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The scope of our service includes PSV Sizing pressure relief valve sizing and the pressure relief system sizing calculation based on API 521/520/2000 standard and ASME code. Storage tank pressure and vacuum relief valve sizing is also one of our services. In details, PSV Pressure relief valve sizing calculation will be performed for every possible pressure relief scenarios (Fire, Blocked Discharge, Reflux Failure, Thermal, Abnormal Heat Input, Split Tube In Exchanger, Auto Control Failure, Power Failure, Instrument Air Failure, Valve Left Open, Steam Out, Equipment Failure, Heat Loss, Chemical Reaction etc.) According to calculation results, the PSV datasheet and specification will be developed based on the controlling scenario. The type of PSV pressure relief valves required will be specified also. It could be a Conventional PSV, Balanced Bellows PSV, Pilot Operated PSV, a Rupture Disk with or without a PSV and so on. In the PSV sizing calculation, pressure drop of the PSV inlet and outlet header will be calculated so that the PSV can be sized and selected properly. Flare header, knock out drum, vent stack or flare stack calculation and design will be performed if required. In case that multiple PSV discharge to a common header of a relief system, a detailed analysis of the relieving load for various global relieving cases (unit wide or plant wide power failure, instrument air failure, cooling water failure and so on) will be performed. Flare header, knock out drum, vent stack or flare stack calculation and design will also be performed if required. Determining PSV superimposed back pressure and built-up back pressure is an important step in PSV sizing and relief system design.
Doesn’t matter if it is a new PSV design or an existing PSV verification, they are all in our service scope. If PSV already exist but plant operating conditions have changed or process equipment have changed, we can verify if the existing PSV orifice sizes are big enough or not with the calculations mentioned above. If we can then suggest the required PSV changes or required relief system changes.
New flare stack design and existing stack verification can also be provided if required. By calculating the flare radiation the required stack height can be determined. In case that an existing stack does not meet the height requirement, a mitigation measure will be suggested, such as water spray, shields and so on.
Relief Valve Sizing Projects
Hundreds of various types of relieve valves have been sized, specified, purchased and installed with our help in the past 20+ years. A number of flare systems has been installed or revamped in refinery, gas plant, chemical plant, oil field and so on. Some projects are as small as a single PSV sizing, other projects are as big as a large flare system in a refinery. For details of some of our PSV pressure relief valve sizing and relief system design projects, please click here.
In the execution of a project, typically we starts with information collection, such as collecting related and up to date P&ID and Piping ISO drawings, equipment and instrument datasheet and specification, actual plant operating conditions, everything related to the pressure relief valve and relief system. Sometimes site visit is required in order to verify some important information. At the same time, client will be contacted to clarify the requirement of the project. At the very beginning of a project we will make ourselves clearly understand what is the the project design basis and what is the scope of work of the project. This is very important and we pay a lot of attention to this first step. It help us maintain a high quality score and minimize rework that in turn made all our projects on schedule and on budget.
With the accurate information and a good understanding to client requirement, our experienced engineers can normally finish the calculation and project design quickly and easily. As you know our engineers have performed the similar calculation and design numerous times. What we need to do is simply going through the sizing and design procedures applied to this specific project and make sure the correct calculation method is used according to API standard and ASME code. Even if there is some unusual issue need a study in the project, our engineers can typical get a solution pretty quick. Our engineers have all the tools and expertise to find a solution to any difficult issue.
The final step in the project execution is another very important step to us, and many other companies do not pay a lot of attention to it. This step is to perform document checking and quality assurance and control. It is our believe that any person can make mistake. A very good engineer can also make a mistake some time. All design document must be checked and all calculation must be verified. We will not allow any design document being delivered without going through a strict review and checking process. This is another reason why our projects were 100% success without any rework.
Deliverables
Relief valve sizing and flare system design is a comprehensive task that requires a lot of calculations also generates many document. All these calculation and document will be delivered to project owners not only for the purchase and construction of the project, but also for future reference in case any further changes are required in the future. Document is also required for regulation compliance purpose. Depending on the specific scope of a project, here are some typical document being prepared and delivered:
- PSV sizing calculation report for each PSV. In the report is the detailed calculations of each PSV with up to 15 calculations of different scenarios. The report also identify the control scenario that the PSV selection is based on.
- PSV datasheet or specification for each PSV. In the datasheet the requirement of the PSV is specified based on the control scenario. PSV datasheet or specification is typically used in RFQ (request for quotation) for PSV purchase.
- PSV list. A summary list of all PSV required in this project.
- PSV quotation. If requested, we can obtain PSV quotations from qualified PSV manufactures.
- Relief system calculation report. It summarize the calculation of the relief system including gas velocity in relief headers, back pressure at each piping branches, relief header sizes, knock out drum dimension, flare stack or vent stack dimension, all other information required for relief system design and installation.
- Equipment datasheet for required equipment in relief system.
- Equipment list. A summary of all equipment required in the project.
- Instrument datasheet for instrument required in the project.
- Instrument list. A summary of all the instrument required in the project.
- Related drawings and document
In addition to sizing the PSV, we also help our client to find the best solution to address the pressure relief issues. Sometimes the best solution to a PSV capacity problem is not necessary to replace the PSV. Similarly, the best solution to a relief system capacity problem is not necessary to expand the relief system. With our extensive experience and know how, we have help our client saved millions of dollars by providing our client the most economic solution while making sure that the PSV and relief system meet all the API standard and ASME code requirement.
Since we have performed PSV sizing and relief system design so many times, it wouldn’t take us much time to size a PSV and suggest you the best solution. This in turn can save you a lot of engineering cost and the total project cost. Please contact us if you have only one single PSV need to be looked at, or you have a complicated relief system need to be looked at. If you have any questions or need any help, please feel free to contact our engineer for a free consultation.
