SAFETY VALVE FOR STEAM SYSTEMS: STRUCTURE, OPERATION PRINCIPLES & SELECTION GUIDE 2025 | PHUC MINH ENGINEERING

1. What is a Safety Valve?

A Safety Valve is a mandatory pressure-protection device used in boilers, steam pipelines, heat exchangers, and pressure vessels.
When system pressure exceeds the set value, the valve automatically opens to release steam, helping to:

• Prevent boiler explosion

• Reduce sudden pressure spikes

• Protect equipment and operators

• Maintain stable and safe operation

Phuc Minh Engineering is a trusted supplier of EN/ASME-standard safety valves in Vietnam:
📞 0902 800 728 – 0907 450 506
📩 info@pm-e.vn

2. Structure of a Safety Valve

A standard steam safety valve consists of:

1. Body – brass, cast iron, carbon steel, stainless steel

2. Spring – adjusts the set pressure

3. Disc – seals and opens during relief

4. Stem – transfers force

5. Cap – protects the adjustment mechanism

6. Outlet – straight or 90°

Safety valves must withstand:

• High pressure (PN16–PN64)

• Temperatures of 180–350°C

• Corrosive or clean environments (depending on material)

3. Operating Principle of a Safety Valve

✅ Normal condition: valve closed

The compressed spring keeps the disc tightly sealed.

✅ Overpressure: valve opens

Steam pressure overcomes spring force → valve pops open → releases steam.

✅ Pressure returns to safe level: valve closes

Spring pushes the disc back to the sealed position.

The valve works fully automatically without electricity or operator intervention.

4. Types of Safety Valves

4.1. By discharge design

4.2. By material

• Brass – clean steam, low pressure

• Cast iron – medium boilers

• Carbon steel – high-pressure steam

• Stainless steel 304/316 – chemicals, food industry

5. Applications of Safety Valves

Safety valves are essential in:

✅ Steam boilers
✅ Steam distribution lines
✅ Heating systems
✅ Autoclaves & dryers
✅ Pressure vessels
✅ Food, textile, wood, chemical, F&B factories

6. How to Select a Safety Valve (2025 Guide)

6.1. Key selection criteria

1. Set Pressure

   • Choose working pressure + 10–15%

2. Valve size (DN15–DN100)

   • Based on required relieving capacity

3. Material selection

   • Clean steam → Brass

   • Medium boilers → Cast iron

   • High temp/high pressure → Carbon steel or stainless steel

4. Standards

   • EN ISO 4126, ASME Section VIII, JIS

5. Connection type

   • Threaded: DN15–DN25

   • Flanged: DN25–DN100

7. Common Mistakes When Choosing Safety Valves

❌ Selecting by pipe size only
❌ Ignoring required relieving rate
❌ Using threaded valves for high pressure
❌ Incorrect set pressure adjustment
❌ No periodic inspection

8. Signs a Safety Valve Is Faulty

• Continuous steam leakage

• Valve does not fully close

• Strong vibration during discharge

• Blocked due to debris

• Weak spring → incorrect set pressure

➡ Immediate maintenance or replacement is required to prevent boiler explosion risks.

✅ 9. Why Choose Phuc Minh Engineering?

Phuc Minh provides:

✅ Engineering consultation based on EN/ASME standards
✅ Genuine products with full CO/CQ documents
✅ Installation – inspection – maintenance services
✅ Available stock from DN15–DN100

PHUC MINH ENGINEERING CO., LTD
🌐 Website: https://pm-e.vn
📞 Hotline: +84 902 800 728 – +84 907 450 506
📧 Email: info@pm-e.vn

PME is committed to providing optimized, effective, and sustainable solutions to help manufacturers reduce costs and enhance competitiveness.