Management of Change Guide: Replacement of Fisher 685 Actuators with Fisher 785C Double-Acting Springless Actuators
Fisher Management of Change Guide: Replacement of Fisher 685 Actuators with Fisher 785C Double-Acting Springless Actuators Manuals & Guides
Management of Change Guide
May 2019
D352798X012
Replacement of Fisher™ 685 Actuators with
Fisher™ 785C Double-Acting Springless Actuators
Table of Contents
Management of Change ..................................2
Background ....................................................2
Question & Answer Checklist ..........................2
Comparison of Fisher 785C and 685 Actuators 5
Basic Design and Features ................................................... 5
Weight ............................................................................... 7
Envelope Dimensions ......................................................... 7
Conclusion ......................................................9
Management of Change
Management of Change (MOC) is a procedure used to proactively manage changes
that have the potential to impact safety or the process within a plant. Evaluating
new techniques for improving MOC approval procedures can have an impact on
plant efciency. Historically, upgrading obsolete products or replacing existing
process control equipment had been delayed or abandoned due to the extensive
paperwork involved in completing a complex MOC approval sheet.
Background
The Fisher 785C Series is a double-acting springless or single-acting or doubleacting spring-return actuator that provides accurate, high thrust output for up
to 610 mm (24 inch) travel sliding-stem valve applications. The purpose of this
document is to simplify the transition from existing double-acting springless piston
actuator technologies to the Fisher 785C double-acting springless actuator.
Contained in this guide are two sections, the rst contains questions and answers
and the second compares the Fisher 785C actuator to the Fisher 685 actuator.
The rst section helps users complete MOC approval documents when replacing
existing actuators with the 785C model. The second section helps users better
understand the differences and similarities between the 785C and the 685 actuator.
MOC: Fisher 685 to 785C Actuators
May 2019
D352798X012
Question & Answer Checklist
Q: Does the proposed modication cause any changes to the piping and
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instrumentation diagram (P&ID)?
A: No.
Q: Does the proposed modication change process chemistry,
technology, or operating and control philosophies?
A: No.
Q: Does the proposed modication change how the existing plant is
operated?
A: No.
Q: Does the proposed modication change process ows?
A: No.
Figure 1. Fisher 785C double-acting
springless actuator
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Q: Does the proposed modication change existing pressure relief cases?
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A: No.
Q: Does the proposed modication change the process description?
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A: No.
Q: Have the codes and standards to which the new equipment was
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designed changed?
A: No.
Q: Does the proposed modication change the materials of construction,
such as a change in material form (cast, forged, or alloy)?
A: No. The plant can specify the materials of constructions as desired.
MOC: Fisher 685 to 785C Actuators
May 2019
D352798X012
Q: Does the proposed modication introduce new equipment items that
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require periodic predictive maintenance?
A: No. The new equipment items will require the same periodic
predictive maintenance required by the old equipment items.
Q: Does the proposed modication change existing operator training
requirements?
A: No. Please refer to the instruction manual when performing
maintenance on the Fisher 785C actuator.
Q: Does the proposed modication introduce new equipment items
that require spare parts, training manuals, maintenance procedures
or training to teach the maintenance department how to maintain
them?
A: Yes, however the new equipment items have the same theory of
operation and maintenance procedures as the old equipment items.
Documentation for training and maintenance can be obtained in the
instruction manual or by contacting your local Emerson sales ofce.
Q: Does the proposed modication introduce new equipment items that
require spares or obsolete spares for existing equipment?
A: Yes. Spares for old equipment items cannot be used with new
equipment items due to differences in dimensions. Documentation
on recommended spares can be obtained by providing the two serial
numbers, located on the actuator, to your local Emerson sales ofce.
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