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GSK Manufacturing
Aranda de Duero, SPAIN
STEAM AND CONDENSATE ENERGY AUDIT REPORT
PROJECT N° 30275
1 Emission E. Morin R. Ivanov 04/02/2011 Item Description Established Checked out Date
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 2 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
TABLE OF CONTENTS
1 Executive summary ................................................................................................................... 4
2 Steam budget and summary of potential savings ...................................................................... 6
3 Optimisation project n°1: Reduce Boilers Blowdown rate ......................................................... 8
3.1 CURRENT SITUATION .............................................................................................................................. 8
3.2 OPTIMIZATION ....................................................................................................................................... 9
3.3 SAVINGS CALCULATION ........................................................................................................................ 10
3.4 INVESTMENTS ...................................................................................................................................... 11
4 Optimisation project n°2: Reduce flash steam losses from feedwater tank ............................. 12
4.1 CURRENT SITUATION ............................................................................................................................ 12
4.2 OPTIMIZATION ..................................................................................................................................... 15
4.3 SAVINGS CALCULATION ........................................................................................................................ 16
4.4 INVESTMENT ........................................................................................................................................ 19
5 Optimisation project n°3: Improve steam ancillaries insulation ............................................... 21
5.1 CURRENT SITUATION ............................................................................................................................ 21
5.2 OPTIMIZATION ..................................................................................................................................... 22
5.3 SAVINGS CALCULATION ........................................................................................................................ 22
5.4 INVESTMENTS ...................................................................................................................................... 23
6 Optimisation project n°4: Replace failed steam traps.............................................................. 24
6.1 CURRENT SITUATION ............................................................................................................................ 24
6.2 OPTIMIZATION ..................................................................................................................................... 25
6.3 SAVINGS CALCULATION ........................................................................................................................ 25
6.4 INVESTMENT ........................................................................................................................................ 26
7 Summary of deviations noticed during the audit ...................................................................... 27
7.1 STEAM GENERATION ............................................................................................................................ 27
7.2 STEAM DISTRIBUTION ........................................................................................................................... 28
7.3 STEAM USERS ..................................................................................................................................... 29
7.4 CONDENSATE RETURN ......................................................................................................................... 32
8 Complete check list of all verifications done during the audit ................................................... 33
9 Recommended complementary studies................................................................................... 35
9.1 ADDITIONAL ENERGY-SAVING OPTIMISATIONS ........................................................................................ 35
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 3 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
9.2 ADDITIONAL OPERATIONAL OPTIMISATIONS ............................................................................................ 36
10 Appendix N°1: Determination of the January 2011 boiler house efficiency .............................. 37
11 Appendix N°2: Steam Pressure Controlled Heat Exchangers at Low Load .............................. 40
11.1 CURRENT SITUATION ............................................................................................................................ 40
11.2 OPTIMIZATION ..................................................................................................................................... 43
11.3 SAVINGS ............................................................................................................................................. 45
11.4 INVESTMENTS ...................................................................................................................................... 45
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 4 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
1 Executive summary
The energy audit conducted from January 17th till January 20th 2011 by Armstrong covers the 4 parts
of the steam loop: boiler house, steam distribution, steam consumption and condensate return.
GSK factory located at Aranda de Duero, in Spain, produces medicines as liquids, aerosols and
tablets.
Steam is mainly used by:
- Coils to produce hot air for fluid bed dryers, coating machines (GLATT) and dehumidifier
(Munters)
- Heat exchangers for sanitization, hot water production, pure steam generation
- Double jackets for reactors heating
Steam is distributed at 7 barg from the new boiler house since one year. The former boiler house is
now stopped. All steam is distributed from the Eagle building to tunnel 2 area and tunnel 1 area.
Steam pressure is then locally reduced to 6, 4 or 2 barg.
Steam is produced by 2 steam generators (Clayton), gas-fired, with a capacity of 3 tons/hr.
The average steam production of the boiler house during the audit is estimated at 0,9 tons/hr. The
steam consumption was low due to the stop of activities in the Eagle Building.
As an indicator, if we use some figures recorded in the old boiler house 2 years ago, your average
steam consumption was about 2 tons/hr.
Our calculations based upon data collected during the audit show a current steam price of 29,5 €
per ton, and an annual steam budget estimated at 133 300 €.
The steam and condensate lines are generally correctly sized.
Insulation of steam ancillaries can be improved.
The steam distribution system is under trapped, especially in front of control valves, resulting in a
serious risk of steam leaks caused by corrosion, erosion and water hammering.
All Condensate that could be recovered is sent back to the boiler house using 3 pumping traps units.
Condensate return ratio was calculated to be 70% during the audit.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 5 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
In order to identify steam leaks, operational problems etc., a steam trap survey was carried out ; in
total 98 traps were tested. The trap survey showed 15% of failed traps (leaking and plugged).
The savings calculated for optimization projects in this report were based upon engineering
assumptions, observations and standard engineering practices.
We estimate the potential energy savings of at least 9% of the estimated steam budget, which
represents a yearly saving of about 377 MWh, 72 tons of CO2 and 11 850 € (see projects 1-3-4).
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 6 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
2 Steam budget and summary of potential savings
The former boiler house (Energy Central 1) was equipped by meters for all energies (gas, water,
steam, condensate) and data were recorded in a global supervision system.
However the new boiler house (Energy Central 2) is not as well equipped. There are only 1 water
meter and 2 gas meters (one for each steam generator) but data is not regularly reported.
Therefore we cannot know your gas consumption for the last 12 months and we cannot calculate
your steam production for the previous year.
Nevertheless, based upon the utility figures during our visit on site in January 2011, we can
estimate:
Boilers steam generation:
• Total yearly steam generation: 3472 MWh (4516 t/year)
• Steam cost: 38.4 €/MWh (29.5 €/t)
• Total yearly steam budget: 133 300 €/year
• Efficiency estimated: 86% (see calculation in appendix n°1)
Basic data considered:
• Gas unit costs : 25 €/MWh hhv
• Gas High Heating Value : 42.1 MJ/Nm³
• Electricity unit costs : 0.064 €/kWh
• Water costs :
o 0.35 €/m³ for city water
o 9000 €/year for Chemicals
o Total = 5 €/m³
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 7 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Summary of identified energy-saving optimizations and their estimated yearly results:
Note: projects n°1, 3 and 4 should be prioritized as it is simple solutions easy to implement with a
payback time close to 1 year :
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 8 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
3 Optimisation project n°1: Reduce Boilers Blowdown rate
3.1 Current situation
Water impurities and chemicals concentrate (due to evaporation) in a Clayton system as in any
other steam boiler.
To avoid boiler problems, water must be periodically discharged or “blown down” from the boiler to
control the concentrations of suspended and total dissolved solids in the boiler.
The importance of boiler blowdown is often overlooked. If the blowdown rate is too high, you waste
energy (water, fuel, chemicals). If high concentrations are maintained, (too low blowdown) it may
lead to scaling, reduced efficiency, and could lead to water carryover into the steam compromising
the steam quality (wet steam).
Comparing to conventional firetubes steam boilers, Clayton Steam Generators have reduced
blowdown because of two factors:
• Steam Generator is a forced circulation boiler and can tolerate relatively high TDS levels in
the feedwater – as high as 8550 ppm (normal range is 3000-6000 ppm)
• Water that is blowndown is separator trap return water that has been concentrated in the
separator by a factor of, typically, 4 to 5.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 9 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Because condensate from Clayton separator returns to the feedwater tank, the feedwater will be
concentrated and "cycled up" as in normal boiler water. In other words, the feedwater in the
feedwater tank will have the same composition as the coil water.
Therefore the blowdown rate is calculated with the following formula:
% Blowdown = C make-up water
(C Feedwater – C make-up water )
Where :
C Feed water = the measured TDS concentration in the feedwater tank
C make-up water = the measured TDS concentration in the make-up water
- The blowdown system installed on the 2 Clayton in the new boiler house is automatic: the
valve opens every 2 hours during 4 minutes.
According to Nalco monthly water analysis since June 2010, average TDS concentration values are:
- Feed water =50 ppm
- Make up water = 1520 ppm
Therefore your average blowdown rate is 3.4 %
3.2 Optimization
According to the water treatment manual from Clayton, the following water conditions must be
maintained in the feedwater (boiler water) at all operating times:
• Zero hardness
• pH 10.5–11.5 (normal range), maximum of 12.5
• Oxygen free with an excess sulfite residual of 50–100 ppm
• Maximum TDS of 8,550 ppm (normal range 3,000-6,000)
• Maximum dissolved iron of 5 ppm
• Free of suspended solids
• Maximum silica of 120 ppm with the proper OH alkalinity
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 10 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
According to your water analysis, TDS concentration is half of the lowest value recommended by
Clayton. Therefore you could reduce at least by 2 the blowdown rate.
The easiest solution is to change the duration of blowdown valves opening defined in the BMS
system. In agreement with Nalco, you can reduce the blowdown duration to 2 minutes every 2 hours
for example.
Another solution consists in installing a TDS probe on the feedwater line and control the blowdown
valve continuously.
3.3 Savings calculation
Reduce Blowdown rate Existing Proposed Savings
Make-up water TDS ppm 50,0 50,0
Feedwater TDS ppm 1520,0 3000,0
Blowdown rate % 3,40 1,69 1,71
Water savings Existing Proposed Savings
Steam production of the boiler kg/h 1000,0 1000,0
Blowdown flow kg/h 34,0 16,9 17,1
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 11 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Treated Water unit costs €/m3 5,0 5,0
Water costs €/yr 1063 530 533
Fuel savings Existing Proposed Savings
Sensible heat Blowdown kj/kg 721,0 721,0
Sensible heat make up water kj/kg 50,0 50,0
Sensible heat differential kj/kg 671,0 671,0
Energy used kj/h 22823 11373 11450
Boiler efficiency % 86,0 86,0
Operating hours hr 6240 6240
Fuel used MWh/yr 46,0 22,9 23,08
Fuel unit costs €/MWh 25,0 25,0
Fuel costs €/year 1150 573 577
CO2 savings Existing Proposed Savings
Energy used Gj/yr 166 83 83
CO2 emissions kg CO2/GJ 50,6 50,6 50,6
CO2 produced t/yr 9,5 4,7 4,7
Total savings Existing Existing Proposed
Total costs €/yr 2211 1102 1109
Total energy saved by reducing the blowdown rate is estimated at 1110 €/year.
3.4 Investments
No investment is required to change the blowdown frequency on the BMS System.
However we estimate the budget to install a TDS controlled blowdown valve at 9000 €.
Payback time for this optimization would be more than 7 years.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 12 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
4 Optimisation project n°2: Reduce flash steam losses from feedwater
tank
4.1 Current situation
In the new boiler house, 7 barg saturated steam is produced by 2 Clayton generators.
The principle of steam production is the following:
Make-up water and return condensate are blend in the feedwater tank. Feedwater is pumped into
the heating coil, flowing through the spiral single passage section of the coil in a direction opposite
of the combustion gases, where it is rapidly heated to steam temperature. As the fluid leaves the
generator section, it passes through helically wound water wall section, into the separator nozzle in
the steam separator. The centrifugal force in the nozzle separates dry steam from excess water,
which returns to the lower section in the separator. Steam is delivered through the steam discharge
outlet located at the top of the steam separator. The excess water is returned to the feedwater
through the steam trap.
This system allows delivering 99% dry steam within a short time.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 13 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
In order to keep the coil wet at all operating conditions and assure a very good steam quality, a
minimum of 20% excess water is required.
This part of excess water is heated from feedwater tank temperature to saturation (170°C/7 barg)
and evacuated by the steam trap at the separator outlet. This condensate is then sent to the
atmospheric feedwater tank.
Consequently a part of condensate will vaporize from 7 to 0 barg generating 13.5% of flash steam in
the feedwater tank.
Condensate from separator going back to the feedwater tank is useful to maintain the feedwater at
high temperature (90°C minimum required).
We indeed observed that the average temperature in the tank is above 95°C.
Therefore, no extra-steam is needed to maintain the temperature.
However the feedwater tank is still overheated.
Usually, condensate from separator is connected to the bottom of the feedwater tank (under the
water level) using a sparger tube :
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 14 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
This configuration allows maximizing the heat usage and insures a good homogenization of
feedwater temperature in the tank.
However in the new boilerhouse, condensate is connected to the top of the feedwater tank :
Consequently, flash steam generated is not completely condensed and is evacuated through the
vent to the atmosphere.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 15 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Excess feedwater load
In theory, a minimum of 20% excess water is required for a good operation of the steam generator.
This percentage is set and the feedwater pump has a fixed pumping rate.
It is possible to check if the amount of excess water is in a normal range as it is directly linked to the
amount of condensate evacuated from the steam trap.
The Clayton booklet explains how :
We did measure the opening time for the steam trap when the Clayton was at 25-30% load. I was
about 10 minutes per hour. This value is too high considering the explanation above. We therefore
conclude that the amount of excess water set is too high (about 40%) and so is the amount of flash
steam generated in the feedwater tank.
4.2 Optimization
To prevent from too much flash steam loss at the feedwater tank vent we recommend to:
1. Check with your Clayton distributor if a technician can reduce the amount of excess
water pumped to run properly the generators
2. Move condensate connections from the top to the bottom of the feedwater tank using
a sparger tube : it will help to have an homogeneous feedwater temperature in the
tank
3. Recover condensate heat to preheat combustion air up to 50°C. The solution consists
in installing a coil to heat combustion air using a part of condensate from Clayton
separator.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 16 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
4.3 Savings calculation
Considering our observations and measurement on site, we can estimate the cost of this flash
steam loss:
Fuel savings Existing
% of revaporisation (7 to 0 barg) 13,5%
Flash steam flow estimated ton/h 0,066
safety factor 10%
Energy loss kW 37
operating hours hr 6240
yearly Energy used MWh/year 232
boiler efficiency % 86
Fuel used MWh/year hhv 300
Fuel unit costs €/MWh hhv 25
Fuel costs €/year 7506
CO2 savings Existing
Energy used Gj/yr 1081
CO2 emissions kg CO2/GJ 50,6
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 17 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
CO2 produced t/yr 55
Water savings Existing
Flash steam flow estimated kg/h 0,066
safety factor 10%
Yearly water lost m³/year 371
Water unit costs €/m3 5,0
Water costs €/yr 1853
In conclusion, we estimate the total potential savings at 9360 €/year.
1. Solution 1 : reduce excess feed water rate on the pump
Considering your installation, the Clayton specialist technician will decide how much it is possible to
reduce the amount of excess water pumped.
The following table shows savings calculation if the rate is decreased by 10% :
Fuel savings Existing Proposed Savings
Feewater flow m³/hr 1,1 1,1
Excess feedwater rate % 40% 30% 10%
Excess water flow / condensate m³/hr 0,44 0,33 0,11
% of revaporisation (7 to 0 barg) 13,5% 13,5%
Flash steam flow estimated ton/h 0,059 0,045 0,015
Energy loss kW 37 28 9
operating hours hr 6240 6240
yearly Energy used MWh/year 232 174 58
boiler efficiency % 86 86
Fuel used MWh/year hhv 300 225 75
Fuel unit costs €/MWh hhv 25 25
Fuel costs €/year 7506 5629 1876
CO2 savings Existing Proposed Savings
Energy used Gj/yr 1081 811 270
CO2 emissions kg CO2/GJ 50,6 50,6
CO2 produced t/yr 55 41 14
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 18 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Water savings Existing Proposed Savings
Flash steam flow estimated kg/h 0,059 0,045 0,015
Yearly water lost m³/year 371 278
Water unit costs €/m3 5,0 5,0
Water costs €/yr 1853 1390 463
The total savings would be 2340 €/year.
2. Solution 2 : Move the condensate connections to the bottom of the tank with a sparger tube
The modification will imply an increase of the feedwater temperature pumped to the generators.
We estimate this increase at 5°C. The efficiency gain on steam production will be about 0.5%.
Boiler efficiency Existing Proposed Savings
Feedwater temperature °C 93,0 98,0
Boiler efficiency % 86,0 86,5 0,5
Fuel savings Existing Proposed Savings
yearly Energy used GJ/yr 12499,2 12499
Boiler efficiency % 86,0 86,5 0,5
Fuel used MWh/yr hhv 4486 4460 25,93
Fuel unit costs €/MWh hhv 25,0 25,0
Fuel costs €/year 112145 111496 648
CO2 savings Existing Proposed Savings
Energy used Gj/yr 16149 16055 93
CO2 emissions kg CO2/GJ 50,6 51
CO2 produced t/yr 817 812 5
Savings are poor (less than 1000 €) because steam production is very low. If the steam demand
increases, savings will follow.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 19 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
3. Solution 3 : preheat combustion air using hot condensate
The preheating of combustion air from ambient to 50°C will lead to an efficiency improvement by
1.5%:
Boiler efficiency Existing Proposed Savings
Intake air temperature (average) °C 18,0 50,0
Stacks temperature °C 120,0 120,0
Oxygene content % 7,0 7,0
Boiler efficiency % 86,0 87,5 1,5
Fuel savings Existing Proposed Savings
yearly Energy used GJ/yr 12499,2 12499
Boiler efficiency % 86,0 87,5 1,5
Fuel used MWh/yr hhv 4486 4409 76,90
Fuel unit costs €/MWh hhv 25,0 25,0
Fuel costs €/year 112145 110222 1922
CO2 savings Existing Proposed Savings
Energy used Gj/yr 16149 15872 277
CO2 emissions kg CO2/GJ 50,6 51
CO2 produced t/yr 817 803 14
4.4 Investment
1. Solution 1 : reduce excess feed water rate on the pump
Budgetary cost for this project is estimated under 1000 €.
Payback time for this optimization is less than 6 Months.
2. Solution 2 : Move the condensate connections to the bottom of the tank with a sparger tube
Budgetary cost for this project is 3000 €.
Payback time for this optimization is about 55 Months.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 20 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
3. Solution 3 : preheat combustion air using hot condenste
Budgetary cost for this project is 13 100€.
Including:
- Air ducts, condensate coil, valves, controls
- Installation work
At level of steam generation seen during the audit, payback time for this optimization is about 82
Months.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 21 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
5 Optimisation project n°3: Improve steam ancillaries insulation
5.1 Current situation
Not only for safety reason, must hot surfaces have effective insulation to
prevent excessive heat loss by radiation. The basic function of insulation
is to retard the flow of unwanted heat transfer. There is more chance of
part of steam to condense during distribution if the pipelines are not
properly insulated.
There is a closely interrelated efficiency between boilers and their
distribution systems. The losses occurred in the distribution systems have
a significant impact on boiler operations. When these losses are minimized, boiler plant efficiency is
improved.
We observed some valves and filters on steam lines which are not insulated in your steam
distribution system.
The following table shows the non-insulated equipments identified during the audit:
Location Ancillaries length or DN Pressure loss
type number (mm) (barg) (W)
Boiler house (Eagle)
Back Pressure valves valve 2 80 7 2106
Eagle building
2nd floor South valve 2 100 7 2796
Pressure Reducing Station strainer 1 100 7 1398
Pressure Reducing Station valve 1 100 4 1137
GLATT 6115 valve 2 32 4 745
2nd Floor North Lavado valve 1 32 4 373
2nd Floor North Lavado valve 1 40 4 425
4th floor south valve 3 40 2 1069
4th floor south strainer 1 40 2 356
Tunnel 2 aera
1st floor VP37 valve 1 50 6 618
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 22 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
VP43 valve 1 50 6 618
near VP43 strainer 1 50 6 618
VP44 valve 1 40 4 425
to MDU1500 strainer 1 40 4 425
Glatt sala 544 - VP56 valve 2 32 6 869
Glatt sala 544 - VP56 strainer 1 32 6 435
Glatt sala 531 - VP50 valve 1 32 4 373
Glatt sala 535 - VP38 valve 1 32 6 435
Glatt sala 535 - VP38 strainer 1 32 6 435
Tunnel 1 aera
VP16 valve 1 65 3 614
VP4 valve 1 65 3 614
The total radiation loss is calculated at 16882 W.
5.2 Optimization
We recommend installing insulated jackets on all ancillaries located in
steam lines above DN25. These jackets are easy to remove in case of
maintenance operations.
5.3 Savings calculation
SAVINGS Calculation
Total radiation losses 16882 W
Operating hours 6240 h
Annual loss (time corrected) 105,3 MWh/yr
Steam production efficiency 86,0% (lhv)
Annual primary energy loss 122,5 MWh lhv/yr
Annual primary energy loss 135,6 MWh hhv/yr
Fuel cost 25,00 €/MWh
Annual financial loss 3391 €/yr
CO2 emissions 24,7 t CO2/year
Savings calculated are 3400 €/year.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 23 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
5.4 Investments
Budgetary cost for this project is 6000 €.
Including:
- On site measurement to prepare tailor-made manufacturing of the jackets
- Supply of insulation jackets
- Installation
Payback time for this optimization is less than 21 Months.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 24 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
6 Optimisation project n°4: Replace failed steam traps
6.1 Current situation
A full trap survey was done during our audit. There are 98 steam traps identified and listed on your
steam system drawings. 15 of the installed traps were failing (13 leaking, 2 plugged) and 34 could
not be tested as the units were out of service.
The details of the trap survey and its results are available on SteamStar trap management online
platform.
Here are the access parameters of this trap survey:
Login : beatriz.herrero@gsk.com
Full Name : Beatriz Herrero Gonzalo
Password : B34Tr1ZH3Rr3
Website : www.steamstar.com
Summary of results:
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 25 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
6.2 Optimization
We recommend replacing all steam traps indentified as failed.
Leaking steam traps mean losses of steam. It may also reduce condensate evacuation from process
by creating a back-pressure in the return lines.
Besides, steam in condensate return lines may generate water hammers which can damage your
installation and ancillaries (valves, pressure reducing valve, heat exchangers).
Blocked traps compromise steam quality and cause corrosion and erosion of steam lines and
auxiliaries, resulting in high maintenance costs and increased down time due to system failures.
These traps should be individually evaluated and should be cleaned or replaced by correctly sized
and installed traps.
Some of failed traps were not installed properly (reversed or inclined).
We also noticed a wrong selection for traps n°14-34-35, the pressure differential available is 4.5
barg whereas the steam pressure is 7 barg.
6.3 Savings calculation
Fuel savings Existing
Steam losses calculated by Steamstar kg/h 50,450
Energy loss kW 29
operating hours hr 6240
yearly Energy used MWh/year 179
boiler efficiency % 86
Fuel used MWh/year hhv 231
Fuel unit costs €/MWh hhv 25
Fuel costs €/year 5780
CO2 savings Existing
Energy used Gj/yr 832
CO2 emissions kg CO2/GJ 50,6
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 26 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
CO2 produced t/yr 42
Water savings Existing
Steam losses kg/h 50,450
Yearly water lost m³/year 315
Water unit costs €/m3 5,0
Water costs €/yr 1574
Total savings would be 7350 €/year.
6.4 Investment
The budgetary cost for replacing all failing traps is 8000 €.
Including:
- Equipments supply (traps)
- Installation by a mechanical contractor
- Project management
Payback time for replacing all failing traps, including blocked traps, is 13 Months.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 27 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
7 Summary of deviations noticed during the audit
7.1 Steam generation
Steam is produced by the Energy Central 2 since 2010. This new boiler house is not well monitored
yet.
Gas meters data on the 2 steam generators are not read regularly. As natural gas is also used for
hot water boilers in the Energy Central 1, it is not possible at the moment to know exactly fuel
consumption used to produce steam.
The make-up water meter is reported every day during the daily maintenance (decalcify water).
Some other data are measured and reported to the BMS System:
However some of these probes do not work properly (stacks temperatures, steam temperature) and
only steam pressure is recorded (trends available).
Consequently it is not possible to check on a regular basis the good functioning of the new boiler
house.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 28 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Gas meters should at least be reported once per month. The best would be to connect meters to the
BMS system (same for water) and record values.
We also recommend you to check if the steam and condensate flowmeters used in the old boiler
house cannot be moved to the new steam production system.
7.2 Steam distribution
Missing condensate drain points
Poor drainage of steam lines will cause accumulation of condensate in the steam distribution
system, thus causing a serious safety hazard for water hammering.
Also on many locations there are no drip legs installed on steam lines in front of control valves. In
some situations there are several meters vertical steam line above a control valve, without a drain
point (especially for Munters feed). When these valves are in a closed position condensate will
accumulate in front of these control valves, and sub-cool. This sub-cooled condensate is aggressive
(low PH) and will cause corrosion of the valves and piping. Also there is a risk for thermo shock and
water hammering. Furthermore accumulated condensate will compromise steam quality and cause
early wear of piping and ancillaries due to erosion.
Steam line size between Eagle and Tunnel 1&2
We have checked the steam line size for the connection between Eagle and Tunnel 1&2.
« Low point »
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 29 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Steam is distributed at 6 barg in a DN65 pipe. As steam velocity should not exceed 30 m/s in the
pipe, the maximum steam flow you could sent safely to Tunnel 1&2 is 1220 kg/hr.
Steam lines DESIGN
Steam pressure 6 Bar(g)
X value 1,00
Line diameter DN 65
Flow 1220 kg/h
Steam velocity 30,0 m/s max 30,0 m/s
Steam temperature 164,9 °C
specific volume 0,27 m3/kg
Steam enthalpy 2763 kJ/kg X= 1,00
Sensible heat 697 kJ/kg
Latent heat 2066 kJ/kg X= 1,00
Latent input 700,1 kW
Currently it is not a problem as your real steam consumption for these areas is lower. However, if for
some reason the steam demand is increased you have to be aware of this limit.
7.3 Steam users
Main steam users are the GLATT systems and the dehumidifier Munters which need hot air.
The factory use 8 GLATT and 9 Munters in the whole site.
-GLATT systems (for coating machines and fluid bed dryers)
Each air handling unit is equipped with 2 or 3 steam coils.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 30 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
The first one is called the “anti-freezing” coil. It is used to pre-heat outside air to 20-30°C.
Often the control valve is a thermostatic one and it is not protected by a drain point upfront.
Therefore this valve may leak rapidly.
Besides, considering the low temperature setting, the steam load in the coil may be low and there
may not be enough pressure to push condensate in the return line. This condition leads to flooded
coils which decrease the heat efficiency and generate slight water hammers. (see appendix n°2 for
detailed explanation)
The second and third steam coils are used to heat the air to 75-85°C. Most of them are equipped
with an automatic ON/OFF valve upfront the control valve. This prevent from steam leaks. However,
we highly recommend installing a steam trap in front of control valves which are installed in “low
point” to prevent from water hammering.
.
The GLATT equipments installed in the Eagle building are also equipped with start-up steam traps.
This steam traps open only with a pressure differential less than 1.5 barg. It allows evacuating
condensate to the sewer when steam pressure is less than back-pressure.
We observed that finally the valves after these steam traps are closed because you lose too much
condensate to the sewer. To avoid this situation you could install a system to push condensate in
the return at any operating condition (see appendix n°2).
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 31 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
-Dehumidifier Munters (for air conditioning)
The Munters system uses a desiccant rotor to remove humidity from outside air.
This desiccant rotor needs to be regenerated using hot air.
The air is heated by a steam coil up to 125°C.
Steam pressure needed is 4.25 barg (indicated in Munters datasheet).
Steam feeding lines are well equipped with control valves and automatic ON/OFF valves.
However there is no drainage point before all valves. Consequently, when the valve is closed,
condensate accumulates in steam line.
- Steam pressure levels
Many pressure reducing stations are installed on steam distribution lines.
However the steam pressure level is not always adapted to the need.
Munters dehumidifiers are designed to use 4.25 barg, but we have seen some equipment fed with 4
barg or even 2 barg steam. Therefore the desiccant regeneration may not be efficient and the
humidity control hazardous.
For GLATT dryers, steam pressure levels are also various:
- WSG120-sala 531, GLATT1350-sala 535 = 3 barg
- GLATT-sala 544 = 4.5 barg
- WSG120-sala 602, Climatiz.Recubrid.- sala 607 = 5 barg
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 32 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
- GLATT 6115-6102-6106, Eagle = 4 barg
Steam pressure levels should be adjusted considering these parameters:
� Hot air temperature needed
� The lower the steam pressure, the higher the latent heat which is transferred in
the coil
� The lower the pressure, the higher the specific volume (attention to be paid to
steam pipe size)
� If steam pressure is less than condensate return back-pressure, you may cause
condensate accumulation inside the coil.
-Linea AVAMYS (2 double jacketed reactors)
We observed that there is only one steam trap for the 2 condensate outlets of reactors.
This configuration can only work if the reactors do not run in the same time; otherwise you may have
troubles to evacuate condensate from one of the reactors to the return line.
7.4 Condensate return
Condensate from Tunnel 1 area is collected and sent to Tunnel 2 area with an old pumping-trap.
The condensate header and the pump have been relocated recently and the steam trap on the
motive steam line has not been re-installed. We recommend you to insert the steam trap again to
prevent from rapid erosion and steam leaks on the check valve at the pump steam inlet.
In a general way, there is no high back pressure in condensate return lines as you use 3
atmospheric condensate pumps. In Tunnel 1 and Eagle they are located at the same level or under
steam users. Thus condensate back-pressure is close to 0.
However in tunnel 1, some steam users located on the first floor are “under” the condensate pump
installed on the second floor. Therefore these steam users may be more sensitive to condensate
return back-pressure.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 33 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
8 Complete check list of all verifications done during the audit
Potential optimisation Status Comments
STEAM GENERATION
Steam pressure setting OK 7 barg is good compromise. 6 barg would certainly
be too low for distribution (lines sizing restrictions)
Feed water temp. to the boilers OK 93°C measured on the feedwater pump. Clayton
requires a minimum of 90°C
Stack temperature in front of
economizer
NA Not possible to measure on Clayton boilers.
Stack temperature after economizer OK Refer to combustion analysis or temperatures
reported in the BMS system (when repaired)
Combustion air temperature To be improved Ambient
Oxygen rate OK 5-7% depending on the firing rate
Boiler sizing OK
Boiler blow down rate To be improved Could be reduced to fit with Clayton
recommendations
Refer to optimization project n°1
Deaerator pressure NA Atmospheric feedwater tank
Feed-water pre-heating NA
Boiler stand-by time and volatility of
steam demand
OK Clayton steam generators have a good response
for these conditions
Boiler blow-down recovery NA Blowdown is too low at current steam demand to
recover energy within 5 years payback
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 34 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
STEAM DISTRIBUTION
External leaks of steam or condensate
from pipes, flanges, etc.
OK No leak has been observed during the audit
System design, trapping points etc. To be improved Steam lines have all been interconnected to
distribute steam in both ways (from and to Eagle).
Steam line between Eagle and tunnels 1 and 2 is
undersized for high steam demands.
It misses many trapping points in front of control
valves and in “low points”.
Insulation To be improved Refer to optimization project n°3
Steam quality To be improved Steam quality is good at the outlet of the boiler
house but is progressively decreased by the lack of
drip legs in front of steam users
Steam pressure level To be improved There are many pressure reducing stations. The
pressure level is not always adapted to the steam
usage.
Water hammering OK No water hammering has been observed in the
distribution lines
STEAM USERS
Condensate drainage and air venting
from heat exchangers
OK
Steam traps To be improved 15% failed traps identified
Some traps are wrongly mounted (inclined,
reversed)
CONDENSATE AND FLASH STEAM RECOVERY
Condensate recovered OK
Sizing of condensate return lines OK
Flash steam recovery To be improved Flash steam could be recovered on condensate
receivers. A vent condenser exists in tunnel 2 but is
not used anymore.
Water hammering OK
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
9 Recommended complementary studies
9.1 Additional energy-saving optimisations
Flash steam recovery
We have observed a significant flash steam loss from the vent of condensate header-tunnel 2.
A part of it is probably due to the leaking traps.
Therefore when the failed traps are replaced, the losses should be lower.
We noticed during our visit that there is a heat exchanger installed on the vent line. A part of sanitary
hot water was used to condense flash steam. However this recovery does not work anymore as this
sanitary hot water loop is no longer used in the building. The valves are closed.
We could not get any data about this vent condenser during the audit (kW ?, water flow ?).
However, it could be interesting to use this equipment in the future if you can find a need of water
preheating in the same area.
We have estimated some potential savings :
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Fuel savings Existing
Flash steam flow estimated ton/h 0,020
Energy loss kW 13
operating hours hr 6240
yearly Energy used MWh/year 78
boiler efficiency % 86
Fuel used MWh/year hhv 101
Fuel unit costs €/MWh hhv 25
Fuel costs €/year 2527
Water savings Existing
Flash steam flow estimated kg/h 0,020
Yearly water lost m³/year 125
Water unit costs €/m3 5,0
Water costs €/yr 624
CO2 savings Existing
Energy used Gj/yr 364
CO2 emissions kg CO2/GJ 50,6
CO2 produced t/yr 18
9.2 Additional operational optimisations
Flooded heat exchangers:
Poor drainage of condensate from low temperature controlled heat exchangers could have an
impact on productivity (decreased heat exchange surface and unstable heating temperature) and on
maintenance (leaking heat exchangers due to corrosion and water hammering). The reasons for this
phenomenon and possible solutions are described in details in appendix 2. Almost all anti-freezing
coils on GLATT equipments are operating under these conditions. In case flooding of heat
exchangers starts creating important productivity and maintenance problems, we recommend
studying in more details the best solution for each concerned heat exchanger.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
Page 37 of 45
To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
10 Appendix N°1: Determination of the January 2011 boiler house
efficiency
BOILER SIMULATION CLAYTON
Boiler operating hours (incl. hot stand-by hours) 6.240 hours/year
1. Fuel power input % LHV
Fuel type: 8
Fuel consumption during operating hours 61,1 Nm3/h
Specific weight of the fuel 0,77 kg/Nm3
Fuel consumption 47,2 kg/h
Lower heating value (LHV) 49318 kJ/kg (=38082 kJ/Nm3)
Higher heating value (HHV) 54608 kJ/kg (=42167 kJ/Nm3)
Fuel unit costs 25 €/MWh HHV (= 0,29 €/Nm3)
Fuel power input (LHV) 646,6 kW 100%
Fuel power input (HHV) 716,0 kW
Steam pressure 7 Bar(g) / 170,4°C sat.
Enthalpy steam 2768 kJ/kg
Temperature feed water to the boiler/eco 93 °C
Enthalpy feed water 389 kJ/kg
Latent heat of the steam 2380 kJ/kg
Max. theoretical steam production 0,98 ton/h
2a. Combustion losses (boiler only)
Temperature stack after boiler 160 °C
Temperature ambient air 18 °C
Excess air 45,0 %
Oxygen % flue gas (Dry volume) 7,00 %
Stack flow 15,82 Nm3/Nm3 fuel
Total stack flow 966,8 Nm3/h
Specific heat stack 1,37 kJ/Nm³.K
Power in stack (sensible heat) 52,14 kW -8,1%
2c. Economizer (non condensing)
Temperature stack after economizer 120 °C
Economizer inlet water temperature 93,0 °C
Economizer outlet water temperature 102,6 °C
Heat transfer efficiency 100%
Power recovered by economizer 14,7 kW 2,3%
2d. Air preheating from external source (Top of boiler house)
Combustion air required 14,85 Nm3/Nm3 fuel
Total combustion air flow 907,8 Nm3/h
Normal combustion air temperature 18,0 °C
Preheated combustion air temperature 18,0 °C Power recovered by air preheating 0,0 kW 0,0%
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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3. Radiation losses
Boiler capacity 3,1 ton/h (=2MW)
Load 32 %
Radiation losses at full load 0,2 %
Radiation losses 4,1 kW -0,6%
4. Blow down
TDS Make-up water 50,0 ppm
TDS Feed water boiler 1520,0 ppm
Boiler water lost by blow down + carry over 3,4 % of steam output (30,4cycles)
Boiler feed water flow 1,319 ton/h
Boiler water lost by blow down + carry over
0,043
ton/h
X-value of the steam from the boiler 1,000
Blow down flow remaining 0,043 ton/h
Enthalpy blow down water 721 kJ/kg
Temperature make up water 12,0 °C
Enthalpy make up water 50,2 kJ/kg
Total Blow Down losses (Boiler + Deaerator) 8,1 kW -1,3%
Blow down losses compensated by boiler only 4,0 kW -0,6%
5. Energy losses due to excess of water
Feed water tank pressure 0,0 bar(g)
% of revaporisation (7 to 0 barg) 13,5%
Water excess 40,0 %
Feed water flow 1,319 ton/h
Condensate flow out of separator 0,484 ton/h
Condensate enthalpy 721 kJ/kg
Temperature make up water 12,0 °C
Enthalpy make up water 50,2 kJ/kg
Flash steam flow 0,066 ton/h
Energy loss from condensate 44,7 kW -6,9%
6. Boiler Efficiency and Fuel Costs
Net power output in steam from the boiler 556,4 kW ( 3472 MWh) 86,0%
Net steam production boiler 0,791 ton/h = 4938 t/year Boiler efficiency on LHV 86,05 %
BOILERHOUSE SIMULATION
Boiler house operating hours 6.240 hours/year
6. Steam consumption feed water tank % LHV
Measured make up water flow 0,29 m3/h
Enthalpy make-up water 50,16 kJ/kg
Feed water flow to boilers 1,32 m3/hr
Enthalpy feed water 388,74 kJ/kg
Enthalpy condensate from separator (liquid phasis) 712,30 kJ/kg
Enthalpy flash steam from condensate (separator) 2259,04 kJ/kg
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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To the attention of Ms. Beatriz Herrero-Gonzalo Established by E. Morin
Temperature condensate from factory 95,00 °C
Condensate flow (from factory) 0,50 t/hr
Over heat 41,11 kW
Estimated flash flow lost 0,066 t/hr
Condensate return rate 69,3%
10. Overall Boiler House Efficiency
Net total power output from the boiler house (incl. CHP) 556,4 kW 100,0%
Boiler house efficiency on LHV 86,0 %
Boiler house efficiency on HHV 77,7 %
Annual fuel consumption (LHV) 4.035 MWh/year
Annual fuel consumption (HHV) 4.468 MWh/year
Annual CO2 emissions (50,6 kg/GJ / 182,2 kg/MWh HHV) 814 tons/year
Annual fuel costs 111.694 €/year
10a. Steam generation and steam costs
Net total steam power output from the boiler house 556,4 kW 100,0%
Net total steam heat output from the boiler house 3.472 MWh/year
Net dry steam production boiler house 0,724 ton/h = 4516 t/year
Annual fuel consumption (LHV) 4.035 MWh/year
Annual fuel consumption (HHV) 4.468 MWh/year
Fuel costs for steam generation 111.694 €/year 83,8%
Electricity unit costs 0,064 €/kWh
Electrical power for the boilerhouse 30 kW
Electricity costs 11.981 €/year 9,0%
Make up water unit costs 0,35 €/m3
Make up water costs 628 €/year 0,5%
Costs for chemicals 9.000 €/year 6,8%
Sewer unit costs 0,00 €/m3
Sewer costs 0 €/year 0,0%
CO2 unit costs 0,00 €/ton
CO2 Emissions ( 180,3 kg/ton of dry boiler house steam) 814 ton/year
CO2 costs 0 €/year 0,0%
Total variable steam costs 133.303 €/year 100%
Total costs steam from boiler house 29,52 €/ton
Total costs steam from boiler house 0,0384 €/kWh
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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11 Appendix N°2: Steam Pressure Controlled Heat Exchangers at Low
Load
11.1 Current situation
Within the steam system, there are several pressure controlled heat exchangers operating at low
loads. Within these heat exchangers, liquids or gasses (air) are heated along with the steam. Most
of the time the desired medium temperature is below 100°C, and the heat exchanger is working at
partial load. Under these conditions, regardless of brand or model, problems may occur due to the
physical properties of the steam.
An audit is only a short visit on site, in which it is impossible to see all operating conditions. Most
problems with heat exchangers only occur at certain conditions. For instance, operation of heat
exchangers for building heating may only be a real problem during the fall and the spring, when
partial loads are typical. Due to the variability of these problems they are often not recognized in
time, and can cause process bottlenecks, loss of production, loss of temperature control and
increased maintenance costs.
Control of steam pressure can be designed in two ways: modulating or on-off. In both cases the
control valves are modulated by the measured temperature of the heated media. Steam pressure
controlled heat exchangers at low loads almost always produce sub-cooled condensate.
Modulating Controls
The steam pressure after a modulating control valve is always lower than the steam pressure in the
up steam lines, unless the system is working at full load which is a rare operating condition.
When heating a product to a temperature below 100ºC, the required steam temperature will often be
close to 100ºC, as the latent heat of the steam is used to transfer the energy as the steam
condenses. Steam temperatures lower than 100ºC, has a pressure below atmospheric pressure. If
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GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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the steam pressure after the steam control valve is less than the pressure in the condensate line,
there will be no driving force (pressure differential) available to push the condensate out of the heat
exchanger and move it to the condensate receiver. The condensate will back up in the heat
exchanger, and will become flooded. This situation is often called a “stall situation”. As the
condensate backs up in the heat exchanger, it will exchange sensible heat with the product, where
the condensate becomes sub-cooled (matching the product temperature). The infrared pictures
below show the condensate backing up in a heat exchanger and the resulting temperature
differences in it.
The more a heat exchanger is oversized, the sooner it will operate at a partial load and the more
the condensate will sub-cool.
In the best case scenario the control system will balance the steam/product differential. However, in
most cases the following is observed:
Due to the condensate backing up the amount of heated surface in the heat exchanger is reduced,
and the desired set point product temperature cannot be reached. As a reaction to this, the steam
control valve will open, thus providing enough pressure differential to push out the condensate.
When this happens all the heating surface in the heat exchanger is available again causing a
sudden rise in the product temperature. There will be an overshoot in temperature which the
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GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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controls will try to correct by closing the steam control valve. This cycle will repeat and control valves
will “hunt” searching for balance. Hunting control valves, and actuators, wear quicker and tend to
leak. The most critical aspect of cycling control valves is that the frequent changes in temperature
will cause local material stresses in the heat exchanger, which over time can cause failures and
leaks (especially in stainless steel). In addition the presence of relatively cold condensate may
cause water hammer and corrosion inside the heat exchanger which can also lead to leaks.
Lowering the condensate back pressure will reduce the risk of condensate backing up in the heat
exchanger, which provides two system improvements. First, it will reduce the loss of exchanger
capacity, and second, it reduces the risk of water hammer. Often when condensate is backing up,
the condensate lines are drained to the sewer. This is only a temporary fix and is a great loss of
energy and can raise waste water temperatures above safe limits.
On-off controls
As with modulating controls, very similar conditions occur in an on-off control. The steam valve
opens when there is a heat demand. A positive pressure differential is created, and the condensate
in the heat exchanger is pushed out. The heating surface in the heat exchanger is exposed and the
capacity rises. Before all of the condensate is pushed out, the desired temperature is reached and
the steam valve closes. During this cycle the steam trap does not receive condensate with a
temperature above 100ºC.
When the steam valve closes, the steam in the heat exchanger will condense, thus creating a
vacuum in the heat exchanger. This vacuum will pull condensate back from the condensate line
unless there is a check valve in place. The condensate inside the heat exchanger will continue to
cool down (sub-cool). When the steam valve opens again, the hot steam will be in contact with the
relatively cold condensate. When this occurs there is a serious risk for thermal water hammer to
occur. Over time these water hammers, and the presence of cold aggressive condensate, can cause
leaks.
Installing a vacuum breaker and a check valve may eliminate the vacuum and the backing-up of
condensate, but it will also allow air to enter the system. This air has to be vented from the heat
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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exchanger otherwise it will reduce the effective steam temperature, and as a result, the heat
exchanger’s capacity. Air in the condensate system will cause corrosion.
11.2 Optimization
A number of solutions have been developed to solve the problems with heat exchangers at
low/partial loads. Finding the most effective and efficient solution would require custom tailored
engineering. Basically there are three methods to remove the condensate from a flooded heat
exchanger with steam pressure control:
• a closed loop pumping trap
• a Posipressure system
• a safety drain trap
A closed loop pumping trap arrangements uses a balancing line to equalize the pressure in the heat
exchanger and the pumping trap. Condensate will drain by gravity toward the pump, and will be
pushed out using steam pressure. The diagram below shows a typical setup:
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Date: 04/02/2011
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A Posipressure system allows air or nitrogen to push out the condensate as soon as the steam
pressure inside the heat exchanger is less than the back pressure in the condensate system. The
diagram below shows a typical setup for this arrangement:
A safety drain is a second trap that is sized to handle the same load as the primary trap. It is
located above the primary trap and discharges into an open sewer. When there is sufficient
differential pressure across the primary trap to operate normally, condensate drains from the drip
point, through the primary trap, and up to the overhead return line. When the differential pressure is
reduced to the point where the condensate cannot rise to the return, it backs up in the drip leg and
enters the safety drain. The safety drain then discharges the condensate by gravity.
STEAM AND CONDENSATE AUDIT
Project N°30275
GSK MANUFACTURING Aranda, Spain
Date: 04/02/2011
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11.3 Savings
The installation of closed loop pumping trap systems, or a Posipressure system, will return
condensate back to the boiler house. Often on flooded heat exchangers this condensate is drained
to sewer and therefore lost. It can increase the heat exchangers capacity, and may speed up
production processes. More important are the savings achieved from improved system reliability
and controllability, however these are often difficult to quantify. The safety drain will not improve the
condensate return, but will save the coil from freezing and prevent process time downs and
maintenance labour to repair.
11.4 Investments
Average budgetary cost for the installation of a closed loop pumping trap system on an existing heat
exchanger is 14000 €.
Average budgetary cost for the installation of a Posipressure system on an existing heat exchanger
is 8000 €.
Average budgetary cost for the installation of a Safety Drain on an existing heat exchanger is 1700€.
Included:
- Equipments supply (piping, pumping trap / Posipressure, valves etc. )
- Installation by a mechanical contractor
- Engineering and project management
Payback time for these optimizations depends on the specific situation.
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