Steam lines

Complying with theoretical steam requirements for smokeless flaring may require using an imprac- 

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Boiler Water Treatment. Alkanolamines, in general, provide excellent corrosion protection to steel in many appHcations. When used in boiler water treatment, AMP provides excellent protection to steel and copper in steam lines through efficient absorption of CO2, effectual distribution ratio for... 

The ignition temperature is the minimum temperature required to initiate or cause self-sustained combustion. Table 2 also Hsts ignition temperatures of several common ethers. Attention is directed to the particularly low ignition temperature of ethyl ether, especially with reference to some common ignition sources such as a lighted cigarette (732°C) or a pressurized (0.7 MPa or 100 psi) steam line (180°C). 

Figure 5-23. Interior of the nose cone showing terminus of the cooling steam line. The interior shielding consists of a 2-in. (50.8-mm) insulation thickness.

An alternate means of reboiler control is to remove the control valve from the steam line and provide a condensate level controller for the chest cascaded from the tray temperature. The alternate method uses A tube surface for control, with the condensate covering more or less tube surface to vary the area exposed to condensing stream. Condensing area is many times more effective for heat transfer than area covered by relatively stagnant condensate. The reboiler must have extra surface to allow part of its surface to be derated for control purposes. 

Example. A trap on a 150 psi steam line has been found to be blowing live steam on the basis of contact pyrometer measurements taken immediately upstream and downstream of the trap. The catalog rating of the trap is 5,000Ib/hr at saturation temperature (°F sub-cooled) at 150 psi. 

It is easy to improperly design a steam trap. The design must work for two circumstances and often a designer will check only one of these. The circumstance often overlooked is as follows On startup or upset the steam control valve can open wide so that the steam chest (assume for this discussion that we are speaking of a reboiler) pressure rises to full steam line pressure. At a... 

Low-density steam under vacuum conditions can cause a linear velocity to be higher than is allowable with steam lines. 

The confusion matrix (NSAC-60) is a method that identifies potential operator errors lemming from incorrect diagnosis of an event. It can be used to identify the potential for an operator to conclude that a small LOCA has occurred, when it is actually a steam line break. This provides a method for identifying a wrong operator response to an off-normal plant condition. It is particularly useful in Step 5 of the. SHARP procedures, Documentation requirements are presented in Table 4.5-2. 

Core damage can result most likely from heat imbalance. Figure 6.3-3 is an example from the Indian Point PRA that uses heat imbalance to approach completeness. This diagram shows that cote damage may result from either a loss of cooling or excess power (or both). The direct causes of insufficient heat removal may be loss of flow, makeup water, steam flow, or heat extraction by the turbine. Indirect causes are reactor trip or steam line break inside or outside of containment. Cau.ses of excess power production are rod withdrawal, boron removal, and cold water injection. 

F.xamples of initiating events considered in five PRAs are provided by Joksimovich et al. (lhS3) and presented as Table 6.3-5. The occurrence frequencies vary from a high of 3.7/yr for turbine and reactor trip at Zion to a low of lE-6/yr for a large steam line break outside of containment at Big Rock Point. Another low frequency is 2E-6/yr for ATWS from the loss of one feedwater pump, also at Big Rock Point. Surprisingly, these are less than a large LOCA (IE- 5/yr) at the same plant. Except for Big Rock Point, this table provides no information on externalities. 

Improve the current capability to isolate steam lines leaving the powerhouse to ensure that the steam system can be protected from piping mpiurcs hcmiIc the powerhouse... 

A mechanic was affected by fumes while working on a steam drum. One of the steam lines from the drum was used for stripping a process column operating at a gauge pressure of 30 psi (2 bar). A valve on the line to the column was closed, but the line was not slip-plated. When the steam pressure was blown off, vapors from the column came back through the leaking valve into the steam lines (Figure 1-3). 

The company concerned normally used slip-plates to isolate equipment under repair. On this occasion, no slip-plate was fitted because it was only a steam line. However, steam and other service lines in plant areas are easily contaminated by process materials, especially when there is a direct connection to process equipment. In these cases, the equipment under repair should be positively isolated by slip-plating or disconnection before maintenance. 

There was a leak on the line supplj ing steam to a plant. To avoid a shutdown, a hot tap and stopple was carried out, that is, the line was bypassed and the leaking section plugged off (stoppled) while in use. The job went well mechanically, but the leak continued. It was then found that the leak was not coming from the steam line but from a hot condensate line next to it. The condensate flashed as it leaked, and the leak looked like a steam leak [26],... 

Explosion from a Steam Line Report of Preliminaiy Inquiry No. 3471, Her Majesty s Stationery Office, London, 1975. 

Liquefied gas leaked into a steam line that had been blown down. Ice then formed on the outside of the steam line. 

High pressure steam lines Low pressure steam lines Vacuum steam lines Compressed air lines Refrigerant vapor lines High pressure Low pressure Refrigerant liquid Brine lines Ventilating ducts Register grilles... 

Figure 2-32 is a convenient chart for handling most in-plant steam line problems. For long transmission lines over 200 feet, the line should be calculated in sections in order to re-establish the steam specific density. Normally an estimated average p should be selected for each line increment to obtain good results. 

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