Six Sigma Steam System Management

Copyright 2015 Spirax-Sarco Inc. All Rights Reserved

Six Sigma Steam System Management

Steam facilities are complex systems with many potential points of failure, even the smallest of
which can increase cost and risk if left untended. In order to identify and improve weak points
in a system, a methodology must be applied in a consistent manner.
Six Sigma, DMAIC, is a data-driven improvement cycle that is applied to business processes to
achieve measurable, reproducible results. By applying Six Sigma principles, areas of cost and
risk can be identified and rectified.
Six Sigma, DMAIC, is comprised of five phases: Define, Measure, Analyze, Improve and Control.
When each of these phases is applied to steam system management, problems are identified,
baselines are established, causes of inefficiencies are targeted, operations are improved, and
optimal operating conditions become the normal state of business.

Phase 1: Define
The first step in Six Sigma, DMAIC, is the Define phase. In this phase, steam system
stakeholders identify problems, goals, and benefits. Resources, both available and required,
are also identified at this point.
Problems in steam systems are usually caused by leaks, damage, and energy loss. An
understanding of the damage these types of failures can cause is necessary to the Define
phase.
Leaks. Leaks affect the efficient operation of equipment. Inefficient operations result in
higher costs, and even small leaks can result in significant losses over time. Although cost is
an important metric when justifying the expense of repairs, it is not the only concern; leaks
can also endanger people, assets, and the environment. In some industries government
regulations and internal policies require operators to respond to leaks, and failure to cure
breakdowns can result in fines and negative public perception.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Damage. Damage results in inefficient operations, which are experienced in forms such as
fouled exchangers, wet steam, and poor control of condensate.
Causes of damage include two phase flow, high velocity flow, and water hammer (see Figure 1).

Figure 1: Water hammer cycle

Two phase flow occurs when a hot stream mixes with a cold stream. In steam systems, this
happens in a condensate return line as a steam trap discharges hot condensate, under
pressure, to a lower pressure. The condensate temperature must drop very quickly to the
boiling point of the lower pressure. The surplus heat re-evaporates a portion of the
condensate into flash steam. The two phase flow is believed to occur when partially-failed
steam traps allow condensate and steam to leak into the condensate header. In steam and
condensate return piping, two phase flow results in frictional drop and can lead to can lead to
accumulation, causing slugs of condensate, which come into contact and damage pipe support.
High velocity flow damages infrastructure by causing erosion of fittings and pipes.
Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

High velocity water flow can occur when high capacity steam traps cycle with an on/off
motion discharge, in some cases creating flash steam velocity in excess of 627 ft/s (428 mph).
Water hammer erodes pipes, damages pipe supports, and can cause an under-designed system
to fail. It occurs when a slug forms a wave that can then travel within the piping system,
causing damage when changes in direction and terrain are encountered and when pipe valves
provide a restriction. This damage mechanism can be caused by incorrect trap selection,
faulty steam trap operation, or poor piping design. These three mechanisms have led to line
leaks at elbows (geometry changes), valve bonnet leaks, and damage to vessels at nozzle
attachments (see Figure 2).

Figure 2: Water hammer damage

Energy loss. Steam costs are incurred from unrecovered condensate through additional
make-up water costs and lost heat energy. Lost condensate loses its heat energy and is
typically routed to a process or non-recovered drain. Lost condensate, which is filtered and
demineralized or reverse osmosis water, has a cost associated with it and its heat energy.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Phase 2: Measure

The Measure phase of Six Sigma includes the establishment of a baseline and the collection of
data for analysis. In steam systems, the identification and elimination of defects in the
physical system are the best method for reducing costs.
A properly functioning system with strong mechanical integrity saves costs by mitigating
unexpected repairs, reducing energy loss, reducing product loss, and preventing fines and
clean-up expenses. The most critical systems should be inspected on a semi-monthly basis,
while routine inspections for maintenance and repair should be carried out annually. At one
studied steam facility, the steam drums are state-licensed and on a 5-year internal inspection
frequency. The drums are routinely inspected to find wall erosion, evidence of demister
damage, and other mechanical damage.
Surveys should be conducted at a frequency based on pressure and trap population. Steam
trap surveys measure lost steam as a cost to a facility to justify maintenance and repair. Trap
surveys also identify failed closed traps, cold traps, and disconnected or out of service traps.
The DOE (Department of Energy) and EPRI (Electric Power Research Institute) both
recommend that organizations set a frequency for steam trap inspection based on the
pressures of the steam, the uses of the steam, and the steam trap population number. The cost
of repairing blown-through or failed open traps is justified by the return on investment based
on lost steam.
Steam leak surveys are recommended as a complement to steam trap surveys. These identify
steam leaks, which cause the loss of the energy of useful steam; reduce the overall reliability of
the plant by making leaks an accepted part of the landscape; and create safety risks for
employees. Additionally, most surveys for leaks utilize equipment that can be easily employed
for other utility leaks, such as compressed air and nitrogen. Both of these are a source of
potential costs to the facility that can be located and repaired during steam leak activities.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Phase 3: Analyze
With the results of the surveys completed, the systems can be analyzed and the root cause
identified. This is the third phase of Six Sigma, DMAIC.
The mechanical integrity of a system depends on proper inspection, maintenance, and flow
management procedures. Particularly, leaks must be appropriately addressed and risk
assessed in high pressure systems.
Different types of leaks cause different types of damage. Pipes are damaged by gasket leaks
and erosions, valves are damaged by packing leaks, and vessels are damaged by gasket leaks,
bad nozzles, and erosion.
Damage to piping is most often detected through wall erosion at geometry changes. This
damage is most commonly seen on vessel inlets and where level control systems supply
condensate to headers on condensate flash drums. This condition creates the possibility for
water hammer when cool condensate mixes with warm condensate. It also creates the
condition for localized high velocity that can create damaging erosion in the piping component.
Another condition that damages valves is the mixing of condensate streams and high velocity
flows. This damage has been observed in gasket leaks in manual valves, which has been
attributed to water hammer and from high velocity streams noted at the discharge of valves
used for level control.
Water hammer impacts mechanical integrity through equipment damage. Erosion of the
automated globe valves (control valves) has been observed and is best mitigated by
addressing the root cause of excess velocity. Erosion damage has resulted in loss of
containment issues and higher than normal wall losses as measured during routine thickness
inspection as part of the site on-stream mechanical integrity program.
Vessel damage is typically associated with the same root causes of piping and valve damage:
water hammer and erosion. Common vessel damage can include the loss of containment of
inlet nozzles from water hammer; temperature stratification in vessels causing gasket leaks
nozzles; and through-wall erosion on inlet nozzles.
Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

A severe incident occurred in New York City when a 20-inch 180 psig steam line failed
underground. New York City transports over 25 billion pounds of steam at 180 psig each year
through 105 miles of underground tunnels containing steam piping. Manholes and water
vapor are visible at street level. Rain enters the tunnels and sometimes submerges the lower
elevations of steam piping. This flooding can increase steam condensation in the submerged
pipes, leading to the accumulation of large quantities of condensate unless it is effectively
removed. The flooding can also cause the formation of large water slugs that, in turn, lead to
water hammer.

Figure 3: Water Hammer Damage

In this incident, a series of plugged steam traps allowed condensate to back up in the lower
sections of the steam main. The condensate led to water hammer, which led to an
explosion, and high pressure steam erupted from a large hole that had erupted in the street.
The result was significant soil and civil and property damage.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Phase 4: Improve

In the Improve phase of Six Sigma, all the previous work is put into action. Now is the time to
improve the system through recommendations and changes. Risks must be assessed with
regard to loss of containment and personnel exposure, as well as costs. Steps should be taken
to prevent accidents, adhere to government regulations, and retain products. Facilities should
implement the results of steam trap surveys as follows:
Replace any identified failed open steam traps to prevent steam loss.
Re-check cold and out of service traps and replace as necessary.
Repair all steam and utility leaks.
Replace missing and damaged insulation.
Rework application piping to ensure optimum steam trap performance.
Modify piping to reduce high velocity condensate that causes water hammer
and erosion.
Add blowdown and condensate recovery packages.
Improve steam tracing efficiency.
Improve heat exchanger operation.
Create best practices through site specifications

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Trap Checking Frequency with Respect to Trap Applications

Application

Trap-Checking Frequency

All

After initial installation and/or maintenance

Steam tracing-outdoor,

At the start of seasonal use and at the coldest part

low pressure

of the season, not less than twice a year

Steam tracing-all others

Once a quarter with emphasis during cold periods

Steam drip and turbine

Major concern is condensate backup and open

drain

bypasses. Check:
Below 300 psi

Monthly

300-600 psi

Semi-monthly or Monthly

Above 600 psi

Semi-monthly

Process traps

Major concern is condensate backup and operating

pressure. Check monthly.

Notes:
1. The scheduling and frequency of a checking program can be readjusted
after the results have been monitored over a period of time. In nuclear
power plants, ALARA considerations also influence scheduling of steam
trap checking.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

Six Sigma Steam System Management

Areas of improvement that can reduce costs are makeup water, lost heating energy, and lost
condensate.
Makeup water. Makeup water is water added to a steam system to compensate for water lost
to leakage or evaporation. Costs associated with makeup water are raw water, treatment
costs, chemical costs, resin and membranes associated with maintenance costs from
operations, and technicians costs per gallon for variable costs. Damage mechanisms related
to faulty equipment or poor makeup can include water side corrosion from improper chemical
or dissolved oxygen. The makeup water is normally a surface water (river or lake) source or
well water (underground), with each source having costs incurred with filtration and
purification. This highlights the need for proper inspection of deaerator equipment,
consistent water sampling of steam systems per recommended practices, and proper online
analyzer operation.
Lost heating energy. Poor water quality can affect heating by internally fouling heating
surfaces. This fouling can lead to poor heat transfer requiring frequent cleaning. The fouling
can also lead to the establishment of corrosion cells in the normally clean boiler feed water
system. This can be a problem in both fired and waste heat boilers. Attention to proper blow
down, inspection of systems during outages for abnormal conditions and damage, and use of
time-based cleaning for establishment of passivation are recommended techniques for long
term reliability.
Lost condensate. Lost condensate loses its heat energy, resulting in waste and, therefore,
cost. Lost condensate is typically routed to a process or non-recovered drain. The steam
purity and the process uses require differing levels of cleanliness. Typically, steam used to
power turbines is the cleanest and has the most critical cleanliness / chemical requirements.
Condensate streams blowing to grade and drains should be evaluated for return and capture
to reduce makeup costs and volumes.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

10

Six Sigma Steam System Management

Design reviews of the system

While any steps taken to repair, replace, or modify parts of a system will deliver some benefits,
a full design review of the system is necessary to achieve optimal improvement. These
reviews examine repeat failure locations for erosion. Once a pattern of poor reliability is
observed, the areas involved in the failures should be targeted for design improvements or
review in order to improve the reliability of the steam and condensate system.
For example, one studied facility has several locations where a cycling steam trap is utilized
for reboiler level control. These locations have seen repeated cycling when system volume
surges, resulting in erosion and damaged downstream equipment. Additionally, several level
control locations feeding deaerator levels exhibited erosion, which too was suspected to be
caused by high flow issues. In cases such as this, a resizing of the line or metallurgy change
should be considered. Level controls in other locations have seen similar issues. These should
be modified to improve the systems reliability and inherent safety when possible.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

11

Six Sigma Steam System Management

Phase 5: Control

The Control phase of Six Sigma ensures that the work done in the previous phases is
maintained through continual measurement and application of improvements.
Control of costs begins with awareness and communication. The cost of steam impacts the
facility and each employee in the form of reliability, shared costs, and internal failures from
root causes such as waterside corrosion and velocity-induced erosion. Such costs increase the
overall plant costs and decrease the competitiveness and profitability of the facility.
Reliability costs are captured in equipment costs to repair, lost opportunity from unavailable
equipment, and repetitive outages. Shared costs increase the cost of operations for the users
as well, since these costs are typically an allocation to all users.
A unit or site becomes more competitive when it is able to reduce operational costs, which can
only be achieved by constant vigilance. The reporting of all deficiencies and issues within the
facility ensures proper investigation and recording for follow-up. Poor reliability and
operation of equipment needs to be documented to build history and costs associated with
operation of equipment that is less than adequate, and tracking mechanisms must be in place
to guide budgeting decisions for continuing elimination of root causes and design
improvements to correct defects.

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

12

Six Sigma Steam System Management

Mechanical integrity practices and improvements include a raised awareness of steam issues,
which should lead to a review of piping design for systems experiencing accelerated erosion
and water hammer for root cause analysis. An increased focus on velocity issues and erosion
elimination must also be developed, and all personnel involved in the operations,
maintenance, and management of the facility must be informed about how to highlight
maintenance and properly prioritize asset care.

Conclusion
System optimization is an important metric for energy and defect detection. As more plants
focus on better efficiency and integration, the importance of sustainable system maintenance
and design review is greater.
The working of a maintenance program represents the partnership between the site
operations experts and steam trap experts. A partnership allows opportunities to be
discovered and solutions to be provided for continued efficiency and reliability. In order to
achieve optimization, steam system facilities must:

Conduct a review of systems throughout a facility

Standardize component replacement to reduce field work and expedite repairs

Eliminate threaded connections at sites, except for universal connectors

Reduce warehouse inventory through standardization

Move the focus on failures to a focus on reliability and leveraging defect elimination
with vendors

Set up automated preventative maintenance plans for sustainability, including

inspections, surveys, and design reviews and improvements

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

13

Six Sigma Steam System Management

Bibliography
Chemical & Process Technology. (2010, February 27). Problems Caused by Two Phase GasLiquid Flow. Retrieved 28 2015, February, from Chemical & Process Technology:
http://webwormcpt.blogspot.com/2010/02/problems-caused-by-two-phase-gas-liquid.html
Smith, G., & McQuillan, K. W. (n.d.). Understanding and control of fugitive emissions. Retrieved
28 2015, February, from LDAR Envolve:
http://www.ldarenvolve.com/downloads/control_emissions.pdf
US DOT PHMSA. (n.d.). Integrity Management: A risk-based approach to improving pipeline
safety. Retrieved 28 2015, February, from U.S. Department of Transportation Pipeline &
Hazardous Materials Safety Administration:
http://primis.phmsa.dot.gov/comm/IM.htm?nocache=2619

Spirax Sarco contact Neil Davies, Market Development Manager

ndavies@spirax.com

14