Measuring Pressure

Description

This section is from the book "Principles And Practice Of Plumbing", by John Joseph Cosgrove. Also available from Amazon: Principles and Practice of Plumbing.

Measuring Pressure

The pressure of water in closed systems is indicated by a pressure gauge. The construction of a pressure gauge is shown in Fig. 60. In this illustration the dial face is removed to show the interior construction. A bent tube a, of elliptical cross-section, made of metal of the required elasticity, has its bottom end firmly attached to the gauge case, and its upper end left free to move. To the upper end is attached a lever b, which is so connected to a pointer in front of a graduated index dial that any movement of the tube will be indicated by the pointer.

The principle of its operation is as follows: If a bent tube of elliptical cross section be subjected to an internal pressure, the force exerted will tend to straighten the tube. This is due to the fact that a force exerted within a tube of elliptical cross section tends to make it take a circular form; to do so, the inner arc of the bent tube must lengthen and the outer arc shorten and the combined effort will straighten the tube in direct proportion to the pressure exerted. The straightening of the tube imparts a movement to the register hand which indicates on the face of the gauge the intensity of the pressure.

Fig. 60

Table XXIV - Heads And Pressures Of Water


Feet Head	Pressure per Square Inch	Feet Head	Pressure per Square Inch	Feet Head	Pressure per Square Inch	Feet Head	Pressure per Square Inch	Feet Head	Pressure per Square Inch
1	0.43	49	21.22	97	42.01	145	62.81	193	83.60
2	0.86	50	21,65	98	42.45	146	63.24	194	84.03
3	1.30	51	22.09	99	42.88	147	63.67	195	84.47
4	1.73	52	22.52	100	43.31	148	64.10	196	84.90
5	2.16	53	22.95	101	43.75	149	64.54	197	85.33
6	2.59	54	23.39	102	44.18	150	64.97	198	85.76
7	3.03	55	23.82	103	44.61	151	65.40	199	86.20
8	3.46	56	24.26	104	45.05	152	65.84	200	86.63
9	3.89	57	24.69	105	45.48	153	66.27	201	87.07
10	4.33	58	25.12	106	45.91	154	66.70	202	87.50
11	4.76	59	25.55	107	46.34	155	67.14	203	87.93
12	5.20	60	25.99	108	46.78	156	67.57	204	88.36
13	5.63	61	26.42	109	47.21	157	68.00	205	88.80
14	6.06	62	26.89	110	47.64	158	68.43	206	89.23
15	6.49	63	27.29	111	48.08	159	68.87	207	89.66
16	6.93	64	27.72	112	48.51	160	69.31	208	90.10
17	7.36	65	28.15	113	48.94	161	69.74	209	90.53
18	7.79	66	28.58	114	49.38	162	70.17	210	90.96
19	8.22	67	29.02	115	49.81	163	70.61	211	91.39
20	8.66	68	29.45	116	50.24	164	71.04	212	91.83
21	9.09	69	29.88	117	50.68	165	71.47	213	92.26
22	9.53	70	30.32	118	51.11	166	71.91	214	92.69
23	9.96	71	30.75	119	51.54	167	72.34	215	93.13
24	10.39	72	31.18	120	51.98	168	72.77	216	93.56
25	10.82	73	31.62	121	52.41	169	73.20	217	93.99
26	11.26	74	32.05	122	52.84	170	73.64	218	94.43
27	11.69	75	32.48	123	53.28	171	74.07	219	94.86
28	12.12	76	32.92	124	53.71	172	74.50	220	95.30
29	12.55	77	33.35	125	54.15	173	74.94	221	95.73
30	12.99	78	33.78	126	54.58	174	75.37	222	96.16
31	13.42	79	34.21	127	55.01	175	75.80	223	96.60
32	13.86	80	34.65	128	55.44	176	76.23	224	97.03
33	14.29	81	35.08	129	55.88	177	76.67	225	97.46
34	14.72	82	35.52	130	56.31	178	77.10	226	97.90
35	15.16	83	35.95	131	56.74	179	77.53	227	98.33
36	15.59	84	36.39	132	57.18	180	77.97	228	98.76
37	16.02	85	36.82	133	57.61	181	78.40	229	99.20
38	16.45	86	37.25	134	58.04	182	78.84	230	99.63
39	16.89	8T	37.68	135	58.48	183	79.27	231	100.06
40	17.32	88	38.12	136	58.91	184	79.70	232	100.49
41	17.75	89	38.55	137	59.34	185	80.14	233	100.93
42	18.19	90	38.98	138	59.77	186	80.57	234	101.36
43	18.62	91	39.42	139	60.21	187	81.00	235	101.79
44	19.05	92	39.85	140	60.64	188	81.43	236	102.23
45	19.49	93	40.28	141	61.07	189	81.87	237	102.66
46	19.92	94	40.72	142	61.51	190	82.30	238	103.09
47	20.35	95	41.15	143	61.94	191	82.73	239	103.53
48	20.79	96	41.58	144	62.37	192	83.17	240	103.96

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Measuring Pressure

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Measuring Pressure

Table XXIV - Heads And Pressures Of Water

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