Pressure Switches Material Selection Criteria & Design

This article is about Pressure Switches Material Selection Criteria & Design For Pressure Measurement of Instrumentation and Control Systems as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.

Pressure Switches Material Selection Criteria & Design

Material Receiving General Checklist for Instrumentation & Control

General Requirements

Purchase Order and Instrument specification sheet criteria shall be confirmed and compared with instrument stainless steel tags / labels and nameplates, and shipment checked for damage, prior to acceptance of the shipment
Verify that all the instruments are from technically acceptable vendors. (Attachment 1)
All instrumentation purchases from manufactures that are not technically acceptable vendors, a request for technical evaluation, with justifications, shall be submitted in writing to the General Supervisor, Process Instrumentation Division, P&CSD.

“Pressure switches containing electrical contacts shall be in accordance with the specified electrical area classification.
Comment: Hermetically sealed contacts are preferred.
[PIP PCCPR001, Sec.4.3.1 April 2007]”
Pressure switches shall be selected to operate in a range that allows switch actuation to take place above the midpoint to ensure greatest accuracy. [PIP PCCPR001, Sec.4.3.2 April 2007]
Pressure switch deadband shall be compatible with the application. (when the process runs close to the switch setting, a large deadband may prevent the switch from resetting after the trip has cleared). [PIP PCCPR001, Sec.4.3.3 April 2007]
Instruments and control systems shall operate continuously under the following ambient air temperatures without any degradation of the manufacturer’s guaranteed performance:

“As a minimum, all pressure devices shall be specified with over-range protection to 1-1/2 times the maximum system operating pressure.
[PIP PCCPR001 Sec 4.1.4 April 2007]”
Materials selection for pressure device wetted parts shall be type 304 or 316 stainless steel with TFE gaskets, unless other materials are required by process. [PIP PCCPR001 Sec 4.1.7 April 2007]
Switch Process side connections shall be 1/2 inch NPT. Connections for pneumatic tubing shall be 1/4 inch NPT female, minimum. Electrical conduit connection shall be 1/2 inch or 3/4 inch NPT.
Electric switch contacts shall be snap acting, single-pole, double-throw (SPDT) as a minimum. The contact rating shall be sufficient to operate solenoids, relays, or other devices as specified in the data sheet without the need for additional or interposing relays. Hermetically sealed switch contacts are preferable.
Switch actuation, as the result of increasing or decreasing pressure must be specified.

International Codes and Standards for Pressure Switches Material

1. Flow Nozzle Material Selection Criteria Design & Flow Measurement
2. Venturi Tube Material Selection Criteria Design & Flow Measurement

3. SAES-J-002 -Technically acceptable instruments, 23 June 2008
4. SAES-J-003 – Instrumentation Basic Design, 16 January 2008
5. SAES-J-200 – Pressure, 18 May 2008
6. PIP PCCPR001 – Pressure Measurement Criteria.

1. Attachment 1: Approved Vendor list SAES-J-002.