1. Scope and purpose
This manual establishes a standard operating procedure for maintenance, set pressure verification, and leak testing of direct-acting relief valves used in UNITEC industrial systems. The procedure meets the requirements of DSTU standards EN 1268 and ISO 4126. This maintenance is mandatory to ensure the integrity of pressurized systems and prevent critical equipment failures.
2. Safety measures
WARNING: Working with pressurized systems is life-threatening. Before starting any disassembly or testing of the valve, make sure the system is fully depressurized.
- Perform the LOTO (Lockout/Tagout) procedure: Isolate the valve from pressure sources by installing blind flanges or closing and mechanically blocking the shut-off valves.
- Personal protective equipment (PPE): Mandatory use of protective glasses, gloves, resistant to chemical substances, protective shoes and overalls.
- Hazardous Energy: Never point the valve outlet at people or critical equipment during testing.
3. Tools and materials
| Tool/Material | Specification | Quantity |
|---|
| Stand for hydraulic or pneumatic tests | Able to create pressure up to 1.5x of the working pressure | 1 |
| Calibrated manometer | Accuracy class 0.5 or better | 2 |
| Torque wrench | The range is 20-200 Nm | 1 |
| A set of keys | Metric | 1 set |
| Silicone grease | For seals (environmentally compatible) | 1 tube |
| Certified seals | According to the manufacturer's specification | As needed |
4. Preliminary review
| Object | Admission criteria | Notes |
|---|
| Valve body | Absence of cracks, deep corrosion | Visual inspection |
| Valve stem | Straight, without burrs | Check progress |
| Sealing surface | Absence of ulcers, erosion | Use a magnifying glass |
5. Step-by-step testing procedure
- Preparation and disassembly: Remove the valve from the pipeline after performing the LOTO procedure. Avoid damage to flange surfaces when using a crowbar.
- Cleaning and debugging: Remove the remnants of the working environment. Clean the internal components.
- Verification of actuation pressure: Place the valve on the test bench. Gradually increase the pressure until the moment of activation. Record the pressure. It must correspond to passport data with a tolerance of ±3%. Do not exceed the rate of pressure increase by more than 0.1 bar/sec.
- Leak Test: Maintain the pressure at 90% of the operating pressure. Check the outlet for leaks using soapy water or a flow meter. No more than 1 bubble per minute (for valves with a metal seat) or complete absence (for soft seals) is allowed.
- Adjustment (if necessary): Use the spring adjustment screw. Turn clockwise to increase actuation pressure.
- Assembly: Use new seals. Tighten the body bolts evenly in a criss-cross pattern to a torque of 85 Nm (for 2" valves).
6. Post-service verification
| Test | Expected result | Status (Pass/Fail) |
|---|
| Actuation pressure | According to the passport ±3% | |
| Hermeticity | According to the requirements of the class | |
7. Troubleshooting
| Symptom | A possible reason | action |
|---|
| The valve leaks at operating pressure | Contamination of the saddle | Disassembly and cleaning |
| Does not work at the set pressure | Stem hanging | Cleaning and lubrication of the rod |
| Vibration (Chatter) | High back pressure | Checking drainage |
8. Service schedule
| The task | Frequency | time | Level |
|---|
| Visual inspection | Every month | 15 min | Operator |
| Full testing | Annually | 2 hours | Technician |
9. Spare parts
| Description | Typical specification | Category UNITEC |
|---|
| A set of seals | Viton / PTFE | Valve sealing |
| Spring | AISI 316 stainless steel | Mechanical components |
To order spare parts, visit UNITEC-D e-catalog.
10. Links
- DSTU EN 1268-1: Safety devices for pressure systems
- ISO 4126: Safety valves
- Valve manufacturer's documentation (production number)
