Dosing
Common Terminology for Dosing systems explained
Pressure Relief Valves (safety valves or bypass valves)
Pressure relief valves protect expensive capital equipment such as the pump, system, or tank from an upset condition (pressure spikes, over pressurization, a closed valve, etc.). They are a normally closed valve that operates (opens) when the pressure exceeds the pre-set value. They allow the excess pressure to be bypassed and safely discharged back into the supply tank or inlet piping. They maximize the uptime and ensure proper function for all ancillary devices connected.
Back Pressure Valves (loading valves / Anti-syphon Valves)
Back pressure ensures that dosing pump outputs have consistent flows. They do this by applying a minimum constant pressure that a pump must push against to maintain reliable check valve seating (closing). Consistent closure of its suction and discharge check valves on reciprocating pumps (like a diaphragm or plunger pump) allow for higher accuracy and stable operation. An anti-siphon valve is also a very important function, ensuring that a Venturi is not created which could override the metering pump. This function cannot be achieved with a check valve.
Calibration Columns (calibration cylinders)
Calibration columns are used to measure flow and help calibrate metering/dosing pumps. The column is usually connected at the inlet of a pump with a shut-off valve between the tank and the column and one at the bottom of the column. This allows for isolation between the tank and pump and the column and the pump & tank. With the calibration column full, the valve leading to the tank will be closed and allow the pump to start drawing down the fluid. The fluid is measured at the start, and then again from 30 seconds to a few minutes depending on the size, flow, and type of pump/operation. Based on the delta between the two readings over a fixed amount of time will provide the use a flow rate (lph, gph, lpm, gpm, etc.).
Injection Valves (injection quills)
Injection valves are like injection quills with one major difference. Although they both allow for passage of liquid from a feed line into the of a process line, an injection valve has one additional feature: it has an integral check valve. This check valve does not allow process fluid to enter or travel back up the injection line. This extra benefit keeps the two liquids separated at the mating interface.
Withdrawable injection lance (Also called Corporation Stops)
Withdrawable lances are like an injection valve; however, they have additional features. They allow for the injector to be removed without having to turn off the process flow. They incorporate a shut-off valve and a form of radial seal. The quill can be retracted while sealed until it reaches a point at which a shut-off valve (usually a ball valve) can be closed, and then the quill can be safely removed without leakage. They usually have a locking mechanism to ensure the quill does not slide out under system pressure and a hard stopping point (via chain or cable) to stop the quill from sliding all the way out when being serviced.
1300 PIPING (1300 747 464)
V 4.1
PAAS Source Book 227
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