Industrial instrumentation

Industrial instrumentation measures process pressure and temperature at the same points where the valves work. KTN Valves supplies bimetal thermometers from −80 °C to +550 °C, stainless steel Bourdon tube pressure gauges and pressure transmitters with a 4-20 mA output, all of European manufacture and with standard process connections.

What industrial instrumentation is and what it is for

Industrial instrumentation covers the devices that measure pressure and temperature in the pipe and pass that value to the operator or to the control system. A gauge and a thermometer give a local reading with no power supply. A transmitter turns the physical value into a 4-20 mA signal, so the PLC can log it, raise alarms and drive a control valve.

Instruments supplied by KTN

• Bimetal thermometers: direct-reading dial, −80 °C to +550 °C, in axial, radial and adjustable-angle designs.
• Bourdon tube pressure gauges: stainless steel case and measuring element for steam, chemicals and outdoor service.
• Pressure transmitters: thick-film ceramic cell, thin-film steel diaphragm, display version and submersible version for level.
• Full range by variable: pressure instrumentation and temperature instrumentation.

How to choose the scale range

The normal working point should sit in the middle third of the scale. EN 837-2 states it for pressure gauges: under steady load the working value should not exceed 75 % of full scale, and under fluctuating load, 65 %. A 0-10 bar gauge reading 2 bar works in the least accurate part of the dial; 0-4 bar is the correct span for that duty. Oversizing the scale costs resolution and does not protect the instrument: a snubber handles pulsation and, on steam, a pigtail siphon isolates the element. The elastic element is explained in the KTN guide on how a Bourdon tube manometer works.

Process connection and thermowell

The thermometer is fitted in a thermowell, threaded or welded into the pipe. The thermowell allows replacement without draining the line and shields the stem from pressure, erosion and corrosion. Immersion length must place the bulb in the central flow stream; a short immersion reads pipe wall temperature. Mechanical calculation against vortex-shedding vibration follows ASME PTC 19.3 TW. Connections are standard, BSP to ISO 228 or NPT to ASME B1.20.1, the same threads used on KTN threaded valves.

Pressure transmitters and the 4-20 mA signal

The thick-film ceramic cell runs dry, with no fill fluid, and withstands abrasion and aggressive media: treated water, slurries, dilute chemicals. The thin-film diaphragm on stainless steel takes higher pressures and overpressure, and is the usual choice in hydraulics and steam. The display version shows the value in the field. The submersible transmitter measures hydrostatic level in wells and tanks: one metre of water column equals 0.098 bar. A two-wire 4-20 mA output tolerates voltage drop over long cable runs and, under NAMUR NE 43, a current below 3.6 mA or above 21 mA reports a loop fault.

Instrumentation and valves from one supplier

Specifying a skid with a single supplier shortens engineering work: one bill of materials with consistent threads and flanges, one certificate of origin, one technical contact and one lead time. It removes the classic split-supply failure, a gauge with an NPT thread when the tapping is BSP. KTN ships the valve, its actuator package and the instrument on the same order.

Applications and industries

KTN supplies instrumentation to petrochemical, chemical, oil & gas, power generation, steam and thermal oil, water treatment and desalination, food and beverage, pharmaceutical, pulp and paper, mining, marine and HVAC plants. Steam and thermal oil circuits combine a bimetal thermometer in a thermowell with a gauge protected by a siphon. In intakes and treatment plants, the submersible transmitter measures well level.

Buying instrumentation direct from the manufacturer

KTN sells direct to end users and distributors, with no middleman, and holds stock of the most common industrial instrumentation references for immediate dispatch. Every order ships with a certificate of origin, and 3.1 material certificates are issued on request. For a quotation, state the fluid, working pressure and temperature, scale range and connection type. Distributor enquiries are welcome.

Why KTN

KTN Valves (Kara Technology News, S.L.) manufactures industrial valves in Rubí, Barcelona, under an ISO 9001 quality system and with Bureau Veritas inspection. The instrumentation in its catalogue is of European manufacture and is selected to work with those valves: matching threads, consistent ranges and one technical contact.

Related categories

For closed-loop regulation, control valves. To operate the valve from the control system, valve automation. Strainers, sight glasses and expansion joints are in industrial accessories. The complete range is in industrial valves. For diameter equivalences, use the DN to inches conversion table.

Frequently asked questions

What scale range should I choose for a pressure gauge?

Choose the span so that working pressure falls in the middle third of the scale. EN 837-2 advises staying below 75 % of full scale under steady load and 65 % under fluctuating load. For 2 bar working pressure, a 0-4 bar gauge reads better than a 0-10 bar one.

What temperature range does a bimetal thermometer cover?

Bimetal thermometers in the KTN catalogue cover −80 °C to +550 °C, with a direct-reading dial and no power supply. Outside that range, or where the process needs an electrical signal and continuous logging, a Pt100 probe or a thermocouple is the right instrument.

Do I need a thermowell to install the thermometer?

On pressurised pipework, yes. The thermowell lets you remove the instrument without draining the line and protects the stem from erosion and corrosion. The bulb should sit in the central flow stream, and mechanical sizing against vibration follows ASME PTC 19.3 TW.

What is the difference between a pressure gauge and a pressure transmitter?

The gauge gives a local dial reading and needs no power supply. The transmitter converts pressure into a 4-20 mA signal that reaches the PLC and enables alarms, logging and automatic valve control. Many lines carry both: the transmitter for the loop, the gauge for field verification.

Can a pressure transmitter be used to measure level?

Yes. The submersible transmitter hangs inside the well or tank and measures the liquid column above the diaphragm: one metre of water equals 0.098 bar. With the fluid density, that pressure converts into level. It is the standard solution for intakes, ponds and open tanks.