WIKA TW70 Flanged, Threaded or Weld-In Protection Tube

WIKA TW70 flanged, threaded or weld-in protection tube

The WIKA TW70 is a protection tube offered in three connection styles: weld-in (TW70-K), flanged (TW70-F) and threaded (TW70-M). It is built from tube and closed with a welded tip, so the length can be very variable and the material range wide, from stainless steel 304, 316 and 310 to A106, Alloy 600 and Alloy X. The manufacturer positions it for low and medium process loads in the chemical and petrochemical industries, process technology, equipment manufacturing, plant construction, boilers, incinerators, furnaces and reactor vessels. Seven Star LLC supplies the TW70 in Oman and the GCC as an independent supplier in Muscat.

TW70 versions explained

The version letter is the key to the order: TW70-K is a weld-in connection for pipe sizes DN ¼, ½, ¾ and 1 in; TW70-F is a flange connection per ASME B16.5, EN 1092-1 or DIN 2527 with a raised face allowance of 3 mm (⅛ in); TW70-M is a threaded connection with an NPT thread of ½, ¾, 1, 1¼ or 1½ in. In every version the thermometer connects with a ¼, ½, ¾ or 1 NPT thread, and other connections can be requested.

Technical specifications of the TW70

Understanding the dimensions

Three lengths appear in the drawing: the insertion length U that reaches into the medium, the head length H that carries the thermometer connection, and the overall tube length P. The very long maximum insertion of 5,000 mm is the main reason to choose the TW70 over bar-stock thermowells that top out at 800 mm in one piece, for instance in boilers, furnaces and reactors where the thermometer has to reach far into the vessel. For the threaded version the data sheet gives a wall dimension KE depending on the thread: 5.78 mm for ¼ NPT, 8.13 mm for ½ NPT, 8.61 mm for ¾ NPT and 10.16 mm for 1 NPT. A full-penetration weld is available on request for the weld-in type.

Operating limits and wake frequency for the TW70

As with other WIKA thermowells, the permissible temperature and pressure depend on the tube design (dimensions, material, coating) and on process conditions such as flow rate and medium density. The manufacturer offers a wake frequency calculation to Dittrich/Klotter as an engineered service on request, checking vortex-induced vibration and static loads over temperature. Long insertion lengths are especially sensitive to this, so request the calculation whenever the tube is long or the flow fast.

Related models: TW45, TW10, TW15 and TW20

The TW70 and the TW45 are both protection tubes for low and medium loads, but TW45 follows DIN 43772 with fixed G threads and short standard lengths, while the TW70 offers NPT and flange options and very long lengths. For high loads, move to the solid-bar TW10, TW15, TW20 or TW25.

Selection and ordering checklist for the TW70

• Version: K, F or M.
• Material, including any special alloy for hot or corrosive service.
• Pipe size and schedule, or flange standard and rating.
• Thermometer thread N.
• Insertion length U, head length H and total length P.
• Whether assembly with a thermometer is needed.
• Certificate level and wake frequency calculation request.

Choosing between the three TW70 versions

The version is normally dictated by the nozzle that already exists on the equipment. A weld-in TW70-K removes a potential leak path and is preferred on lines that must stay tight for years, but it cannot be removed without cutting. A flanged TW70-F can be pulled for inspection or replacement and is the usual option on reactor and vessel nozzles that already carry a flange of the right rating. A threaded TW70-M is the quickest to fit on utility lines and where the plant allows NPT joints. Material follows the same logic: stainless 304 or 316 for general chemical duty, 310 or Alloy 600 for higher temperature oxidising atmospheres, and A106 for carbon steel piping classes where the tube must match the pipe.

Installation and maintenance of the TW70

Support long tubes against vibration where the plant design requires it, and make sure the welded or flanged joint is done to the project specification. Use gaskets suited to the flange facing, and avoid contact between the tube tip and the vessel internals during insertion. In service, check the tube at shutdowns for scaling, oxidation and tip erosion, which is likely in furnaces and incinerators.

Typical applications in Oman and the GCC

Furnaces and fired heaters, waste heat boilers, incinerators, reactors and process vessels in refineries, petrochemical plants and power stations around the Gulf commonly need long protection tubes in heat-resistant alloys. The TW70 fits those jobs, in addition to general chemical lines.

Information to send with an RFQ for the TW70

• Version, material and connection details.
• U, H and P lengths.
• Thermometer thread.
• Process temperature, pressure and flow.
• Certificates, quantity and delivery.

Documents and quotation

The WIKA data sheet TW 95.70 for the TW70 is attached on this page. Please send your specification and Seven Star LLC will respond as an independent supplier, without claiming any official WIKA role.