Ashford Instrumentation Ltd - Installation & Maintenance Guide For Pressure Transmitters

Installation & Maintenance Guide For Pressure Transmitters

This installation guide must be read in-conjunction with the manufacturers handbook or datasheet where available and any other details or information supplied with the pressure transmitter. This guide is not intended to replace the manufacturer’s literature but to supplement them or give guidance if the manufacturer’s instructions are not available. Pressure transmitters should only be installed, used and serviced by persons who are familiar with the instruments operating manual as well as with the application together with National regulations on occupational safety and accident prevention. When selecting a pressure or vacuum transmitter for a particular application , the following points must be taken into consideration and must be acted upon where appropriate to remain in accordance with all relevant European standards and for the general safety of users and the protection of plant and equipment.

Application

1. Pressure transmitters are suitable for use on any liquid or gaseous media which is not highly viscous, which does not crystallize or solidify, which does not have any special hygienic or sterile connection requirements.

2. It is vitally important that the process media is at a temperature which is within the normal temperature span of the instrument (see instrument specification data sheet) and which is not corrosive to the selected wetted parts of the instrument (see material selection guide or contact the pressure transmitter manufacturer if in any doubt).

3. Extreme caution should be taken when using a pressure transmitter on explosive, flammable, toxic or oxidising materials and should only be specified and installed by a competent and qualified instrument engineer.

4. Consideration should also be taken to meet certification requirements such as ATEX, Germanischer Lloyd (GL) or Det Norske Veritas (DNV) etc.5. Extra consideration should be taken to select the appropriate instrument if the application calls for an intrinsically safe or explosion proof device. Such transmitters will always be clearly marked or labeled with the relevant certification. If in any doubt do not fit the transmitter and seek further advice from the manufacturer.

General

1. Pressure transmitters should never be pressurized beyond their maximum range (please refer to individual data sheets). The maximum allowable pressure range should always be marked on the transmitter. If in any doubt do not fit the transmitter and seek further advice from the manufacturer

2. The process medium must not be of a nature to corrode or damage the selected wetted materials of the transmitter.

3. Transmitters for use on Oxygen, or Acetylene should be specifically manufactured and cleaned for this purpose. The transmitter will be marked accordingly.

4. If the atmosphere surrounding the pressure transmitter is corrosive, suitable protection must be specified or a suitable material for construction must be selected.

5. Where pulsation and vibration are present, suitable precautions must be taken as these conditions can seriously reduce the life of the pressure transmitter if they are not compensated for.

6. It is always recommended that a suitable isolation valve be fitted between the transmitter and the ‘line’ to allow the pressure transmitter to be removed for repair and calibration without disturbing the process.

7. Pressure transmitters should never be fitted on applications above or below the manufacturers recommended span for both medium or ambient temperature.

Installation of pressure transmitters.

1. Please keep in mind that this device is an electronic precision measuring device. Handle the device carefully and properly to avoid any damages.

2. In hydraulic systems always position the pressure transmitters in such a way that the pressure port is pointing upwards – vertically mounting.

3. When fitting pressure transmitters, the connection must always be tightened using the flats or hex that are provided. The transmitter must NEVER be tightened using the case. Where parallel threads are used, a tight joint must be made using a suitable washer or bonded seal. A pressure joint should not be made with a parallel thread, only tapered threads are suitable for pressure joints. When fitting a tapered thread a suitable seal material such as PTFE tape must be used.

4. Where a pressure transmitter is being used on liquid, the lines should be full of liquid and care should be taken to avoid loops where air or vapor can cause air locks or accumulate.

5. Transmitters with ¼” BSP threads should typically be tightened to a maximum of 20Nm, ½” BSP threads should typically be tightened to a maximum of 50 Nm. Transmitters with ¼” NPT or BSPT threads should typically be tightened to a maximum of 30Nm, ½” NPT or BSPT threads should typically be tightened to a maximum of 70 Nm. Please note this information is given as guidance only, please refer to the transmitter manufacturer for specific data.

6. Where a transmitter is to be used on air or gas, the pipe-work should rise continuously to the transmitter thus allowing any moisture or condensed liquid to drain away from the pressure transmitter.

7. Care must always be taken to ensure that any process fluid is not allowed to freeze within the pressure transmitter as this will cause damage to the instrument and may cause an indicating error. Special consideration must be taken when using a pressure transmitter on exposed water applications.

8. If there is a potential hazard of the transmitter being hit by lightning or exposed to over-voltage when installed outdoors, we recommend the installation of a sufficiently dimensioned overvoltage protection device be used.

Electrical installation of pressure transmitters.

1. As with all electronic devices, pressure transmitters should only be installed by a suitably trained and qualified person. Before fitting, please consult the wiring details supplied with the transmitter. If in any doubt do not fit the transmitter and seek further advice from the manufacturer

2. Establish the electrical connection for the device according to the pin configuration shown on the information plate usually located on the side of the transmitter.

3. For electrical connection a shielded and twisted multi-core cable is recommended.

4. Please ensure only the correct power supply is used, this information can be found on the transmitter information plate.

5. Special care must be taken when wiring an intrinsically safe or explosion proof transmitter to ensure the correct barrier and/or other safety devices have been selected.

6. If an error is detected in the output signal or the device does not appear to be working correctly please contact the device manufacturer for further assistance.

Maintenance.

1. All pressure transmitters should be regularly tested to ensure their accuracy because during the life of a transmitter the offset and the full scale point can shift. This work must be undertaken by qualified personnel within a controlled calibration laboratory.

2. Pressure transmitters are designed to be maintenance free. If desired the device can be cleaned using non-aggressive cleaning solutions.

Repair.

1. It is not recommended that repairs are carried out by unqualified personnel.

2. We recommend all transmitters are returned to the manufacturer for repair work. Please note that if the transmitter has been exposed to hazardous substances a declaration of decontamination is also required.

3. Where chemical or hygienic seals are fitted to the transmitter it is critical that the pressure transmitter and the chemical/hygienic seal are never separated. Please note that chemical/hygienic seals are fitted under vacuum conditions and operate using a 100% filled system. The instrument is calibrated as a unit and must be repaired in the same manner.

Disposal

All pressure transmitters should be disposed according to the European Directives 2002/96/EC and 2003/108/EC (on waste electrical and electronic equipment). Waste of electrical and electronic equipment must not be disposed by domestic refuse. Please note that special consideration is required for the disposal if the device has been in contact with hazardous substances.

Warranty Conditions

Generally speaking all of our pressure transmitters are covered by a minimum of 12 months warranty from the date of delivery. All warranty claims become void in cases of improper use, modifications or damages to the device. Damaged diaphragms are not accepted as warranty case. Likewise, there is no claim for warranty service if the defects have developed as a result of normal wear.

Spares.

As we have stated above, pressure transmitters should only be repaired by qualified personnel in controlled conditions. With this in mind, we do not have a recommended spares list for pressure transmitters.