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Pressure Switches - General Information

Pressure Switches - General Information
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Pressure Switches - General Information - 1

Data sheet Date Page GENERAL INFORMATION FOR PRESSURE AND TEMPERATURE SWITCHES INTRODUCTION All pressure switches are of automatic reset and tested and manufactured under ISO9001 and comply with the following. Connection threads All switches have threads according to : EN 837-1/7.3.1 – 7.3.2 – 7.3.3 and 7.3.4. Parallel pipe thread (symbol G) according ISO 228-1. Tapered pipe thread (symbol NPT) according ANSI/ASME B1.20.1. Weatherproof standard for switches IP65 (IEC529). Oxygen and acetylene version Wetted parts materials comply with EN 29539 and EN 837-1/9.7.2/S1. Free of oil and grease. Certified material specification All stainless steel and other exotic materials used in production for connections, flanges, bourdon tubes, diaphragms (wetted parts of the pressure switches) etc. are traceable, all materials are according to DIN EN 10204 – 2.2 or 3.1 (b). PED directive All the pressure switches are manufactured according to PED directive in cat. III, with release of relative conformity declaration. The PED directive is not applicable to the temperature switches since these instruments are not pressure apparatus. ATEX directive Pressure switches may be manufactured in accordance with ATEX directive gr. II cat. 1/2GD with protection mode EExdIICT6 or supplied with conformity declaration for use in Intrinsically Safe circuits EExiaIICT6. Temperature switches are instead available with conformity declaration for use in Intrinsically Safe circuits EExiaIICT6 Quality control PCI’s instruments are produced under the rigid codes of the instrumentation industry and QA standards ENISO9001:2008. Our company ISO procedures are continuously controlled and monitored by NQA. TERMINALOGY Pressure or temperature switch : is a blind instrument, sensitive to the changes of the measured process variable and opens or closes an electric circuit at a pre-set value. Deadband (or differential of the micro switch ) : is the difference between the pre-set value and the value at which the micro switch resets. Repeatability : It is the shift of the switching point against the set point value initially calibrated during successive switching .It is indicated in percentage of the full scale. To evaluate the quality of a switch, it is not important to verify the accuracy but its value of repeatability since the accuracy of the set point depends only by the accuracy of the test instrument used to calibrate the set point _______________________________________________________________________________________________ PCI (Process System Solutions) Ltd, Unit 7 Slaidburn Crescent, Southport, Merseyside, PR9 9YF, UK, Tel: +44 (0) 1704 509090, Fax: +44 (0) 1704 509091, email: sales@pci-instruments.com, Website: www.pci-instruments.com

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Pressure Switches - General Information - 2

Data sheet Date Page INSTRUMENT SELECTION GUIDE The following requirements must be considered when selecting a pressure switch : 1. 2. 3. 4. Working conditions Function required Type of micro switch Area classification These will be analyzed with the possible options for each requirement 1. WORKING CONDITIONS It is important to know the working conditions the gauge will be operating in. Things to consider are: • • • • • Fluid nature Fluid temperature Working pressure Pulsating pressure and vibrations Ambient conditions The switch’s efficiency and life depend on knowing the above conditions....

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Pressure Switches - General Information - 3

Data sheet Date Page 2. FUNCTION REQUIREDD All sensing elements are factory or site configurable. Against traditional instruments with internal counter-reaction spring, this type of instrument warrants a higher sensitivity and offers more configuration possibilities allowing for example: - the use of 2 independent micro switches with fixed differential: With this type of instrument, is possible to operate for example a function of alarm HIGH-LOW alarm or HIGH-HIGH or LOW-LOW (which means 2 micro switches with 2 different set point) with the same instrument - the use of 1 or 2 independent...

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Pressure Switches - General Information - 4

Data sheet Date Page SENSING ELEMENT For the PRESSURE SWITCHES, are used 3 different type of sensing elements. Bourdon tube type Diaphragm Capsule or bellow Bourdon tube pressure switch: the sensing element is a metal tube drawn in elliptical section and shaped in form “C” horse-shore, or spiral. One end is closed while the other is joined to a socket which the process connection is manufactured from. Movement is than transferred to the actuation mechanism of the switch. These instruments are used for high pressure ranges. Diaphragm type pressure switch: The sensing element is a corrugated...

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