Steam Locking

Steam locking may occur in systems where drainage lines from equipment to traps must run upward. Steam trapping consists basically of separating condensate from steam. This can occur naturally as a result of gravity. Whenever possible, drainage lines from equipment to traps should slope downward. 

Inlet piping must be adequate to avoid water hammer and poor trap performance. They should not be undersized. To avoid sudden flashing of condensate, with its attendant problems, the line should be  

Large loads can sometimes be best handled with multiple traps in parallel if level control is not justified. Multiple banks of traps for a single load have the advantage that the loss of a single unit does not result in a complete shutdown. One or more of the traps can be valved out of service at reduced loads also. Traps in parallel must be installed in the same horizontal plane. 

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Depending on capital investment limitations, extruders may be heated by passing steam through the barrel jacket and/or by direct steam injection. Low-cost autogenous machines, which create heat by friction between the feed material and the surfaces of the barrel, screw and steam locks, and do not require steam-generating equipment, are also used (Wiejratne et al., 2004). This process is referred to as dry extrusion, and the extruder can be powered by a farm tractor and was originally developed to cook whole soybeans on-farm to prepare feeds. 

At 0119 10, the operator began to increase the rate of feedwater return to reduce the recirculation flow to increase the water level in the steam drums. At 0119 45, the reduced inlet water. stopped water from boiling in the core. The absence of the steam voids reduced the reactivity, and control rods were withdrawn, such that only 6 to 8 rods were in the reactor, rather than the required 30. Then, to avoid reactor trip from steam drum or feedwater signals, their scram circuils v ere locked out (a safety regulation violation). 

When a boiler may not be shut down for maintenance of the level control chambers isolating valves can be fitted between the water-level control and the steam space. In this instance, the valves must be capable of being locked in the open position and the key retained by a responsible person. When these valves are closed during maintenance periods the boiler must be under manual attendance. Fitting of these valves should only be with the agreement of the insurance company responsible for the boiler. Drains from the water-level controls and level gauges should be collected at a manifold or sealed tundish before running to the blowdown vessel. 

On-off control of steam systems can result in the formation of a partial vacuum, leading to condensate locking... 

All valves or taps controlling the entry of steam or hot water are closed and securely locked. Where the boiler has a blow-off pipe in common with one or more other boilers or delivering into a common blow-off vessel or sump, the blow-off valve or tap on each boiler is so constructed that it can only be opened by a key which cannot be removed until the valve or tap is closed. There can be only one key in use for that set of blow-off valves or taps. 

NOTE Sampling steam and condensate lines in large process plants such as smelters, pulp and paper plants, steel mills, and the like is potentially dangerous. Site rules must be followed and the use of proper safety equipment employed (safety equipment includes helmet, gloves, goggles, and occasionally a respirator). Under certain operating conditions, confined space permits and tag-out or lock-out rules may be necessary and a minimum of two persons required before work begins. 

All necessary permissions and standard safety procedures must be complied with before any cleaning work is carried out. This includes locking out the steam header and FW valves with chains and padlocks and attaching safety tags. 

KRW Figure 2.5 illustrates key features of this gasifier. Coal and limestone, crushed to below 1/4," are transferred from feed storage to the KRW fluidized-bed gasifier via a lock hopper system. Gasification takes place by mixing steam and... 

Vapor binding, or air lock, is another common cause of household radiator malfunction. Often, the vapor accumulating in the radiator is CO,2, rather than air. The C02 originates from the thermal decomposition of carbonates in the boiler. Regardless, air and C02 form a noncondensable vapor in the radiator. These noncondensables mix with the steam in the radiator. The noncondensables then reduce the concentration of the steam, by dilution. The diluted steam has a lower partial pressure than pure steam. The lower the partial pressure of the steam, the more difficult it is to condense. As the rate of condensation of the steam drops, so does the heat radiated by the radiator. 

Reactor Coolant Pumps. As indicated by Fig. 8, four reactor coolant pumps are used, two for each steam generator, The pumps are vertical, single-bottom-suction, horizontal-discharge, motor-driven centrifugal units. The pump impeller is keyed and locked to its shaft, A complex system of... 

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