S-E VZ29 / VZ39 / VZ49 Valve Body produces excessive let by due to S-E MZ20 series Actuator Manual Override set to value other than ZERO .

Issue

S-E VZ29 / VZ39 / VZ49 Valve Body produces excessive let-by.
 

Product Line

Field Devices

Environment

S-E VZ29 2-port Valve Body controlled by S-E MZ20 series Actuator.

S-E VZ39 3-port Valve Body controlled by S-E MZ20 series Actuator.

S-E VZ49 4-port Valve Body controlled by S-E MZ20 series Actuator.

Cause

S-E MZ20 series Actuator Manual Override set to value other than ZERO

Resolution

1.  Check S-E MZ20 series Actuator Manual Override facility is set to ZERO.

2.  If S-E MZ20 series Actuator Manual Override facility is set to ZERO then investigate Valve Body condition / duty compatibility.

Instances of excessive let-by experienced with S-E Valve Bodies from the VZ29 / VZ39 / VZ49 family may result from the setting of the Manual Override facility on the S-E MZ20 series Actuator controlling it, rather than the Valve Body itself.

S-E MZ20A and MZ20B Actuators include a Manual Override facility, comprising a screw, accessed through a hole in the top of the Actuator, which may be raised and lowered by means of a 3mm Allen Key inserted through the hole in the top of the Actuator.

The Manual Override position is required to be set to ZERO upon manufacture.  If the screw is not set to the ZERO position prior to dispatch however, then this may result in the Valve Spindle being depressed by the amount of Manual Override applied.

Where a Valve Body is letting by excessively, then initially the Actuator Manual Override setting should be checked and reset to ZERO if necessary.