Parshall Flumes
6Pages

arkon ^ ^ flow systems Arkon Flow Systems, s.r.o. Registration address: Berkova 92, 612 00 Brno, Czech Republic Correspondence address: Novackova 11, 614 00 Brno, Czech Republic VAT No: CZ27683826, Company Reg. No: 27683826 Tel: +420 543214822, Tel / Fax: +420 543215249 www.arkon.co.uk, email: office@arkon.co.uk

Parshall flume is a flow rafe device with a wide range of application. It can be used for flow measurement in creeks, irrigation and/or drainage channels, sewer outfalls. Waste Water Treatment Plants, etc. Main advantages can be summarised as follows: a) A relatively low energy loss( 3-4 times lower than in sharp-crested weirs), b) A small sensitivity to a velocity distribution in an approach channel, c) Flow rate measurement even under drowned conditions, d) Velocities inside Parshall flumes are high enough to prevent them from the deposition of sediments or accumulation of debris, e)...

1.- The Parshall flume function The flow rate measurement is based on the assumption that the critical flow is produced by constricting the width in the throat and then raising the bottom. The flow changes from subcritical to supercritical and then the measurement of a single depth is sufficient to determine the discharge. The water level is measured and recorded either in the center line of the approach channel using an ultrasonic level sensor or inside a stilling manhole (which can be a part of Parshall flume) by means of a float with a mechanical transfer to a flow rate, or using a...

(parameters are listed in cm, flume weights in kg) Rating curve for a depth ha inside a stilling manhole: Q = a * hba ... [m3/s,rm] /1 / ha ... flow depth in the distance B before the throat [m] Equation for discharge in case that the flow depth is measured at a distance B' can be sent to the client. Checking the drowned conditions: The actual value of a ratio hd to ha must be lower than the values specified in Table 2 ha ... flow depth at a distance B before the throat [m], hd ... water depth behind the flume, see Figure 1 [m],

Arkon Flow Systems, s.r.o.

Parshall flumes are made of polypropylene and are designed to measure for water flow measurements. The flume is resistant to air temperatures (up to 80 oC), however, water inside the flume must not get frozen. Moreover, Parshall flume can stand up well the solutions of inorganic salts, acids and bases that do not exhibit strong oxidation properties, and a majority of organic solvents. It is recommended once a year to clean a stilling manhole and a connecting pipe between the flume and the manhole. In flows carrying sediments, it is recommended to carry out the inspection and maintenance...