Data Sheet for Product

Powermite 599 Series MZ Series Zone Control Two-way Valves Technical Instructions
Document No. 155-198P25
December 29, 2009
Siemens Industry, Inc. Page 7
Operation
Figure 3 shows the normally open valve in the open or full flow position and the normally
closed valve in the closed or zero flow position. The valve spring provides the necessary
force to hold the stem in the raised or normal position.
In the event of power failure, a fail-safe actuator returns the valve to its normal position.
Fail-in-place actuators will hold the last commanded position. See the Technical
Instructions of the various actuators for additional information.
Figure 3.
Sizing
The sizing of a valve is important for correct system operation. An undersized valve will
not have sufficient capacity at maximum load. An oversized valve can initiate cycling,
and the seat and throttling plug can be damaged because of the restricted opening.
Correct sizing of the control valve for actual expected conditions is considered essential
for good control.
The following variables must be determined:
• The medium to be controlled: water, etc.
• The maximum inlet temperature and pressure of the medium at the valve.
• The pressure differential that will exist across the valve under maximum load
demand.
• The maximum capacity the valve must deliver.
• The maximum line pressure differential the valve actuator must close against.
See Application Bulletin (AB)-1 Control Valve Selection and Sizing (155-285) for further
recommendations.
See Tables 3 through 6 for valve capacities.
Mounting and
Installation
Install the valve so that the flow follows the direction of the arrow indicated on the valve
body.
For best performance, install the valve assembly with the actuator above the valve body.
The valve and actuator can be installed in any position between vertical and horizontal.
It is not recommended to install the valve assembly so that the actuator is below
horizontal or upside down.