OXYGEN PROBE

  1. The zirconia sensor has been developed by CSIRO Australia, where zirconia pellet is joined to ceramic tube. Two methods of this jointing were developed. The initial technique developed is known as reaction (chemical) bonding. This technique results in highly unreliable joint as chemicals used react with various corrosive gases and other elements present in the flue gas/furnace atmosphere. Thus the life of sensor is uncertain/unpredictable.
  2. The later technique was developed by CSIRO, where the zirconia pellet is eutectically welded to super refractory tube and no chemicals are used for bonding. This technique has given excellent results in terms of realibility and long life of the sensor which enables RASKIN to provide one year warrantly for oxygen probes. This technique is available exclusively to Ceramic Oxide Fabricators and through them to Raskin in India.
  3. Raskin oxygen probes have several special features :
    1. Outer sheath (for probe ST) is made of special material Sandvik 253 MA. Schedule 40 thickness which can withstand both carburising and oxidising atmospheres. Even when exposed to high temperature and mounting horizontally, this does not cause bending.
    2. Using special catalyst, the internal probe resistance has been considerably reduced progressively providing accurate signal and faster response, over long periods.
    3. Probes are engineered to facilitate refurbishing unlike some other makes which need replacement at the end of catalyst service life.

Raskin Probes have been standardised as per the following dimensions

PROBE TYPE

HOT LENGTH
"L" MM

ST 500M

500

ST 600M

600

ST 700M

700

ST 800M

800

ST 900M

900

ADVANTAGES OF RASKIN IN SITU, OXYGEN PROBE

RASKIN ST / HT (unheated) oxygen probes are designed for operation in the radiant temperature zone and not in the flue or stack. They have the following distinct advantages over the other oxygen probes.

  1. Accurate measurement of O2 nearer the point of combustion. Probes positioned in the stack cannot give a true picture specially due to air leakages between the combustion zone and the stack. Also they do not give early warning of possible incomplete combustion. Specially in a package boiler where in-complete combustion in the 1st pass (flame tube) results in after burning in the 2nd pass and hence does not get detected in the stack.
  2. Instantaneous response (<1 second) to the combustion reaction which results in tighter control and greater safety.
  3. RASKIN probes do not require heating to 700°C, thus no heater is necessary. This means lower maintenance cost, a more reliable probe and a safer probe with no risk of explosion.
  4. Installation at the rear of the package boiler is easier. In many cases, the probe can be inserted through a sight glass port or refractory plug.
  5. RASKIN Oxygen Probes are characterised by robust construction and are designed to withstand aggressive furnace atmospheres and temperatures (900-1500°C HT and 600-1000°C ST). Further these probes can be refurbished to increase service life and maintain operating efficiency. Oxygen Probes incorporate a TC as an option.
  6. RASKIN has been in this field for over 18 years and has got vast accumulated experience. This experience is used in engineering and supply of oxygen probe systems to achieve tighter process and quality control.

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