Add or select a valve to start.
Check relief valve sizing, inlet loss and back pressure, then compile a valve booklet, per API 520 and 521.
Add or select a valve to start.
Select a valve.
Add a tag for each pressure safety valve, then follow the numbered steps with the Next and Back buttons to enter the installed data: set pressure, orifice and type, connection sizes, the protected equipment and its MAWP, the fluid at relieving conditions, the inlet and outlet pipe runs with their fittings, any isolation valves with their lock or car seal position, and the overpressure scenarios of API 521 Table 1.
The tool calculates the relieving rate for each credible gas or vapor scenario (blocked outlet with a compressor, control valve wide open or gas blowby, fire on wetted or gas filled equipment, or a rate you import from a simulator), sizes the orifice per API 520 Part I and compares it with the installed valve, on the effective API 526 basis and on the certified basis (actual area and certified Kd) without mixing the two.
It then checks the piping and installation: inlet loss against 3% of set pressure at rated flow (API 520 Part II 7.3.4), built up and total back pressure from the outlet line with Crane TP 410 fitting losses and compressible flow to the exit (API 520 Part II 6.3.1), isolation valve rules (API 520 Part II 8), and set pressure and accumulation limits (ASME VIII-1 UG-153, UG-155). Every finding shows its clause and a recommended action, and each valve gets a status of PASS, REVIEW, FAIL or INCOMPLETE.
Outputs are a booklet per valve with an arrangement schematic drawn from your data, a facility summary and action list on screen, a revision log, and a comparison of any two revisions that lists the changed inputs and results for management of change. Liquid, two phase and steam relief are flagged as outside the scope of the tool.
Gas and vapor relief only. Results are for review by the engineer of record and are not a certification. Saved projects are kept encrypted on this site for 30 days after your last save or open, then deleted.
It checks that the installed relief valve can pass the required rate and that the piping around it does not defeat it: the required orifice area for the governing scenario against the installed orifice, set pressure and accumulation limits (ASME VIII-1 UG-153 and UG-155, API 520 Part I Table 4), inlet pressure loss, built up and total back pressure for the valve type, isolation valves locked or sealed open, and the documentation of each overpressure scenario. The result is a status per valve and a list of findings, each with its code reference.
API 520 Part II 7.3.4 and ASME VIII-1 Appendix M-6 limit the non recoverable pressure loss between the protected equipment and the valve inlet to 3% of the valve set pressure, calculated at the rated capacity of the valve. Losses above 3% call for an engineering analysis (API 520 Part II 7.3.6) because the valve can chatter and its capacity is reduced (7.3.2). The tool builds the loss from your inlet pipe lengths, sizes and fittings using Crane TP 410 resistance coefficients.
For a conventional spring loaded valve the built up back pressure is limited to the allowable overpressure, about 10% of set pressure for a valve set at MAWP with 10% accumulation (API 520 Part I 5.3.3.1, ASME VIII-1 Appendix M-9(c)). A balanced bellows valve is typically good for total back pressure up to about 50% of set pressure, but the manufacturer decides. On a pilot operated valve the back pressure does not affect lift. The tool calculates the back pressure from your outlet line with compressible flow, where the exit pressure is ambient or the choking pressure (API 520 Part II 6.3.1).
Gas and vapor service. It calculates blocked outlet with a compressor or a known inflow, control valve wide open or gas blowby (ISA 75.01.01 flow equations), fire on liquid wetted equipment (API 521 Equations 7, 8 and 23) and fire on gas filled equipment (Equations 10 to 14), or takes a rate you enter or import. Liquid, two phase and steam relief, hydraulic expansion and tank venting are flagged as outside the tool and no valve size is calculated for them.
Ten sections for each valve: the valve data sheet, the protected system with an arrangement schematic of the inlet piping, isolation valves and outlet piping drawn from your inputs, the scenario table (API 521 Table 1), the governing case and sizing, the installed device with a comparison to vendor values, the inlet line, the outlet line and back pressure, isolation valves and installation checks, a pass and fail summary with items for the engineer, and the references and assumptions the tool supplied. It opens as a print ready page you can save as a PDF.
Your entries are calculated on the site's server for each result but are not stored there unless you choose to. They autosave in your own browser. Save to the vault stores the project encrypted on the site for 30 days after you last save or open it and gives you a 5 digit PIN; the PIN is the only way to open it and nobody can recover a lost one. The PIN is short, so treat the vault as light protection. Do not put anything in a project that you are not allowed to store with a third party.
Issue a revision when the data is ready: it freezes the valve data with who prepared it and why it changed. After a change, compare the issued revision with the working copy. The tool recalculates both and lists every changed input and the effect on the required rate, area, utilization, inlet loss and back pressure, with new and resolved findings. The change report carries the blank lines for the technical basis, safety impact and authorization that management of change under 29 CFR 1910.119(l) asks for.
No. It is a validation aid that shows how the entered data measures against the cited standards and compiles the documentation. Results, assumptions and any value the tool supplied must be reviewed by the engineer of record, and the tool does not stamp or certify anything.