Month: September 2025

The following constraints need to be considered when using the

positioner for SIL safety applications:

• Only the 4 to 20 mA setpoint signal is used for the safety

function, all other inputs or not part of the safety function.

• The proof-test specified within this safety manual (or an

equivalent test as specified for the final SIS safety

function) shall be performed before activating the safety

operation and in periodical cycles as demanded by the

final PFDAVG demands.

• The device is installed per manufacturer’s instructions

• The safety-related system (safety logic solver) must be

able to force the 0 mA signal direct or by using a safety

capable switch on the 4 to 20 mA signal.

• Materials are compatible with the final process conditions.

• The environmental, measurement and application limits

stated within the referenced documentations must be

considered accordingly for the SIL safety application.

The positioner safety function is declared as Type A element

with HFT=0 according to IEC 61508 capable to be used for SIL

Functional Safety Functions up to SIL 2.

According to IEC 61508-2. 7.4.7.4 a useful lifetime, based on

experience should be assumed.

The components of the positioner do not contain any specific

components with a reduced useful lifetime that are contributing

to the dangerous undetected failure rates.

Because the positioner is a moving masses system supplied by

instrumented air the final device usage and environmental

operating conditions (e.g., no/many open-close cycles,

good/bad supply air quality) will have an impact on the usefullifetime.

Therefore, the useful lifetime should be evaluated by the end

user according to the final plant experience data.

The Periodic Proof-Test methods within chapter Periodic Proof

Test and Maintenance on page 9 are suggested to validate the

correct safety function.

When final plant experience, proof testing and related field

monitoring data indicates a limiting useful lifetime by related

operating conditions, then the plant experience-based lifetime

must be used and considered on the failure rates, proof-test

intervals, and replacement intervals.

The safety function is activated if the electrical 4 to 20 mA

setpoint signal is set to 0 mA. This 0 mA signal might be forced

as direct logic solver/DCS output or by an additional electrical

open/close switch within the 4 to 20 mA setpoint line.

As reaction on the 0 mA signal the electronics, firmware &

position measurement is deactivated and bypassed, and the

mechanical pneumatic system of the positioner will be

depressurized into the fail-safe position.

The return spring of the attached pneumatic actuator will move

the valve to a safe end position (OPEN or CLOSED) subsequently.

The final safe state is achieved if the valve is located in the safe end position.

The time taken to reach the expected safe end position at the

process valve is only partly determined by the positioner; it is

also dependent on the attached actuator and valve assembly and

further external conditions, therefore the correct safety function

as expected within the final application must be checked during

installation & commissioning and the end user is responsible to

validate whether the safe state is achieved in the expected

direction and within the expected time frame.

Application area

The TZIDC is an electronically configurable 2-wire 4 to 20 mA valve positioner with HART® communication capabilities designed for

mounting on pneumatic linear or rotary actuators.

The TZIDC-200 is a variant designed with a flameproof enclosure as explosion protection concept.

The integrated I/P module with subsequent pneumatic amplifier is used to control the attached pneumatic actuator.

The SIL Safety Function is intended to open or close actuator/valves assemblies as emergency application.

By providing 0 mA as control/setpoint signal the positioner depressurizes the fail-safe actuator which return spring moves the valve

to a predefined, safe end position (either OPEN or CLOSED).

Figure 1 is demonstrating the safety instrumented function as example on a Tank Overfill Protection.

The TZIDC pneumatic system can be supplied in four versions: for single acting or double acting actuators and each with the ‘fail

safe’ or ‘fail-freeze’ safety behavior.

The SIL Safety Function is limited to the version: ‘single-acting, fail safe‘ in conjunction with pneumatic fail-safe actuators with

spring-return mechanism.

Additional instructions for

IEC 61508 compliant devices

from HW Rev. 05.xx

Introduction

Safety Manual for TZIDC / TZIDC-200 digital

Positioner.

The TZIDC / TZIDC-200 is an intelligent digital

positioner for communication via HART within the

positioner product range.

Application area

The TZIDC is an electronically configurable 2-wire 4 to 20 mA valve positioner with HART® communication capabilities designed for

mounting on pneumatic linear or rotary actuators.

The TZIDC-200 is a variant designed with a flameproof enclosure as explosion protection concept.

The integrated I/P module with subsequent pneumatic amplifier is used to control the attached pneumatic actuator.

The SIL Safety Function is intended to open or close actuator/valves assemblies as emergency application.

By providing 0 mA as control/setpoint signal the positioner depressurizes the fail-safe actuator which return spring moves the valve

to a predefined, safe end position (either OPEN or CLOSED).

Operating parameters

The following operating parameters can be set manually if required:

Setpoint signal

0 … 100 % freely selectable for split-range operation

For 4 … 20 mA and HART version:

— Signal min. 4 mA, max. signal 20 mA (0 … 100%)

— Min. range 20 % (3.2 mA)

— Recommended range > 50 % (8.0 mA)

Action (setpoint signal)

Increasing:

Position value 0 … 100 % = direction 0 … 100 %

Decreasing:

Setpoint signal 100 … 0% = direction 0 … 100%

Characteristic curve (travel = f {setpoint signal})

Linear, equal percentage 1:25 or 1:50 or 25:1 or 50:1 or freely

configurable with 20 reference points.

Travel limit

The positioning travel, i.e. the stroke or angle of rotation, can

be reduced as required within the full range of 0 … 100 %,

provided that a minimum value of 20% is observed.

Device parameters

General remarks

Microprocessor-based position control in the positioner

optimizes control. The positioner features high-precision

control functions and high operational reliability. Due to their

elaborate structure and easy accessibility, the device

parameters can be quickly adapted to the respective application.

The total range of parameters includes:

— Operating parameters

— Adjustment parameters

— Monitoring parameters

— Diagnostics parameters

— Maintenance parameters

Operating parameters

The following operating parameters can be set manually if required:

Setpoint signal

0 … 100 % freely selectable for split-range operation

For 4 … 20 mA and HART version:

— Signal min. 4 mA, max. signal 20 mA (0 … 100%)

— Min. range 20 % (3.2 mA)

— Recommended range > 50 % (8.0 mA)

Action (setpoint signal)

Increasing:

Position value 0 … 100 % = direction 0 … 100 %

Decreasing:

Setpoint signal 100 … 0% = direction 0 … 100%

Characteristic curve (travel = f {setpoint signal})

Linear, equal percentage 1:25 or 1:50 or 25:1 or 50:1 or freely

configurable with 20 reference points.

“Fail-safe” function

If the electrical supply power fails, the positioner output 1 is

depressurized, and the pneumatic actuator’s return spring

moves the valve to the defined safe position. In case of a

double-acting actuator the second output 2 is additionally pressurized.

Change from two to one column

“Fail-freeze” function

If the electrical supply power fails, the positioner output 1 (and

2. if applicable) is closed and the pneumatic actuator stops

(“freezes”) the valve in the current position. If the compressed

air supply power fails, the positioner depressurizes the actuator.

The TZIDC-200 is an electronically configurable positioner with

communication capabilities designed for mounting to

pneumatic linear or part-turn actuators. It features a small and

compact design, a modular construction, and an excellent

cost-performance ratio.

Fully automatic determination of the control parameters and

adaptation to the final control element yield considerable time

savings and an optimal control behavior.

Pneumatics

An I/P module with subsequent pneumatic amplifier is used to

control the pneumatic actuator. The well-proven I/P module

proportionally converts the permanent electrical setpoint signal

from the CPU into a pneumatic signal used to adjust a 3/3 way valve.

The air flow for pressurizing or depressurizing the actuator is

continuously adjusted. As a result, excellent control is

achieved. When reaching the setpoint, the 3/3-way valve is

closed in center position to minimize the air consumption.

Four different pneumatics versions are available: for single

acting or double-acting actuators, each with “fail-safe” or “fail freeze” function.

“Fail-safe” function

If the electrical supply power fails, the positioner output 1 is

depressurized, and the pneumatic actuator’s return spring

moves the valve to the defined safe position. In case of a

double-acting actuator the second output 2 is additionally pressurized.

Change from two to one column

“Fail-freeze” function

If the electrical supply power fails, the positioner output 1 (and

2. if applicable) is closed and the pneumatic actuator stops

(“freezes”) the valve in the current position. If the compressed

air supply power fails, the positioner depressurizes the actuator.

Brief description

The TZIDC-200 is an electronically configurable positioner with

communication capabilities designed for mounting to

pneumatic linear or part-turn actuators. It features a small and

compact design, a modular construction, and an excellent

cost-performance ratio.

Fully automatic determination of the control parameters and

adaptation to the final control element yield considerable time

savings and an optimal control behavior.

Pneumatics

An I/P module with subsequent pneumatic amplifier is used to

control the pneumatic actuator. The well-proven I/P module

proportionally converts the permanent electrical setpoint signal

from the CPU into a pneumatic signal used to adjust a 3/3 way valve.

The air flow for pressurizing or depressurizing the actuator is

continuously adjusted. As a result, excellent control is

achieved. When reaching the setpoint, the 3/3-way valve is

closed in center position to minimize the air consumption.

Four different pneumatics versions are available: for single

acting or double-acting actuators, each with “fail-safe” or “fail freeze” function.