API 570 Examination Formulas

Sl #	Formula Description	Formula		Para/Ref. No				Ref. Code
1	Soil Resistivity (ohm-cm)	= 191.5 x d x R		10.10.1.4.3				API 574 2009 Edition
	The number 191.5 is a constant that takes into account the mathematical equation for the mass of the Soil, and a conversion factor to convert feet to centimeters. "d" is the distance in feet between any 0f the equally spaced pins (with all of the pins in a straight line), "R" is a resistance factor of the voltage drop across the two inner pins divided by the induced current flow in the earth between the two outer pins.
2	Minimum Allowable Working Pressure (MAWP)	MAWP = 2SEt/D		Table 4				API 570 2009 Edition
	"S" is the allowable unit stress at the design temperature, In pounds per square inch (kilopascals), "E" is the longitudinal quality factor. '"t" is the corroded thickness, means actual measured thickness minus twice of calculated corrosion to next inspection period in inches (millimeters), "P" is the internal design gauge pressure of the pipe. in pounds per square inch (kilopascals), "D" is the OD of the pipe, in inches (millimeters)
3	Temperature Conversion	Tc = 5/9 x (Tf - 32)
		Tc = temperature in degrees Celsius, Tf = temperature in degrees Fahrenheit
4	Temperature Conversion	Tf = 9/5 x Tc + 32
		Tc = temperature in degrees Celsius, Tf = temperature in degrees Fahrenheit
5	Toe to Toe Distance Patch Plate	=√Dt		8.1.4				API 570 2009 Edition
		D = Inside Diameter of Pipe, t = Thickness of Patch Plate
6	Minimum Required Pipe Thickness	tm = t + c t = PD/ 2(SEW + PY)		304.1.1 & 304.1.2				B31.3 2010 Edition
	The minimum thickness, T, for the pipe selected, considering manufacturer’s minus tolerance, shall be not less than tm. (b) The following nomenclature is used in the equations for pressure design of straight pipe: c = sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances. For threaded components, the nominal thread depth (dimension h of ASME B1.20.1 or equivalent) shall apply. For machined surfaces or grooves where the tolerance is not specified, the tolerance shall be assumed to be 0.5 mm (0.02 in.) in addition to the specified depth of the cut. D = outside diameter of pipe as listed in tables of standards or specifications or as measured d = inside diameter of pipe. For pressure design calculation, the inside diameter of the pipe is the maximum value allowable under the purchase specification. E = quality factor from Table A-1A or A-1B, P = internal design gage pressure, S = stress value for material from Table A-1, T = pipe wall thickness (measured or minimum in accordance with the purchase specification), t = pressure design thickness, as calculated in accordance with para. 304.1.2 for internal pressure or as determined in accordance with para. 304.1.3 for external pressure, tm = minimum required thickness, including mechanical, corrosion, and erosion allowances, W = weld joint strength reduction factor in accordance with para. 302.3.5(e), Y = coefficient from Table 304.1.1, valid for t < D/6 and for materials shown. The value of Y may be interpolated for intermediate temperatures. For t ≥ D/6, Y = d + 2c /D + d + 2c
7	Pressure Design Thickness (Barlow)	t = PD/2SE		11.1.2				API 574 2009 Edition
	"t" is the pressure design thickness for internal pressure. in inches (millimeters), "P" is the internal design gauge pressure of the pipe. in pounds per square inch (kilopascals), "D" is the OD of the pipe, in inches (millimeters), "S" is the allowable unit stress at the design temperature, In pounds per square inch (kilopascals), "E" is the longitudinal quality factor.
8	Pressure Design Thickness Valve and Flanged Fittings	tm = t + c t = 1 .5[PD / 2(SE)]		11.2				API 574 2009 Edition
	t is the pressure design thickness for internal pressure. in inches (millimetes); P is the internal design gauge pressure of the pipe. in pounds per square inch (kilopascals); D is the OD of the pipe, in inches (millimeters); S is the allowable unit stress at the design temperature. in pounds per square inch (kilopascals); E is the longitudinal quality factor.
9	Minimum Required lank Thickness	tm = dg√3P / 16SEW  + C		304.5.3				B31.3 2010 Edition
	c = sum of allowances defined in para. 304.1.1, dg = inside diameter of gasket for raised or flat face flanges, or the gasket pitch diameter for ring joint and fully retained gasketed flanges, E = same as defined in para. 304.1.1, P = design gage pressure, S = same as defined in para. 304.1.1, W = same as defined in para. 304.1.1
10	Hydro Test Pressure	PT = 1.5 x P x Rr					345.4.2	B31.3 2010 Edition
	where P = internal design gage pressure, PT = minimum test gage pressure, Rr = ratio of ST/S for pipe or components without established ratings, but shall not exceed 6.5, = ratio of the component pressure rating at the test temperature to the component pressure rating at the component design temperature for components with established ratings, but shall not exceed 6.5 S = allowable stress value at component design temperature (see Table A-1), ST = allowable stress value at test temperature
11	Flange and Flanged Fittings Hydro Test Pressure	PT = 1.5 x 100°F (38°C) rating duration NPS ≤ 2 = 60 sec. NPS ≥ 2½ ≤ 8 = 120 sec. NPS  ≥ 10 = 180 sec.		2.6 8.2.2 8.2.4				B16.5 2009 Edition
		Rating from Table 1A and Table 2 (Test pressure round off to next higher 1 bar or 25 psi
12	Pneumatic Test Pressure	PT = 1.1 x Design Pressure		345.5.4				B31.3 2010 Edition
13	Fillet Weld Weld Size for Slip on Flange (Xmin) Branch Fillet weld Throat Size (tc)	LEG = 1.414 x Throat Throat = Leg x 0.707 Xmin = lesser of 1.4 x T or thickness of hub tc = lesser of 0.7 x Tb   or 6 mm (1⁄4 in.)		328.5.2 328.5.4				B31.3 2010 Edition
		T = Thickness of pipe, Tb = Thickness of branch, tc = throat of branch fillet weld
14	Flanged Fittings subminimum area	D = 0.35√dtm			6.1.2			B16.5 2009 Edition
15	Flanged Fittings subminimum thickness	= 0.75 x tm				D = Diameter of Subminimum Thickness area d = Inside diameter of Pipe tm = Minimum Thickness of Flanged Fittings wall thickness from the tables.
16	Flanged Fittings subminimum area edge to edge distance	= 1.75√dtm
17	Remaining Life	RL = tactual - trequired / Cr		7.1.1					API 570 2009 Edition
18	Long-term Corrosion	LT = tinitial - tactual / time (years)
19	Short-term Corrosion	ST = tinitial - tactual / time (years)
	RL = Remaining life Cr = Corrosion rate, LT = Long term corrosion rate, ST = Short term corrosion rate, time = time in years between tinitial and tactual
20	Tension Test	TSA = ∏R²		Sec. IX				ASME SEC. IX 2010 Edition
		RSA = Width x Thickness
		TS = Load/Area
		Load = Area x Tensile Strength
	TSA = Turned Specimen Area, TS = Tensile Strength, RSA = Reduce Specimen Area
21	PWHT BRANCH CONNECTION (Covering Thickness)	2 x Thickness for Given Material in Table 331.1.1 or >16mm (⅝ in) for P1 materials >13mm (½ in) for P3, 4, 5, or 10A materials		331.1.1 331.1.3				B31.3 2010 Edition
	Sketch 1	b + tc
	Sketch 2	h + tc
	Sketch 3	b + tc or Ṫ + tc
	Sketch 4	h + r + tc
	Sketch 5	b + tc
	b = Thickness of branch, h = Thickness of header, r = Thickness of reinforcement pad

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