Disk pressure tests

Fiddle, J.P., Bernard , R., Broudeur, R., Roux, C., and Rapin, M., Disk pressure testing of hydrogen environment embrittlement, in Hydrogen Embrittlement Testing, STP 543, 221-253, Philadelphia, PA ASTM International, 1974. 

Fidelle, J. P., Bemardi, R., Broudeur, R., et al., Disk Pressure Testing of Hydrogen Environment Embrittlement, in Hydrogen Embrittlement Testing, ASTM STP 543, ASTM International, West Conshohocken, PA, 1974, pp. 221-253. 

As allowed by code [1], the average of the manufacturer s disks burst tests could be stamped, for example, (144 + 160.5)/2 = 152.3 psig with an actual 5% of 152.3 psig allowed for actual burst pressure of any disk at the operating temperature. 

Before being used for flow experiments, each disk was tested with helium for acceptability. The rate of helium flow at 10-cm. pressure gradient across the disk was measured at several mean pressures between 5 and 50 cm. Unless the mass of gas passing per unit time was constant—i.e., the flow through the disk followed Knudsen s law—the disk was rejected. About one disk in ten passed this test the others showed increased flow at high pressures. 

Table 3.24 The effect of thickness of copper rupture disk on deflagration of black powder using modified time/pressure test... 

The long-chain structure by itself, as exemplified by n-aliphatic hydrocarbons, shows no extreme-pressure lubricant functionality. Evidently the additive action is connected with the carboxylate ester and the sulfide structures. To demonstrate this, Dorinson isolated an ester/ sulfide component from sulfurized methyl undecylenate, identified its structure, synthesized an organosulfide-ester with this structure, and showed that the lubricant additive activity was the same for the fraction separated from sulfurized methyl undecylenate end for the synthetic material. The data, summarized ib Fig. 11-15, were obtained tiy pin-and-disk wear tests with hardened steel rubbing specimens and show the effect of contact pressure on the depth-rate of wear. The significant feature is the change from a low rate of wear, relatively insensitive to increase of pressure in the range 0.276-1.724 GPa (40,000-250,000 Ib/in ), to pressure-sensitive increase of wear rate at 1.724 GPa and higher. 

Figure 11-15. Sulfurized fatty esters as extreme-pressure additives. Pin and disk wear test at 85.85 cm/s with hardened steel. I Sulfurized methyl undecylenate, 1.22% S in lubricant. II Sulfurized methyl un-...

Figure 11-16. Interaction of organosulfides and fatty esters as extreme-pressure additives. Pin and disk wear test at 85.85 cm/s with hardened steel. I Di-sec-octyl disulfide, 1.17% S in lubricant. II Methyl laurate, 8.8% in lubricant. Ill Di-sec-octyl disulfide (17 mmoles/IOOgm) + methyl laurate (33 mmoles/100 gm), 1.06% S + 7.2% ester in lubricant. IV Base oil. V Synthetic 1,20-dicarbomethoxy-9,12-diroethyl-l0,11-dithiaeicosane (18 mmoles/100 gm). Data by A. Dorinson [63].

Laboratory studies were done with flat-sheet membrane. Membrane coupons were mounted as disks in high pressure test cells. With safety considerations CO2 in nitrogen (instead of methane) was used as feed in order to avoid the explosion potential with... 

Rupture disks are cheaper than relief valves and do not require ongoing maintenance and routine pressure testing. After a high-pressure release, a mpture disk simply needs to be replaced whereas relief valves need to be reset and tested. 

An important application of the HMT is the test for ferrous inclusions in high pressure turbine disks made from a non-magnetic metal alloy. On principle, such ferrous inclusions can be introduced during the manufacturing process and, if present, they can be the origin of cracks in these most critical parts. Therefore such tests are stringent necessary. 

The venting capabihty EF and therefore the effective vent area of the explosion door is normally smaller than the capabihty of a plastic or aluminum foil rupture disk with the same area. Therefore, such devices need testing to determine the mechanical strength before actual use, and the venting capability or the pressure rise, respectively. 

An 800-gal reaetor eontaining a styrene mixture with a speeifie heat of 0.6 eal/gm °C has a 10-in. rupture disk and a vent line with equivalent length = 400. The vessel MAWP is 100 psig and the rupture disk set pressure is 20 psig. The styrene mixture had a self-heat rate of 60°C/min at 170°C as it is tempered in a DIERS venting test. Determine the allowable reaetor mixture eharge to limit the overpressure to 10% over the set pressure. 

After the disk has been manufactured and tested, it is stamped with the rated burst pressure. The rated (stamped) burst pressure is established by bursting a minimum of two disks and averaging the pressures at which the disks burst. This average is the rated (stamped) burst pressure of the disk. Standard rupture disks above 15 psig 72°F are provided with a burst tolerance of 5% of the rated (stamped) burst pressure. This is in accordance with the ASME code. Burst tolerances for disks below 15 psig 72°F are oudined in Table 7-2. Burst tolerance applies only to the rated (stamped) burst pressure of the disk. Burst certificates are provided with each disk lot. 

The coefficient of discharge, Ko, is the actual flow divided by the theoretical flow and must be determined by tests for each type or style and size of rupture disk as well as pressure-relieving valve. For rupture disks, the minimum net flow area is the calculated net area after a complete burst of the disk, making allowance for any structural members that could reduce the net flow area of the disk. For sizing, the net flow area must not exceed the nominal pipe size area of the rupture disk assembly [1]. 

The Code requires that the disks be burst on test by one of three methods using four sample disks, but not less than 5% from each lot. Figure 7-32 illustrates test results for burst pressure versus temperature of a disk design, all fabricated from the same material, and of the same diameter. 

For flow tested combinations, see a few typical data in Table 7-12. Note, for example, that using a Continental disk reverse acting knife blade rupture disc with a Crosby JOS/JBS pressure relief valve that the combined effect is to multiply the rated capacity of the Crosby valve by a multiplier of 0.985 for a set pressure in the 60-74 psig range... 

Using a nomograph requires only the vessel volume in meters, selecting the dust class. St-1, St-2 or St-3 from Table 7-28. Using Tables 7-29 or 7-30 select the Kst value determined experimentally. The reduced pressure, Pfed. (maximum pressure actually developed during a vented deflagration, termed reduced explosion pressure) must not exceed strength of vessel (see earlier discussion) and the Psut, i.e., the vent device release pressure. Note that the static activation pressure, Pjj, must be determined from experimental tests of the manufacture of relief panels such as rupture disks. 

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