What surge control equipment does this calculator size?

This calculator sizes three types of surge control equipment: surge tanks (volume sizing), bladder accumulators (pre-charge pressure and volume), and relief valves (orifice sizing per API 520/521 and API 526).

What causes pressure surges in liquid pipelines?

Pressure surges (water hammer) are caused by rapid valve closure, pump trip or startup, and flow rate changes. The resulting pressure waves can exceed the pipeline MAOP and damage equipment if not properly mitigated.

What standards apply to pipeline surge control equipment sizing?

Surge control equipment sizing follows API 520 and API 521 for relief valve sizing methodology, API 526 for standard orifice designations, and ASME Section VIII for pressure vessel design of surge tanks and accumulators.

How do you set the pre-charge pressure on a bladder accumulator?

Pre-charge pressure is typically set to 90% of the minimum system operating pressure using dry nitrogen. This keeps the bladder in contact with the fluid during normal operation while maximizing usable volume for surge absorption.

What is the API 526 orifice designation for relief valves?

API 526 defines standard orifice letter designations (D through T) with effective areas from 0.110 to 26.0 square inches. After calculating the required orifice area per API 520, select the next larger standard orifice from API 526.

Surge Control Sizing Calculator | Tank & Valve

Surge Tank

Open or closed tank volume sizing

Tank

Accumulator

Gas-charged bladder accumulator

Bladder

Relief Valve

Orifice area per API 520/526

PSV

Common Parameters

Liquid Specific Gravity

Operating Pressure

psig

Surge Pressure Rise

psi

Flow Rate

GPM

Valve Closure Time

sec

Surge Tank Parameters

Pipe Inside Diameter

Pipeline Length

Flow Velocity

ft/s

Wave Speed

ft/s

Tank Type

Accumulator Parameters

Min System Pressure

psig

Liquid Volume Required

gal

Pre-charge Pressure

psig

Polytropic Exponent (n)

Relief Valve Parameters

Set Pressure

psig

Backpressure

psig

Discharge Coefficient (C_d)

Viscosity Correction (K_v)

Overpressure

Learn the Theory

Understand surge tank sizing, accumulator pre-charge, and relief valve orifice calculations

Read Engineering Guide

Key Equations

Surge Tank:
V = Q × t_closure × SF

Accumulator:
P₁V₁ⁿ = P₂V₂ⁿ

Relief Valve:
A = Q / (38·C_d·K_w·K_v·√(ΔP/SG))

V = Required volume (gal)

Q = Flow rate (GPM)

SF = Safety factor

P₁, P₂ = Pre-charge / max pressure (psia)

n = Polytropic exponent

A = Required orifice area (in²)

C_d = Discharge coefficient

K_w = Backpressure correction

K_v = Viscosity correction

Standards & References

API 520 Part I
Sizing and Selection of Pressure-Relieving Devices
API 521
Pressure-Relieving and Depressuring Systems
API 526
Flanged Steel Pressure-Relief Valves (orifice designations)
ASME B31.4
Pipeline Transportation Systems for Liquids

Important Notes

Surge Tanks: Open tanks eliminate surge; closed tanks require gas cushion
Accumulators: Pre-charge at 80-90% of minimum system pressure
Relief Valves: Typically 10% overpressure for non-fire cases
Safety Factor: Apply 1.1-1.25 for tank and accumulator volumes
API 526 Orifices: Select next larger standard orifice designation
Professional Review: Verify with licensed PE for final design

Surge Control Equipment Sizing Calculator

Common Parameters

Surge Tank Parameters

Accumulator Parameters

Relief Valve Parameters

Learn the Theory

Results

Key Equations

Standards & References

Important Notes

Surge Control Equipment Sizing Calculator

Common Parameters

Surge Tank Parameters

Accumulator Parameters

Relief Valve Parameters

Learn the Theory

Results

Key Equations

Standards & References

Important Notes

Related Calculators

Water Hammer & Surge

Liquid Pipeline Hydraulics

Pump Station Spacing

Liquid Properties

Relief Valve Sizing

Liquid Pipeline Hydraulics