The correct installation of a pressure transmitter is crucial to its measurement accuracy, stability and service life. The following are the key steps and precautions for installing a pressure transmitter, following industrial standards:
I. Preparation Before Installation
Read the manual: carefully read the installation, operation and maintenance manual provided by the manufacturer to understand the requirements of the specific model (such as installation orientation, media compatibility, environmental limits, etc.).
Check the equipment: confirm that the model, range, accuracy, process connection, electrical connection and explosion-proof rating meet the design requirements.
Prepare tools and materials: suitable wrenches, PTFE tape/sealant (selected according to the medium and specifications), cables, connectors, impulse lines, valves (primary valve, secondary valve, drain/vent valve), pipe fittings, brackets, etc.
Safety first:
Isolate the process: ensure that the process at the installation point has been safely isolated (close the upstream valve) and that the pressure has been fully released to a safe state.
Follow safety procedures: wear appropriate personal protective equipment (PPE) and follow the workplace lockout/tagout (LOTO) procedures, especially in hazardous areas (flammable, explosive or toxic environments).
II. Installing the Pressure Transmitter Body
Location selection:
Close to the pressure tapping point: while meeting maintenance space requirements, stay as close as possible to the pressure tapping point to shorten the impulse line.
Environment: avoid high temperature, strong vibration and highly corrosive environments. Meet the ambient temperature and humidity requirements specified for the transmitter.
Maintainability: reserve enough operating space to facilitate wiring, commissioning, calibration and maintenance.
Anti-freezing and rain protection: if installed outdoors or in a low-temperature environment, consider installing an instrument protection box or insulation box.
Process connection position: ensure that the transmitter's process connections (high-pressure side and low-pressure side) correspond correctly to the impulse lines (pay special attention to H/L for differential pressure transmitters).
Fixing:
Use the mounting bracket provided by the manufacturer or matching mounting hardware. Firmly install the bracket on a wall, column, platform or process pipe (2"and above). When installing on a pipe, be careful to avoid excessive stress. Ensure the transmitter is installed firmly with no obvious vibration.
Orientation:
Most transmitters are insensitive to installation orientation, but some models (especially older ones or those with internal filling liquid) may have requirements (such as capillary remote seal systems); be sure to consult the manual to confirm. Ensure the electrical connection (junction box) faces downward or horizontally to prevent water ingress. Ensure the display (if any) is easy to observe.
Connecting the impulse lines:
Install a secondary valve in front of the transmitter to isolate the transmitter and the impulse line for easy maintenance. Install a three-valve manifold or five-valve manifold between the secondary valve and the transmitter (especially important for differential pressure transmitters).
The functions of the valve manifold are:
Equalizing valve: equalizes the high and low pressure sides (differential pressure) and releases pressure during zero calibration.
High-pressure valve / low-pressure valve: isolate the high and low pressure sides respectively. (The five-valve manifold has two additional drain/vent valves.)
Use appropriate pipe fittings and seals (gaskets, O-rings, PTFE tape, etc.), and connect strictly according to the specified tightening torque to ensure no leakage. Do not over-tighten. When connecting, be careful to avoid applying excessive mechanical stress (torque or bending moment) to the transmitter body.
III. Electrical Wiring
Power off: ensure the power supply is disconnected.
Cable selection: use cables that meet the specifications (wire diameter, shielding, insulation grade). Twisted-pair shielded cable is usually used to reduce interference.
Terminals: connect the power wires (+/-), signal wires (if separately led out) and ground wire correctly according to the transmitter wiring diagram (usually on the nameplate or inside the cover).
Polarity: pay attention to the positive and negative poles of the power supply; never connect them in reverse.
Shield grounding: the cable shield should be grounded at a single point on the control room side (usually at the safety barrier, DCS/PLC card side or a dedicated grounding bar), and the transmitter-side shield should be left floating or insulated (never ground both ends, to avoid forming a ground loop that introduces interference). Follow the grounding specifications of the control system.
Enclosure grounding: use a separate ground wire to connect the transmitter enclosure to a good instrument grounding grid/grounding bar (following the principle of equipotential grounding). This is important for both safety (explosion-proof, electric shock prevention) and interference resistance.
Explosion-proof requirements: in hazardous areas, cable entry devices (cable glands/explosion-proof connectors) that meet the explosion-proof requirements must be used, and they must be correctly installed and sealed (meeting the required IP and Ex ratings).
Waterproofing: ensure the sealing ring of the junction box cover is intact and the cover is tightened to prevent water ingress.
Cable routing: properly secure the cables (using cable trays, cable ties, etc.), and avoid laying them parallel to or crossing power cables; if parallel or crossing is unavoidable, keep sufficient distance or cross perpendicularly.
IV. Post-Installation Inspection and Commissioning
Visual inspection: confirm that all connections are correct and firm, the bracket is stable, and the valve states are correct (primary valve open? secondary valve closed? equalizing valve closed?).
Leak test: extremely important!
Slowly open the primary valve.
Slowly open the secondary valve (or the high/low pressure valves of the manifold).
Carefully check all connection points (valves, fittings, transmitter body connections) with soapy water or a dedicated leak-detection fluid.
If there is a leak, immediately close the valve, release the pressure, then re-tighten or replace the seals.
Power-on test:
Confirm that the supply voltage meets the requirements.
Turn on the power:
Check whether the transmitter has a display (if any) and whether the status light is normal.
