MANUAL OF FLOW CONTROL VALVES (PLUNGER TYPE)

1. Introduction

Scope

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

Applications

Plunger Valves regulate flow and pressure by moving an axial plunger over a fixed seat cylinder. The symmetrical annular flow path gives low noise and high cavitation resistance, which makes them suitable for high differential pressure throttling duties such as:

• Water Transmission Mains
• Reservoir Inlet and Outlet Control
• Pump Station Discharge Control
• Turbine Bypass and Hydropower Plants
• Water Treatment Plants
• Pressure Breaking Chambers
• Flow Metering and Distribution Chambers
• Industrial Process Water Systems

Purpose

The Plunger Valve provides precise, stable regulation across a wide flow range and can also be used as a slow-closing shut-off device to limit surge during pump start and stop sequences.

2. Installation Guidelines

Pre-Installation Inspection

Before installation:

• Verify valve size, pressure rating, trim configuration, and material specifications against the datasheet.
• Inspect the valve, actuator, and gearbox for transportation damage.
• Confirm the plunger moves freely over its full travel.
• Remove all protective covers, flange protectors, and packaging materials.

Pipeline Preparation

• Clean and flush the pipeline before installation.
• Remove debris, welding slag, stones, rust, and foreign particles.
• Ensure proper pipeline alignment and that flanges are parallel.
• Provide adequate anchoring and thrust restraint for the pipeline.

Installation Position

• Install with the flow direction arrow matching the actual direction of flow.
• Horizontal installation with the actuator upright is preferred.
• Provide the straight pipe runs upstream and downstream specified in the hydraulic design.
• Where sustained cavitation is possible, maintain the downstream back pressure assumed in the design.
• Provide isolation valves on both sides for servicing.

Mounting Requirements

• Support the valve independently; do not let it carry pipeline loads.
• Maintain clearance above the valve for removal of the actuator and internals.
• Tighten flange bolts evenly in a diagonal sequence.
• Do not use the actuator or gearbox as a lifting point.

Installation Precautions

• Ensure the chamber is drained and ventilated where the valve is installed below ground.
• Route power and control cabling clear of moving parts and heat sources.
• Protect the valve from site dust and construction debris until commissioning.
• Do not operate the valve to clear debris from the pipeline.

3. Operation Instructions

Initial Startup

1. Confirm the pipeline is flushed and free of debris.
2. Confirm the actuator power supply and control signal are correct.
3. Stroke the valve fully open and fully closed and verify the end limits and position indicator.
4. Set the opening and closing times as given in the surge analysis.
5. Fill the line slowly with the valve partly open to avoid air entrapment.
6. Check all joints and the gland for leakage.
7. Place the valve in its normal control mode and observe stable operation.

Normal Operation

During operation:

• The plunger moves axially over the seat cylinder to vary the annular flow area.
• Flow or pressure is regulated smoothly over the valve travel.
• Slow opening and closing limits surge pressures in the pipeline.
• The position indicator shows the actual plunger travel.

Operating Precautions

• Operate within the rated pressure, differential pressure, and temperature limits.
• Avoid prolonged operation at very small openings where cavitation can occur.
• Do not exceed the opening and closing times derived from the surge study.
• Do not operate the handwheel or gearbox against a seized plunger.
• Report vibration, noise, or erratic travel for investigation.

4. Maintenance Schedule

Monthly Inspection

• Inspect the body, flanges, and gland for leakage.
• Verify that the position indicator agrees with the command.
• Listen for abnormal noise or vibration during travel.
• Check the actuator enclosure for water ingress.

Quarterly Inspection

• Operate the valve through its full travel to prevent seizure.
• Check and top up gearbox lubrication.
• Inspect and adjust the packing gland where leakage is observed.
• Inspect external coating and touch up damaged areas.
• Verify chamber drainage.

Annual Inspection

• Record the full stroke time in both directions.
• Dismantle and inspect the plunger, seat ring, and guide bushes for wear or cavitation damage.
• Inspect the trim or slotted cylinder where fitted.
• Replace packing, gaskets, and O-rings.
• Inspect the stem and thrust bearings.
• Re-verify the end limits after reassembly and carry out seat leakage testing.
• Record all findings in the maintenance log.

Recommended Spare Parts

• Plunger Assembly
• Seat Ring
• Trim / Slotted Cylinder
• Guide Bushes
• Stem
• Packing Set
• O-Rings & Gaskets
• Thrust Bearings
• Gearbox Service Kit
• Fasteners

5. Warranty Coverage

Warranty Exclusions

Warranty does not cover:

• Improper installation.
• Damage caused by debris or contaminated water.
• Cavitation damage from operation outside the specified duty point.
• Surge damage caused by operating times shorter than those specified.
• Operation beyond rated pressure or differential pressure.
• Unauthorized modifications.
• Corrosion due to incompatible media.
• Normal wear and tear.

6. Expected Service Life

Factors Affecting Service Life

• Water Quality
• Differential Pressure Across the Trim
• Cavitation Exposure
• Frequency of Operation
• Maintenance Practices
• Corrosion Exposure
• Operating Environment

Operating within the designed cavitation limits significantly extends trim and seat life.

7. Customer Responsibilities

The customer shall:

• Ensure proper installation as per this manual.
• Operate within rated limits and within the designed duty range.
• Maintain the opening and closing times given in the surge analysis.
• Maintain chamber drainage and actuator weather protection.
• Conduct routine inspections and exercise the valve periodically.
• Maintain installation 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
• 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.
• Isolate and lock out the actuator power supply before working on the valve.
• Never place hands or tools inside the valve bore while it is energised.
• Wear appropriate PPE during servicing.
• Follow all site safety regulations and confined space procedures for valve chambers.
• Use approved lifting methods for large-size valves and actuators.

Document Retention

Maintain installation records, surge study and operating time settings, maintenance logs, inspection reports, and warranty documentation throughout the service life of the Flow Control Valve for future reference and warranty support.