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.

---