PRVs by Others

1. Purpose

This procedure summarizes Inflection Point Engineering’s practice for Pressure Relief Valves (PRVs) designated “BY OTHERS” on Inflection Point Engineering’s P&IDs.

2. General

Inflection Point Engineering has been designating specific PRVs “BY OTHERS” on our P&IDs since 2000. This practice started as a result of a policy change to stop specifying thermal expansion and proportioning pump protection PRVs. Many customers perceive relief analysis for these and similar types of PRVs as a routine activity that is better performed by a contractor.

3. Equipment to be shown with a PRV designated “BY OTHERS”

Unless the Engineering Agreement states otherwise, designate a PRV “BY OTHERS” on the P&ID for the following equipment types and relief cases. For a PRV designated “BY OTHERS”, do not list an item number on the P&ID, or issue an 807 specification.

Heat exchangers: external fire and thermal expansion relief cases only. (If the exchanger needs protection against tube rupture by a PRV, tube rupture analysis is still required. If the exchanger and LP system are designed to the ten-thirteenths rule, the tube rupture relief case is eliminated as a sizing case. Reference Procedure .)

Water coolers and condensers: cooling water – external fire and thermal expansion relief cases only.

Turbine exhaust service: blocked outlet relief case.

Positive displacement pump (proportioning and reciprocating) protection service: blocked outlet relief case.

Feed filters, coalescers, and other such equipment items that are to be sized by vendors based on a duty specification. The typical relief scenario is external fire. Contractor will also need to evaluate other relief cases e.g. blocked outlet, once all the equipment has been procured.

Other equipment items or categories for which Inflection Point Engineering has agreed with the customer that we will not perform the relief analysis or the PRV sizing and selection.

Contractor will reference other Inflection Point Engineering Project Specifications to obtain design conditions and equipment metallurgy for the above PRV services. The contractor may need to reference EDI information for relevant process stream compositions to generate appropriate relief conditions.4. P&ID Representation

• Draw an arrow pointing to the PRV and indicate PRV (BY OTHERS). If the PRV needs Monel trim because it is in wet chlorides service, add an “M” designation at the PRV.

The discharge location shall be shown on the P&ID in accordance with Procedure IPE-TM-807-04, Attachment 8.

General Note

The following General Note should be used in the 807 Project Specification (see latest version of tool ):

“Equipment items that can be blocked-in require overpressure protection using a PRV or administrative controls to prevent overpressure due to fire, thermal expansion, or blocked outlet. If there is a PRV shown “By Others” at an equipment location on Inflection Point Engineering’s P&ID, it is the responsibility of the customer and/or contractor to determine the method of overpressure protection, determine the relief loads based upon purchased equipment, and size any PRVs found necessary.”