5
Operation and Maintenance
High-pressure drops in the main supply lines should be eliminated. The lower the operating supply pressure, the more operating steam
is required by the thermocompressor. A steam pressure gauge should be located as close to the high-pressure steam inlet as possible.
The suction connection:
The low-pressure suction line should be the same diameter as the suction connection of the thermocompressor and it should be as free
from any restrictions as practical. Here too, a steam pressure gauge should be located as close to the suction connection as possible.
The discharge connection:
Likewise, the mixed discharge connection should be the same diameter as the thermocompressor discharge outlet. Care should be
taken to avoid placing any restrictions or undue obstructions in the discharge line that will have the effect of increasing the discharge
pressure above that of the design value. It is therefore important to design the discharge line correctly. If the discharge pressure is
increased beyond the design value, the thermocompressor will not operate correctly or efficiently.
Utilities
In the case of a thermocompressor, the basic utility is a supply of quality dry steam. For an efficient design it is essential to know the
minimum steam pressure that will be experienced at the high-pressure inlet to the thermocompressor.
Under critical flow conditions, lowering the steam pressure below that of the design value may cause the thermocompressor to chatter
and become unstable in operation.
Under sub critical flow conditions, lowering the steam pressure below that of the design value could result in a serious loss of capacity,
coupled with a resultant loss of compressive ability.
Conversely, the use of steam pressures above the design value will not enhance the performance of the unit and, if the steam
pressure is considerably above the design value, the performance could be adversely affected due to the throats of the nozzle and
diffuser being overloaded. Wet steam will cause poor performance and, in addition, will also erode the internal components of the
thermocompressor which will cause further losses in performance. Any superheat present in the steam supply to the thermocompressor
must be taken into consideration at the final design stage. Significant amounts of superheat will affect the unit’s performance
because the steam nozzle and diffuser throats will be undersized and this situation, if dry saturated steam is not available, can only be
corrected by a change in the design of the nozzle and diffuser.
Inspection
In order to help ensure trouble-free service and to obtain maximum operational economy, it is recommended that a periodic
inspection of the thermocompressor internals be conducted. The frequency of this inspection will naturally vary and will depend
upon the type of service and the quality of the steam supply. A thermocompressor that is used in corrosive or erosive service must be
inspected more frequently than one that is used in non-corrosive or non-erosive service. An acceptable minimum practice would be
to inspect the thermocompressor whenever related equipment is inspected; examining, in particular, the following main areas: the
nozzle, diffuser, and spindle tip for any signs of wear, damage, or debris. A visual examination will normally be all that is required. If
the diffuser and steam nozzle is smooth and round and neither erosion nor corrosion is indicated, then replacement is not required.
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