All instrument piping system or tubing runs should be routed to meet the following requirements:
- They should be kept as short as possible.
- They should not cause any obstruction that would prohibit personnel or traffic access.
- They should not interfere with other equipment items ‘ accessibility for maintenance.
- They should avoid potential fire risk areas or hot environments.
- They should be located with sufficient clearance to allow lagging on adjacent pipework that may be required.
- The number of joints should be kept to a minimum consistent with good practice.
- All piping and tubing from supports attached to firm steelworks or structures (not handrails) should be adequately supported along its entire length.
For air supply:
- Branch headers should be provided to supply individual instruments or groups of instruments.
- Tappings should be allowed to cater for future expansion.
- Branch headers should be self-draining and have adequate drainage/blow-off facilities.
- Each instrument air user should have an individual filter regulator.
For Pneumatic Signals:
For these signals, copper tubing is most commonly used.
- PVC outer sheath is used.
- For its entire length, pneumatic tubing should be installed on a cable tray or similar supporting steelwork and securely clamped at regular intervals.
- The signals to the control room should be marshalled in a remote junction box.
These are the lines that contain process fluid that run between the impulse connection of the instrument and the tapping point of the process and usually consist of tube and pipe fittings or tube and compression fittings.
Impulse lines should be designed to be as short as possible and should be installed so that they are self-draining for liquids and self-venting for vapours or gases.