Gordon England Surface Engineering Forum

Plasma Gas Flow Information

Primary gas and helium secondary gas flowmeters on the Metco 7MC and earlier plasma consols are calibrated with nitrogen at 50 psi @ 70^oF. Using theoretical gas flow calculations, the actual flow rate of different gases ( argon, helium ) and gases at pressures other than the 50 psi can be calculated.

Theorectical gas flow calculations cannot be used on the 7MC hydrogen secondary flowmeters due to the positioning of the flow adjusting valve before the flowmeter tube. This causes the flowmeters operating pressure to be dictated from back pressure rather than the regulated input.

A gas flow experiment was run to establish data for conversion of plasma gas flow settings to actual flow rates for various operating conditions.The experiment was set up using a 7MC / 9MB plasma spray system fitted with master 7MC flowmeters. Actual flow rates and pressures were measured using massflowmeter and pressure calibration equipment.

Observation:

Actual primary flows agree very well with that predicted from theorectical calculation.
The actual flow of hydrogen secondary gas for a particular flowmeter setting was effected by back pressure in the system after the flowmeter.
The higher the back pressure, the higher the actual flow for a constant flowmeter setting for hydrogen secondary gas.
Primary and secondary gas flows, nozzle bore size and plasma on/off produce significant effect on back pressure.
7Mc current settings between 300-500 amps appeared to have an insignificant effect on back pressure and could be ignored.
GH/732 and GP/733 nozzles gave slightly different hydrogen flow rates for the same flowmeter setting. The narrow bore GP/733 nozzle giving higher back pressure. Only these two nozzle types were tested, but it is expected that wide bore nozzles like the G/730 or 720 would give similar results to the GH/732 and the narrow bored nozzles like the GE/731 or 704 would be similar to the GP/733.

Plasma gas flow correction / conversion calculators

CONVERSION CALCULATORS

Convert between Different Units of Measurement

Index of Unit Converters

HEAT TRANSFER
COEFFICIENT

SPECIFIC HEAT
CAPACITY

VOLUMETRIC
HEAT CAPACITY

Unit Prefixes

Plasma
Gas Flow

Hardness
MPa - GPa

Computing
Bits and Bytes

To use the measurement conversion calculators simply enter a number value into the desired field and click calculate. All results shown will be equivalent values. Values are given to seven significant figures ( the odd result may show 9's or 0's over running). Values of 10 000 or greater will be displayed in the e-format e.g. 2.3456e7 which equals 2.3456 x 10⁷ or 23 456 000. Values lower than 0.001 will be displayed in the e-format e.g. 2.3456e-5 which equals 2.3456 x 10^-5 or 0.000 023456. The calculators require that your browser has java script enabled. View all measurement unit conversion calculators on the same page (may not work with all browsers; requires Iframe).

Si Units:

	SI Base Units
	SI Derived Units
		expressed with special names
		expressed in terms of SI base units
		expressed in terms in terms of SI units with special names
	SI Unit Prefixes
	Non-SI Units
		accepted by SI
		currently accepted by SI
		derived CGS units with special names
		other non-SI units
	Constants
	Glossary of Units

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