Steam Express-Issue Jan
MICA (P) 180/12/2010
S$2.00
Q1
Jan-Mar 2011
Expertise • Solutions • Sustainability
Fixed Orifice Device ....
the
‘Hole’
Truth
raining condensate from a steam system sounds like a very simple task and it would be if the
system were totally stable and non-variable. In reality the condensate drainage device must
D
be capable of operating over a wide range of conditions determined by the actual application.
All drainage devices must be capable of draining enough condensate not to cause flooding of the
system, remove air and non-condensibles when system is pressurised with steam and not waste
valuable energy while in operation.
There are many types of steam trap available in the market i.e. mechanical, thermodynamic and
temperature operated steam traps. In all cases, these traps will open when condensate is present
and allow it to flow through and close before live steam reached the discharge orifice. The reason
why there are several types of steam traps is to fit the wide variation of drainage requirements
needed. No one type of steam trap will cover the array of drainage applications. To say a fixed
orifice steam trap will work in every application being both effective and efficient is ludicrous.
Fixed Orifice steam traps are devices containing a hole of predetermined diameter to allow a
calculated amount of condensate to flow under specific pressure conditions. In practice, condensate
loads and steam pressures can vary considerably. For instance, start-up and running loads can
differ considerably along with steam pressure which will change due to the actions of temperature
controls. These varying conditions can result in the fixed orifice either holding back condensate in
the process or passing live steam, which can affect plant performance and compromise safety.
Continues on page 2 >>>
Cover Story • P1
<<< Continues from page 1
Fixed orifices are often sized on running conditions, so that they hold back enough condensate and
do not pass steam. If this is so, at start-up, they are undersized to a greater degree and the steam
space stands a good chance of waterlogging. An undersized drainage device can also cause severe
water hammer, which could lead to equipment failure and downtime. Inadequate sizing will also
slow heating processes thus reducing output from vital equipment lowering overall production from
the plant. To avoid undersizing, the hole will then be effectively oversized for running conditions,
and the device will pass live steam. To balance, the size of hole is usually a compromise between
the two conditions, such that, at some points in between, the hole is correctly sized.
Corrosion and service life of plant
Continual waterlogging significantly increases the risk of corrosion in the steam space. It is not
unusual to find that after fitting fixed orifice traps, plant service life is reduced below that which may
be expected with proper steam traps.
A proper steam trap should be able to achieve sufficient capacity at all pressures and flowrates
present in the application. It can then pass hot condensate without leaking steam under any
condition. To achieve this, the size of the hole must vary in the trap. It must be large enough to meet
the worst condition, and then have some means of reducing the effective orifice flow area when
the capacity becomes too great. This exactly describes the operation of a conventional steam trap
which varies automatically to varying conditions.
Maintenance Free?
Historically, plugging has been the biggest problem with orifice devices. To overcome, they
generally use a 100-mesh screen ahead of the orifice to prevent orifice plugging, but that creates
another problem with the screen plugging with solids from the system. These small size orifice
diameters can still lead to a plugging problem due to precipitants, which drop out of solution when
the condensate flashes through the orifice. Depending on how clean the condensate is, plugging
can be a real maintenance headache.
Do They Save Energy Compared to Conventional Steam Traps?
The answer to the energy savings question really is "it depends." In order for a fixed orifice steam
trap to be effective, the condensate load must be relatively constant, the orifice must be sized
correctly, the steam should be clean, pH must be controlled, and the strainer placed in front of the
orifice must be periodically blown down.
Fixed orifice traps would likely save energy for systems with a long inspection/maintenance interval
and with large numbers of failed conventional traps. Conversely, fixed orifice traps could release
more live steam if oversized or an existing system which is effectively maintained and the percentage
of failed traps is low.
Advantages and Disadvantages of a fixed orifice device
Advantages
Disadvantages
Can be used successfully when If sized on running load, fixed orifice traps will waterlog
pressures and loads are constant.
on start-up, reducing plant performance over this period,
increasing start-up times and the risk of corrosion.
There are no moving parts
If sized on start-up load, fixed orifice traps will waste steam
when the plant is running, effectively increasing running
costs.
Fixed orifice traps often block with dirt due to the small size
of orifice.
The cost of replacing a heat exchanger due to corrosion
will be far higher than the cost of replacing the fixed orifice
trap with a steam trap.
Cover Story • P2
Steam Tools for iPhone, iPod
iPad on the iTunes App Store
and
H
ave you downloaded the new Spirax Sarco Steam Tools App?
The Steam Tools App enables quick and easy access to both our steam
tables and saturated steam pipe sizing tools.
The Steam Tables cover the thermodynamic data properties for water / steam,
supporting the design and operation of the steam / water equipment.
The Pipe Sizing Tool allows access to saturated steam pipeline data, helping you to easily size a
steam pipeline.
For your free download, go to App Store on your iPhone, iPod and iPad and search for ‘Steam
Tools’. Alternately, you may also download the application from iTunes via the internet at:
http://itunes.apple.com/us/app/steam-tools/id378289552?mt=8#
Spirax Happenings • P3
SP400 and SP500 Digital Positioners
S
pirax Sarco new SP400 and SP500 have been developed as part of our continuous
improvement programme for instrumentation, to be in-lined with the dynamic requirements of
our valued customers.
SP400
The SP400 is available as either a linear or rotary version.
It is designed for customer who wants a positioner with a
simple user-interface, one button commissioning, reliability
and accuracy.
The SP400 unit is supplied with a universal mounting kit making
them quick and easy to assemble. They operate on a nonmagnetic feedback system which is very easy to set-up and will
not suffer wear, vibration or dirt problem.
A simple auto-stroke routine makes it extremely quick and easy to commission and the keypad
provide trouble free navigation through the menu system. Manual operation is available at the
touch of a button.
The SP400 has very low air consumption and therefore negligible running costs, making it very
attractive to any customer wishing to lower their carbon impact.
SP500
The SP500 is a fully featured communicating smart valve
positioner for demanding applications that has been designed
for easy commissioning with its user-friendly interface and
straight forward set-up procedure.
The use of piezo-electric technology at the heart of the
positioner ensures accurate conversion of signal-to-position
and gives it unrivalled reliability when compared to traditional
positioner technology.
It has an adaptive action that compensates for fluctuation in supply pressure and valve stem
friction, thus enabling guaranteed process stability. The innovative non-contact feedback system
eliminates hysteresis and ensures accuracy.
The SP500 has negligible running costs and fewer components in the overall design mean
guaranteed long-term reliability and reduced lifecycle running costs saving maintenance time.
Product Highlights • P4
Key Features and Benefits
Key Features
Key Reasons
Key Benefits
One-touch
commissioning
For standard singleacting applications
Reduces time and
cost
Non-contact Hall
effect feedback
device
Ensures immunity
from corrosion and
hysteresis
Gives accurate
feedback
Energy efficient
Digital air control,
near zero air
consumption at
controlled position
Low running cost
Programmable
functions via integral
keypad
Easy and quick to
commission, easy
optimisation of valve
performance
Control application
optimised to
application
requirement
Low impedance
design
Multi-unit installations
possible from one
4-20 mA signal
Saves controller
power and eliminates
the need for auxiliary
power supplies
Product Highlights • P5
Holiday shutdown …. Are you ready?
With holiday seasons like Christmas, New Year and Lunar New Year lining up the calendar, everyone
else is planning for a holiday getaway …. probably not for the maintenance staff as this is a great
time to get important jobs done without worrying about disrupting normal plant operations.
Careful planning is the key to making the most of this valuable opportunity. Use our checklist to help
you plan your holiday shutdown work program.
Maintenance Check List
• Carry out a steam trap survey to assess steam traps.
• Check flow meters are correctly calibrated.
• Check condensate pumps are working correctly.
• Check for any loose or missing lagging.
• Is all the condensate being returned to the boilerhouse?
• Check flanges and stop valve stems for leaks.
• Check steam separators are installed prior to plant control
equipment to ensure dry steam is delivered to the process.
• Check for leaks from vent pipes of safety valves.
• Check pipe supports that may have worked loose.
• Check pressure gauges for damages. Do they need calibration or
replacement?
• Ensure control valves are shutting off properly and not hunting. Recalibrate the positioner when cold.
Need help? Call Spirax Sarco service engineer at the location near
you (turn to back page for contacts).
Cool Tips For Hot Issues • P6
Q
A
How can we ensure that our boiler is operating at its best performance?
There are many things you can do to ensure your boiler is operating at its best performance. They
are listed below in no particular priority:
• Always run the boiler at its rated pressure.
• Do not run the boiler above its rated output. For consistency, steam boilers are rated to
o
evaporate steam at atmospheric pressure and with a feedwater temperature of 100 C. If the
boiler pressure is higher and the feedwater temperature is lower (which is always the case),
then the boiler’s actual maximum output will be less than its rated output, typically derated by
about 6 to 7%. You might see the boiler rated in terms of 5000 kg/h ‘From and At’ or ‘F & A’.
Its maximum continuous rating, MCR, will always be less.
• If designing a new steam system, ensure that the highest practical pressure is used to distribute
the steam, and choose a boiler that operates at the same pressure.
• Keep the TDS of the boiler water within
recommended limits. This can only be
achieved realistically by automatic
blowdown systems.
• Monitor the boiler water TDS and chemical
constituency regularly to ensure the boiler
water treatment is correct.
• Maintain the boiler feedwater at the highest
practical temperature.
• Return as much condensate as possible
from the plant to the feedtank.
• Ensure you recover heat from the TDS
blowdown to the feedtank.
In this column, we feature customers’ questions and answers provided by our Technical and Training
Manager, Mr Chng Poh Beng.
Simply send your questions marked “Dear TC” to [email protected] or to fax number
65-6459 6854. Kindly indicate if you do not wish to have your name and/or your company’s name
published. We reserve the right to edit the questions and not to publish them. If your question is published
in Steam Express, you will receive a corporate gift.
Dear TC • P7
NG
Spirax Sarco Pte Ltd
(Hong Kong Branch)
Unit 1507, 15/F, Prosperity
Center, Chong Yip Street,
Kwun Tong, Kowloon,
Hong Kong
PH
IL IP
PI N E S
Spirax Sarco Pte Ltd
(Philippines Branch)
Natividad Building
2308 Chino Roces Ave Ext
Makati City, Philippines
VI E
Tel: (63) 2812 8654
Fax: (63) 2812 8673
Contact: Peter Rorison
E-mail: [email protected]
sg.spiraxsarco.com
TN
G
AP
O
NE
S IA
Spirax Sarco Rep Office
Jln Zeni No. 4
Mampang Parapatan
Jakarta 12790, Indonesia
Tel: (62) 021 797 3332
Fax: (62) 021 798 2156
Contact: Cosner Tambunan
E-mail: [email protected]
petrologmum.co.id
ORE
Spirax Sarco Pte Ltd
(Regional Office)
464 Tagore Industrial Avenue
Singapore 787833
PT Petrolog Multi
Usaha Mandiri
Jln Zeni No. 4
Mampang Prapatan
Jakarta 12790, Indonesia
Tel: (65) 6 349 0480
Fax: (65) 6 459 6854
Contact: Kwek Chin Leong
E-mail: [email protected]
sg.spiraxsarco.com
Tel: (62) 021 790 1480
Fax: (62) 021 798 2156
Contact: Budi Setiawan
E-mail: [email protected]
petrologmum.co.id
SI N
TH
E
Tel: (852) 2754 9828
Fax: (852) 2754 3660
Contact: Alfred Wong
E-mail: [email protected]
sg.spiraxsarco.com
D
KO
IN
HO
N
G
AM
Spirax Sarco Vietnam
Rep Office
64 / 22 Pho Quang, Ward 2
Tan Binh Dist, Ho Chi Minh City
Vietnam
PT Centrindo Palmax
Blok.F No.2-3 Kompleks
Brayan, Prima JI. KL. Yos
Sudaruso, Tanjung Mulia
Medan, Indonesia
Tel: (84) 08 9974324
Fax: (84) 08 4086909
Contact: Nguyen Thanh Hai
E-mail: [email protected]
hcm.vnn.vn
Tel: (62-61) 6642784-6642785
Fax: (62-61) 6642786
Contact: Sugianto
E-mail: [email protected]
centrindo.com
Spirax Sarco Customer Experience Improvement
Spirax Sarco Customer Experience Improvement is a channel for YOU, our valued customer, to
share your views on your experience in partnering us. We welcome views on any facet of our
business.
Get in-touch with our Customer Experience Improvement:
 Stephanie Cheong
 [email protected]
 (65) 6349 0472
 (65) 6459 6854
Website: www.spiraxsarco.com/sg Email: [email protected]
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