Mechanical Engineering Startup Jobs in Riverside, CA

Nikkiso Clean Energy & Industrial Gases is a leading provider of cryogenic pumps, heat exchangers, process systems, services, and solutions for the LNG and industrial gases industry. We are a subsidiary of Nikkiso Company Ltd, a leading industrial manufacturer headquartered in Tokyo, Japan, with over $1.5 B in annual revenue, 8000 + employees worldwide, and publicly traded on the Tokyo Stock Exchange.

The Senior Process Engineer leads process system design and technical definition for skid-mounted and modular process packages in an EPC execution environment. This role is responsible for developing and validating the process design basis, ensuring system operability, and integrating process requirements across mechanical, I&C, and package design.

A core responsibility of this role is ownership of process simulation models, ensuring that simulation results are accurate, validated, and fully aligned with design deliverables, vendor data, and operating philosophy.

The position requires strong experience in oil & gas, LNG, cryogenic, or industrial gas systems, with the ability to translate simulation outputs into practical, fabrication-ready engineering solutions.

Process Design & System Definition

• Develop and lead:
• Process Design Basis
• PFDs (Process Flow Diagrams)
• P&IDs (Piping & Instrumentation Diagrams)
• Heat & Material Balances
• Utility balances
• Line sizing calculations
• Relief and flare calculations
• Define operating philosophy including startup, shutdown, turndown, and upset conditions
• Ensure accurate representation of process control strategies within P&IDs

Process Simulation (Core Responsibility)

• Develop, own, and maintain steady-state and dynamic process simulation models using:
• Aspen HYSYS
• Validate simulation models against:
• Design basis
• Vendor data
• Operating conditions
• Perform sensitivity studies and optimization analyses
• Generate simulation-based deliverables including:
• Stream tables
• Equipment duty calculations
• Control strategy inputs
• Support dynamic simulation where required for control philosophy validation
• Ensure alignment between simulation outputs and engineering deliverables (PFDs, datasheets, P&IDs)

Engineering Deliverables

• Develop and review:
• Process datasheets (equipment, valves, instruments)
• Control narratives (in coordination with I&C)
• Cause & effect inputs
• Process calculations and reports
• Ensure consistency between simulation models and issued documentation

Integration & Coordination

• Work closely with Mechanical, I&C, and Design teams to ensure:
• Equipment sizing aligns with simulation outputs
• Control philosophy reflects process dynamics
• Layout supports operability and maintainability
• Participate in HAZOP, design reviews, and interdisciplinary coordination

Vendor & Package Integration

• Define process requirements for vendor packages
• Review vendor process design, calculations, and performance guarantees
• Validate vendor data against simulation assumptions
• Ensure seamless integration of vendor systems into overall process package

Fabrication & Execution Support

• Ensure process design is aligned with skid fabrication constraints
• Support FAT, commissioning, startup, and troubleshooting
• Resolve process-related issues during fabrication and operation

Standards & Compliance

• Ensure compliance with industry standards and client specifications
• Support safety, operability, and reliability reviews

• Bachelor's degree in Chemical Engineering
• 10-15+ years of experience in oil & gas, LNG, cryogenic, or EPC industries
• Advanced proficiency in process simulation tools (Aspen HYSYS, Aspen Plus, UniSim)
• Strong experience linking simulation outputs to engineering deliverables
• Experience with skid-mounted systems and modular design
• Strong understanding of ENGINEERING workflows

Preferred Qualifications

• Experience with dynamic simulation and control validation
• Experience with cryogenic or industrial gas processes
• Background in packaged equipment or modular systems

Desired Attributes

• Strong system-level thinking
• Ability to translate simulation into practical design decisions
• Strong coordination and communication skills
• Execution-focused mindset

Work Environmental and Physical Demands:

• In order to perform the duties of this job, the employee may be required to stand, walk, sit, reach with hands and arms, climb or balance, stoop or kneel, talk and hear, and use fingers and hands to feel objects, tools or controls.
• Overtime may be necessary as the workload dictates. This may include week days, weekends, nights and/or holidays.
• Job will generally be performed in an office environment, but may require travel to a customer's office, production facility or industrial/construction job site. Conditions will vary at each location, but the conditions listed above will generally apply.

The knowledge, skills and abilities listed above are typically acquired through the levels of education and experience listed. An equivalent combination of education and/or experience that provides an applicant with the listed knowledge, skills and abilities required to perform the essential duties and responsibilities of the job, may be accepted.

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice. 

Salary: $85,000 - $120,000 annually

Nikkiso CE&IG is proud to be an equal opportunity employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, or protected veteran status and will not be discriminated against on the basis of disability.