Steam Leaks in the Orifice Plate

Causes

• There are several potential causes for steam leaks in orifice plates. They include faults in the design, improper installation and corrosion. The plates need to be maintained in order to function properly. An orifice plate wears out -- just like any other mechanical part.

Measuring Steam Loss

• You can calculate steam loss with Napier's Equation. The formula is W = 24.24 x Pa x D2. In the formula "W" stands for leakage rate expressed in pounds per hour, or lb/hr. "Pa" equals the pressure drop across the orifice expressed in pounds per square inch absolute, or psia. "D" is the diameter of the orifice that is leaking steam.

Effects of Pressure

• One way to lower steam loss is to reduce pressure. In Napier's formula, the lower number for "Pa," the smaller the leakage rate. A chart provided by AWC in Reference 3 provides an easy way to calculate the rate of leak without performing mathematical calculations. A look at that chart confirms that lower pressure equals less leakage.

Costs

• AWC uses the example of $9 per 1,000 lbs of steam for determining the cost of lost steam. For example, if you are losing 103 pounds per hour your yearly cost will be $8,120. A small steam leak in an orifice plate adds up quickly.