Fisher 657 & 667 Diaphragm Actuators
The difference between the 657 and 667
Fisher sells these as a pair because they're the same actuator with one thing flipped - which way the stem travels when loading pressure rises.
- 657 - direct-acting. More pressure pushes the stem down.
- 667 - reverse-acting. More pressure pulls the stem up.
Which one you need depends on the valve's failure position - fail closed uses the 657, fail open uses the 667. Send us the model number if you're not sure.
Products Description
Both models turn a pneumatic control signal into the linear motion a control valve needs. Mounted on the valve yoke, the actuator moves the stem up or down so the valve plug follows the control system - reliably, across years of operation.
Key features
- Spring-opposed diaphragm design - simple, few moving parts, easy to service in the field.
- Positioner-ready - accepts standard Fisher positioners and valve controllers, including the 3582i and DVC6200.
Specifications
| Parameter | Value |
|---|---|
| Brand / Model | Fisher 657 & 667 Diaphragm Actuators |
| Type | Spring-opposed diaphragm actuator (linear) |
| Action | 657: direct-acting · 667: reverse-acting |
| Max. casing pressure | 3.4 bar (50 psig) standard; up to 5.2 bar (75 psig) on select sizes |
| Diaphragm | Nitrile on nylon fabric |
| Mounting | Yoke mount; accepts positioners (3582i, DVC6200, etc.) |
Applications
- Oil refining & petrochemical - globe control valves on process units
- LNG & gas processing - stable travel under changing loads
- Power plants - feedwater, steam, and general control loops
- Chemical & industrial manufacturing - general pneumatic control
Why buy from Century Weiye
- Ample stock, fast delivery - common models in stock, normally shipped within 1–2 weeks.
- 10+ years of hands-on experience - our core team worked for years at Fisher's China office; we know both the specs and the field conditions.
- Deep factory partnerships worldwide - long-term sourcing across multiple countries keeps supply stable and traceable.
Send us your valve model and the travel you need, and we'll come back with the right size, a price, and a lead time - usually within 24 hours.
WhatsApp / Phone: +85292039110
Email: serena@valve-sjwy.com
FAQ
Q: What's the difference between the 657 and 667?
A: The 657 is direct-acting - rising pressure moves the stem down. The 667 is reverse-acting - rising pressure retracts the stem. The choice depends on the valve's fail-open/fail-closed requirement.
Q: How do I know which one I need?
A: It's set by the valve's failure position. Fail-closed valves take the 657; fail-open valves take the 667. Send us the valve model and we'll confirm.
Q: Which valves do they fit?
A: They mount on the yoke of Fisher globe-style control valves (EZ, ED, ES, ET, EW series) and other compatible linear valves.
Q: Can I mount a positioner on them? A:
Yes - standard Fisher positioners such as the 3582i pneumatic positioner and DVC6200 digital valve controller fit directly.
Q: Is it in stock, and how fast do you ship?
A: Common sizes are in stock and normally ship within 1–2 weeks. Send the size and quantity for a confirmed lead time.
Q: Is the product genuine?
A: Yes - 100% genuine Fisher (Emerson) products, traceable and sourced from stable channels. No counterfeits.
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