Kalsi Engineering has successfully performed numerous/systematic root-cause investigations of components/equipment used in nuclear power plants and in the oil field and petrochemical industries. KEI’s success is a direct result of our experience with a wide range of valve and equipment failure modes, expert use of state-of-the-art engineering tools, and sound understanding of the engineering first-principles.
Root-cause investigations commonly performed by KEI™ include the failure modes discussed below. Key examples demonstrating extensive experience in performing root-cause investigation related to the failure modes below are discussed later.
Design limitation or flaws that are either unidentified or ignored during selection often form the common thread for almost all failures. Design limitation can include improper material selection, unanticipated binding, wedging or impact loading due to unacceptably large clearances or unintended interferences resulting from improper part tolerancing.
System/Component Interaction can reveal subtle weaknesses in the design of equipment. Problems resulting from system/component interactions include pressure locking and thermal binding of mechanical components, accelerated wear and/or fatigue, or increased operating forces due to increases in side-load forces caused by external loads. System/component interactions can greatly be affected by improper equipment sizing and selection (e.g., check valve disk instability due to improper sizing and/ friction or installation). System/component interaction can lead to valve control instability which results in accelerated wear due to frequent hunting.
Seat Sealing Failure typically results due to a local loss of contact pressure. The potential causes of the loss in contact pressure can vary greatly. Common factors include pressure-induced, thermal gradient-induced, and external-load-induced seat distortions.
Safety Relief Valve Set Point Drift is a common problem experienced in SRVs used in power plants and chemical plants. Set point drift can result from corrosion bonding between the plug and seat, uneven thermal growth between the bonnet and spindle, a change in shear modulus due to time-dependency in the mean temperature of the spring, and an increase in the motive force associated with abnormal bushing wear between the spindle and guide bushing.
Mechanical/Flow-Induced Vibration can contribute to several failure modes including accelerated/abnormal wear, accelerated fatigue failure, which can cause an increase in required operating forces to overcome damage to sliding/guiding surfaces.
Mechanical Overload can initiate several failure modes including complete/partial component separation, gross deformation resulting in binding, and plastic deformation-induced preload loss.
Fatigue Failures can result from high-load low-cycle loading or low-load high-cycle loading. The complete root-cause may identify improper material selection, improper system design, or unacceptable system-component interactions.
- Failures due to Thermal Distortion/Stresses
- Failures due to Improper Material Selection
- Valve/System Interaction
- Non-Uniform Thermal Loading — Pooled Condensate
- Contact Bandwidth, Contact Pressure and Maintenance Practices
- Main Seat Leakage
- Pilot Seat Leaks
- Listing of Relevant Root-cause Investigations to support FMEAs in Nuclear Power Plants