hydrants and treatment plants.
Fire Protection
OS&Y gate valves for sprinkler and hydrant systems.
Power & Steam
Metal-seated wedge gates for high-temperature steam lines.
Mining & Slurry
Knife gate valves for abrasive and viscous process streams.
