MOOG D661 Nameplate Codes: Model Number and Type Designation
Model Number and Type Designation serve different purposes on a D661 nameplate. The first identifies a factory-assigned model; the second describes flow, pressure, spool, pilot and electrical configuration. Together they explain how the original valve was configured.
A product listed as D661-4506 helps identify that model. The digits 4506 cannot simply be divided into 45 L/min, a pressure rating and a current value. Find these characteristics in their respective Type Designation fields.
What the identifiers tell you
| Nameplate field | Meaning | Practical use |
|---|---|---|
| Model Number | Factory-assigned model identifier | Identify the original product and records |
| Type Designation | Configuration codes | Distinguish flow, pressure, pilot and interface options |
| Serial Number | Individual product identity | Trace separate valves and repair histories |
The D661-G…A ordering diagram marks Model Designation as factory assigned and lists flow and interfaces separately under Type Designation. These fields do not replace one another.
The following codes belong to the D661-G…A catalogue. D661 suffixes identify different versions, so this table does not apply unchanged to every D661 variant.
Flow code 30 corresponds to 80 L/min in this table
The ordering table lists each flow code at two pressure drops. Code 30 is 80 L/min at 70 bar total valve drop and approximately 30 L/min at 10 bar total drop.
| Flow code | At 70 bar total valve drop | At 10 bar total valve drop |
|---|---|---|
| 08 | 20 L/min | 8 L/min |
| 15 | 40 L/min | 15 L/min |
| 30 | 80 L/min | 30 L/min |
| 35 | 90 L/min | 35 L/min |
| 45 | 120 L/min | 45 L/min |
| 60 | 160 L/min | 60 L/min |
| 75 | 200 L/min | 75 L/min |
An old valve marked with flow code 30 and a supply list saying only “30 L/min” can appear inconsistent when the two records use different reference drops. They may describe the same flow option.
Record the pressure condition alongside flow, such as 80 L/min at 70 bar total valve drop. This prevents confusing code numbers, low-drop flow and rated flow. See the D661 model and flow guide.
O and S describe different flow characteristics
Spool code O specifies a four-way, approximately critically lapped spool with a linear flow characteristic. S identifies a curvilinear characteristic. This changes the relationship between smaller commands and flow.
Suppose an existing machine uses a small command for feed and a large command for rapid return. A replacement with the same full-opening flow but a different characteristic can change the relationship between existing settings and speed. A full-opening flow check alone will miss this difference.
Match the flow characteristic as well as rated flow. Preserving it when the controller program is unchanged reduces the speed adjustment required.
Pilot codes 4, 5, 6 and 7
| Pilot code | Supply | Return |
|---|---|---|
| 4 | Internal | Internal |
| 5 | External | Internal |
| 6 | External | External |
| 7 | Internal | External |
An original externally supplied and externally drained installation has separate X/Y paths. Replacing it with an internally supplied and internally drained configuration changes pilot conditions even when NG10 mounting and main-stage flow match.
This distinction matters during low-pressure operation, at higher return backpressure or with a separate pilot unit. See D661 internal and external pilot supply.
The same ±10 V command can have different feedback
| Signal code | Command input | Spool-position feedback |
|---|---|---|
| D | ±10 V | 2–10 V |
| M | ±10 V | 4–20 mA |
| X | ±10 mA | 4–20 mA |
An original M interface accepts ±10 V and sends 4–20 mA feedback. Replacing it with D retains voltage command but changes feedback to voltage. Reading that output through the old current-input setup gives incorrect results.
The midpoint is 12 mA for 4–20 mA spool feedback and 6 V for 2–10 V feedback. Spool-position feedback is not a cylinder-stroke measurement.
Read pressure and power-off codes in their own fields
This catalogue lists B, H and K pressure codes with 70, 280 and 350 bar ratings. Some H port capabilities also depend on external X/Y arrangements. Interpret pressure alongside the relevant ports and pilot configuration.
The same letter can mean different things in different fields. Signal code D identifies an electrical interface; D elsewhere or in another series may mean something else. Follow field position rather than assigning one universal meaning to a letter.
Power-off position and enable functions are separate configuration items too. Preserve the required unloading, flow path or defined shutdown position rather than ending checks after a successful powered test.
Conclusion
Model Number identifies the product; Type Designation explains its configuration. For replacement, align flow and reference pressure drop, spool characteristic, pilot connections and electrical interface. These fields reveal more than interpreting the digits following D661 as universal parameter codes.