The correct installation of pressure transmitters is crucial for their measurement accuracy, stability, and service life. The following are the key steps and precautions for installing pressure transmitters, following industry standards:
1、 Preparation before installation
Read the instruction manual: Carefully read the installation, operation, and maintenance manual provided by the manufacturer to understand the requirements of specific models (such as installation direction, media compatibility, environmental limitations, etc.).
Check the equipment: confirm that the model, range, accuracy, process interface, electrical interface, explosion-proof level, etc. meet the design requirements.
Prepare tools and materials: suitable wrenches, raw tape/sealant (selected according to the medium and specifications), cables, joints, pressure pipes, valves (primary valves, secondary valves, drain valves/exhaust valves), fittings, brackets, etc.
safety first:
Isolation process: Ensure that the process at the installation point has been safely isolated (by closing the upstream valve) and the pressure has been completely released to a safe state.
Comply with safety regulations: Wear appropriate personal protective equipment (PPE), follow workplace lockout/tagout (LOTO) procedures, especially in hazardous areas (flammable, explosive, toxic environments).
2、 Install the pressure transmitter body
Location selection:
Approaching the pressure point: On the premise of meeting the maintenance space requirements, try to get as close to the pressure point as possible to shorten the pressure pipe.
Environment: Avoid high temperatures, strong vibrations, and corrosive environments. Meet the environmental temperature and humidity requirements specified by the transmitter.
Maintainability: Reserve sufficient operating space for wiring, debugging, calibration, and maintenance.
Anti freezing and rainproof: If installed outdoors or in low-temperature environments, consider installing instrument protection boxes or insulation boxes.
Process connection position: Ensure that the process interface (high pressure side, low pressure side) of the transmitter corresponds correctly to the impulse pipe (pay special attention to H/L for differential pressure transmitters).
Fixed:
Use the installation bracket or matching installation hardware provided by the manufacturer. Firmly install the bracket on walls, columns, platforms, or process pipelines (2 "and above). When installing on pipelines, be careful to avoid excessive stress. Ensure that the transmitter is securely installed without significant vibration.
Direction:
Most transmitters are not sensitive to installation direction, but some models (especially older models or those with internal liquid filling) may have requirements (such as capillary remote transmission sealing systems), and it is necessary to consult the manual for confirmation. Ensure that the electrical interface (junction box) is facing downwards or horizontally to prevent water ingress. Ensure that the display screen (if any) is easy to observe.
Connect the pressure pipe:
Install a secondary valve in front of the transmitter to isolate the transmitter from the impulse piping for ease of maintenance. Install a three valve or five valve group between the secondary valve and the transmitter (especially important for differential pressure transmitters).
The function of the valve group is to:
Balance valve: balance the high and low pressure sides (differential pressure) and release pressure during zero calibration.
High pressure valve/low pressure valve: isolate the high and low pressure sides separately. (The five valve group has two additional drain/exhaust valves).
Use appropriate pipe joints and seals (gaskets, O-rings, raw tape, etc.), strictly tighten the connection according to the specified torque to ensure no leakage. Do not overtighten. When connecting, be careful to avoid applying excessive mechanical stress (torque or bending moment) to the transmitter body.
3、 Electrical wiring
Power off operation: Ensure that the power is disconnected.
Cable selection: Use cables that meet the specifications (wire diameter, shielding, insulation level). Twisted pair shielded cables are usually used to reduce interference.
Wiring terminal: Connect the power line (+/-), signal line (if separately led out), and grounding wire correctly according to the transmitter wiring diagram (usually on the inside of the nameplate or cover plate).
Polarity: Pay attention to the positive and negative poles of the power supply and do not connect them in reverse.
Shielding layer grounding: The cable shielding layer should be grounded at a single point at the control room end (usually at the safety barrier, DCS/PLC card end, or dedicated grounding bar), and the shielding layer at the transmitter end should be suspended or insulated (do not ground both ends to avoid interference caused by the formation of a ground loop). Follow the grounding specifications of the control system.
Shell grounding: Use a separate grounding wire to connect the transmitter housing to a good instrument grounding grid/grounding bar (following the principle of equipotential grounding). This is important for safety (explosion prevention, electric shock prevention) and anti-interference.
Explosion proof requirements: In hazardous areas, cable entry devices (gland heads/explosion-proof joints) that meet explosion-proof requirements must be used, and they must be correctly installed and sealed (to meet the required explosion-proof levels IP and Ex).
Waterproof: Ensure that the sealing ring of the junction box cover is intact and the cover is tightened to prevent water ingress.
Wiring: Secure the cables properly (using cable trays, zip ties, etc.), avoiding parallel or intersecting with power cables. If parallel or intersecting is necessary, sufficient distance or vertical crossing should be maintained.
4、 Post installation inspection and debugging
Visual inspection: Confirm that all connections are correct and secure, the brackets are stable, and the valve status is correct (primary valve open? Secondary valve closed? Balance valve closed?).
Leakage testing: extremely important!
Slowly open the valve once.
Slowly open the secondary valve (or the high/low pressure valve of the valve group).
Carefully inspect all connection points (valves, joints, transmitter body interfaces) with soapy water or specialized leak detector.
If there is a leak, immediately close the valve, release the pressure, and then re tighten or replace the seal.
Power on test:
Confirm that the power supply voltage meets the requirements.
Connect the power supply:
Check if the transmitter displays (if any) and if the status light is working properly.
