Ametek 241CE II Operator's Manual page 24

1-8 | Model 241CE II Hydrocarbon Dewpoint Analyzer
Heatsink
Optical Systems
O-ring
Sample Inlet/Outlet
Pressure Regulator
Purge Air (Gas)
Purge/Shut In Solenoid Valve Controls the flow of the sample gas. At the start of the Purging/Hold
Relief Valve
Bypass Valve
Vent Line
Electrical Leads
Absorbs heat from the Mirror during the Cooling Stage. The heat is
then transferred to the atmosphere through the Heatsink fins. During
the Warming Stage, the Heatsink serves as a passive source of heat
by using the surrounding ambient temperature to heat the mirror.
The Model 241CE II Analyzer employs two Optical Systems in its
Measuring Cell:
• One detects hydrocarbon condensation on the rough, black surface.
• One detects water condensation on the smooth, reflective surface.
(This water dewpoint measurement is for internal use only, used for
compensation in the calculation of HCDP measurements.)
For each optical system, light from a light-emitting diode (LED) is
directed to a mirror surface through a Polycarbonate Window. The
optic-path windows are truncated cones and thus will remain seated
firmly even with high-pressure gas samples in the Measuring Cell.
The placement of the optic-path windows and Phototransistors are not
symmetric, as suggested by Figure 1-3. These elements are located,
by design, so that when condensation occurs – either hydrocarbon on
the rough surface, or water on the smooth surface – the intensity of
light at the respective phototransistor increases. This arrangement is
possible because of the different wetting properties of the two types of
liquids.
The gas sample chamber is formed by the Mirror Support and the
cavity machined within the aluminum cylinder. The gas seal between
the two parts is created by an o-ring.
The Sample Gas Inlet and Outlet channels are simply bored through
the aluminum cylinder. Both the Sample Inlet and Outlet connections
contain flame arrestors.
Used to adjust the sample gas flow rate. This regulator is labelled
"Flow Adjustment" on the analyzer backpan.
The purge air (gas) supply creates a dry atmosphere within the
Thermoelectric Cooler (TEC) compartment to prevent ice from forming,
which can damage the cooler.
Stage, the solenoid valve is opened to allow the sample gas to purge
through the Measuring Cell. At the end of the Purging/Hold Stage, the
solenoid valve is closed to stop the flow and to enable the Measuring
Cell to equilibrate to the process stream pressure.
The overpressure Relief Valve, which is set to release at 13.8 BARG
(200 PSIG), prevents the solenoid valve from becoming over-
pressurized (attaining full line pressure) in the case of a failure of the
pressure regulator.
The Bypass Valve allows a small flow rate during the measuring cycle.
The flow rate through the bypass is approximately one-tenth of the
Purge/Hold Stage cycle flow (called a "trickle purge").
Vents the used sample gas to atmosphere or to an approved low
pressure (<50 PSIG) flare header .
The analyzer is controlled by a single Microcontroller board which,
along with the power supplies and other electronic
is contained in an enclosure separate from the Measuring Cell
Assembly (Figure 1-4). Communication between the Microcontroller
board and the Measuring Cell Assembly is via Electrical Leads which
pass through the Measuring Cell seal mounting assembly. The
Microcontroller monitors the mirror temperature, controls the mirror
cooling rate, adjusts the brightness level of the LEDs, monitors the
light intensities at the phototransistors, controls the sample valve, and
determines whether a dewpoint is detected.
components,