Parsjahd Products - Thermowells

Thermowells are tubular shields inserted into and fastened on an existing pipeline or vessel and accept numerous types of temperature probes including RTDs and thermocouples. They are used to protect temperature sensors from harmful working conditions and to facilitate the repair or replacement of sensors without interrupting the process being monitored.



  • Materials
    • In general, the thermowell material to be chosen for an installation is governed mainly by the corrosion conditions the well will face. The high polish given to all stainless and Monel wells provides maximum corrosion resistance. Our thermowells are available in common and special grades of stainless steel, Chrome-molybdenum steel, Silicone bronze, Hastelloy B & C, Nickel, Titanium, and Monel. Tantalum jackets are also available.
  • Manufacturing Method
    • Depending on working pressure and flow rate, thermowell bodies can be manufactured by either machining a bar stock (normally for high pressure, high flow rate applications) or by using standard tubes sealed by welded caps (normally for low pressure, low flow rates, or vessels and tanks).
  • Velocity Ratings of Wells
    • Well failures, in many cases, are not due to improper choice of wall thickness or material. Less familiar, and more dangerous, are the vibrational effects to which wells are subjected. Fluid, flowing by the well, forms a turbulent wake (called the Von Karman Trail) which has a definite frequency based on the diameter of the well and the velocity of the fluid. It is important that the well have sufficient stiffness so that the wake frequency will never equal the natural frequency of the well itself. If the natural frequency of the well were to coincide with the wake frequency, the well would vibrate to destruction and break off in the piping.
      Velocity rating and wake frequency of Pars Jahd thermowells is calculated upon customer's request and according to J.W. Murdock's formulae and criteria.
  • Wake Frequency Calculation Standard
    • ASME PTC 19.3-2010
  • Standard Wake Frequency Ratio
    • 1. 0.8 for medium service
    • 2. 0.4 for sever one
  • Cladding / Overlaying
    • In cases where only the surface of the thermowell needs to have a specific property (e.g. resistance to corrosion) and its core a different property (e.g. toughness), it is a common practice to manufacture the thermowell by cladding or overlaying the core material with proper material for the surface. This can be both economically and mechanically beneficent. Coating can be carried out by metal spray technique, while TIG Welding and Electric Arc Welding are used for overlaying. Stellite, Inconel, etc. are common overlay materials.
  • Standard “U” Length
    • U=220mm
    • U=250mm
    • U=300mm
    • U=350mm
    • U=500mm
    • *Consult factory for others value.
  • Standard Size and Rating (for flanged type)
    • 1 ½”, 300#, RF
    • 1 ½”, 600#, RF
    • 1 ½”, 1500#, RTJ
    • 2”, 300#, RF
    • 2”, 600#, RF
    • *Other rating on request