Proper maintenance of instrumentation is crucial to ensure the accuracy and reliability of the measurement systems. Below are 20 critical areas you should avoid during instrumentation maintenance to ensure safety, efficiency, and longevity of the equipment.
1. Never Mix Signal Cables with Power Cables
Avoid using a single multi-core cable for both signal transmission and power supply. This can lead to interference, affecting the signal quality and compromising the performance of the equipment. Always separate signal cables and power cables.
2. Do Not Oil Oxygen Lines and Instrumentation
When servicing oxygen lines, never apply oil. Oil can cause a fire hazard in oxygen-rich environments. Additionally, ensure that pressure gauges and transmitters are not mixed with standard instruments, as this could lead to incorrect readings and potential equipment failure.
3. When Disconnecting Cables, Secure the Ends to Prevent Short Circuits
Always ensure that the wire ends are properly insulated and protected during disconnection to avoid short-circuiting. This precaution is essential to prevent electrical damage and safety hazards.
4. Avoid Intermediate Cable Connections
Do not have any intermediate connections in cables. All connections should be made directly between the equipment and the control systems to minimize the risk of signal degradation and reliability issues.
5. Ensure Proper Grounding of Shielded Cables
For single-ended shielded cables, grounding should be done at the control room side. Improper grounding can cause interference and lead to measurement errors.
6. Ensure Protective Hoses Are Positioned Below Instrument Inlets to Prevent Water Ingress
When installing instruments, ensure that protective hoses are installed below the instrument’s input ports to prevent water from entering the device, which could lead to malfunction or corrosion.
7. Install Instrument Protection Boxes for Outdoor Installations
If instruments are installed outdoors, it is advisable to install protective enclosures. This extra layer of protection ensures that environmental factors, such as rain or dust, do not affect the instrument’s performance.
8. Separate Different Cables in Cable Trays
When laying cables in cable trays, ensure that intrinsic safety cables, power cables, and signal cables are separated by partitions. This helps to prevent interference between different types of cables.
9. Avoid Using Spade Connectors on Compensation Leads
Compensation leads should never be connected using spade connectors. Using improper connectors could result in contact between different conductors, causing measurement errors and potential damage to the system.
10. Follow Protocols for Instrument Maintenance
When handling instruments during production or maintenance, especially in both indoor and outdoor environments, always follow the established procedures. Notify the operations team, and in some cases, get written acknowledgment before starting any maintenance work.
11. Ensure Proper Lightning Protection for Instrumentation in High-Risk Areas
In areas prone to lightning, connect field instruments to surge protectors and then to safety barriers before linking them to the control systems (DCS, SIS, etc.). This setup helps minimize damage from power surges during lightning events.
12. Take Preventive Measures Against Rodents in Control Rooms
It’s crucial to implement rodent control measures in the control room. There have been cases where rats urinated on SIS cards, causing plant shutdowns. These situations result in significant financial losses. Always back up the control system before making any modifications.
13. Complete Individual and Loop Testing Before Full System Integration
Before connecting instruments to the entire system, complete individual testing for each instrument. Once the installation is finished, perform loop testing to ensure everything works properly before initiating full system integration.
14. Have Process Personnel Present During Instrument Maintenance
Always have process engineers or operators present when performing maintenance on instruments during plant operation. Ignoring this could lead to larger issues that affect plant safety and performance.
15. Coordinate with Process Personnel and Verify Power Shutdown
Prior to dismantling powered instruments, consult with the process team to confirm the current operational state. Always switch off the power, and use a multimeter to verify that the power has been completely turned off before proceeding.
16. Select the Correct Flow Meter Based on Process Conditions
Ensure that the flow meter is selected according to the medium being measured, temperature, and pressure. Flow compensation should be considered to ensure accurate measurement. Always account for any special installation requirements of the flow meters.
17. Ensure Proper Sealing and Drainage for Control Room Cable Entries
When routing cables into the control room, design the cable trays with bends to prevent rainwater from entering the room. Proper sealing is essential to avoid water damage to sensitive instruments inside the control room.
18. Install Valves in Proper Positions to Avoid Contaminants
When introducing gas or air from the main pipe, install the valve at least 90 degrees above the pipe’s centerline to prevent dirt and other debris from entering the instrument, which could cause malfunction or inaccuracies.
19. Protect Outdoor Cables from Rain and Ensure Proper Sealing in Explosion-Proof Areas
For outdoor cable installations, make sure to incorporate rainproof measures. In explosion-proof environments, ensure that cable entry points are well sealed to prevent the ingress of hazardous substances.
20. Regular Maintenance and Testing of Alarm and Audio Equipment
Alarms and audio devices play a critical role in notifying operators of potential issues. Ensure that these devices are regularly maintained and fully operational. A malfunctioning alarm system can result in disastrous consequences in the event of a process failure.