To keep in mind before installing a pressure transmitter

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The following points should be checked before installing a pressure transmitter.

ENVIRONMENTAL CONDITIONS

The equipment considered and the complete installation shall be suitable for continuous operation under the following site conditions:

Operating
a) Temperature : 0 ~ 50 0C
b) Relative Humidity : 98%

Storage
a) Temperature : (-)5 ~ 60 0C
b) Relative Humidity : 98%

CLASSIFICATION OF HAZARDOUS AREA FOR INSTRUMENT

The instrument should be suitable for installation in Hazardous Process area in Hydrocarbon installation.

Explosion Protection Method for Hazardous Area should be as mentioned in equipment data sheet. If same is not mentioned in equipment data sheet following hazardous Area classification should be applicable : Class I, DIV. I, Group C&D as per API RP-500

Pressure transmitter should be suitable for area classification. The instrument should meet following standard/requirement as minimum:

Intrinsically safe as per Ex ia II B T4(as per IEC 60079) & explosion proof E Ex d IIB T4 (as per IS2148 /IEC 60079), Weather proof to IP 65(as per IS12063/IEC 60529) or better.

Transmitters should be immune to Radio frequency interference due to walkie-talkie, paging system, communication system etc. All electronic modules shall be designed for short circuit protection.

MATERIAL & CONSTRUCTION

Pressure transmitter body studs should be high tensile stainless steel, or other corrosion resistant material for higher stress levels. Pressure transmitter parts should be resistant to the corrosive properties of the process fluid and ambient conditions to which they are exposed.

Pressure transmitter should be tropic alised to protect against humidity, moisture and fungal growth.

It should be painted with Acid & alkali proof (epoxy coated) and suitable for mounting and should comply electromagnetic compatibility requirements.

SENSOR & ELECTRONICS

Pressure transmitter should be electronic , SMART, 2 wire transmitter with 4 to 20 mA output with HART protocol.

Pressure transmitter should use 24 VDC nominal as operating voltage and shall be protected against short circuit & reverse voltage.

Span should be continuously adjustable over the transmitter range.

All pressure transmitters should be provided with integral output meters. The output meter should be suitable for use in the hazardous area.

It should comply accuracy requirement including linearity, hysteresis, repeatability and temperature and response time should be less than 300 ms and it should have built in lightning protection. It should have good turn down ratio.

Load capability should be min. 500 ohms at 24V DC.

Adjustment: Zero & span – both internal through software & external (external setting adjustment shall have locking adjustment). It should have over range protection of 150% of max range and over pressure limit of min 150% of max range. All terminals for electric connections should be clearly marked & labelled.

LOCAL FIELD INDICATOR

Pressure transmitters should have digital integral LCD type local field indicator. Local indicator shall be suitable to display 4 ½ digits & engineering units.

MOUNTING ACCESSORIES/ CABLE GLAND/ TAG

Mounting accessories and including bracket should be made available before installing the transmitter. Suitable cable gland should be ready. The transmitter should be tagged before installing..

CALIBRATION AND TESTING:

Finally the pressure transmitter should be calibrated with both zero and span settings. HART communicator may be used for testing.