Pressure Switches

IPE Engineering Practice IPE-EP-12-1-20

Document number: IPE-EP-12-1-20 · Section: 12 — Instruments and Controls

SCOPE

This Practice contains detail requirements for pressure switches.
Any deviation from this Practice must be approved by the procedure described in EP 1–1–3.
A revision bar indicates all changes made to this Revision.

2.0 REFERENCES

The following codes and standards shall be considered as part of this Practice. All documents shall be the latest editions in force on the date of issuance of this Practice.

STANDARDS AND PUBLICATIONS

IPE Engineering Practices
EP 1–1–3 Deviations to IPE Engineering Practices EP 12–1–1 Control Systems EP 12–1–2 Supplemental Requirements for Control Systems EP 12–1–20 DS Pressure Switches Data Sheet
ASME
B 1.20.1 Pipe Threads General Purpose (Inch)
NEMA
ICS 6 Enclosures for Industrials Controls and Systems
NFPA
70 National Electrical Code

DEFINITIONS

Contractor - Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
Inspector - A Inflection Point Engineering, LLC appointed engineer or inspector.
Manufacturer - The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a manufacturer by a contractor or the Owner. An indirect order is one issued to a manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
Owner - Inflection Point Engineering, LLC.
Owner’s Engineer - A Inflection Point Engineering, LLC appointed engineer.
Purchaser - The party placing a direct purchase order. The purchaser is the Owner’s designated representative.

DESIGN AND MATERIALS

General
The equipment shall consists of an actuating element with a switch or switches enclosed in a case or housing.
Switches shall consists of one or more sets of contacts. The contact form and rating shall conform to the Data Sheet EP 12–1–20 DS.
Pipe threads shall be tapered and shall conform to ASME B1.20.1
Design materials not specified shall be in accordance with the manufacturer’s standards suitable for the operating and design conditions specified on the Data Sheets. Manufacturer’s shall inform the purchaser of the suitability of the materials for the service specified.
Direct connected type pressure switches shall preferable be designs that preclude entrance of process fluids into the conduit. Switches should meet the requirements of Paragraph 501-5 (f)(3) of the NEC.
As a minimum, housings shall be of the following Types as defined in NEMA ICS 6:
Housings for pneumatic receiver type switches in non-hazardous areas (as noted on the Instrument Data Sheet), may be general purpose equivalent to NEMA Type 1.
All other housings shall be suitable for the NEC class as specified on the Data Sheet.
Switch contact material should be of noble metal.
Direct Connected Pressure Switches
Actuating elements for directed connected pressure switches shall be snap acting diaphragm or bourdon tubes, arranged to operate the contacts per the range specified on the Data Sheet.
All wetted parts of element housing shall be type 316 stainless steel material unless otherwise specified on the Data Sheet.
Seal diaphragms and ”O” rings materials shall be suitable for the process fluid and other service conditions as specified on the Data Sheet.
Pressure switches shall be designed for the design temperature and pressure specified on the Data Sheet.
Pressure setting values for the range specified should be indicated on a calibrated scale.
When specified, diaphragm seal devices for isolating the actuating element from the process fluid shall be of the direct mounted type, designed to permit cleaning without removal of the diaphragm or loss of fill liquid.
Diaphragm seal devices shall be furnished completely assembled with the pressure switch.
Pressure connections in the bottom of housings shall be internally threaded 3/4 inch NPT.
Diaphragm shall be stainless steel: diaphragm rings and bottom bowls shall be carbon steel unless service conditions dictate the use of other materials.
The entire system between the diaphragm and the bourdon tube shall be filled with an inert liquid (i.e. silicone) suitable for a temperature range of at least 0 to 400oF.
Pneumatic Receiver Switches

Actuating elements for pneumatic switches shall be spring opposed bellows, diaphragm, or bourdon tubes arranged to operate the contacts with a maximum dead band pressure differential of approximately 0.5 psi. The pneumatic input range is normally 3 to 15 psig. The adjustable switch range shall be at least 2 to 16 psig.

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