- Model
- LUGB-SUP / LUGB-SUP-C
- Media
- Liquid, gas and steam, including saturated and superheated steam
- Nominal size
- DN15 to DN300 as a full-bore body; DN300 to DN1000 as an insertion type
- Accuracy
- 1.0 % to 2.5 % of reading, according to medium, size and compensation
- Medium temperature
- Up to 300 °C on the integral form and 330 °C on the conventional form
- Range ratio
- Given as 8:1 at the stated reference densities, 1:6 to 1:25 by size, and up to 1:30 on the flagship form
- Output
- Pulse, 4-20 mA and RS-485, with HART optional
- Supply
- 24 V DC, or an internal 3.6 V lithium battery
- Display
- LCD showing instantaneous and total flow together, in m³/h, L/min, Nm³/h, NL/min or t/h
- Compensation
- Standard, temperature only, pressure only, or both, integral or separate
A vortex meter answers the steam question. Where a plant wants to know how much energy it is buying, moving or losing, the medium is usually steam or compressed air, and the instruments that measure conductive liquids are of no use on either. The vortex meter measures them without a moving part, and that combination is the reason it appears at the top of almost every boiler house energy account.
What it asks for in return is a stream it can count. The instrument reads a rhythm rather than a level or a pressure, and a rhythm needs regular shedding, which is why the conditions around the body matter as much as the body itself.
How the measurement is made
A bluff body is fixed across the bore. As steam passes it, vortices are shed alternately from the two sides, and each shed vortex takes a small pressure pulse from the edge behind it. A sensor in the body detects that alternation and the electronics count it. Across the band the body is designed for, the counting frequency is proportional to velocity, so a known bore converts it into a volume per hour.
The signal being a frequency is what makes the type durable in this duty. A frequency does not drift the way an analogue span drifts, and it does not need a moving element that steam and heat will eventually seize. What it does need is that the medium stay in one phase while it is inside the meter. Droplets in wet steam disturb the shedding, and a gas that condenses in the body does the same, which is why the material is explicit that the device is not offered for two-phase flow and why a dry-steam separator upstream is often part of the answer rather than a separate project.
What the body is asked to survive
Two independent sets of conditions act on the instrument, and they are usually stated separately because they are survived by different parts. The medium conditions - temperature, pressure, whether the steam is saturated or superheated - are met by the body, the sensor and the sealing. The ambient conditions - vibration, weather, whether the line is insulated and how hot the space around the head becomes - are met by the housing and, over years, by the electronics.
The material behind this page describes the flagship form as having a thicker body for lines carrying high-frequency vibration and a sensor assembly on a square-section support, which is an answer to the second set of conditions rather than the first. That is worth noting, because vibration at the shedding frequency is indistinguishable from flow: a meter that is vibrating is not merely inaccurate, it is reading something that is not there.
Volumetric and compensated readings
What a vortex meter produces is a volume, and for steam and gas a volume is rarely the figure the buyer needs. A cubic metre of steam at one pressure contains a different amount of energy from a cubic metre at another, so a total taken without compensation changes whenever the boiler load or the line pressure changes, even when the same energy has been delivered.
Compensation corrects for that by measuring temperature and pressure and converting the volume to a mass or to a standard volume. It can be arranged integrally, with the sensing at the meter, or separately, with a flow computer taking an external temperature sensor and pressure transmitter. The material describes the separate arrangement as the one for superheated steam, high-temperature lines and overhead pipework, which is a practical distinction: the sensing points have to be reachable and correctly placed, and on a hot overhead line that is easier to arrange away from the meter.
Whether compensation is needed is a question about the account being kept, not about the meter. A line metered only to see whether it is running needs no compensation; a line metered to bill energy does.
Installation and the straight run
The body has to see a settled, swirl-free profile, and the material gives 10 DN upstream and 5 DN downstream as the normal requirement. Those figures belong to the instrument, not to the site, so where the available space is shorter the layout has to be settled before the meter is ordered rather than after. A disturbance close to the body - an elbow, a partly open valve, a reducer, a thermowell - is read as a change in flow and appears as an error that no calibration can remove.
Two further points from the material are worth carrying into the installation. Welding should be done before the meter is fitted, because welding current passing through the instrument can damage its electronics even when it is not powered. And the mounting attitude is part of the duty: a body set above a hot line ages faster than one set to the side, so steam and high-temperature gas installations are advised to have the body support angled away from vertical.
Measurement limitations and selection considerations
The material states plainly that it is not offered for wet steam or two-phase flow, and that is the first limitation to check rather than the last. The second is velocity: below a certain figure the shedding stops being regular and the low end of the range is set by the physics of the body rather than by an electronic limit, which is why a pipe oversized for its flow makes a poor vortex installation.
The material also leaves three figures unsettled, and they are the ones a buyer normally compares first. The range ratio is given in three different ways - 8:1 at the stated reference densities, 1:6 to 1:25 for the conventional form, and up to 1:30 in the feature list - and the material itself notes that the ratio changes with medium density, so none of the three can be applied to an arbitrary medium without checking. The medium temperature is given under two schemes that overlap. And the accuracy is expressed both as a class and as a percentage of reading, which are different quantities and should not be converted into each other. All three are listed below as information required rather than resolved here.
Ordering
The items that fix the answer are the medium and whether it is steam, gas or liquid; whether the steam is dry; the minimum, normal and maximum flow; the medium temperature and pressure and whether they vary; the pipe outside diameter with the wall thickness and the flange standard; whether a compensated mass or standard volume is required; the outputs and what will read them; whether a supply exists at the point of installation; and the straight run available upstream and downstream. A line description with a sketch of the proposed point is enough to issue a covering quotation, which can then be refined as the siting is agreed. Quantity, destination port and required delivery date complete the enquiry.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
