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What is Electrical Resistance Corrosion Probe?

asked Apr 16, 2015 in Material by palagianomar (590 points)

2 Answers

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answered Apr 17, 2015 by cchang219 (2,310 points) | selected Apr 21, 2015 by odadmin
 
Best answer

There are two types of Electrical Resistance Corrosion Probes:

Retractable Corrosion Probes

  • The design of retractable type probes should incorporate features to:
    • Prevent accidental blowout of the assembly from a pressurized system.
    • Indicate probe assembly withdrawal limits (i.e., when the probe has cleared the access valve).
    • Minimize the risk of accidental closure of the access valve while the probe is inserted.
  • The corrosion probe body should include a velocity shield or stop ring that is sized to prevent the probe from being accidentally withdrawn through the packing gland.  The velocity shield or stop ring should be welded to the probe body. This should be done to ensure accidental blow-out does not occur under any circumstances.
  • Lesson Learned: In 1984 at the Baytown Refinery, a corrosion probe "blew out," resulting in a release of product to the atmosphere.  Luckily, no fire or other damage occurred, nor was anyone injured.  However, this incident was a timely reminder that retractable corrosion probe assemblies must be suitably designed to prevent blow-out.
  • Corrosion coupons can be inserted into a process stream by attaching them directly to a corrosion probe body, with the probe element removed, or to a coupon-holding shield, with the probe element in place.  In either case, the requirements for installing these corrosion coupons are the same as for retractable corrosion probes.
  • The installation of retractable-type probes should be such that retraction of the corrosion probe is not in the vertically downward direction. This is a safety precaution to prevent accidental injury to personnel when removing corrosion probes.  A probe that is retracted vertically downwards is more likely to injure personnel than those retracted horizontally.  Horizontally retracted probes can be approached from the side which means personnel are not standing directly in front of the probe during insertion or retraction.
  • Consideration should be given to ease of handling of the retracting tool (i.e., the pressure rating of the probe system should not be disproportionately high). To assure the greatest ease in probe installation and removal, the pressure rating of the probe shall reflect the expected service pressure.  If the pressure rating is too high, the retractor tool may become too large and difficult to handle.
  • A probe retractor device should be used for temperatures greater than 150°F (66°C) or pressures greater than 150 psi (10.2 bar).

Non-Retractable Probes

  • It is preferred that all corrosion probes be retractable while onstream.  At pressures above approximately 1000 psi (68 bar), retractable probes are not recommended.  Where corrosion probes are required in high pressure systems greater than 1000 psi (68 bar), a non-retractable type probe should be installed.
  • Connections for installation of nonretractable probes, including hydrogen finger probes, should be with flanged fittings unless otherwise specified.
  • Flange fitting assemblies should be supplied with mating flanges.
+1 vote
answered Apr 16, 2015 by josvanden (3,240 points)
An electrical resistance corrosion probe includes a corrosion sensing element, a probe body with appropriate fittings for insertion into the system and an end connector for attachment to a meter, or wiring to a multiplexor, which electronically monitors the progress of corrosion.

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