1. What is NPSH?

NPSH (Net Positive Suction Head) is a measure of the pressure available at the suction port of a pump to avoid cavitation. It defines rules for suction head to prevent pump damage and ensure proper operation.

2. How Does the Calculator Work?

The calculator uses the NPSH equation:

Where:

• \( P_{atm} \) — Atmospheric pressure (ft)
• \( P_{vap} \) — Vapor pressure of the fluid (ft)
• \( H_{suction} \) — Suction head (ft)
• \( \text{Friction Loss} \) — Pipe friction losses (ft)

Explanation: The equation calculates the available pressure head at the pump suction after accounting for all losses.

3. Importance of NPSH Calculation

Details: Proper NPSH calculation is crucial for pump selection and operation to prevent cavitation, which can cause vibration, noise, and damage to pump components.

4. Using the Calculator

Tips: Enter all values in feet of head. Ensure atmospheric and vapor pressures are for the correct elevation and fluid temperature. Friction loss should include all losses in the suction piping.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between NPSH available and NPSH required?
A: NPSH available is calculated from the system characteristics, while NPSH required is specified by the pump manufacturer. Available must exceed required.

Q2: What is a typical safety margin for NPSH?
A: Generally 3-5 feet or 10-20% above the pump's required NPSH, whichever is greater.

Q3: How does elevation affect NPSH?
A: Higher elevations reduce atmospheric pressure, decreasing NPSH available.

Q4: What happens if NPSH is insufficient?
A: Cavitation occurs, causing noise, vibration, reduced performance, and potential pump damage.

Q5: How can I increase NPSH available?
A: By reducing suction lift, increasing pipe diameter, minimizing fittings, or cooling the liquid to reduce vapor pressure.