MANUAL OF CHECK VALVES

1. Introduction

Scope

This manual provides guidelines for the installation, operation, inspection, maintenance, warranty coverage, and service procedures for Check Valves manufactured and supplied by GM Dalui & Sons.

Applications

Check Valves are automatic valves designed to permit flow in one direction and prevent reverse flow. They are commonly used in:

• Water Supply Systems
• Pumping Stations
• Water Treatment Plants
• Sewage Treatment Plants
• Irrigation Networks
• Industrial Pipelines
• HVAC Systems
• Fire Protection Systems
• Power Plants

Check Valves protect pumps, compressors, and pipelines from damage caused by backflow and pressure surges.

2. Installation Guidelines

Pre-Installation Inspection

Before installation:

• Verify valve size, pressure rating, and material specifications.
• Inspect valve for shipping or handling damage.
• Confirm flow direction indicated by the arrow on the valve body.
• Ensure valve internals move freely.

Pipeline Preparation

• Flush pipeline thoroughly before installation.
• Remove welding slag, rust, sand, and debris.
• Ensure proper pipeline alignment.
• Avoid excessive pipe stress on the valve body.

Valve Orientation

Swing Check Valve

• Install in horizontal pipelines.
• Flow direction must follow arrow marking.
• Cover hinge pin should be positioned at the top.

Dual Plate Check Valve

• Suitable for horizontal and vertical upward flow installations.
• Ensure proper spring-assisted closure alignment.

Non-Slam / Zero Velocity Check Valve

• Install according to manufacturer recommendations.
• Ensure adequate upstream and downstream straight pipe lengths.

Flange Installation

• Use appropriate gasket material.
• Tighten bolts evenly in cross-pattern sequence.
• Avoid excessive tightening.

3. Operation Instructions

Automatic Operation

Check Valves operate automatically:

• Forward flow opens the valve.
• Reverse flow causes automatic closure.
• No manual operation is normally required.

Operating Precautions

• Never force valve open or closed.
• Ensure flow direction matches valve marking.
• Avoid installing undersized valves.
• Do not use check valves as isolation valves.
• Prevent operation outside pressure and temperature ratings.

Startup Procedure

1. Verify installation orientation.
2. Slowly introduce flow into the pipeline.
3. Observe valve performance.
4. Check for leakage or abnormal vibration.
5. Monitor pressure fluctuations during initial operation.

4. Maintenance Schedule

Monthly Inspection

• Check for external leakage.
• Listen for abnormal noise or chatter.
• Inspect flange joints.
• Verify proper system performance.

Quarterly Inspection

• Inspect valve body coating.
• Check hinge pin or spring assembly condition.
• Examine disc movement where accessible.
• Verify backflow prevention performance.

Annual Inspection

• Remove and inspect internal components.
• Check disc wear.
• Inspect seat surfaces.
• Examine spring mechanism (if applicable).
• Replace worn seals and gaskets.
• Perform operational testing.

Recommended Spare Parts

• Disc Assembly
• Seat Rings
• Springs
• Hinge Pins
• Bushings
• O-Rings
• Gaskets
• Fasteners

5. Warranty Coverage

Warranty Exclusions

Warranty shall not apply to:

• Incorrect installation.
• Reverse installation.
• Water hammer damage.
• Excessive pressure conditions.
• Corrosive media beyond design limits.
• Unauthorized repairs or modifications.
• Normal wear and tear.

6. Expected Service Life

Factors Affecting Service Life

• Flow Velocity
• Pressure Fluctuations
• Water Quality
• Frequency of Operation
• Water Hammer Events
• Maintenance Practices
• Environmental Conditions

Regular inspection significantly increases service life.

7. Customer Responsibilities

The customer is responsible for:

• Ensuring proper installation.
• Following recommended operating practices.
• Conducting periodic inspections.
• Maintaining service records.
• Preventing excessive water hammer.
• Reporting defects promptly.
• Operating within rated limits.

Failure to follow these guidelines may void warranty coverage.

8. Warranty Claim Procedure

Step 1 – Submit Claim

Provide:

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

Step 2 – Technical Assessment

GM Dalui & Sons will:

• Review warranty documentation.
• Assess operating conditions.
• Evaluate installation practices.
• Determine warranty applicability.

Step 3 – Inspection

Where required:

• Site inspection may be conducted.
• Valve may be returned for detailed examination.

Step 4 – Resolution

Depending on findings:

• Repair
• Component Replacement
• Valve Replacement
• Technical Recommendations

will be provided as per warranty terms.

Safety Precautions

• Depressurize the pipeline before maintenance.
• Never dismantle the valve under pressure.
• Wear appropriate PPE during inspection.
• Use proper lifting equipment for large valves.
• Follow all plant safety procedures.