Purge test

Actual requirements of a specific installation are governed by the sum of the heat losses from the stack drum and collecting lines. Steam purge tests of a refinery installation indicated an additional... 

Nitrogen and oxygen gas purging tests were performed to determine the effect of oxygen concentration in electrolytes on corrosion behavior. The partial pressure of dissolved oxygen did affect the corrosion rate compared to those under ambient experimental conditions. The corrosion rate under a pure oxygen atmosphere for zVJ s and dp/s samples in 0.1 M HCl increased in the initial exposure period by a small amount, then remained at a rate comparable to that of samples exposed only to a... 

Fig. 2-21 Effect of potential on the current density and on the reduction in area for X65 steel in seawater (slow strain test, e = 2 X 10" s ), (a) Air purging, (h) nitrogen purging, (c) COj purging.

Pressure Testing, Cleaning, Flushing, Drying, and Purging... 

These three checklists concern utilities, pressure testing/purging," and mechanical equipment. See Tables 1 and 2 and the list following the tables. 

Procedural Checklist Ensures Safe, Complete Pressure-Testing and Purging of Process Equipment... 

Purging (Oj removal) Alternately depressure and repressure system to test (or header) pressure, until O2 by meter is less than 3.0%. Regularly check O2 meter to ensure its accuracy. Passing leak check at test (or N2 header) pressure. ... 

Significant errors will arise if gas purity is not accounted for. It should be noted that the code lays down no conditions for this, and a figure of 99 / or better should be targeted. In order to obtain a good purity at the start, all pipe joints should be taped and the system evacuated to a low vacuum several times with intermediated purging with the test gas to remove the residual contaminants. 

The two liter carbon canister does not exhibit the HC release during the run loss portion of the test, nor does it release more than the allowable level of HC during the three day diumals. Thus, for the given vehicle configuration and the level of purge volume obtained by the vehicle, it is clear that a two liter carbon canister is required for this vehicle to pass the EPA certification requirement. This conclusion has an effect on the cost of the evaporative control system, in that the additional activated carbon volume and canister size will have an added cost, as will any additional hardware required to mount the larger canister on the vehicle. 

The comparison made in Section 6.1 demonstrates the important effect the amount of purge has on the performance of the carbon canister in terms of limiting the amoimt of HC release. This effect is also shown in the data presented in Fig. 21. In this example, the vehicle has been subjected to the same test cycle sequence as before, but in this case two different levels of purging are examined. Also, a two liter canister is used on the vehicle for the testing at both purge levels, in order to see the effect of purge level on a single canister volume. 

Fig. 21. Effect of purge volume on three-day test sequence 6.3 Return vs. return-less fuel systems...

The example vehicle has been run through the test sequence using a two liter carbon canister and a 150 BV purge level. Fig. 22 presents the results for both a return and retum-less fuel system used in the vehicle. As shown, the fuel vapor temperature and the amount of fuel vapor generated are both lower for the retum-less system. This reduces the amount of HC adsorption required in the carbon canister, and it also reduces the amount of HC emissions in the test sequence, fhe return fuel system used with the stated purge volume and canister size emits an unacceptable level of HC during one of the diurnal sequences (2.12 grams), while the retum-less system emission values are well below the acceptable level. 

A gas seal shall be furnished if required to reduee purge gas requirements. The gas seal shall be self draining. The gas seal must be qualified by test data showing oxygen eoneentration below the seal at proposed purge rate and at least 50 mph simulated wind eondition. 

The amount of process plant that can be defined accurately as automatic is relatively small, and manual intervention is often involved at some stage. The relevant design criteria are therefore often IM/12 or IM/18. In practice, fully automatic burner controllers tested and certified by British Gas are available that comply with the requirements of BS 5885. Although these have features which may not be applicable to non-automatic plant, it may be more appropriate to use such a controller, particularly as its safety is well proven. It may also be less expensive than buying and installing separate timers, relays, etc. For some processes (for example, those that do not need and cannot tolerate a long purge) such controllers may not be appropriate. 

Existing installations may be tested with fuel gas or inert gas. Air may also be used subject to correct purging procedures. 

After testing for soundness it will be necessary to safely introduce gas into the pipework displacing the air or inert gas that is in it. Similarly, if pipework is decommissioned for any reason fuel gas must be displaced by air or inert gas. This is a requirement of the Gas Safety (Installation and Use) Regulations, Regulation 21. Guidance on recommended procedures is given in the British Gas publication Purging Procedures for Non-Domestic Gas Installations (IM/2). 

After soundness testing and purging, a competent person must commission the item of plant. It is a requirement of the Gas Safety (Installation and Use) Regulations, Regulation 33, that an appliance is fully commissioned at the time that gas is made available to it or that it is isolated in such a manner that it cannot be used. 

Purge points shall be fitted at section isolation valves, at the end of pipe runs and at other suitable positions to facilitate the correct purging of pipes. Pressure test points should be fitted at the outlet of each section-isolating valve. 

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