Analyzer Systems

1. Sample loop. Conditioned gas runs continuously through a fixed-volume loop, so a fresh, representative sample is always waiting at known pressure and temperature.
2. Injection. A diaphragm valve changes over and helium carrier sweeps the trapped loop onto the columns. The cycle is timed and takes about five minutes.
3. Separation. Packed columns at constant temperature let the light components through first and hold the heavier ones back, so the mixture arrives as a sequence. A timed backflush returns the heaviest ends as one hexanes-plus peak.
4. Detection. A thermal-conductivity detector sees each peak. Peak area gives mole fraction, and from the composition come heating value, Wobbe index and relative density.

1. Sample loop. The same principle, but the whole sample path is inert and sulphur-passivated: sulphur compounds are reactive at ppm level and would be lost before they were measured.
2. Injection. The loop is injected onto a column chosen to resolve hydrogen sulphide, carbonyl sulphide and the mercaptans from the bulk hydrocarbons.
3. Separation. The sulphur species elute one after another while the hydrocarbon matrix passes largely unseen by the detector.
4. Flame photometric detection. Each compound burns in a hydrogen-rich flame and excited sulphur emits violet-blue light to a photomultiplier. H₂S and carbonyl sulphide arrive separately, the mercaptans as one backflushed group, and the three sum to total sulphur.

1. Purge and shut-in. Gas is filtered in three stages and swept through the cell at the measuring pressure. The outlet solenoid then closes: the cell stays at line pressure, but the sample in it is held still.
2. Cooling. Thermoelectric coolers drive the mirror down — five degrees a minute, then two once it is within fifteen of the last dew point — read by a platinum resistor inside the mirror itself.
3. Dew point. One cover, two surfaces: rough black and polished. Condensing hydrocarbons spread across the rough one and the returning light rises; water beads on the polished one, which is how the two are told apart. The mirror temperature at that instant is the dew point.
4. Warming. The coolers reverse until the film has gone, the solenoid reopens and flow resumes. Nothing is consumed. A cycle takes twenty to thirty minutes and holds the dew point to about a degree.

Modelled on the AMETEK 241CE II from its operator's guide and data sheet. The measuring cell is bolted outside the flameproof enclosure, so the sample never enters it. Sizes the manufacturer does not publish are estimated.

1. Sample in. No conditioning train to speak of: particulate filtering and a liquid separator, then one to two litres a minute past a cell held in a heated oven so nothing drops out of the gas phase.
2. The laser. One temperature-controlled diode laser, fibre-coupled and split two ways: a sealed reference cell on one leg, a GRIN lens into the sample cell on the other. Neither the laser nor the detector touches the gas.
3. Absorption. The beam runs the cell, reflects off a gold mirror and returns to an InGaAs detector. Swept across one water line, where methane does not absorb, the bite taken out of the light is the moisture.
4. Line-lock and result. The reference cell holds the laser on the line and verifies the reading continuously, so there is no calibration gas and no routine calibration. ppmV and a water dew point go to the display, to 4–20 mA and to Modbus.

Modelled on the AMETEK 5100HD from its data sheet and manual: a fibre-coupled diode laser splits into a sealed reference cell that keeps the reading locked and a heated sample cell. Sizes the manufacturer does not publish are estimated.