In an EPC (Engineering, Procurement, and Construction) organization, control valve engineering is typically executed in structured phases to ensure technical accuracy, compliance, and smooth procurement. Although workflows may vary slightly between EPC companies, the overall methodology generally follows three major phases. Here it is divided in to three major phases and each phases are subdivided in to different work flows.
Phase I – Engineering & Sizing
Phase II – Client Review Cycles & Material Requisition (MR) Preparation
Phase III – Procurement Lifecycle
phase-1 – engineering and sizing
Preliminary Control Valve Sizing (Process Engineering)
The preliminary control valve sizing is carried out by the Process Engineering Team based on hydraulic and process calculations.
process team responsibilites
The process team performs detailed calculations to determine the Required Cv (Flow Coefficient) by using the below process parameters and analyses the sizing output for any chocking, cavitation, flashing or noise issue.
- Flow rates (Minimum / Normal / Maximum)
- Inlet and outlet pressures
- Operating temperature
- Fluid properties (density, viscosity, vapor pressure, etc.)
- Choked flow verification
- Cavitation analysis
- Flashing check
- Noise prediction (if required)
- Preliminary pressure drop selection
- Tentative valve type selection (Globe / Ball / Angle / etc.)
- valve characteristics selection.
deliverables
The output of this stage includes:
- Preliminary Cv calculation
- Process data sheet
The sizing calculation is then issued for Inter Discipline Check (IDC). IDC reviewers are assigned based on the project-specific IDC matrix (which varies between EPC companies). IDC is intended for technical verification—not for getting new design inputs from other department.
Typically, the following disciplines review the calculation:
- Process
- Piping
The IDC team verifies:
- Cv calculation accuracy
- Process data correctness
- Choked flow check
- Cavitation check
- Flashing check
- Noise calculations
- Piping details
After addressing all IDC comments and obtaining clearance from the Process team, the sizing calculation is formally released to the Instrumentation team.
Workflow 2 – Instrument Engineering Datasheet Preparation
Once the sizing calculation is released, the Instrumentation Engineering Team prepares the Control Valve Datasheet.
Inputs Used by Instrumentation Team
- Approved process data
- Final sizing calculations
- P&ID
- Piping material specification
- Project specifications
- Client standards
Instrumentation Team Responsibilities
Based on the above inputs, the Instrument team defines:
- Valve body type
- Trim type
- Material of construction
- Actuator type (Pneumatic / Electric)
- Fail action (Fail Open / Fail Close / Fail Last)
- Positioner type
- Accessories (Solenoid Valve, AFR, Limit Switch, etc.)
- Leakage class (ANSI/IEC)
- Noise trim requirements
The final output is the Control Valve Datasheet and it will issued to relevant discipline for IDC (Inter discipline check) as per IDC matrix. The main department in the IDC matrix shall be process, piping and QA/QC .If the valve is motor-operated (MOV), the Electrical Team must be included in the IDC. This is a critical interface because the Electrical team uses this information to: Size power feeders ,Determine motor load requirements.
The datasheet is cross-checked against:
Process data,P&ID,Line class,Project specifications,Piping specifications,Material compatibility,
This structured workflow ensures
- Technical accuracy
- Proper interdisciplinary coordination
- Compliance with project and client requirements
- Smooth transition into Material Requisition (MR) preparation and procurement
phase-II-client review stage
After the Control Valve Datasheet is prepared and internally approved, it is submitted to the Client for review and approval. The approval process typically involves multiple revision cycles before reaching final acceptance.
Typical Client Review Cycle is given below
Rev A
Rev B
IFA (Issued for Approval)
IFP (Issued for Purchase).Issue for purchase specifically for datasheets.
Depending on project complexity and client requirements, additional revisions may be required.
Parallel Activity – Early Procurement Initiation
Since control valves are generally classified as long lead items, EPC companies do not wait for complete client approval before initiating procurement activities. In most projects The procurement process begins immediately after receiving Rev A client comments. Client comments are incorporated progressively during subsequent revisions. Final purchasing activities are aligned with the IFP (Issued for Purchase) stage.This proactive approach helps prevent project schedule delays.The detailed procurement lifecycle is explained in Phase III.
Material Requisition (MR) Preparation
In parallel with the client review cycle, the Instrumentation team prepares the Material Requisition (MR) package. The MR serves as the primary document for initiating vendor inquiries and procurement activities. The Instrumentation Team Prepares the MR that includes.
- Control Valve Datasheet
- Valve Specifications
- Scope of Supply
- Inspection Requirements
- Painting Specifications
- Packing and Preservation Specifications
- Testing Requirements (Hydrostatic Test / Seat Leakage Test)
- Documentation Requirements
- VDRL (Vendor Document Requirement List)
- QAP (Quality Assurance Plan), if required
phase-iii- proceurement lifecycle
Based on the MR RFQ are floated to the vendor as per the the client vendor list. RFQ shall be issued to atlest 3 vendors as per procurement policy.
workflow-3 vendor proposal
Based on the RFQ vendor submit the below details.
Vendor submits:
- Technical Offer
- Commercial Offer
- Valve sizing calculation
- Compliance statement
- Deviations list
- Preliminary datasheet filled by the Vendor. All the VTA fields shall be filled by the vendor. This has to be specifically mentioned in the MR.
Important:
Vendor may recalculate Cv and may suggest trim modification.
workflow-4 technical bid evaluation
At this stage EPC shall evaluate all the vendor details like valve sizing, trim material , technical and commercial details. Each and every details to be compare with the MR documents and if there any deviation other than specified by the vendor shall e addressed to the client for clarity. TBE shall also to be send to the client for approval.
During Technical bid Evaluation Instrument + Process +piping review the below details. All clarifications are addressed to company with technical query.
- Vendor Cv calculation
- Noise level
- Actuator sizing
- Accessories
- Material compliance
- Deviation list
workflow-5 commercial bid evaluation
The following details shall be evaluated in the Commercial Bid Evaluation (CBE). This is normally done by the procurement engineer and QA/QC engineer. Procurement team evaluate the following details.
- Price
- Delivery
- Payment terms
- Warranty
- LD clause
- Final vendor selected
workflow-6 purchase order
Final PO send to the selected vendor and the post order activities will start. Post order activities start with the KOM(KICK OFF MEETING). In KOM vendor describes about the organization structure, contact point for this project and schedule. The following details shall be addressed by the vendor during the KOM.
- organization structure
- Focal point for this specified PO
- Document submission schedule
- Manufacturing schedule
- Inspection plan
- Clarification of deviations
Based on the KOM vendor submit the VDRL documents that mentioned in the MR for this purchase order. The VDRL shall be reviewed by the EPC and client(PMC).
Vendor Documentation as per VDRL. The VDRL shall include as minimum as
- Final Datasheet ( vendor shall fill the VTA/VTC portions, make ,model)
- GA drawing
- Valve sizing calculation
- Actuator sizing calculation
- Material certificates
- QAP- Quality Assurance Procedure
- ITP- Inspection Test Plan
- Test procedures
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