MANUAL OF CONTROL VALVES

1. Introduction

Scope

This manual provides guidelines for the installation, operation, maintenance, inspection, warranty coverage, and service procedures for Control Valves used in water supply, wastewater, process, and industrial pipeline systems.

Applications

Control Valves regulate flow, pressure, level, or temperature by modulating the valve opening in response to a signal from a controller or pilot system. They are commonly used in:

• Water Treatment Plants
• Water Distribution Networks
• Pumping Stations
• Sewage Treatment Plants
• Industrial Process Pipelines
• Boiler Feed and Steam Systems
• Chemical and Petrochemical Plants
• Power Plant Auxiliary Systems

Purpose

The Control Valve is the final control element of a regulating loop. The actuator positions the plug or disc against the seat so that the flow area, and therefore the controlled variable, follows the command signal.

2. Installation Guidelines

Pre-Installation Inspection

Before installation:

• Verify valve size, pressure rating, trim characteristic, and material specifications against the datasheet.
• Inspect the valve, actuator, and positioner for transportation damage.
• Confirm the actuator fail-safe action (fail-open or fail-close) matches the process requirement.
• Remove all protective covers, flange protectors, and packaging materials.

Pipeline Preparation

• Clean and flush the pipeline before installation.
• Remove debris, welding slag, scale, and foreign particles.
• Install an upstream strainer where the medium may carry solids.
• Ensure proper pipeline alignment so that no pipe stress is transferred to the valve body.

Installation Position

• Install with the flow direction arrow matching the actual direction of flow.
• Preferred orientation is a horizontal line with the actuator vertically upright.
• Provide straight pipe runs upstream and downstream as given in the project hydraulic design.
• Provide isolation valves and a manual bypass line where uninterrupted service is required.

Instrument and Utility Connections

• Connect clean, dry, oil-free instrument air to the actuator and positioner.
• Use the air supply pressure stated on the actuator nameplate.
• Route and terminate control and feedback cabling as per the project wiring diagram.
• Protect tubing and cabling from mechanical damage and heat sources.

Installation Precautions

• Support the valve and actuator independently where their weight is significant.
• Maintain clearance above and around the actuator for calibration and removal.
• Tighten flange bolts evenly in a diagonal sequence.
• Do not use the actuator or positioner as a lifting point.

3. Operation Instructions

Initial Startup

1. Confirm the pipeline is flushed and the upstream strainer is clean.
2. Apply the rated instrument air supply and verify there are no leaks.
3. Stroke the valve fully open and fully closed and confirm smooth travel against the position indicator.
4. Verify the positioner calibration at 0%, 50%, and 100% of signal.
5. Confirm the fail-safe position on loss of air and on loss of signal.
6. Pressurise the line gradually and check all joints for leakage.
7. Place the loop in automatic and observe stable control.

Normal Operation

During operation:

• The controller signal is converted by the positioner into actuator movement.
• The plug or disc modulates the flow area to hold the controlled variable at setpoint.
• The position feedback confirms that the valve has reached the demanded travel.
• Continuous operation very close to the seat should be avoided to limit trim wear.

Operating Precautions

• Operate within the rated pressure, differential pressure, and temperature limits.
• Avoid prolonged operation under cavitating or flashing conditions.
• Do not throttle with a valve selected for isolation duty only.
• Isolate and depressurise before any adjustment to the packing or trim.
• Report hunting, sluggish response, or audible noise for investigation.

4. Maintenance Schedule

Monthly Inspection

• Inspect for body, bonnet, and packing leakage.
• Check instrument air supply pressure and air filter condition.
• Verify that the position indicator agrees with the control signal.
• Observe control loop stability.

Quarterly Inspection

• Drain the air filter regulator and replace the filter element if contaminated.
• Check the actuator stem and linkage for free movement.
• Inspect and tighten the packing gland where leakage is observed.
• Clean the upstream strainer.
• Inspect external coating for corrosion.

Annual Inspection

• Perform a full stroke test and record the travel against signal.
• Recalibrate the positioner and confirm the fail-safe action.
• Dismantle and inspect the plug, seat, cage, and guide bushes for wear or erosion.
• Replace packing, gaskets, and O-rings.
• Check actuator springs and diaphragm condition.
• Carry out seat leakage testing after reassembly.
• Record all findings in the maintenance log.

Recommended Spare Parts

• Plug / Disc Assembly
• Seat Ring
• Cage or Trim Set
• Stem
• Packing Set
• Actuator Diaphragm
• Actuator Spring
• O-Rings & Gaskets
• Positioner Service Kit
• Fasteners

5. Warranty Coverage

Warranty Exclusions

Warranty does not cover:

• Improper installation.
• Damage caused by debris or contaminated media.
• Operation beyond rated pressure, differential pressure, or temperature.
• Damage from cavitation or flashing outside the specified duty.
• Contaminated, wet, or oily instrument air supply.
• Unauthorized modification or recalibration by untrained personnel.
• Corrosion due to incompatible media.
• Normal wear and tear.

6. Expected Service Life

Factors Affecting Service Life

• Fluid Cleanliness
• Differential Pressure Across the Trim
• Frequency and Range of Modulation
• Instrument Air Quality
• Maintenance Practices
• Corrosion Exposure
• Operating Environment

Clean instrument air and regular trim inspection significantly extend service life.

7. Customer Responsibilities

The customer shall:

• Ensure proper installation as per this manual.
• Supply clean, dry, oil-free instrument air at the rated pressure.
• Operate within rated limits.
• Keep upstream strainers clean.
• Conduct routine inspections and calibration checks.
• Maintain installation, calibration, and maintenance records.
• Use approved spare parts.
• Report abnormalities promptly.

Failure to comply may affect warranty eligibility.

8. Warranty Claim Procedure

Step 1 – Claim Submission

Provide:

• Purchase Order Number
• Invoice Copy
• Valve Identification Details
• Installation Date
• Operating Conditions
• Calibration Records
• Description of Defect
• Photographs of Installation

Step 2 – Technical Evaluation

The submitted information will be reviewed to determine:

• Installation compliance
• Operating conditions
• Maintenance history
• Warranty applicability

Step 3 – Inspection

Where necessary:

• Site inspection may be conducted.
• Valve may be requested for factory examination.

Step 4 – Resolution

Based on technical findings, one of the following may be provided:

• Repair
• Component Replacement
• Valve Replacement
• Technical Recommendations

Safety Precautions

• Isolate, depressurize, and drain the line before maintenance.
• Disconnect and vent the instrument air supply before working on the actuator.
• Never defeat the spring retention on spring-return actuators; stored energy can cause injury.
• Wear appropriate PPE during servicing.
• Follow all site safety regulations and lockout procedures.
• Use approved lifting methods for large-size valves and actuators.

Document Retention

Maintain installation records, calibration certificates, maintenance logs, inspection reports, and warranty documentation throughout the service life of the Control Valve for future reference and warranty support.