Calculate flow rate through control valves and regulators for Propane systems.
Vapor (Gas)
Liquid
Calculation Results
Pressure Drop (ΔP):0
Flow Rate:0
Energy Capacity:0
Understanding Flow Rates in 1.5 Inch CV Series Valves
When designing piping systems for propane, selecting the correct valve size and understanding the Cv (Flow Coefficient) is critical for system efficiency and safety. A 1.5 inch valve is a standard size in commercial and industrial propane distribution, often found in tank manifolds and vaporizers.
What is the Cv Value?
The Cv value, or flow coefficient, represents the volume of 60°F water (in US gallons) that will flow through a valve per minute with a pressure drop of 1 PSI. For a 1.5 inch series valve, Cv values typically range from 15 to 55 depending on the internal geometry (globe, ball, or butterfly design).
Propane Properties for Calculation
Propane Vapor Specific Gravity: 1.52 (relative to air)
Propane Liquid Specific Gravity: 0.504 (relative to water)
Energy Content: 2,500 BTU per cubic foot (Vapor) or 91,500 BTU per gallon (Liquid).
Formula Used
For Propane Vapor (Gas), we utilize the standard gas flow equation:
Q = 1360 * Cv * P1 * SQRT(ΔP / (P1 * G * T))
Where:
Q = Flow rate in SCFH
P1 = Inlet Pressure (Absolute)
ΔP = Pressure Drop
G = Specific Gravity (1.52)
T = Absolute Temperature (Rankine)
Typical 1.5 Inch Valve Cv Reference Table
Valve Type (1.5″)
Standard Cv Range
Common Application
Globe Valve
18 – 26
Throttling / Control
Ball Valve (Full Port)
45 – 60
On/Off Service
Butterfly Valve
35 – 50
Large Volume Vapor
Critical Flow (Choked Flow)
In propane systems, if the outlet pressure (P2) is less than approximately 50% of the inlet pressure (P1), "choked flow" occurs. In this state, increasing the pressure drop further will not increase the flow rate because the gas has reached sonic velocity. This calculator handles sub-critical flow calculations for standard industrial applications.
function toggleState() {
var type = document.getElementById('flowType').value;
var sgInput = document.getElementById('specificGravity');
var tempGroup = document.getElementById('tempGroup');
if (type === 'liquid') {
sgInput.value = '0.504';
tempGroup.style.display = 'none';
} else {
sgInput.value = '1.52';
tempGroup.style.display = 'flex';
}
}
function calculatePropaneFlow() {
var type = document.getElementById('flowType').value;
var cv = parseFloat(document.getElementById('cvValue').value);
var p1 = parseFloat(document.getElementById('inletPressure').value);
var p2 = parseFloat(document.getElementById('outletPressure').value);
var sg = parseFloat(document.getElementById('specificGravity').value);
var tempF = parseFloat(document.getElementById('gasTemp').value);
if (isNaN(cv) || isNaN(p1) || isNaN(p2) || isNaN(sg)) {
alert("Please enter valid numeric values.");
return;
}
var deltaP = p1 – p2;
if (deltaP (p1Abs * 0.5)) {
dpUsed = p1Abs * 0.5; // Cap at critical drop
}
flowRate = 1360 * cv * p1Abs * Math.sqrt(dpUsed / (p1Abs * sg * tRankine));
btuRate = flowRate * 2500; // SCFH * BTU/cu ft
document.getElementById('flowLabel').innerText = "Flow Rate (SCFH):";
document.getElementById('resFlow').innerText = Math.round(flowRate).toLocaleString() + " SCFH";
document.getElementById('resBTU').innerText = (btuRate / 1000000).toFixed(2) + " Million BTU/hr";
}
document.getElementById('results').style.display = 'block';
}