WIKA Model 55 Stainless Steel Bimetal Thermometer, EN 13190

Overview

The WIKA Model 55 is a bimetal dial thermometer developed and manufactured to EN 13190 for the requirements of the process industry. It is made completely from stainless steel, from the case and bayonet ring to the stem and process connection, and is used in chemical and petrochemical plants, oil and gas facilities, power stations and water and wastewater installations, particularly where the environment or the medium is aggressive. Scale ranges cover -70 to +600 °C, dial sizes are 63, 100 and 160 mm, and stem lengths can be specified individually from 63 to 1,000 mm.

Seven Star LLC supplies the WIKA Model 55 to operators, EPC contractors and maintenance teams across Oman and the GCC, with engineering support in Muscat. For engineers looking for a thermometer supplier in Oman, it offers a single, well-documented model that covers most local temperature indication points in a plant, from cooling water at 30 °C to hot oil and steam lines.

Measuring Principle

The measuring element of the WIKA Model 55 is a bimetal coil: two metal strips with different coefficients of thermal expansion are bonded together and wound into a helix inside the stem. When the temperature changes, the two layers expand by different amounts and the coil twists. This rotation is passed through a movement to the pointer, which reads directly on the dial. The thermometer needs no power or transmitter and gives a reliable local reading even when the control system is unavailable.

Accuracy of the WIKA Model 55 is class 1 per EN 13190 within the measuring range, which is marked on the dial by two triangles; the scale range extends beyond it. For continuous loading up to one year, the thermometer should operate within the measuring range, while the full scale range may be used for short periods of up to 24 hours. Overtemperature stability is 100 % of the scale range for ranges up to 120 °C and 50 % for ranges from 120 to 280 °C. A pointer with micro adjustment and optional zero adjustment on the rear of the case allow fine setting.

Engineering Design of the WIKA Model 55

The WIKA Model 55 case and bayonet ring are stainless steel 304, or 316L where the highest corrosion resistance is required. Windows can be instrument glass, laminated safety glass, or polycarbonate on NS 63. Three mounting styles are available: back mount (axial), lower mount (radial), and an adjustable stem and dial version whose head swivels 90° and rotates 360° so the dial can face the operator after installation. A silicone oil case filling can be added to damp pointer vibration, usable up to 250 °C at the probe.

The stem and wetted process connection are stainless steel 316, with stem diameters of 6, 8, 10 or 12 mm. Process connections include G 1/2 B, 1/2 NPT, M20 x 1.5, female G 1/2 B, 1/2 NPT or M24 x 1.5, or a plain stem, in designs ranging from a fixed male thread to a union nut or compression fitting sliding on the stem. Maximum static pressure at the stem is 25 bar, and WIKA recommends a thermowell such as models TW10 to TW30 for higher process loads or where the instrument must be removed during operation.

Key Features

The WIKA Model 55 is chosen for durability in harsh process and climatic conditions:

• Completely stainless steel construction, with 316L case option.
• Class 1 accuracy per EN 13190.
• Scale ranges from -70 to +600 °C in °C, °F or dual scales.
• Dial sizes 63, 100 and 160 mm in back mount, lower mount or adjustable stem and dial versions.
• Individual stem lengths from 63 to 1,000 mm and stem diameters of 6 to 12 mm.
• Ambient temperature range of -40 to +70 °C on the case, with POLARgauge versions down to -70 °C.
• Ingress protection IP65, IP66 or IP67, and optional silicone oil filling.
• QR code on the dial for instrument-specific information and certificates.

Industrial Applications

In Omani oil and gas fields, refineries and gas plants, the WIKA Model 55 is installed on heat exchanger inlets and outlets, lube oil systems, compressor discharge lines, tank heating circuits and utility steam headers, typically in a WIKA thermowell so it can be replaced without shutting down. Its stainless steel construction suits the salty, humid atmosphere of coastal sites in Sohar, Sur and Duqm, as well as dusty desert locations where cases are exposed to high daytime temperatures.

Power stations and desalination plants use the WIKA Model 55 on cooling water, boiler feed and auxiliary systems, while chemical plants and water treatment works apply it to dosing tanks and process lines. In district cooling plants it gives a direct reading of chilled water supply and return temperatures next to the equipment. Seven Star LLC supplies the WIKA Model 55 in the dial size, range, stem length and connection required, and provides the official data sheet.

Technical Specifications

Specifications for the WIKA Model 55 are taken from WIKA data sheet TM 55.01 (03/2025):

How to Order

For a WIKA Model 55 offer, send Seven Star LLC the thermometer schedule with tag numbers, scale range, dial size, mounting style, stem length and diameter, process connection and any thermowell requirements. Our Muscat team will confirm the configuration, advise on delivery to sites in Oman and the GCC, and supply the WIKA data sheet for approval. For electrical temperature measurement on the same points, see the WIKA TR10 RTD sensor, the WIKA TR12-B process resistance thermometer and the Endress+Hauser TR10 Omnigrad M RTD thermometer.