P IDs

The layout can only be started after a process flow diagram is available. The process flow diagram includes information such as the principal equipment items and order of the process flow. A sized equipment Hst is also useful from the standpoint of knowing what spaces are required to fit the equipment. Availabihty of a preliminary piping and instmmentation drawing (P ID) provides more information to aid in spacing equipment and thinking about piperack requirements. 

P IDs (piping and instrumentation diagrams) should identify instruments, sample locations, the presence of sample valves, nozzle blinding, and control points. Of particular importance are the bypasses and alternate feed locations. The isolation valves in these hues may leak and can distort the interpretation of the measurements. 

Unit layout as installed is the next step of preparation. This may take some effort if analysts have not been involvea with the unit prior to the plant-performance analysis. The equipment in the plant should correspond to that shown on the PFDs and P IDs. Wmere differences are found, analysts must seek explanations. While a hne-by-line trace is not required, details of the equipment installation and condition must be understood. It is particularly useful to correlate the sample and measurement locations and the bypasses shown on the P IDs to those ac tuaUy piped in the unit. Gas vents and liquid (particularly water-phase) discharges may have been added to the unit based on operating experience out not shown on the P IDs. While these flows may ultimately be small within the context of plant-performance an ysis, they may have sufficient impact to alter conclusions regarding trace component flows, particularly those that have a tendency to build in a process. 

Sampling locations for the unit test should be readily and safely accessible. The sample gatherer should be able to easily access the sample point. An isolation valve should be installed at the location. If a blind is installed, this should be modified in advance of the test. The sample locations shown on the P IDs must be compared against the actual locations on the equipment. Experienced operators may provide insight into the suitability of the location in question. 

Piping and Instrument Diagram (P ID) A diagram that shows the details about the piping, vessels, and instrumentation. 

Have appropriate revisions been made to process safety information, P IDs, and operating procedures ... 

Other current data such as written reports, memos, instruction sheets, P IDs... 

Small businesses eovered by this rule often will have proeesses that have less storage volume and less eapaeity, and may be less eomplieated than proeesses at a large faeility. Therefore, OSHA would antieipate that the less eomplex methodologies would be used to meet the proeess hazard analysis eriteria in the standard. These proeess hazard analyses ean be done in less time and with fewer people being involved. A less eomplex proeess generally means that less data, P IDs, and proeess information are needed to perform a proeess hazard analysis. 

For new processes, the employer will find a PHA helpful in improving the design and construction of the process from a reliability and quality point of view. The safe operation of the new process is enhanced by making use of the PHA recommendations before final installations are completed. P IDs should be completed, the operating procedures in place, and the operating staff trained to run the process, before startup. The initial startup procedures and normal operating procedures must be fully evaluated as part of the prestartup review to ensure a safe transfer into the normal operating mode. 

Piping and Instrument diagrams (P IDs - not shown) may be even more appropriate for showing these details and to provide information for PSA. The P IDs are used to describe the relationships between equipment and instrumentation and other relevant information that enhances clarity. 

PrH A improves the safety, reliability and quality of the design and construction of a new or old process. P IDs must be correct as constructed operating, startup and shutdown procedures must be validated, and the operating staff must be trained before startup. Incident inr estigation recommendations, compliance audits or PrHA recommendations need resolution before startup. 

Step I Defining the System - Collect the information needed to perform the analysis. Information needs include system descriptions, schematics, P IDs, logic diagrams, and operating procedures. Step 2 Establishing Inputs/Outputs - Every GO model begins with at least one input aiul may have many interfacing inputs. The output of the model is determined by the success criteria. 

P Eautt tree. Event tree, and Eiping and instrumentation diagram (P ID) graphically develops and edio leuu inr -. event trees, and P tDs. 

FEP, fault tree, gvent tree and piping instrumentation diagram (P ID) editor, accesses ihe package of graphical tools for risk assessment. These tools include the event tree, fault tree and P ID graphical editors. The event tree and fault tree editors are in PSAPACK the P ID editor is in FEP. The event tree editor is used for graphical construction and modification of event trees. The fault tree editor does the same for fault trees the P ID editor does the same for construction and modification of P IDs used in a PSA. 

Make sure your company s short-term objectives (e.g., updating aii P IDs) are consistent with broader PSM goais (e.g., accurate process safety information), sind communicate them in ways that clearly encourage work habits and procedures that support PSM performance. For exampie, your employees need to understand that the company will achieve its goal of reducing reportable incidents by changing its PSM procedures, not its reporting processes. 

Process knowledge and documentation Define P IDs needed Establish management system for future updates... 

Similarly, if you consider the preparation and updating of P IDs as a process, customers would be those employees who use P IDs for engineering, design, or training. Suppliers would be all personnel (engineering, operations, others) who have responsibility for assuring the accuracy and dissemination of P lDs. 

FIGURE 5.1 Flammable Liquid Storage Tank P ID (from Ozog, 1985). 

This phase is where the basic design work, such as process flow design, is performed. Piping and instrumentation diagrams (P IDs) and equipment... 

---