Page 58 - ECLECTIC MARCH-2022 INSIDE PAGES_p2.indd
P. 58
cost of the excess coal can then be calculated by Valve - #Unit Bonnet Conventional Proposed Model
multiplying the excess coal per ton to the cost of coal Temp Approach
per ton. 20V012 - #1
(C) Passing Trap defective in
Cost of Excess Water 50V013 - #2 133 bypass line
Passing
To replenish the amount of leakage steam in a cycle, BM 69- #1 183 Valve not
demineralized water needs to be supplied. BM 69- #2 Passing shut fully
SH 3- #1 146 Passing
Cost of excess demin water = lost water (l) * cost of 268 Passing Valve Gland Leak
BM 56-#2 116
manufacturing one liter of demin water (15) Passing Valve Gland Leak
191
BFP Related Excess Cost Valve not
shut fully
Internally leaking valves results in the BFP’s consuming
more power to feed the additional feed water into Close to Boiler
the boiler. The determination of the excess power Drum & 1st
required by the BFP’s for an increase in flow rate can be Isolating Vv
determined by pump affinity laws for centrifugal pumps.
BFP losses are only considered for valves which dump So, out of the 10 valves only 1 found to be actually passing.
into atmosphere. Now mode of selection for valve renewal will depend on
the quantity of leakage and the financial losses incurred.
Using the mathematical model we get:
Table 2:
Other losses like blowing more air through the boiler to Valve # Unit Quantity of Loss (` / month)
facilitate the excess coal being burned is not considered loss (Kg/s) 57151/-*
in this analysis as the additional power required by the
fans to blow the excess air will be insignificant as the 25B013 #1 0.0054*
power consumption ratio to air volume is small in fans.
*Sample calculation in appendix.
APPLICATION IN BBGS RECOMMENDATION
In FY 2020-21, a total 6 HED valves were identified with a) The portion of the un-insulated pipe must be properly
high bonnet temperature. All these valves were tagged demarcated so that no personnel can come in the
as passing using conventional thermography. These vicinity of a high temperature zone.
valves were in the range of 1500 class to 2500 special
class motorized globe valves of 25 to 100NB size. But after b) If possible the insulation and lagging sheet should
thorough inspection the following result was obtained: be fitted on the pipe after necessary temperature
measurements.
Table 1: Bonnet Conventional Proposed Model
Temp Approach c) Within 72 hours of unit synchronization, all HED valve
Valve - #Unit to be checked once to ensure tight shut off otherwise
(C) necessary rectification to be done before the internal
25B013 - #1 270 leakage passage propagates through steam cutting.
CRD-6 - #1 178
49V025 - #1 101 d) Temperature readings should be taken quarterly to
get a pattern of the valve performance.
25V035 - #1 134
Passing Passing. CONCLUSION
Passing
Passing Gland leak The standardization of check points has been done
based on observations at BBGS for last 3 years. Gradual
Passing Due to operation improvement can be observed in number of renewed
of bypass trap
Trap defective in
bypass line
58
multiplying the excess coal per ton to the cost of coal Temp Approach
per ton. 20V012 - #1
(C) Passing Trap defective in
Cost of Excess Water 50V013 - #2 133 bypass line
Passing
To replenish the amount of leakage steam in a cycle, BM 69- #1 183 Valve not
demineralized water needs to be supplied. BM 69- #2 Passing shut fully
SH 3- #1 146 Passing
Cost of excess demin water = lost water (l) * cost of 268 Passing Valve Gland Leak
BM 56-#2 116
manufacturing one liter of demin water (15) Passing Valve Gland Leak
191
BFP Related Excess Cost Valve not
shut fully
Internally leaking valves results in the BFP’s consuming
more power to feed the additional feed water into Close to Boiler
the boiler. The determination of the excess power Drum & 1st
required by the BFP’s for an increase in flow rate can be Isolating Vv
determined by pump affinity laws for centrifugal pumps.
BFP losses are only considered for valves which dump So, out of the 10 valves only 1 found to be actually passing.
into atmosphere. Now mode of selection for valve renewal will depend on
the quantity of leakage and the financial losses incurred.
Using the mathematical model we get:
Table 2:
Other losses like blowing more air through the boiler to Valve # Unit Quantity of Loss (` / month)
facilitate the excess coal being burned is not considered loss (Kg/s) 57151/-*
in this analysis as the additional power required by the
fans to blow the excess air will be insignificant as the 25B013 #1 0.0054*
power consumption ratio to air volume is small in fans.
*Sample calculation in appendix.
APPLICATION IN BBGS RECOMMENDATION
In FY 2020-21, a total 6 HED valves were identified with a) The portion of the un-insulated pipe must be properly
high bonnet temperature. All these valves were tagged demarcated so that no personnel can come in the
as passing using conventional thermography. These vicinity of a high temperature zone.
valves were in the range of 1500 class to 2500 special
class motorized globe valves of 25 to 100NB size. But after b) If possible the insulation and lagging sheet should
thorough inspection the following result was obtained: be fitted on the pipe after necessary temperature
measurements.
Table 1: Bonnet Conventional Proposed Model
Temp Approach c) Within 72 hours of unit synchronization, all HED valve
Valve - #Unit to be checked once to ensure tight shut off otherwise
(C) necessary rectification to be done before the internal
25B013 - #1 270 leakage passage propagates through steam cutting.
CRD-6 - #1 178
49V025 - #1 101 d) Temperature readings should be taken quarterly to
get a pattern of the valve performance.
25V035 - #1 134
Passing Passing. CONCLUSION
Passing
Passing Gland leak The standardization of check points has been done
based on observations at BBGS for last 3 years. Gradual
Passing Due to operation improvement can be observed in number of renewed
of bypass trap
Trap defective in
bypass line
58
