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PT Notes

PHA Practices to Avoid - Improper Worksheet Entries

PT Notes is a series of topical technical notes on process safety provided periodically by Primatech for your benefit. Please feel free to provide feedback.

This PT Note is the third in a series to help you ensure your PHA studies follow best practices. Poorly conducted studies expose companies to regulatory and legal liabilities that can cost millions of dollars.

PHA Practitioners should avoid making worksheet entries that can create problems. Several cases are discussed in this PT Note.

Avoid Blank Entries

Generally, blank entries should be avoided in PHA worksheets. For example, if no causes, consequences, safeguards, etc. can be identified, rather than leaving a blank space, an entry such as “None identified”, “None”, or “None identified within the project charter” should be made. Otherwise, reviewers may believe that entries have been omitted inadvertently. A possible exception is when documenting recommendations and the scenario risk value is such that a recommendation for risk reduction is not needed. Some practitioners leave the worksheet blank in such cases although an entry such as “No recommendations required” is preferable which makes report review easier.

Of course, after a “None identified” type entry in columns such as Causes and Consequences, the remaining columns are left blank as there is no hazard scenario to document. However, after a “None identified” type entry in some other columns, such as Safeguards, they may be followed by entries in the remaining columns.

Avoid Most Abbreviations as Permanent Entries

Abbreviations and acronyms are commonly used by PHA study scribes to speed up data entry and because team members use them in discussing the process. However, they should be avoided as permanent worksheet entries unless they are common knowledge and unambiguous. For example, “PSV” generally is understood to mean Pressure Safety Valve in many cases. However, it can also mean Platform Supply Vessel (a ship specially designed to supply offshore oil and gas platforms) in other cases. PHA study team members may understand the use of a particular abbreviation or acronym, but others who subsequently read the PHA report may not. Of course, abbreviations that are part of tag numbers are acceptable in worksheet entries such as Relief Valve, PSV- 22.

Other abbreviations and acronyms may cause confusion within a team, for example, those that have multiple meanings such as “MOC”, which can mean Management of Change or Materials of Construction; “ESD”, which can mean Electrostatic Discharge or Emergency Shutdown; and “MMA”, which can mean Methyl methacrylate or Monomethylamine. Similarly, different abbreviations and acronyms may mean the same thing, for example, heat exchanger may be designated as “HE” or “HX”.

If abbreviations and acronyms are used, they should be added to a reference list as a study proceeds. Temporary abbreviations used to speed up data entry should be replaced subsequently with their full terms before PHA worksheets are finalized.

Avoid Inconsistent Equipment Descriptions

PHA practitioners should avoid using different terms for the same equipment. For example, team members may also refer to a fractionator as a column, splitter, tower, or
still; a receiver as an accumulator or drum; and a reactor as a pot, kettle, or vessel. Use of different terms for the same equipment can confuse not only team members but also reviewers of PHA worksheets. Furthermore, it complicates analysis of worksheets when multiple pieces of equipment appear to be present when in reality only one piece exists.

Avoid Incomplete Entries

Sometimes entries must be left incomplete until additional information becomes available. For example, when the downstream process is studied to identify causes of back pressure upstream, or missing information must be researched, such as the reactivity of process chemicals under abnormal conditions. Such entries should be marked so that they can be found easily later and edited, if necessary. Incomplete entries must not become permanent in PHA worksheets.

Avoid Repeating Scenarios

The same hazard scenario should not be recorded in different places in PHA worksheets. It opens the team to repeated discussion of the same issue that wastes time, complicates modifying details of the scenario in the worksheet when needed, and clutters the worksheet. Instead, a reference to the first instance of the scenario should be inserted. For example, a scenario may be identified when examining temperature deviations in a node for a HAZOP study and then the same scenario is identified when discussing pressure deviations in the node. To avoid repetition, an entry such as “See Temperature, Cause 1, this node” should be made.

Avoid Extraneous Entries

PHA practitioners should avoid making extraneous worksheet entries and should consider whether entries are really warranted. PHA worksheets should not be used as electronic scrap paper. Extraneous worksheet entries can raise issues unnecessarily during review and obscure appropriate entries. Scribes should not make “joke” entries in the worksheet intended for later removal, for example, “The world as we know it will cease to exist”. They may be left in inadvertently and create public relations and legal issues.

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