Summary:
Stainless steel Parshall trough (also called pap slot), is used for open channel flow measurement of auxiliary. In the process of liquid flow, the full pipe flow in open channel flow state of water called (open channel), the application of open channel flow meter place with city water diversion channels, coal-fired power plant cooling water diversion and drainage, sewage disposal flow and drainage, industrial and mining enterprises, wastewater discharge and water conservancy and agricultural irrigation channels.
Material type: glass fiber reinforced plastic, PVC, stainless steel, aluminum alloy. The greater the flow, the wall thickness shall be increased accordingly.
Selection considerations:
1. Parshall flume about channel installation, please users according to site condition.
2. Parshall flume center line to the channel center line overlap, the water flow into Parshall flume not drift.
3. Parshall flume water, flow to the free flow of water. Parshall flume submergence degree less than the critical submergence degree of the rules.
4. Parshall flume upstream channel width should be greater than 5 times of flat section, make water flow into the groove bashir's smoothly. That it has no drift, and channel slope formation of momentum. (see below)
5. Parshall flume installed on the channel is strong. And channel wall, canal bottom link to close, can't leak. Water for the whole department through Parshall flume measurement. Slots are measuring groove bashir's throat.
Features:
1, the groove shape is complex, Parshall flume higher than the price of the weir, and in order to improve the precision requirement of flume parts size accuracy. But also have some other measurement devices incomparable advantages: small water loss (about a quarter of the weir) even have solid matter little precipitation, water, close to the influence of flow rate is small, the relatively small impact on the low side of the water level, etc., so is used to measure the agricultural water, industrial water and other liquid flow.
2, used with open channel flow meter, the size of flow in open channel into the liquid level height. Measure the rate of flow of open channel in the inland waters. Diversion channels such as urban water supply, power plant cooling water diversion and drainage, sewage disposal flow and drainage, industrial and mining enterprises, wastewater discharge and water conservancy and agricultural irrigation channels.
3, open channel flow meter installation commonly used specifications size: (unit: mm)
Calculation principle:
In open channel flow, the greater the level is higher; The smaller the flow rate, the lower level. For normal channel, liquid level and flow no corresponding relation is determined. For the same depth, the size of the flow, but also with the channels of cross-sectional area, slope and roughness. Measuring weir trough installed within the channel, due to the gap of weir or groove reducing than channel cross-sectional area is small, so the channel upstream water level and flow rate depends mainly on the relation between geometry size of weir tank. The same measuring weir trough on different channels, the same level corresponding to the same flow rate. Measuring weir tank to flow into the liquid level. By measuring the amount of water weir tank water level, according to the corresponding measuring weir tank water level - flow relationship, flow.
By upstream flume bashir's contraction, short straight downstream of the throat and diffuser of three parts. Contraction of the bottom of the channel downstream tilt, diffuser and throat channel slot bottom groove bottom of sloping direction opposite.
Other constant terms determine the need to experiment, the general situation is as follows, F = 60 cm, G = 90 cm; K = 8 cm, N - 23 cm x = 5 cm, y = 8 cm; E according to channel depth, upstream water level is higher than 0.1 0.2 cm, 1.00 meters can be used commonly. Flume upstream and downstream bottom protection is for the bottom of the channel high long H function:
Upstream bottom protection L, 2, 4 h;
Downstream bottom protection, L = H (^ 6-8);
At the same time, because in the flume flow velocity is larger, throat water surface fluctuation is very big also, direct have difficulty in measuring water level in the tank. Therefore, in the trench wall setting after observation Wells, Ann measurement scale. Lower than groove bottom sill 20-25 cm, logging and flume horizontal metal or concrete pipe connections are available, and the pipe centerline should be higher than the bottom of the channel 3 cm, upper draft is located in the upstream from the throat throat head end ((2/3), the downstream end of the scale is located in the throat of the tank wall more than 5 cm. Draft of upstream and downstream of the zero point and groove bottom high to flush, observation Wells without slack phenomenon, well integrated by common sense and sediment, sealed by inoue, avoid clutter.
