Almost every process facility requires steam. It is used for heating, drying, power, etc. Steam is an excellent way to convey energy from one process to another. The heat and energy of the steam needs to be measured and controlled into the next stage of the process.
Steam flow and pressure is controlled with an orifice. You can use a fixed orifice, a line sensed pressure regulator, or a full control valve. There is no adjustment with an orifice. A regulator is given a fixed output setpoint, but is not adjustable by the control system. A control valve can vary the orifice size according to the output of the control system which has measured the flow, pressure, and/or temperature from process instrumentation and sensors.
When controlling system, it is always done with an orifice which creates a pressure drop. The higher the flow rate and pressure drop, the noisier the valve will be. There are two problems with noise. First is the loud environment and potential damage to your hearing. The second is that noise is vibration and that vibration can damage the physical components of the valve. 85dB or lower is the ideal noise level. You can avoid high noise by taking the pressure down in small increments rather than one big drop. This can be accomplished within a control valve or through a fixed drop low decibel cassette inline with the control valve.
There is a way to make almost every steam control application low noise and highly reliable. You must select the proper method of controlling and regulating the steam with the proper number of pressure drops. For help with your next steam application, please contact us.
I have had several questions come up in the last couple of days about where to mount differential pressure transmitters in relation to the pipe mounted flow element. There are three different types of fluids that you will want to measure and they require different mounting methods.
First, is dry gases. The DP transmitter must be mounted vertically above the pipe taps so that all potential liquid or condensation in the line will drain back into the pipe.
Second is liquids. The DP will be mounted vertically below the pipe so that the line will always stay full with liquid.
The third is condensing liquids such as steam. These require that the DP transmitter is mounted below the pipe taps, but they must have a vertical water column that is always filled with the same amount of condensate so that the water pressure on the impulse lines remains consistent. The water column will block the high-temperature steam from cooking your transmitter. If you mount it above the pipe and there is no water present, the 300F+ heat will break your transmitter.
This was a very short and basic introduction to mounting and configuring your DP flow system. For more info and a thorough explanation, please contact me via this site.