Nuclear Division · SAE ARP-5316, Storage of Elastomer Seals and Seal Assemblies MIL-HDBK-695E, Rubber products: Recommended Shelf Life MIL-STD-1523, Age Controls of Age-Sensitive

1 | September 23, 2020 | © 2018 Curtiss-Wright

Nuclear Division

Assembly Shelf Life

RAPID Conference, September 2020

By Ararat Torosyan, P.E.



Presentation

Desired Outcome: To understand the assembly shelf life, and its

relation with the parts shelf life and qualified life.

Presentation Outline:

– Definitions

– Parts Shelf Life

– Qualified Life

– Assembly shelf life

– Product Life Milestones

– Sample In-storage maintenance requirements for Assemblies

• Hydraulic Snubbers

• Electro-Hydraulic Actuators

– Key Takeaways



References

EPRI 1022959 (NP-6408), Guidelines for Establishing, Maintaining, and

Extending the Shelf Life capability of Limited Life Items

EPRI TR-100844, Nuclear Power Plant Common Aging Terminology

EPRI 1014800, Elastomer Handbook for Nuclear Power Plants

SAE ARP-5316, Storage of Elastomer Seals and Seal Assemblies

MIL-HDBK-695E, Rubber products: Recommended Shelf Life

MIL-STD-1523, Age Controls of Age-Sensitive Elastomeric Material

IEEE 323 Standard for Qualifying Class 1E Equipment

IEEE 344 Standard for Seismic Qualification of Equipment

IEEE 382 Standard for Qualification of Safety-Related Actuators



Definitions

Limited Life Items: Items whose aging in storage or service would limit their service life.

Shelf Life: The time an item or assembly may be stored without affecting the service life.

Qualified (In-Service) Life: A demonstrated time for an item or unit, through testing, analysis, or experience, to be capable of functioning during specified operating conditions while retaining the ability to perform its safety function in a design basis accident or earthquake.

Service Life: In this presentation, Service Life will be considered same as Qualified Life.

Refurbishment (Assembly): A series of works on the unit to restore it functionally to the like-new condition, including and not limited to, inspection, testing, and replacement of the limited life items.



Remarks

Qualified Life vs. Service Life

– In general, in most industries, the end of service life is defined as when the unit no longer performs its intended function. However in our industry for an EQ item, the service life (qualified life) ends before an accident condition. In other words, its life ends before the end of its functional life to not jeopardize its ability to survive an accident.

The impact of Storage on Qualified Life

– While the storage time and storage conditions impact the qualified life of the equipment, it is minimized by following the manufacturer’s in-storage maintenance requirements.

– As a reference, EPRI 1022959 assumes up to 5% of the demonstrated life at the storage conditions will have no impact on the qualified life.



Part Shelf Life

The time an item may be stored without affecting the service life.



Part Shelf Life

Key Contributors

– Material Type

– Packaging for storage

– Storage Conditions

• Temperature

• Humidity

• Light

• Ozone

• Radiation (if applicable)

Notes

– It is a well established and demonstrated concept in many industries.

– Reliable resources available (SAE ARP 5316, DOE MIL-HDBK-695D, EPRI 1022959)



Qualified (In-Service) Life

A demonstrated time for which an item or unit capable of functioning within

acceptance criteria during specified operating conditions while retaining the

ability to perform its safety function in a design basis accident or earthquake.



Qualified Life

Key Contributors

– In-service environmental conditions

• Temperature

• Humidity

• Radiation

• Vibration

• Amount of usage

– Maintenance

– Refurbishment

Notes

– It is a well established and demonstrated concept in Nuclear industry (IEEE 323, 344, 382)

– One must pay attention to the differences between actual in-service conditions vs. original qualified conditions.



Assembly Shelf Life

The time an assembly may be stored without affecting the service life.



Assembly Shelf Life

Key Contributors

– Packaging

– Storage conditions

– The length of the storage (Short vs. Long)

– Manufacturer’s in-storage maintenance requirements



Assembly Shelf Life

Notes

– Not a well established, demonstrated, or documented concept,

heavily relies on OEM’s recommendations based on their

experience or engineering judgments/evaluations.

– Generally, it is considered a part of service life by most

manufacturers. In other words, service life starts after the

assembly.

– Assembly shelf life may be determined based on the part with the

shortest life. However, considerations shall be given to the

conditions of the parts in the assembly. These conditions may

include physical stress, exposure to chemicals, and packaging.



Product Life Milestones



Total Life Milestones



Assembly Shelf Life Milestones



Example of Manufacturer’s In-Storage Requirements for Assemblies



Hydraulic Snubbers (Component support)

Hydraulic Fluid

Rod Seals

Piston Seals

Control Valves

Reservoir

Spherical

Bearings



Hydraulic Snubbers (component support)

General storage conditions

– For extended storage, the snubber should be stored in its original crate, the crate must be protected in an inside, clean environment with a temperature range of 40F and 120F on flooring not subject to flooding.

Inspections/Intervals

– Semi-Annually

• Visually inspect the snubber and shipping accumulator and its connections and all plugs, valves, rod head, and bling head areas for fluid leakage.

– Annually

• After one year, the unit must be extended through ¼” stroke (minimum) to sustain seal integrity. Upon completion of this activity and repackaging, the unit is good for one additional year. If the unit is stored for an additional year, it must then be retracted through ¼” stroke.

– Bi-Annually

• For every two years that the snubber is stored, a fluid sample shall be taken for analysis.

Storage over five years

– The unit must be tested for functionality per factory ATP, and all limited life items shall be evaluated for service life.



Electro-Hydraulic Actuators (Valve operators)

Hydraulic

Filter

Pump/Motor

Assembly Control Valves

w/soft seals

Hydraulic

AccumulatorHydraulic Fluid

Hydraulic CylinderN2 Stored Energy



Electro-Hydraulic Actuators (valve operators)

General storage conditions

– For extended storage, the actuator should be stored in its original crate,

the crate must be protected in an inside, clean environment with a

temperature range of 40F and 120F on flooring not subject to flooding.

Inspections/Intervals

– Semi-Annually

• The actuator shall be operated one full cycle (open-close-open), using its

pump/motor system.

– Bi-Annually

• For every two years that the actuator is stored, a fluid sample shall be taken

for analysis.

Storage for over five years

– If the actuator is to be stored for over five years, the unit must be tested for

functionality per factory ATP, and all limited life items shall be evaluated for

service life.



Key Takeaways

Assembly Shelf Life and Part Shelf Life are not same.

Determination of assembly shelf life and related in-storage maintenance

requirements should based on engineering evaluation by manufacturer.

In-storage maintenance requirements by the manufacturer is important to

maintain the assembly qualified life.


Thank you

www.cwnuclear.com

Questions?

Ararat Torosyan, P.E.

VP Engineering

[email protected]

714.982.1800

Documents

Nuclear Division · SAE ARP-5316, Storage of Elastomer Seals and Seal Assemblies MIL-HDBK-695E, Rubber products: Recommended Shelf Life MIL-STD-1523, Age Controls of Age-Sensitive