Maxims and Instructions for the Boiler Room / Useful to Engineers, Firemen & Mechanics; Relating to Steam Generators, Pumps, Appliances, Steam Heating, Practical Plumbing, etc.

by N. Hawkins

RULE FOR SAFE INTERNAL PRESSURE

The safe internal pressure on cylindrical shells is found according to the following rule, which has been adopted by the United States Board of Supervising Inspectors, and any boiler shell not found in the tables can be determined by this rule.

Rule.—Multiply one-sixth of the lowest tensile strength found stamped on any plate in the cylindrical shell by the thickness—expressed in inches or parts of an inch—of the thinnest plate in the same cylindrical shell, and divide by the radius or half diameter—also expressed in inches—and the result will be the pressure allowable per square inch of surface for single riveting, to which add twenty per centum for double riveting.

The hydrostatic pressure applied, under this table and rule, must be in the proportion of one hundred and fifty pounds to the square inch, to one hundred pounds to the square inch of the working pressure allowed.

Example.

What pressure should be allowed to be carried on a boiler 60″ diameter, made of plates ³⁄₈″ thick, having a tensile strength of 60,000 pounds? Now then:

6)60,000
———
10,000
3
———
8)30,000
———
Half diam. 30)3750(125. lbs.—if single riveted.
30
——
75
60
——
150 125 + 25 lbs. (20 feet) = 150 for
150 double riveted.

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TABLES SAFE INTERNAL PRESSURE.

Diameter of Boiler.	Thickness of Plates	Pressure.		Pressure.		Pressure.
		Single Riveted	Double Riveted	Single Riveted	Double Riveted	Single Riveted	Double Riveted
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
36 Inches	.21	87.5	105.	97.21	116.65	106.94	128.3
	.23	95.83	114.99	106.47	127.76	117.12	140.54
	.25	104.16	124.99	115.74	138.88	127.31	152.77
	.26	108.33	129.99	120.37	144.44	132.4	158.88
	.29	120.83	144.99	134.25	161.11	147.68	177.21
	.33	137.5	165.	152.77	183.32	168.05	201.66
	.35	145.83	174.99	162.03	194.43	178.23	213.87
	.375	156.25	187.5	173.61	208.33	190.97	229.16
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	116.66	139.99	126.38	151.65	136.11	163.33
	.23	127.77	153.32	138.41	166.09	149.07	178.88
	.25	138.88	166.65	150.46	180.55	162.03	194.43
	.26	144.44	173.32	156.48	187.77	168.51	202.21
	.29	161.11	193.33	174.53	209.43	187.90	225.48
	.33	183.33	219.99	198.61	238.33	213.88	256.65
	.35	194.44	233.32	210.64	252.76	226.84	272.20
	.375	208.33	249.99	225.69	271.82	243.05	291.66
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
40 Inches.	.21	78.75	94.50	87.49	104.98	96.24	115.48
	.23	86.25	103.5	95.83	114.99	105.41	126.49
	.25	93.75	112.5	104.16	124.99	114.58	137.49
	.26	97.5	117.	108.33	129.99	119.16	142.99
	.29	108.75	130.5	120.83	144.99	132.91	159.49
	.3125	117.18	140.61	130.2	156.24	143.22	171.86
	.33	123.75	148.5	137.49	164.98	151.24	181.48
	.35	131.25	157.5	145.83	174.99	160.41	192.49
	.375	140.62	168.74	156.24	187.48	171.87	206.24
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	105.	126.	113.74	136.48	122.49	146.98
	.23	115.	138.	124.58	149.49	134.16	160.99
	.25	125.	150.	135.41	162.49	145.83	174.99
	.26	130.	156.	140.83	68.99	151.66	181.99
	.29	145.	174.	157.08	188.49	169.16	202.99
	.3125	156.25	187.45	169.27	203.12	182.29	218.74
	.33	165.	198.	178.74	214.48	192.49	230.98
	.35	175.	210.	189.58	227.49	204.16	244.99
	.375	187.5	225.	203.12	243.74	218.74	262.48
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
42 Inches.	.21	75.	90.00	83.32	99.99	91.66	109.99
	.23	82.14	98.56	91.23	109.51	100.39	120.46
	.25	89.28	107.13	99.2	119.04	109.12	130.94
	.26	92.85	111.42	103.17	123.8	113.49	136.18
	.29	103.57	124.28	115.07	138.08	126.57	151.85
	.3125	111.6	133.92	124.	148.8	136.4	163.68
	.33	117.85	141.42	130.94	157.12	144.04	172.84
	.35	125.	150.	138.88	166.65	152.77	183.32
	.375	133.92	160.7	148.8	178.56	163.68	196.40
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	100.	120.	108.33	129.99	116.66	139.99
	.23	109.52	131.42	118.65	142.38	127.77	153.32
	.25	119.04	142.84	128.96	154.75	138.88	166.65
	.26	123.8	148.56	134.12	160.94	144.44	173.32
	.29	138.09	165.7	149.6	179.52	161.11	193.33
	.3125	148.74	178.56	161.2	193.44	173.61	208.23
	.33	157.14	188.56	170.23	204.27	183.33	219.99
	.35	166.66	199.99	180.55	216.66	194.44	233.32
	.375	178.57	214.28	193.45	232.14	208.33	249.99
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6.
48 Inches.	.21	65.62	78.74	72.91	87.49	80.2	96.24
	.23	71.87	86.24	79.85	95.82	87.84	105.4
	.25	78.12	93.74	86.8	104.16	95.48	114.57
	.26	81.25	97.50	90.27	108.32	99.3	119.16
	.29	90.62	108.74	100.69	120.82	110.76	132.91
	.3125	97.65	117.18	108.5	130.2	119.35	143.22
	.33	103.12	123.74	114.58	137.49	126.04	151.24
	.35	109.37	131.24	121.52	145.82	133.67	160.4
	.375	117.18	140.61	130.2	156.24	143.22	171.86
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	87.49	104.98	94.79	113.74	102.08	122.49
	.23	95.83	114.99	103.81	124.57	111.8	133.16
	.25	104.16	124.99	112.84	135.4	121.52	145.82
	.26	108.33	129.99	117.36	140.83	126.38	151.65
	.29	120.83	144.99	130.9	157.08	140.97	169.16
	.3125	130.21	156.25	141.05	169.26	151.9	182.28
	.33	137.5	165.	148.95	178.74	160.41	192.49
	.35	145.83	174.99	157.98	189.57	170.13	204.14
	.375	156.25	187.50	169.27	203.12	182.29	218.74
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
54 Inches.	.21	58.33	69.99	64.81	77.77	71.29	85.54
	.23	63.88	76.65	70.98	85.17	78.08	93.69
	.25	69.44	83.32	77.16	92.52	84.87	101.84
	.26	72.22	86.66	80.24	96.28	88.27	105.92
	.29	80.55	96.66	89.5	107.40	98.45	118.14
	.3125	86.8	104.16	96.44	115.72	106.09	127.30
	.33	91.66	109.99	101.84	122.22	112.03	134.43
	.35	97.22	116.66	108.02	129.62	118.82	142.58
	.375	104.16	124.99	115.74	138.88	127.31	152.77
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	77.77	93.32	84.25	101.1	90.74	108.88
	.23	85.18	102.21	92.28	110.73	99.38	119.25
	.25	92.59	111.10	100.3	120.36	108.02	129.62
	.26	96.29	115.54	104.31	125.17	112.44	134.8
	.29	107.41	128.88	116.35	139.62	125.3	150.36
	.3125	115.55	138.66	125.38	150.45	135.03	162.03
	.33	122.22	146.66	132.4	158.88	142.59	171.10
	.35	129.69	155.54	140.43	168.51	151.23	181.47
	.375	138.88	166.65	150.46	180.55	162.03	194.43
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
60 Inches.	.21	52.5	63.	58.33	69.99	64.16	76.99
	.23	57.5	69.	63.88	76.65	70.27	84.32
	.25	62.5	75.	69.44	83.32	76.38	91.65
	.26	65.	78.	72.22	86.66	79.44	95.32
	.29	72.5	87.	80.55	96.66	88.61	106.33
	.3125	78.12	93.74	86.8	104.16	95.48	114.57
	.33	82.5	99.	91.66	109.99	100.83	120.99
	.35	87.5	105.	97.22	116.66	106.94	128.32
	.375	93.75	112.5	104.16	124.99	114.58	137.49
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.21	69.99	84.	75.83	90.99	81.66	97.99
	.23	76.66	91.99	83.05	99.66	89.44	107.32
	.25	83.83	99.99	90.27	108.32	97.22	116.66
	.26	86.66	103.99	93.88	112.65	101.11	121.33
	.29	96.66	115.99	104.72	125.66	112.77	135.32
	.3125	104.18	124.99	112.95	135.54	121.52	145.82
	.33	109.99	132.	119.16	142.99	128.33	153.99
	.35	116.66	139.99	126.38	151.65	136.11	163.33
	.375	125.	150.	135.41	162.49	145.88	174.99
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
66 Inches.	.1875	42.61	51.13	47.34	56.8	52.07	62.49
	.21	42.72	57.26	53.	63.63	58.33	69.99
	.23	52.27	62.72	58.	69.69	63.88	76.65
	.25	56.81	68.17	63.13	75.75	69.44	83.32
	.26	59.09	70.9	65.65	78.78	72.22	86.66
	.29	65.90	79.08	73.23	87.87	80.55	96.66
	.3125	71.	85.2	78.91	94.69	86.89	104.16
	.33	75.	90.	83.33	99.99	91.66	109.99
	.35	79.56	95.47	88.38	106.05	97.22	116.66
	.375	85.22	102.26	94.69	113.62	104.16	124.99
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.1875	56.81	68.17	61.55	73.86	66.28	79.53
	.21	63.63	76.35	68.93	82.71	74.24	89.08
	.23	69.69	83.62	75.5	90.6	81.31	97.57
	.25	75.75	90.90	82.07	98.48	88.37	106.04
	.26	78.78	94.53	85.35	102.42	91.91	110.29
	.29	87.87	105.44	95.2	114.24	102.52	123.02
	.3125	84.69	113.62	102.58	123.09	110.47	132.56
	.33	99.99	120.	108.33	129.99	116.66	139.99
	.35	106.	127.27	114.89	137.86	123.73	148.47
	.375	113.62	136.34	123.1	147.72	132.57	159.08
		45,000 Tensile Strength. 1-6, 7,500		50,000 Tensile Strength. 1-6, 8,333.3		55,000 Tensile Strength. 1-6, 9,166.6
72 Inches.	.1875	39.06	46.87	43.4	52.08	47.74	57.28
	.21	43.75	52.5	48.6	58.33	53.47	64.16
	.23	47.91	57.49	53.24	63.88	58.56	70.27
	.25	52.08	62.49	57.87	69.44	63.65	76.38
	.26	54.16	64.99	60.18	72.22	66.2	79.44
	.29	60.41	72.49	67.12	80.55	73.84	88.60
	.3125	65.10	78.12	72.33	86.8	79.57	95.48
	.33	68.75	82.5	76.38	91.62	84.02	100.82
	.35	72.91	87.49	81.01	97.21	89.11	106.93
	.375	78.12	93.74	86.8	104.16	95.48	114.57
		60,000 Tensile Strength. 1-6, 10,000		65,000 Tensile Strength. 1-6, 10,833.3		70,000 Tensile Strength. 1-6, 11,666.6
	.1875	52.08	62.49	56.42	67.70	60.76	72.91
	.21	53.33	69.99	63.19	75.82	68.06	81.66
	.23	53.88	76.65	66.21	83.05	74.58	89.43
	.25	69.44	83.32	75.22	90.26	81.01	97.21
	.26	72.22	86.66	78.24	93.88	84.25	101.10
	.29	80.55	96.66	87.26	104.71	93.98	112.77
	.3125	86.8	104.16	94.03	112.88	101.27	121.52
	.33	91.66	109.99	99.3	119.16	106.94	128.32
	.35	97.22	116.66	105.32	126.38	113.42	136.1
	.375	104.16	124.99	112.84	135.43	121.52	145.32

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