Piping analyst

The piping designer needs three essential source documents engineering flow diagrams, nomenclature, and equipment elevations. These documents are usually furnished by the piping analyst. 

The specification group provides the piping analyst with detailed design requirements for the piping, valves, and other piping related equipment. 

The project engineering department furnishes the piping analyst special requirements for all utility and auxiliary systems which are not shown on the process flow diagram. 

To do this, the piping analyst decides on the valves required to meet the process and specification requirements including all the instruments shown on the process control diagrams. He then... 

Understanding the positions of sample and other measurement locations within the equipment is also important. The presence or absence of isolation valves needs to be identified. While isolation valves may be too large for effective sampling, their absence will require that pipe fitters add them such that sample valves can be connected. This must be done in advance of any test. If analysts assume that samples are from a liquid stream when they are vapor or that temperature measurements are within a bed instead of outside it, interpretation of results could be corrupted. Analysts should also develop an understanding of control transmitters and stations. The connection between these two may be difficult to identify at this level in fully computer-controlled units. 

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. 

Intent Plant personnel, supplies, and budget are reqiiired to successfully complete a unit test. Piping modifications, sample collection, altered operating conditions, and operation during the test require advance planning and scheduling. Analysts must ensure that these are accomplished prior to the actual test. Some or all of the following may be necessary for a successful unit test. 

Appendix III contains failure rate estimates for various genetic types of mechanical and electrical equipment. Included ate listings of failure rates with range estimates for specified component failure modes, demand probabilities, and times to maintain repair. It also contains some discussion on such special topics as human errors, aircraft crash probabilities, loss of electric power, and pipe breaks. Appendix III contains a great deal of general information of use to analysts on the methodology of data assessment for PRA. 

The topics of consequence and likelihood analysis are fraught with issues that bring into question the accuracy and usefiilness of the results because so many assumptions have to be made, and because the analysts opinions (many of which are implicit) play such an important role. For example, many fires and toxic gas releases start with a leak from a piping system. Yet the size of the leak could vary from a pinhole to a partially failed gasket all the way to a complete guillotine break... 

Another unit in the same chemical complex supplied the hydrochloric acid via pipe-hne. The acid was a by-product of a process that manufactured large quantities of flashing flaimnable liquids. Supervision directed the crew to promptly collect acid samples and dehver them to the Main Lab to analyze for flammables. Lab analysts did not detect the presence of flammable chemicals. 

Some analysts use 2 and 4-inch holes, regardless of pipe size. 

Some analysts use a range of hole sizes from small to large, such as 0.2,1,4 and 6 inches and full bore ruptures for pipes less than 6 inches in diameter. 

Some analysts use more detailed procedures. They suggest that 90% of all pipe failures result in a hole size less than 50% of the pipe area. The following approach is suggested ... 

---