Steam flow measurement in the use of clamp-on method

Abstract

A clamp-on ultrasonic gas flowmeter we had developed has been modified to measure steam flow by newly developed damping material endurable to high temperature. As clamp-on flowmeters are widely used for temporally flow measurement because there is no need for plumbing, most of them are for liquid flow measurement because ultrasonic energy wouldn't get into the fluid as acoustic impedance of the pipe and that of the fluid is widely spread. To measure the gas flow by clamp-on flowmeter, damping material is the key of the measurement because it will dampen the propagating ultrasonic wave in the pipe wall and as a result the weak signal go through the fluid can be observed. If the fluid is steam, endurance for high temperature is also required. With the developed flowmeter, the flow of steam at 0.8MPa in the pipe of 50A SGP can be measured up to 30m/s flow rate. This measurement is reproducible. The flowmeter is compatible to both saturated steam and superheated steam. There is no need to alternate the setup when the type of steam change. The key of this success depends on the newly developed damping material. The base material effectively dampen the ultrasonic wave was explored widely from many types of silicone materials. Dense material was added to increase the acoustic impedance of the damping material. We are now trying to lower the measurable steam pressure and widen the types of target pipes. In the process of this trial, we've already found a damping material with which the received ultrasonic signal captured from the clamp-on transducer on the 25A steam pipe could be observed clearly above the noise level. The pressure of the steam was still 0.9MPa but we're trying to lower the measurable pressure limit.

Keywords

• clamp-on
• ultrasonic
• flow
• flowmeter
• steam
• pipe