Instrument Piping and Tubing QAQC Questionnaires

Tubing Installation

PPPFL‐001

PIP 4.2.8.1 Interconnecting
instrument piping (tubing) between the primary metering

element and the measuring instrument shall be 0.5 inch
AISI Series 300 stainless

steel tubing minimum. Tubing wall thickness shall be 0.89
mm (0.035 inch)

minimum. Applicable piping code and process requirements
shall prevail.

PIP 4.2.8.2 Interconnecting
piping shall be limited to a maximum length of 6 m (20 ft) for

meters in control loops. Interconnecting impulse tubing
between a differential

flow element and a transmitter in compressor suction
service shall be kept as

close as possible or close coupled.

PIP 4.2.8.3 Interconnecting
Seal liquid to protect flow meter impulse tubing and secondary

measurement instrumentation from corrosive fluids or to
provide a stable

hydraulic measuring medium shall be free flowing but not
volatile under normal

process and external ambient conditions. Seal liquids
shall not be miscible with

nor react with the process fluid being measured. Seal
liquids shall be selected so

that their potential for contamination of the process
fluid is acceptable.

PIP 4.2.8.4 (Addition)
PIP PCIDP000 “Differential Pressure Installation Details” shall be
used

for interconnecting the flow Differential Pressure
Instruments to the root valves

of the differential producers.

PIP 4.6.2.c (Addition)
Purging of impulse lines shall be considered only if other methods

have failed to eliminate problems of condensation,
vaporization, corrosion or

plugging.

34SAMSS831

Installation

8.1.1 Pressure
and D/P instruments in liquid or condensable vapor service shall be selfventing

(i.e., mounted below the process connections) with all
impulse lines

sloping downward approximately 1:10 minimum toward the
instrument.

Pressure and D/P instruments in gas service shall be self‐draining
(i.e., mounted

above the process connections) with all lines sloping
downward approximately

1:10 minimum toward the process connection.

8.3 Instrument Piping and Tubing

The instrument piping and tubing installation shall ensure
the reliable and

accurate operation of the instrument(s) involved, and
allow sufficient access for

maintenance, calibration and testing. It shall be possible
to test all alarm and

shutdown initiating devices, without interfering with the
process operation of

the packaged unit.

Instrument tubing shall be adequately supported to
eliminate any vibration

transmission to the instruments or excessive load to the
piping connection,

process line or vessel.

Tubing to and from non‐indicating instruments shall have a
plugged tee or

equivalent test point for calibration and testing
purposes.

All threaded connections shall be tapered per ASME
B1.20.1.

All incoming and outgoing interconnection lines shall
terminate in bulkhead

fittings. The lines shall be marked with the tag numbers
of the corresponding

instruments. Bulkhead fittings shall be installed with
adequate spacing to ensure

that any connection can be removed without the need to
remove other fittings.

9.2.2 Tubing and Fittings

9.2.2.1 Tubing
Stainless
steel tubing shall be seamless, annealed, minimum

wall thickness 1.24 mm, per ASTM A269, Grade TP‐316L.

Instrument air tubing shall be ¼ inch, 3/8 inch, or ½ inch
OD

stainless steel. Wall thickness shall be 0.75 mm or
larger.

9.2.2.2 Fittings
316
stainless steel compression fittings shall be either Crawford

Swagelok, Parker Hannifin A‐Lok, Parker Hannifin Corp. CPI
or

Hoke Gyrolock. Any proposal to use fittings other than
those

listed above shall be reviewed by Supervisor,
Instrumentation

Unit,
Process Instrumentation Division, and P&CSD.