A Practical Guide for Engineers, EPCs, and Project Teams

Field instrument installation is where engineering design meets physical reality. A well-designed instrument, specified with the right materials and accuracy, can still deliver poor performance if installed incorrectly. Conversely, a properly installed instrument—even one with modest specifications—will provide reliable, repeatable measurements over its service life.

This guide covers the essential installation practices for field instruments in process industry projects, drawing on established standards and decades of field experience.

1. The Foundation: Know the Standards

Before any installation begins, the project team must establish which standards apply. The most comprehensive and current standard for process industry instrumentation installation is BS 6739:2024, which supersedes the 2009 edition-1. This code of practice provides recommendations for the design and installation of measurement and control systems instrumentation in the process industry-1, covering:

• Personnel and work equipment safety

• Instrumentation in hazardous areas

• Safety-related instrumentation

• Flow, pressure, temperature, level, density, and mechanical measurements

• Transmitters and controllers

• Instrument piping and tubing

• Cabling, wiring, earthing, and power supply

• Testing, verification, commissioning, and acceptance-3

For projects in specific regions or industries, additional standards may apply. For hazardous area installations, IEC 60079 series governs the selection, installation, and maintenance of electrical equipment-. For control valves, always verify that the size, pressure rating, materials, and end connections match the operating conditions before installation-.

2. Pre-Installation: Preparation Prevents Problems

Before a single instrument is mounted, several critical checks must be completed.

2.1 Verify the Equipment

• Compare the operating data on the nameplate with the design specifications-

• Verify that materials of construction are compatible between the instrument and the process-25

• Check that all required certifications (Ex, SIL, material certificates) are present and valid

• Inspect instruments for shipping damage

2.2 Review Installation Documentation

• Confirm that the installation location matches the approved drawings

• Review the hook-up drawing—this document translates the P&ID symbol into a physical installation-35

• Check for any client-specific standards, especially around instrument tubing gradients (e.g., 1:12 slope requirements)-35

• Understand the scope break between instrument and piping—this is typically defined on the P&ID-

2.3 Site Preparation

• Ensure the mounting location is accessible and safe for installation personnel

• For thermowell installations, verify that draining and cleaning of the pipe is completed and all necessary permits are secured before cutting into the pipe-25

• Protect instruments from dust, dirt, and paint spray during nearby construction activities-

3. Mounting Location: The First Decision

Where an instrument is mounted directly affects its accuracy, reliability, and maintainability.

3.1 General Mounting Principles

3.2 Temperature Considerations

• Observe minimum and maximum permissible ambient and medium temperature limits, considering convection and heat radiation-

• When process media temperature is high, use capillary tubes or pigtail siphons to cool the media before it reaches the sensor-

• For thermowells, locate the pipe penetration in a position that accurately reflects the process temperature-25

3.3 Impulse Line Orientation by Service

The position of the instrument relative to the process tapping point depends on the service--35:

4. Specific Installation Practices by Instrument Type

4.1 Thermowells and Temperature Sensors

Thermowell installation requires attention to several critical factors:

Insertion length: The right length depends largely on the pipe diameter. A common rule of thumb is to insert the thermowell one-third to two-thirds of the way into the fluid stream-21. Other guidelines recommend an insertion length of 10 times the thermowell tip diameter or a minimum of 50mm (2 inches) into the process-21. The goal is to balance the risk of mechanical failure (longer insertion increases fatigue risk) against the risk of measurement error (shorter insertion reduces heat transfer)-21.

Location relative to pipe features: Install the thermowell three to five pipe diameters away from elbows, flowmeters, or other flow-disturbing devices-. For elbow installations, the thermowell tip should be positioned in the centreline of the pipe, with the tip facing upstream to avoid the influence of mixing or swirling-21.

Flow direction: In flowing media, install thermowells with the tip facing downstream to minimise wake vibration and mechanical stress-.

Sensor contact: Ensure the temperature sensor makes contact with the bottom of the thermowell. If the sensor does not bottom out, an insulating air gap is created, introducing measurement lag and error-25.

Transmitter mounting: Direct mounting of the transmitter integrally with the sensor and thermowell improves noise immunity by shortening sensor leads and reducing exposure to EMI-25. If remote mounting is necessary, keep the transmitter in close proximity to the sensor-25.

4.2 Pressure Transmitters

Process connection: When installing threaded sensors, grease the thread with suitable lubrication paste and tighten to the specified torque-. Never force a sensor that does not thread easily into the adapter-.

Mounting considerations: Choose a mounting point that minimises vibration, high temperature, and high humidity-. For remote seal mounting, follow the manufacturer's specific instructions-.

Manifold valving: Proper manifold valving procedures during sensor calibration and service are critical for maintaining transmitter health-12. For 3-valve manifold operation:

• Start-up sequence: Open the equalising valve first, then gradually crack open the high and low pressure isolating valves, and finally close the equalising valve.

• Shutdown sequence: Close the high and low pressure isolating valves first, then open the equalising valve.

This sequence prevents one-sided overpressure that can damage the sensor diaphragm.

4.3 Control Valves

Positioning: Most control valves can be installed in any position, but the most common method is to place the actuator vertically on top of the valve-. If horizontal installation is necessary, additional vertical support for the actuator should be considered-.

Straight pipe runs: Install control valves between sufficient lengths of straight run pipe to minimise turbulence. A typical requirement is 3 pipe diameters upstream and 6 pipe diameters downstream-.

Flow direction: Install the valve body in accordance with the flow direction indicated on the valve or in the manual-.

Installation checklist:

• Verify size, pressure rating, materials, and end connections match the operating conditions-

• Install the valve free of stress and with the least possible vibration-

• Ensure pipes are properly aligned before installation-

• Confirm pipeline cleanliness before installation-

5. Instrument Hook-Up: The Complete Installation

A hook-up drawing provides the detailed instructions for connecting an instrument to the process. Before issuing a hook-up drawing for construction, the instrument engineer must confirm-35:

Tubing slopes require particular attention in hook-up installations-. The standard tubing gradient expectation is often 1:12 (approximately 8% slope) to prevent liquid or gas accumulation-35.

6. Electrical Installation and Grounding

6.1 Wiring Best Practices

• Use shielded twisted pair cables for field instrument connections

• Minimise the length of unshielded wires in control panels

• Ensure cable glands are properly terminated and sealed

• For explosion-proof/flameproof installations, do not remove transmitter covers when power is applied-

6.2 Grounding

Proper grounding is essential for instrument reliability. Each facility has its own guidelines for grounding plant instrumentation-25. General principles include:

• Ground shields at one end only (typically at the control room end) to prevent ground loops

• Ensure the power to the transmitter is off before wiring-

• Follow the facility's specific grounding practices for instrumentation

6.3 Hazardous Area Installations

For installations in hazardous areas:

• Verify that all instruments carry appropriate Ex certification (ATEX, IECEx, or local equivalent)

• Use Ex-certified cable glands and sealing fittings

• For intrinsically safe (IS) circuits, maintain segregation from non-IS wiring

• Follow the specific installation requirements of IEC 60079 series-

7. Commissioning and Verification

After installation is complete, the following steps are essential before handing over to operations:

7.1 Installation Checks

• Verify that instruments are mounted as per hook-up drawings with correct fasteners-

• Confirm stands are securely fixed with the correct bolts, nuts, and washers-

• Visually inspect all welds and ensure cut edges are cleaned and coated as per specification-

• Confirm instrument tag numbers match the design-

7.2 Testing and Calibration

• Perform loop checks to verify continuity from the field instrument to the control system

• Calibrate instruments according to the project's calibration procedure

• Verify that calibration certificates are complete and traceable

• For thermocouple and RTD installations, verify sensor connection and transmitter configuration

7.3 Documentation

• Record as-built installation details

• Complete and file all test and calibration records

• Ensure documentation meets the project's handover requirements-

8. Common Installation Mistakes to Avoid

9. Why Anhui Tiankang Supports Proper Installation

Anhui Tiankang (Group) Co., Ltd. has been manufacturing industrial instruments and cables for nearly five decades. Our instrumentation is designed with installation in mind—clear documentation, standardised connection options, and robust construction that withstands field conditions.

Our product portfolio includes pressure transmitters, temperature sensors, level instruments, flowmeters, instrumentation cables, and accessories—all designed to work together as an integrated system. We provide technical documentation and support to help ensure that your instruments are installed correctly the first time.

10. Conclusion

Field instrument installation is where engineering design is validated. The decisions made during installation—where to mount, how to slope impulse lines, how to terminate cables—directly affect measurement accuracy, instrument life, and plant safety.

Key takeaways:

Remember: A well-installed instrument performs. A poorly installed instrument fails—and the failure is rarely the instrument's fault.

Contact Us

For instrumentation selection, technical documentation, or project support, please contact:

Yin Shuangjie
International Sales Manager
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/

Anhui Tiankang – Your partner for reliable instrumentation solutions.