Oval wheel meter for fuel oil consumption measurement of furnaces

By admin August 12, 2016 3:44 pm IST

  Fuel Oil consumption of furnaces can be measured exactly by means of oval wheel meter. The oval wheel meter being a positive displacement meter measures the volumetric flow of the fuel oil to the burner with very high accuracy and there-fore gives a continuous control of the economic consumption of fuel.
Depending on the burner type, there are different installation requirement for metering. The simplest installation consists of one meter only. This installation, however, is only possible if the flow to the burner is equal to the actual consumption and if there is no return flow. For different burner types and installations we can give the following re-commendations:
System with oil-atomizer burner with one oval wheel meter in the suction pipe to the pump
This system has an oil-atomizer burner. However only one meter is installed in this system in the suction pipe to the pump. The fuel oil which is not burnt (consumed) is re-circulated into the oil-feed pipe downstream of the meter. The re circulated fuel is such not metered again. The advantage of this system arrangement is obvious. Only one meter is required directly registering the actual fuel consumption.
As the oil is being compressed by the injection pump it may tend to expand on the recirculation line but will be compressed again in the burner feed pipe. However, separated air which is not dissolved again may form air bubbles or cushions causing burner failure.
System with oil atomizer burner with one oval wheel meter in the oil feed line and one meter in the return line In systems with oil-atomizer burner the fuel pumped through the strainer, meter and pre-heater to the burner. The oil which is not consumed is returned to the oil tank and measured by the meter in the return line. The actual oil consumption corresponds to the difference between the meter registration in the feed lone and the meter registration in the return line.

With this system two meters are required and to obtain the actual consumption the difference of the registration between the two meters must be calculated. Each meter has a certain, but small inaccuracy. In the worst case the total system error will be the sum of the errors of the two meters. The total system accuracy will increase with decrease return flow.
As the oil is being compressed by the injection pump, it may tend to expand in the return line leading to foaming. Foaming (expansion) will result in a volume increase. The oval wheel meter being a positive displacement meter measures the actual volume (in this case a volume of oil and vapour mixture), which means the reading of the meter in the return line is not correct. It may even happen that according to the meter reading the flow in the return line is higher than the flow in the burner feed line. Such expansion (vaporization) must be prevented by installing a spring-loaded pressure retaining valve downstream of the meter in the return line. Metering system according to this proposal will work reliably.
Oval wheel meters can be provided with pulse transmitters producing a flow proportional pulse signal. These pulses can be used for panel mounted pulse totalizes for flow rate indication. The frequency output from these pulse transmitters may also be used for digital controllers or economizers or may be converted into mAmp-signal
Where burner systems are equipped with two flow meters the pulses from the meter in the return line may electronically be subtracted from the pulse for the meter in the feed line for display of the actual consumption
Toshniwal can supply a complete range of flow-meters from 15 mm (1/2-inch) to 400 mm (16-inch) in double or single case, a variety of pressure and temperature ratings and in various materials of construction (cast steel, aluminium, stainless steel). The meters are complemented by a full range of accessories for the protection of the meter, the elimination of air, mechanical registers, set-stop counters, batching systems and control valves including flow computer options, ticket printers, temperature compensation and pulse outputs to suit most applications. n
Contact Toshniwal Hyvac Pvt Ltd267 Kilpauk Garden Road, Chennai – 600 010Tele: +91-44-26445626 / 8983Email: sales@toshniwal.net  www.toshniwal.net