Fisher Management of Change Guide: Transition from Fisher EHA Valves to Fisher HPA Valves Manuals & Guides
Management of Change Guide
September 2018 / D352301X012
Replacement of Fisher™ EHA with Fisher
HPA Control Valves
Table of Contents
Management of Change ..................................2
Background ....................................................2
Question & Answer Checklist ..........................2
Comparison of Fisher EHA to HPA Control Valves
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Conclusion ......................................................5
Additional Resources ......................................6
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 HP Series control valve is found in every industry that requires ASME
CL900/1500 rated control valves. The globe version is called HP and the angle
version is called HPA. Historically, the Fisher HPA valve was available in NPS 1 and 2
CL900/1500 and CL2500 only, while sizes NPS 3–8 CL900/1500 were available only
in the EHA valve. Emerson Process Management has expanded the HPA valve to
include NPS 3–8 CL900/1500. This was done to simplify the angle valve offering and
modernize the designs. The purpose of this guide is to simplify the transition from
the Fisher EHA valve to the HPA valve.
MOC: EHA to HPA Valves
September 2018 / D352301X012
This MOC guide contains two sections, the rst contains frequently asked questions
with answers to aid users in completing MOC approval documents when upgrading
to the HPA valve. The second section provides a comparison of the HPA and EHA
valve to help users better understand the differences and similarities between them.
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 ow rates?
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A: No.
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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: Will the operating and design conditions (ow, temperature,
pressure) of my line change because of this change?
A: No.
MOC: EHA to HPA Valves
September 2018 / D352301X012
Q: Does the proposed modication change the materials of construction
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such as a change in material form (cast, forged, or alloy)?
A: No, they are both available in the same materials.
Q: Does the proposed modication introduce new equipment items that
require periodic predictive maintenance?
A: No. The new equipment items will require the same periodic
maintenance as required by the old equipment items.
Q: Does the proposed modication change existing operator training
requirements?
A: No, they would both require the same level of training.
Q: Does the proposed modication introduce new equipment items that
require training, manuals, maintenance procedures, or training to
teach maintenance department craftsmen how to maintain them?
A: Yes. The new equipment requires HPA valve specic instruction
manuals, maintenance procedures, and training to maintenance
department. However, if your people have been trained or are familiar
with the HP or HPA valve, they won’t require more training.
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Q: Does the proposed modication introduce new equipment items that
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require spares or obsolete spares for existing equipment?
A: Yes. The spares of the existing equipment items have to be removed
and the spares for the new equipment item are required. Many of
the NPS 3–8 CL900/1500 HPA valve spare parts will be same as your
existing HP spare parts.
Q: Does the proposed modication change the inspection scope or
inspection interval?
A: No.
Comparison of Fisher EHA to HPA Control Valves
The Fisher HPA control valve is very similar to the EHA control valve, but there are
a few construction differences. The EHA valve makes use of hung cage design and
the seat ring is retained by the seat ring retainer, which is threaded to the valve
body. The HPA valve trim has been modernized to be clamped into the body and
is retained by the bonnet bolting force, just like in the HP globe valve. This small
change is a great advancement as no more special maintenance tools are required
to remove the seat ring retainer and thereby remove the seat ring. HPA seat rings
can easily be accessed by simply removing the bonnet and then the cage.
MOC: EHA to HPA Valves
September 2018 / D352301X012
Port and travel of the HPA valve remains the same as the EHA valve and the Cv of
the HPA valve is slightly less than that of the EHA valve. In those cases where the Cv
of NPS 3–8 CL900/1500 HPA is not adequate enough to replace EHA, the HPA valve
shall not be used as the replacement valve [refer to Tables 1 and 2 on page ve]. The
face-to-face dimension of HPA valves is same as that of the EHA valves, and, hence,
no piping change is required.
The EHA valve was available in three different constructions: unbalanced plug
(EHAS), balanced low-temperature (600°F maximum) construction (EHAT),
and balanced high-temperature construction (EHAD). Similarly, there are the
Fisher HPAS, HPAT, and HPAD constructions to cater to the different application
requirements. The HPA valve can be applied in almost all applications where the
EHA valve was used. There are certain applications in which the EHA valve with
intermediate rating was used. In those cases the HPA valve shall not be used as the
replacement valve.
The HPA valve offers similar severe service trims and trim material options as
provided by the EHA valve. Apart from the standard trim combinations, special trim
combinations can be offered to meet customers’ needs.
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MOC: EHA to HPA Valves
September 2018 / D352301X012
Valve Without Liner
NPS Size
3 65.7 64.3 54.4 48.8 63 61.1
4 151 121 112 92.7 140 114
6 244 201 195 165 229 203
8 503 425 395 319 466 378
Table 1. Cv Comparison between CL1500 Rated EHA and HPA Valve Without Liner
NPS Size
3 58.3 64.3 51.6 48.8 56.4 61.1
4 148 121 122 92.7 143 114
6 231 201 182 165 216 203
8 491 425 391 319 459 378
Table 2. Cv Comparison Between CL1500 Rated EHA and HPA Valve With Liner
Linear Characteristics Equal-Percentage Characteristics
EHAD, EHAT HPAD, HPAT EHAD, EHAT HPAD, HPAT EHAD, EHAT HPAD, HPAT
Valve With Liner
Linear Characteristics Equal-Percentage Characteristics
EHAD, EHAT HPAD, HPAT EHAD, EHAT HPAD, HPAT EHAD, EHAT HPAD, HPAT
Modied Equal-Percentage
Characteristics
Modied Equal-Percentage
Characteristics
Conclusion
The Fisher HPA valve is now extended from sizes NPS 1–2 to NPS 1–8. The Fisher
EHA valve will no longer be available as a new assembly; however, spare parts will be
supported until July 2022. The HPA valve should always replace the EHA valve unless
the existing EHA valve utilized an intermediate rating or has higher capacity. As
discussed in the previous sections, the HPA valve offers several advantages over the
EHA valve and they are highlighted below.
Clamped trim design
Easy access to seat ring, no special tools required to remove the seat ring
Same face-to-face dimensions
Same port and travel
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Additional Resources
Contact your local Emerson sales ofce or refer to the following resources for
complete product features:
HPA Instruction Manual (D101634X012)
HPA Bulletin (D101635X012)
MOC: EHA to HPA Valves
September 2018 / D352301X012
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