Physical installation

2.3 Physical installation

• The XL7 is factory-fitted with a process connection specified at the ordering stage. It follows that it should be connected to an appropriate mating fitting on the pipework.
• The only items to connect to the transducer should be the mating fitting and the field cable. The pipework on which the transducer is mounted should be rigidly supported. Any additional support or bracing should be on the pipework, not the transducer. The XL7 is fully supported by the process connection in any orientation.
• When considering the best installation for the transducer, remember most of the actual viscosity measurement takes place around the tip of the sensor. Priority is therefore to ensure the tip is exposed to a good representative flow of the fluid. The remainder of the sensor contributes
  only a very small amount to the measurement, and sensitivity further decreases to zero approaching the process connection. The main concern with the sensor shaft is to limit the possibility of any debris from attaching itself.
• Follow the previous recommendations when deciding the best installation for either pipe or tank measurement.

2.3.1 Pipe installation

• The options for pipe installation are shown in Figure 5 and Figure 6 above. The preferred method is to locate the transducer at a bend, since it allows the sensor to point into the full bore of the pipe for good flow around the tip and can be used down to relatively small pipe sizes.
• Whenever possible, always try to ensure the sensor is positioned in the full flow of the fluid so it experiences a highly representative sample of the bulk of the fluid. Where there is high flowrate and/or the fluid is abrasive or contains heavy debris it may be desirable to retract the sensor into the flange tee. The length of the pipe forming the flange tee will obviously determine the amount of exposed sensor. Figure 5 on page 13. The flange tee should be lagged if there is a risk of  temperature differential forming between the fluid at sensor and the bulk in the vessel, which will
  lead to a local variation in viscosity. 

2.3.2 Tank installation

• Tank installation options are shown in Figure 6 on page 14. Ideally, the sensor tip should be located as far into the tank as possible to promote good fluid circulation and to avoid local viscosity changes sometimes found near the wall of a tank due to temperature variations.
• If there are obstructions, such as a stirring arm, the transducer must be retracted into the flange tee, though no further back than is necessary. Again, if there is risk of temperature differential the tee should be thermally lagged.

2.3.3 Orientation (recessed tee)

• The transducer may be mounted at any angle. However, a mounting which encourages the build-up of debris around the transducer or the formation of an air or gas pocket in a recess should be avoided.
• Therefore, in an installation where the major portion of the transducer shaft is recessed into a long  tee and the liquid to be measured has suspended solids which easily settle out then an angle slightly above the horizontal plane (~ 10°) will usually prevent the build up of settled solids in the pocket. Conversely, if there is a risk of gas or air breakout in the fluid, then an angle slightly below the horizontal plane will reduce the possibility of air or gas entrapment. If there is a risk of both settlement and air/gas build-up then the solid settlement issue should take priority and the tee should point slightly upwards with reference to the horizontal. 

2.3.4 Tightening the process fitting

• It is important from both safety and operational viewpoints that the fitting on the transducer is fully tightened. The XL7 transducer can be supplied with any type of process connection. The three main types are flange, thread and hygienic.

FLANGE FITTING

• Always ensure that the mating flange on the pipework matches, identically, the flange on the instrument. The full specification of the flange on the instrument is given on the Certificate of Conformity. With the appropriate flange tee in place the actual transducer assembly can be installed:

(1) To seal the flanges, a fibre or synthetic rubber seal, such as Viton may be used.
(2) Flanges should be tightened using correct sized bolts fitted with washers on both flanges. Flange bolts must be tight, with tightening order and minimum torque settings in accordance with flange size and  mating determined by the Code for the flange.

PIPE THREAD FITTING

• Ensure that the female thread on the pipework is identical to the thread-type on the instrument. The full specification of the thread on the instrument is given on the Certificate of Conformity.
• With the appropriate thread in place on the pipework the transducer assembly can be installed.
• A parallel thread should be sealed using an independent, removable parallel thread seal such as Dowty type.
• A tapered thead should use an appropriate sealing tape or paste.
• Make sure the fitting is fully tightened using the wrenching flats on the body of the transducer near the thread. Do not try to tighten or loosen the instrument using the transducer enclosure. Failure to fully tighten the fitting can result in an erroneous reading.

HYGIENIC FITTINGS

• The XL7 can be manufactured with many types of hygienic connection options — RJT, IDF, DIN quick-release clamp etc. The full specification of the fitting on the instrument is given on the Certificate of Conformity.
• Ensure that the fitting on the pipework identically matches the size and type of process connection on the instrument. It is equally important that the correct type of seal is used for that particular fitting. The golden rule is to ensure that all fittings are fully tight so that the instrument is rigidly connected to the pipework. Any lock-nuts should be fully wrenched home and quick release clamps strongly secured. Failure to fully tighten the fitting can result in an erroneous reading.
• Make sure any lock nuts or threads are fully tightened using the wrenching flats on the body of the transducer near the thread. Do not try to tighten or loosen the instrument using the transducer enclosure.

2.3.5 Thermal insulation

• Thermal insulation (lagging) must be used if there is a risk of heat differential developing between the fluid at the sensor and the bulk fluid in the pipe or tank. However, the head enclosure and any heatsink must not be lagged (Figure 7).