American Fuel & Petrochemical Manufacturers Environmental Conference
October 20-22, 2013
New Orleans, LA
FINDING AND FIXING HEAT EXCHANGER LEAKS
Author(s):
Taras Lewus – Sage Environmental Consulting, L.P.
ABSTRACT
Monitoring heat exchange systems in organic Hazardous Air Pollutant (HAP) service for leaks using the
Modified El Paso Method (MEPM) is now something all refineries are familiar with. However, there are
varying strategies for how to implement a compliance program to ensure that refineries can identify
leaking heat exchangers and make any necessary repairs within the required timeframe. Here we identify
the benefits and challenges for heat exchange monitoring compliance programs implemented at refineries
nationwide. Specifically, the following aspects of these programs and their impact on compliance will be
discussed:

Challenges in identifying leaking heat exchangers;

Challenges in making timely repairs;

Developing effective response procedures for detected heat exchange system leaks;

Identification of which heat exchangers either require a process unit shutdown/load reduction or
can be bypassed, and when exchangers qualify for the Delay of Repair (DOR) provisions; and

Reasons/observations for unexpected MEPM readings.
REGULATORY BACKGROUND
The National Emission Standards for Hazardous Air Pollutants (NESHAP) from Petroleum Refineries
were initially proposed in July of 1992 and promulgated on August 18, 1995 under 40 CFR Part 63,
Subpart CC (60 FR 42620). This regulation, commonly known as “RMACT I” provides emission
standards for HAP from petroleum refineries. Heat exchange systems were not included as regulated
emission sources in RMACT I as promulgated in 1995. In 2009, RMACT I was amended as part of
United States Environmental Protection Agency’s (US EPA) Risk Technology Review (RTR) to include
provisions for heat exchange systems. The 2009 RMACT I amendments incorporated Maximum
Available Control Technology (MACT) standards for heat exchange systems by requiring refineries to
implement a leak detection and repair program for heat exchangers in organic HAP service. Under the
requirements, non-contact heat exchange systems in organic HAP service at regulated sources are
required to conduct periodic cooling water monitoring and analysis. The monitoring is to be completed
using the MEPM, Revision Number One, dated January 2003, and incorporated into 40 CFR §63.14 by
reference; and when leaks are detected, repair those leaks in accordance with defined schedules.
At new sources that commence construction or reconstruction after September 4, 2007, heat exchange
systems were required to be in compliance with the new source requirements upon initial startup or
October 28, 2009, whichever is later. At sources that commenced construction or reconstruction after
July 14, 1994, but on or before September 4, 2007, heat exchange systems were to be in compliance with
the existing source requirements for heat exchange systems by no later than October 29, 2012.
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Subsequent revisions to the RMACT I language regarding monitoring affected heat exchange systems
were made in 2013, but the requirements for MEPM monitoring and repair of leaks detected above
thresholds remain.
WHAT TYPE OF LEAKS ARE WE SEEING?
The majority of petroleum refineries have identified their affected heat exchange systems as existing
sources requiring compliance no later than October 29, 2012 and have elected to conduct monthly MEPM
monitoring. A MEPM leak action level is then defined as a total strippable hydrocarbon concentration (as
methane) in the stripping gas of 6.2 ppmv. Monitoring data from multiple refiners dating from August
2012 to date was collected and reviewed for notable observations. The following presents a qualitative
summary of observations regarding heat exchange system leak detection and repair from these refineries:

Refineries did a good job of reducing/eliminating any potentially large leaks of greater than 62
ppmv in heat exchange systems before the initial compliance deadline.

The majority of all MEPM results are greater than zero but less than 6.2 ppmv.

Many MEPM results are greater than 3.1 ppmv but less than 6.2 ppmv.

Many leaks greater than 6.2 ppmv that were detected did not qualify for the DOR provisions and
required repair within 45 days.

Leaks with concentrations greater than the Delay or Repair (DOR) limit (62 ppmv) were often
orders of magnitude greater than the limit, and not just slightly above it.
While there are various reasons why a heat exchanger may leak, in general, leaks are most often found in
heat exchangers handling corrosive process fluids and/or fluids that can contain entrained solid
particulates. Intuitively this makes sense as corrosive process fluids and solids passing through heat
exchangers have the potential to degrade or damage the heat exchanger material of construction more so
than other non-corrosive and particulate free fluids. Based on the fact that the majority of all MEPM
results have been observed to be greater than zero but less than 6.2 ppmv, it can be hypothesized that
smaller pinhole leaks in exchangers are more likely the cause for these readings than any large scale heat
exchanger failures. Example MEPM measurements for one cooling tower are provided in the following
graph.
10.00
9.13
9.00
MEPM Reading (ppmv)
8.00
7.00
6.00
5.20 5.04
Limit 6.2
5.00
3.69
4.00
3.00
2.00
3.09
2.42
2.58
2.32
1.63
1.15
1.00
0.00
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Limit 3.1
Based on the results of MEPM heat exchange system monitoring to date the following conclusions can be
drawn:

Many MEPM results are greater than 3.1 ppmv but less than 6.2 ppmv. This leads to the
conclusion that utilizing the option to conduct quarterly monitoring at a reduced 3.1 ppmv leak
definition for an existing heat exchange system would be problematic. Reducing the leak
definition would result in an increased number of detected heat exchange system leaks, which
would then require significant additional efforts to identify and repair. The effort, time, and cost
associated with identifying and repairing additional leaks would therefore likely outweigh the
benefits of the reduced quarterly monitoring frequency.

When large leaks greater than 62 ppmv are detected, plans to locate and repair the leaking
exchanger(s) must be made quickly. The DOR provisions are not allowed when MEPM results
are greater than 62 ppmv, and the 45 day window to repair leaks greater than 62 ppmv has proved
to be a challenge in many cases.

After a large leak greater than 62 ppmv has been repaired it can often take 2-3 days for the heat
exchange system to flush out residual contaminants from the repaired leak. This also presents a
challenge in meeting the 45-day repair window as this additional time for the heat exchange
system to fully purge may be necessary before confirmation/compliance MEPM monitoring can
provide representative “leak-free” results.
BEST PRACTICES IN IDENTIFYING AND REPAIRING LEAKS
Good Communication With Refinery Operations
The most successful best practice in facilitating the efficient identification and repair of leaking heat
exchangers has resulted from maintaining good communication with refinery operations personnel.
When properly engaged in a heat exchanger leak detection program, members of refinery operations are
the most effective personnel available for identifying and locating large and small leaks from heat
exchangers. Specifically, the following best practices have been observed as enhancing communications
between environmental and operations staff and reducing the time required to identify and repair heat
exchange system leaks:
 Environmental Department must keep refinery operations informed of the schedule for every
MEPM monitoring event.
 Environmental Department must keep refinery operations informed of the results for every
MEPM monitoring event and the applicable leak detection limit.
 Refinery operations must have a process to notify the Environmental Department if they believe
there is a leaking heat exchanger even if MEPM monitoring indicating a leak has not been
conducted.
 The use of onsite LDAR contractors for MEPM monitoring has shown to be helpful by
increasing the communication between the Environmental Department and refinery operations
staff in the field.
Qualitative Grab Samples
To date, when a leak has been detected using MEPM monitoring, and in the absence of good
insight/information from refinery operations, one method that has shown to be successful in identifying
the culprit leaking heat exchanger(s) has been qualitative grab sampling. A qualitative grab sample
involves the use of a calibrated FID or equivalent device that may be used to detect organic compounds
within a particular cooling water stream. A sample of the cooling water return from the outlet of
individual heat exchangers is collected in a vial or bottle and covered as soon as possible. The sample
container is then shaken to facilitate the release of volatile compounds from the water into the vapor space
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in the container. The sample container is then opened and the releasing headspace vapor is quickly
measured with an FID (or equivalent). An elevated reading from the FID indicates there are elevated
levels of organics at the cooling water exit of the exchanger and that there is potentially a leak located at
or upstream of the exchanger. The success rate for identifying leaks using qualitative grab sampling is
increased when both the inlet and outlet cooling water for individual heat exchangers are sampled, as this
clearly demonstrates whether the leak is located within the exchanger being sampled.
The benefit of qualitative grab sampling is that it can be conducted more quickly and efficiently in
comparison to MEPM monitoring. It requires less time and labor to identify potential heat exchanger
leaks than if MEPM monitoring is conducted for the potential leaking heat exchangers. However, a
challenge presented by this qualitative sampling procedure is that consistency in sample collection and
monitoring methodology cannot be assured. Additionally, volatile compounds, when present, will
dissipate at different rates from the cooling tower water sample depending on conditions such as
temperature, chemical vapor pressure, etc., and so variation in monitoring results may occur even if the
sampling and monitoring methodology is performed consistently. Finally, not all heat exchangers are
equipped with sufficient sampling locations for identifying the location of a leak to a high degree of
accuracy. Shortcomings aside, qualitative grab sampling has proven to be a successful screening tool in
identifying leaking heat exchangers for many refineries.
Speciation Information For Individual Heat Exchangers
In the event that a leak has been detected using the MEPM, and in the absence of beneficial input from
refinery operations or the ability to grab cooling water samples from individual exchangers, speciation
data has been helpful to identify leaking heat exchangers. If chemical speciation data is available for the
process fluids passing through the potentially leaking heat exchangers, this can be compared against
speciated analytical results from cooling water samples to identify the likely source of the leak. If a grab
sample of contaminated cooling water is collected and analyzed, the specific ‘signature’ of the speciated
organic analytical results may be sufficient to identify which compounds or process fluids may be leaking
into the cooling water and thus which exchanger is most likely to have leaked into the cooling water. For
example, let’s assume a leak has been detected for a heat exchange system with crude oil as well as
naphtha as the process fluids. If a cooling water sample is grabbed and analyzed, and the results indicate
a benzene concentration of greater than 10,000 ppm, we can logically conclude that the naphtha
exchanger(s) are more likely the source of the leak as we know that the benzene concentration in naphtha
are often in this range, and are most often higher than crude oils. This methodology for identifying a
leaking heat exchanger is most helpful when the leak is due to a single bank of heat exchangers (or single
heat exchanger) such that the cooling water sampling and speciation would not yield a wide variety of
different compounds and concentrations.
Reasons/Observations for Unexpected MEPM Results
As refineries continue to gain experience related to their heat exchange system monitoring compliance
programs, they will continue to develop the institutional knowledge and experience to quickly identify
and troubleshoot solutions. However, unexpected results from MEPM monitoring events, including
outlier data points, inconsistent data, and results which do not seem reasonable based on their location or
other factors, still occur with some frequency. Responding effectively in addressing and reducing the
frequency of these events is essential to developing a consistently compliant program. While still in its
infancy compared to other long-standing refinery environmental compliance programs, the following list
provides some observations related to unexpected MEPM monitoring results:

Makeup cooling water is not always “clean” depending on the source.
o
Makeup cooling water can contain CH4 and VOCs resulting in elevated MEPM
measurements that are not the result of a heat exchanger leak.
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
MEPM sampling equipment should be cleaned using appropriate materials or solvents to prevent
‘false-positives’ caused by residual cleaning compounds skewing the monitoring results.

MEPM sampling equipment should be cleaned using appropriate materials or solvents that will
not damage the seals used in the device. Seals are often made of synthetic rubber or other
polymers that may be softened, degraded, or dried out by some cleaning compounds.

FID calibrations must be performed correctly and consistently.

When a refinery utilizes rental or temporary cooling towers, elevated MEPM results have been
more frequently observed.

The MEPM monitoring team must maintain good lines of communications with refinery
operations staff, such that they are kept aware of and account for any potential abnormal
operations taking place during scheduled MEPM monitoring events.
WHAT DOES THE “GOLD” STANDARD PROGRAM INCLUDE?
Refineries have identified and implemented a variety of essential procedures and approaches to address
the requirements of their heat exchange system monitoring compliance programs. While each refinery
has the responsibility to develop a robust and effective heat exchange system monitoring and repair
compliance program that fits their needs, the following list identifies best practices that have been
implemented at top-tier programs:

Maintaining documentation identifying every heat exchanger in the refinery and not limited to
only those in organic HAP service.

Maintaining a simplified diagram identifying all cooling water flows to and returns from each
heat exchanger, with highlighting identifying those in organic HAP service.

Identifying a list of heat exchangers that have sample taps installed at the inlet and/or outlet of
the exchanger, such that grab samples or speciation samples can be easily collected in case of
leaks in the vicinity.

Identifying whether each heat exchanger in organic HAP service can be bypassed or repaired
online.

Maintaining a written compliance manual with associated procedures, including a response
procedure to be implemented when MEPM leaks are detected.

Installing additional sample taps and bypasses for heat exchangers during previous turnarounds
or planning installation of these devices during future shutdowns.

Utilizing a consistent MEPM monitoring team and dedicated monitoring equipment.

Involving refinery operations in the heat exchanger leak compliance program, including ensuring
they are notified of the monitoring schedule and all monitoring results.

Ensuring operations staff notifies the Environmental Department when it is thought there may be
a heat exchanger leak (regardless of the planned MEPM monitoring schedule or if the heat
exchanger is in organic HAP service).
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REFERENCES
1. 40 CFR Part 63, Subpart A – National Emission Standards for Hazardous Air Pollutants General
Provisions
2. 40 CFR Part 63, Subpart CC – National Emission Standards for Hazardous Air Pollutants From
Petroleum Refineries.
3. The Clean Air Act.
4. “Air Stripping Method (Modified El Paso Method) for Determination of Volatile Organic Compound
Emissions from Water Sources,” Revision Number One, dated January 2003, Sampling Procedures
Manual, Appendix P: Cooling Tower Monitoring, prepared by Texas Commission on Environmental
Quality, January 31, 2003 (incorporated by reference—see §63.14).
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