Metering cylinder

Two main types of volumetric filler exist. In the first type, a predetermined volume of liquid can be dosed using either a magnetic inductive volumetric flow meter or a mass flow meter. Alternatively, measuring cylinders can be used that incorporate a level probe. The product is fed to a set level in the metering cylinder, at which point the flow valve is closed off from the supply tank. A typical can filler operating at 1,500 cans of 330 ml capacity per minute will fill as per the supply contract within 2.5 ml. However, a standard deviation for a volumetric filler as low as 0.58 ml has been quoted. As with the probe filler, these fillers are fitted with electro-pneumatic valves, enabling accurate control of the... 

A very feasible and promising approach was to arrange the hot process parts of the machine in total in an oven enclosure provided with means for controlled hot air recirculation. The process parts, including tanks, chemical lines, metering cylinders or pumps, valves, mixing head and mold, can be arranged in different compartments of the oven enclosure for the individual temperature control of the chemicals. 

Figure 7 shows the oven in forward position. All process parts in contact with the chemicals exposed to the hot environment are manufactured from stainless steel. The gear drives for the tank agitatiors and the hydraulic actuators for the mixing head and for the metering cylinders are arranged outside of the enclosure in ambient environment. The drive parts are coupled to the hot parts by insulated connections for preventing heat transfer. 

A filling nozzle connected to the outlet of the metering cylinder releases the concentrate product into the container to be filled. The appropriate filling nozzle is selected according to several criteria. These fall under these general headings ... 

The suspension concentrated product must be chilled to obtain accuracy during filling with propellant 11. Slow evaporation of propellant results in a vapor lock in the tubing and metering cylinder of the filler. This ultimately results in inaccurate filling. The simplest solution to this problem is to chill... 

With product fillers that are not equipped with a purging device, it may be difficult to purge all air remaining in the metering cylinder and tubings. As a result, the first hundred fillings may be inaccurate. The addition of a recirculation system prevents this inconvenience, and, in practice, fillings become more accurate after the first five actuations. 

Propellant Filler Unit. The propellant filler may also be compared with a syringe piston system, as was the concentrate-product filler. When the pneumatic pump pushes on the piston, a very high pressure builds up in the metering cylinder of the filler. A filling head is connected to the outlet of the metering cylinder and allows the introduction of the propellant into the container through the valve. As seen previously, this technique is called pressure filling. 

Valves C and D are called discharge valves. Their function is to prevent any suckback of material into the metering cylinders, which could occur during the charging cycle. 

An important factor in many applications, tanks A (resin) and B (hardener) must be pressurized to achieve meter cylinder recharge within a reasonable time period. In addition, heating of the materials will reduce recharge time. If the proper recharge of the cylinders is not achieved, an off-ratio condition will exist. 

Fig. 5. Double-acting cylinder-type metering system. CVA, CVB—charge (suction) valves DVA, DVB—discharge valves PA, PB—metering cylinders V—hardener bypass TA—resin transfer pump TB—hardener transfer pump G—mixer.

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