1. The Most Important Concept: Cv (Flow Coefficient)

Cv is the number of US gallons of water at 60°F that will flow through a valve in one minute with a pressure drop of 1 psi.

Rule: Select a valve with a Cv equal to or slightly higher than your required Cv.

2. Kinko Angle Seat Valve – Cv Values by Size

Note: Kvs = m³/h of water at 1 bar pressure drop. Cv ≈ 1.16 × Kvs.

3. Step‑by‑Step Sizing for Liquids

Step 1: Gather Required Data

Step 2: Calculate Required Cv

Formula (liquids):

Cv = Q × √(G / ΔP)

Where:

• Q = flow rate in US gallons per minute (GPM)

• G = specific gravity (water = 1)

• ΔP = pressure drop in psi

Quick conversion:

• L/min to GPM: divide by 3.785

• bar to psi: multiply by 14.5

Step 3: Example Calculation

Given:

• Flow rate = 150 L/min → 150 ÷ 3.785 = 39.6 GPM

• Pressure drop allowed = 1 bar → 1 × 14.5 = 14.5 psi

• Specific gravity = 1 (water)

Calculation:
Cv = 39.6 × √(1 / 14.5) = 39.6 × √(0.069) = 39.6 × 0.263 = 10.4

Step 4: Select Valve Size

From Kinko Cv table:

• DN15: Cv = 9.0 (too low — not enough flow)

• DN20: Cv = 14.0 (sufficient — 14.0 > 10.4)

Select: DN20 (3/4″)

4. Step‑by‑Step Sizing for Gases (Compressed Air, Nitrogen)

Gas sizing is different because gases are compressible.

Step 1: Gather Required Data

Step 2: Simplified Rule of Thumb

For compressed air at 6–8 bar, the required Cv is approximately:

Cv ≈ (m³/h at standard conditions) ÷ 20

Example: 50 m³/h ÷ 20 = 2.5 Cv

Step 3: Select Valve Size

From Kinko Cv table:

• DN10: Cv = 4.5 (sufficient for 2.5)

• Any larger size also works but may be oversized

Select: DN10 (3/8″) or DN15 (1/2″) for margin

5. Step‑by‑Step Sizing for Steam

Steam sizing requires special consideration due to high temperature and condensate.

Step 1: Gather Required Data

Step 2: Simplified Sizing Table for Steam (Saturated)

Step 3: Example

Flow required = 200 kg/h → DN25 (300 kg/h capacity) is appropriate.

Select: DN25 (1″)

6. Pressure Drop Verification

After selecting a valve size, verify that the actual pressure drop is acceptable.

Formula (liquids):

ΔP = G × (Q / Cv)²

Example:

• Q = 39.6 GPM

• Cv of DN20 = 14.0

• G = 1

ΔP = 1 × (39.6 / 14.0)² = (2.83)² = 8.0 psi (0.55 bar)

This is less than the allowed 1 bar — acceptable.

7. Velocity Check (Important for Liquids)

High velocity can cause erosion, noise, and cavitation.

Formula: Velocity (m/s) = (Q in m³/s) ÷ (Port area in m²)

Simplified rule: For water, if your flow rate in m³/h is more than 20 × (DN in inches), consider upsizing.

8. Sizing for Viscous Liquids

Viscous liquids (oil, syrup, glue) require larger valves because flow is restricted.

Example: Required Cv = 10, viscosity = 300 cSt → 10 × 1.5 = 15 Cv → choose DN25 (Cv 22) instead of DN20 (Cv 14).

9. Sizing Quick Reference Table (Water)

*Assumes water at 20°C, specific gravity = 1.*

10. Common Sizing Mistakes

11. Kinko Sizing Service

Not sure which size to choose? Kinko offers free sizing assistance.

Contact Kinko with your application data — we will size the valve for you.

12. Summary – Key Takeaways

✅ Cv is the key metric — higher Cv = more flow capacity
✅ Use the formula Cv = Q × √(G/ΔP) for liquids
✅ Use simplified tables for air and steam
✅ Check velocity — avoid >5 m/s for liquids
✅ Apply viscosity correction for thick fluids
✅ Don't assume pipe size = valve size — calculate first
✅ Kinko offers free sizing support — just ask

Proper sizing saves money, improves performance, and extends valve life.

13. Need Help Sizing Your Angle Seat Valve？

Kinko provides:

• complete Cv tables for all sizes

• free sizing consultation

• sample valves for testing

Contact Kinko with your flow, pressure, and media — we will recommend the right size.

Ivan (Mobile:+86-18968769287)
          WhatsApp：+86-13579991606

Wechat:+86-18968769287

Website：www.kinko-flow.com
ZHEJIANG KINKO FLUID EQUIPMENT CO.,LTD