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PSV Datasheet — API 520 / 521 / 526

กรอกครั้งเดียว: sizing (API 520-I) + ΔP ทางเข้า/ออก + แรงปฏิกิริยา (API 520-II) → ใบสเปกครบ

Relieving Case — API 520-I Sizing
Line ΔP — API 520-II
ผู้ช่วยวิเคราะห์ (Design assistant)
PASSAll PSV gas/vapor design checks pass for the entered conditions.
PassOrifice adequacy (API 526)Letter M (+20.7 %)

Letter M (2323 mm²) fits with 20.7 % margin over the required area 1924 mm² — adequate spare capacity for the entered sizing assumptions.

PassInlet ΔP — 3 % rule (API 520-II §4)2.5 % of set

Non-recoverable inlet-line pressure loss 2.5 % of set is within the API 520-II 3 % limit. Chatter and rapid-cycling risk is managed at the current inlet-line geometry.

PassBuilt-up backpressure (API 520-II §7, limit 16 %)8.3 % of set

Built-up backpressure 8.3 % of set is within the 16 % limit for this valve type. The outlet piping resistance does not impair valve lift or certified capacity.

InfoReaction force — open discharge (API 520-II §7.3)3605 N (3.60 kN)

Open-discharge reaction thrust: F = 3605 N (3.60 kN). This is a substantial force that will generate a significant bending moment on the outlet elbow and inlet nozzle — pipe support / sway brace design is required (API 520-II §7.3 / API 521 §5.5).

OVERALL PASS ✓ — API 520-II
Inlet ΔP: 2.5 % of set (limit 3 %) · Built-up BP: 8.3 % of set
API 520-I — Orifice Sizing Result
Required A_req
1923.6 mm²
API 526 Letter
M
Selected area
2322.6 mm²
Margin
+20.7 %
Gas/vapor — choked (critical) · Kb = 1.000 · Kd = 0.975
Lettermm²MarginStatus
K1186-38 %✗ เล็กเกินไป
L1841-4 %✗ เล็กเกินไป
M2323+21 %✓ แนะนำ
N2800+46 %⊕ ใช้แทนได้
P4115+114 %⊕ ใช้แทนได้
API 520-II — Line ΔP + Reaction Force
WARNInlet ΔP: 2.5 % of set (limit 3 %)
ΔP = 30.0 kPa — non-recoverable inlet pressure loss (API 520-II §4)
PASSBuilt-up BP: 8.3 % of set (limit 16 %)
Outlet ΔP = 100.0 kPa — Conventional: 16 % API limit, 10 % rule-of-thumb (API 520-II §7)
Reaction force (open discharge) — API 520-II §7.3
Sonic exit velocity V521.4 m/sMomentum Ẇ·V3515 NPressure term (P₂−Pₐ)·A₂90 NTotal force F3605 NBending moment M1802 N·m
ใบสเปก PSV ครบวงจร — API 520-I / 520-II / 526 (ดาวน์โหลด PDF)
Sizing + ΔP ทางเข้า/ออก + แรงปฏิกิริยา ใส่ไว้แล้ว — ช่องเอกสาร/วัสดุ/vendor แก้ไขได้ก่อนออก RFQ
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PSV / PRESSURE RELIEF VALVE — EQUIPMENT DATASHEET
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PSV / PRESSURE RELIEF VALVE SPECIFICATION SHEET
API 520 / 521 / 526
Rev.0
Customer
Job Name
Location
Job No.
Item Name
Item No.
Type
No. of Req'd
Size
Manufacturer
OPERATING CONDITION
Fluid / Service
Operation
Material Feature
Installed Place
Operating Temperature (°C)
Operating Pressure
Corr. / Eros. caused by
SPECIFICATION
Code Requirement
Body — material
Set Pressure
Trim — material
Overpressure (%)
Bonnet
Back Pressure
Cap
Discharge Coeff. Kd
Inlet Flange
API 526 Letter (selected)MOutlet Flange
Required orifice (mm²)1923.56Selected orifice (mm²)2322.57
Stress Relieved
Radiograph
Accessories
Spare Parts
Remarks
DekEn-PSV-DS / Rev.01
ประกาศใช้วันที่: 2026-08-30
DekEn
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PSV / PRESSURE RELIEF VALVE SPECIFICATION SHEET
API 520 / 521 / 526
Rev.0
RELIEVING CASE / SIZING (API 520-I)
Sizing modeGas / Vapor (API 520-I §5.6)Relieving temperature60.0 °C
Relief mass flow (required)24270.0 kg/hMolecular weight / k / Z44.0 g/mol · k = 1.130 · Z = 1.000
Set / Relief pressure12.000 / 13.200 bargBack pressure / Kb1.013 barg · Kb = 1.000
Flow regimeChoked / sonic flow (critical)Kd0.975
Required orifice A_req1923.558 mm²API 526 letter selectedM
Selected orifice area2322.57 mm²Margin vs A_req20.7 %
Sizing basis
Gas/vapor: API 520-I §5.6. Critical: A = W/(C·Kd·P₁·Kb·Kc)·√(T·Z/M). Subsonic: API 520-I Eq 7 with F₂ correction.
INLET / OUTLET ΔP + REACTION FORCE (API 520-II)
Inlet line ΔP (non-recoverable)30.0 kPa (2.5 % of set) — PASS ✓Limit≤ 3 % of set pressure (API 520-II §4)
Built-up backpressure (outlet ΔP)100.0 kPa (8.3 % of set) — limit ≤ 16 % — PASS ✓Valve type for limitConventional spring-loaded
Open-discharge reaction force F3605 NElbow bending moment M1802 N·m
Reaction formula
F = (Ẇ/g_c)·V + (P₂ − P_a)·A₂ — API 520-II §7.3 (open discharge). g_c = 1 (strict SI). Bending moment = F × lever arm.
SELECTED VALVE
API 526 letter / areaM (2322.57 mm²)Valve styleConventional spring-loaded
Overall verdictOVERALL PASS — inlet ΔP ≤ 3 % + built-up BP within limitInlet ΔP / Built-up BP2.5 % / 8.3 % of set
Set / leak test
Certification
TESTING & REFERENCES
References
API RP 520 Part I (orifice sizing — gas §5.6; steam §5.7); API RP 520 Part II (installation — inlet 3 % §4; built-up BP §7; reaction force §7.3); API STD 521 (disposal / flare sizing); API STD 526 (PSV dimensions + letter sizes); API STD 527 (seat-leak test); ASME VIII Div.1 UG-125. เครื่องคำนวณช่วยตั้งต้น — วิศวกรผู้ออกแบบและผู้ผลิตต้องตรวจสอบและรับรองก่อนออกเอกสาร.
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ดูเวอร์ชันข้อความ (สำหรับวางในอีเมล)
=== PSV DATASHEET (API 520-I + 520-II + API 526) ===
API 520 / 521 / 526

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CUSTOMER         : —
DOC NO. / REV    : — / 0
BY DEKENGINEER.COM
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DATE / OWNER     : 2026-08-30 / —
CUSTOMER PROJ NO.: —
DEKEN PROJECT NO.: —


-- 1. OPERATING CONDITION --
Fluid / Service               : Gas / Vapor
Operation                     : Continuous process
Material Feature              : —
Installed Place               : —
Operating Temperature (°C)    : —
Operating Pressure            : < 12.00 barg (set pressure)
Corr. / Eros. caused by       : —

-- 2. SPECIFICATION --
Code Requirement              : API STD 526 (dimensions); API RP 520-I (sizing); API RP 520-II (installation); API STD 521 (disposal); ASME VIII Div.1 UG-125
Body — material               : ASTM A216 WCB (CS) / A351 CF8M (SS) per service
Set Pressure                  : 12.24 kg/cm²G  (12.000 barg)
Trim — material               : SS 316 / SS 316 nozzle + disc
Overpressure (%)              : 10
Bonnet                        : Open bonnet (gas/steam service)
Back Pressure                 : 1.03 kg/cm²G  (1.013 barg)
Cap                           : Plain cap (non-adjustable)
Discharge Coeff. Kd           : 0.975
Inlet Flange                  : API 526 letter M inlet
API 526 Letter (selected)     : M
Outlet Flange                 : API 526 letter M outlet
Required orifice (mm²)        : 1923.56
Selected orifice (mm²)        : 2322.57
Stress Relieved               : [ ] Yes  [X] None
Radiograph                    : [ ] Full  [ ] Spot  [X] None
Accessories                   : Inlet block valve (CSO); outlet to flare/safe location; tail-pipe support; isolation tag.
Spare Parts                   : Seat/disc kit; spring (set-point specific); gasket set.
Remarks                       : —

-- 3. RELIEVING CASE / SIZING (API 520-I) --
Sizing mode                   : Gas / Vapor (API 520-I §5.6)
Relieving temperature         : 60.0 °C
Relief mass flow (required)   : 24270.0 kg/h
Molecular weight / k / Z      : 44.0 g/mol · k = 1.130 · Z = 1.000
Set / Relief pressure         : 12.000 / 13.200 barg
Back pressure / Kb            : 1.013 barg · Kb = 1.000
Flow regime                   : Choked / sonic flow (critical)
Kd                            : 0.975
Required orifice A_req        : 1923.558 mm²
API 526 letter selected       : M
Selected orifice area         : 2322.57 mm²
Margin vs A_req               : 20.7 %
Sizing basis: Gas/vapor: API 520-I §5.6. Critical: A = W/(C·Kd·P₁·Kb·Kc)·√(T·Z/M). Subsonic: API 520-I Eq 7 with F₂ correction.

-- 4. INLET / OUTLET ΔP + REACTION FORCE (API 520-II) --
Inlet line ΔP (non-recoverable): 30.0 kPa (2.5 % of set) — PASS ✓
Limit                         : ≤ 3 % of set pressure  (API 520-II §4)
Built-up backpressure (outlet ΔP): 100.0 kPa (8.3 % of set) — limit ≤ 16 % — PASS ✓
Valve type for limit          : Conventional spring-loaded
Open-discharge reaction force F: 3605 N
Elbow bending moment M        : 1802 N·m
Reaction formula: F = (Ẇ/g_c)·V + (P₂ − P_a)·A₂ — API 520-II §7.3 (open discharge). g_c = 1 (strict SI). Bending moment = F × lever arm.

-- 5. SELECTED VALVE --
API 526 letter / area         : M  (2322.57 mm²)
Valve style                   : Conventional spring-loaded
Overall verdict               : OVERALL PASS — inlet ΔP ≤ 3 % + built-up BP within limit
Inlet ΔP / Built-up BP        : 2.5 % / 8.3 % of set
Set / leak test               : Air / N₂ (gas set test) per API 527
Certification                 : ASME UV stamp; National Board certificate; API 527 seat-leak test

-- 6. TESTING & REFERENCES --
References: API RP 520 Part I (orifice sizing — gas §5.6; steam §5.7); API RP 520 Part II (installation — inlet 3 % §4; built-up BP §7; reaction force §7.3); API STD 521 (disposal / flare sizing); API STD 526 (PSV dimensions + letter sizes); API STD 527 (seat-leak test); ASME VIII Div.1 UG-125. เครื่องคำนวณช่วยตั้งต้น — วิศวกรผู้ออกแบบและผู้ผลิตต้องตรวจสอบและรับรองก่อนออกเอกสาร.

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