| Spool Diagrams* |
Type |
Spool Options |
Ansi Symbol |
 |
Type I |
Two position, positive lap spool used for conventional 4-way, 2-position applications. Can be used as a normally open or normally closed 3-way valve by simply plugging one cylinder port. Use for air and hydraulic service.
This spool type will be furnished unless otherwise specified. |
Hydraulic
Pneumatic
|
 |
Type II |
Three position, closed center spool with wide lands. All ports are blocked and isolated in the center position. Typically used for "position-and-hold" or "inching" circuits (will not hold position for long periods of time). Use for air and hydraulic service. |
Hydraulic
Pneumatic
|
 |
Type II-A |
Three position, closed center spool with wide lands that are tapered. All ports are blocked and isolated in the center position. The tapering of the lands provides a more linear flow versus spool travel and therefore better speed control. Typically used for "position-and-hold" or "inching" circuits (will not hold position for long periods of time). Use for air and hydraulic service. |
Hydraulic
Pneumatic
|
 |
Type IV |
Three position, cylinder ports blocked with cross drilled spool to allow pressure to bleed to tank port. Do not use in a "series" circuit and limit tank back pressure to 250 PSI maximum. Use for hydraulic service only. |
Hydraulic
|
 |
Type V |
Three position supply blocked with cylinder ports to tank (commonly referred to as exhaust open center in pneumatic terminology). Use for air and hydraulic service. |
Hydraulic
Pneumatic
|
 |
Type VI |
Three position, closed center spool with narrow lands (minimal lap). Spool movement yields almost immediate action. Must be used with sensing devices that will mechanically or electrically position the spool. Use for air and hydraulic service. |
Hydraulic
Pneumatic
|
 |
Type VI-A |
Three position, closed center spool with narrow, tapered lands (spools with positive or negative lap can be supplied for special applications). The tapered lands help decelerate the cylinder as the spool approaches the center position, which assists in reducing shock and system instability. May be used with sensing devices that will mechanically or electrically position the spool. Use for hydraulic service only. |
Hydraulic
|
 |
Type VII |
Two position specially machined spool that allows the valve to become either a 2-way normally open or normally closed unit. May also be used as a pressure selector with two different pressures piped into the cylinder ports with the inlet port being used as a common outlet. Specify the type of service (2-way normally open, normally closed or selector) so that the ports will be marked accordingly. Use for hydraulic service only. Note: Tank port must be left open. |
Hydraulic
2-Way
Hydraulic
Selector
|
 |
Type VIII |
Three position, all ports open to tank. Unique function that can also be suitable for negative lap servo applications. Use for hydraulic service only. |
Hydraulic
|
