canadian puregas equipment limited

Proactive Maintenance  and Air Dryers

Ingolf Plath
C July 14,1996

Canadian Puregas Equipment Limited

Table of Contents

1. Introduction 3
2. Pressurization 4
3. Maintenance 5
3.1. Types of Maintenance 5
3.2. Proactive Maintenance 6
3.3. Allocating for Proactive Maintenance 7
4. Summary 9

1. Introduction

Pressurization of cable was first instituted in the 1940’s to protect
telephone cables from moisture intrusion and subsequent problems due to sheath
and/or splice integrity faults. A dry pure gas such as air was forced, under
pressure, into the cables. This pure gas under pressure within the cable
prevents moisture from entering the cable and purges the cable of any inherent

Over the years, pressurization use has been expanded to include other types
of communication carriers such as F.O. cable, coax and waveguide. Air dryers
have also changed from the original refrigeration type to heatless regenerative
dessicant to the newest technology of permeable membrane dryers.

This discourse shall provide an understanding of the basics of a good maintenance
program and why a maintenance program utilizing the latest techniques is
important for proactive maintenance. This is not a complete in-depth analysis
on pressurization, but rather a primer on maintenance programs to help those
persons who require information to understand the benefits of a good maintenance
program and how it can improve the bottom line.

2. Pressurization

Pressurization of cables is done to preclude moisture from entering within
the sheath of the cable by way of natural humidity and water by way of sheath
faults and susceptible splices and terminations. The ideal outside plant
(cables) will have no leaks, a constant air pressure and low air flow. Due
to the actual integrity of systems and their inherent leaks many systems
were built with air pipe distribution so that the air can be distributed
to extended sections of the cable. Otherwise these sections would have no
flow or pressure as the air introduced at the beginning of the cable would
have exited the cable through the leaks. One of the reasons for this low
cable pressure integrity is the lack of complete monitoring and proactive
maintenance. With a good monitoring system and proactive maintenance
pressurization of the outside plant can be efficiently achieved with a good
quality air source, properly sized and minimal air feeder pipe or none at

When cables were originally pressurized from nitrogen bottles, and if there
were no leaks at all, the pressure in the cable would stabilize. Once the
pressure is stabilized then there is zero flow. Since it is almost impossible
to have a completely airtight system (and there are reasons not to) we always
have air flow into our cables. Air is introduced at the beginning of a cable
at the central office (C.O.) which has a certain flow and pressure. As long
as the flow is constant the pressure in the cable will stay constant. 

The air dryer must provide the air flow necessary to achieve a constant pressure
at its normal capacity. If the dryer must provide higher flows than its normal
rated capacity then a secondary or larger dryer must be installed. If this
is not done or the cable flows not reduced the maintenance costs will increase
dramatically or the dryer will fail. 

Conversely if the dryer need only produce a flow less than its normal capacity
and maintenance is routinely performed according to manufacturer’s
specifications the dryer will last indefinitely. 

3. Maintenance

3.1. Types of Maintenance

There are three types of maintenance that can be performed to maintain a
dryer and correct breakdowns. They are reactive, preventative and predictive

Reactive or emergency maintenance is a repair that is done after a breakdown
has occurred. This is usually due to a dryer operating beyond its normal
capacity or lack of routine maintenance. Too often the main cause is due
to a lack of proper routine maintenance because of a shortage of time, manpower
or skills. This is the most costly and inefficient way to maintain a dryer.
It is analogous to not fixing the hole in the roof of your house until it
is raining, in which case the repair becomes more costly and leads to more
damage and complaints from the customer, i.e. your spouse. Companies that
rely only on reactive maintenance procedures in a highly competitive market
usually lose their customers and their maintenance costs soar until they
become insolvent.

Preventative or preemptive maintenance is scheduled or routine maintenance.
This is the most common form of maintenance which is based on the equipment
manufacturer’s or industry recommendations. It is considered proactive.
This scheduling of maintenance is fundamentally to prevent emergency repairs
by improving or repairing equipment before failure occurs. Preventative
maintenance has a structured and known cost, but due to the nature of a cable
plant and myriad external influences emergencies will not be eliminated.
There will always be unscheduled breakdowns.

Predictive maintenance is unscheduled maintenance based on data collected
from the actual plant. It also falls under the proactive maintenance category.
From the data collected during routine maintenance we can see the condition
of the equipment and plant and base our maintenance procedure upon this
condition. This provides us with information so that we can conduct our
maintenance accordingly and greatly reduce our maintenance and downtime costs.
Recommendations provided from the results of data collected must be followed
to increase the efficiency of the plant and preclude future emergencies.

The three types of maintenance can be compared to the maintenance of a roof.
If you replace the roof covering of your house only when it leaks so thoroughly
that you have water damage this would be considered emergency maintenance.
If you replace your roof when the manufacturer recommends this is considered
preemptive maintenance, even though you may have problems before this time
or the roof covering may have an actual longer life span. If you monitor or
inspect your roof twice a year and repair it before it leaks, be it before
or after the recommendation of the manufacturer, you have performed proactive maintenance
and preempted any emergency and ancillary damage, and received the useful
active life of the product. Your cost of monitoring is minimal compared to
damage costs of emergencies and the cost of unwarranted replacement.

3.2. Proactive Maintenance

In today’s competitive market it is imperative to have your system operating
at peak efficiency without downtime. Predictive maintenance (monitoring)
is completely proactive. A proactive maintenance program produces long-term
gains if properly implemented. Part of this implementation includes training
and purchase of tools to monitor the plant and its trend or contracting of
maintenance to qualified companies. Fully effective proactive maintenance
requires a disciplined and well structured maintenance management program.
Most proactive maintenance programs require a significant corporate investment
in time and resources for implementation. Many companies tend to be penny
wise and pound foolish with maintenance programs which inhibits proactive
maintenance. There are few short-term gains. It is an investment for long
term gains and when fully and correctly implemented those gains are substantial.
Predictive maintenance can deliver benefits to your company on many levels.
Studies have proven that predictive maintenance on average is one third the
cost of reactive maintenance due to continuous savings.

For an example of savings calculate the cost of a repair when a dryer fault
is found and repaired by a technician during routine maintenance before any
problems arise to the cost of repair and downtime if the dryer failed on
a weekend and a cable was lost. These costs can be measured in actual dollar
figures. As a direct result of eliminating emergencies the tangible effects
of any revenue loss can be determined. By implementing a proactive maintenance
program corporations willing to invest resources will gain real tangible

In the communications industry the outside plant is the factory that produces
revenue. The foundation (production machine) of the plant is the cable. The
dryer maintains the cable. If the cable (machine) is maintained there is
no factory downtime and loss of revenue. Other benefits are: savings in personnel
and time, efficient use of ancillary equipment such as air dryers, improvement
of the overall efficiency of the outside plant and customer satisfaction.

3.3. Allocating for Proactive Maintenance

To benefit from a successful proactive maintenance monitoring system proper
allocation of resources is a requirement. First of all a plan must be developed
for implementation. This plan must be adhered to for the success of the program.
The first emphasis in allocation is on the training for the personnel assigned
to the maintenance. When properly trained these same technicians can also
give recommendations on equipment and procedures for efficiency. Untrained
personnel doing improper maintenance will create problems. Education of personnel
contributes to the overall success and acceptance of the proactive maintenance

Proper tools for maintenance means having not only the normal mechanics tools,
but also special tools required to accurately discern the characteristics
of each dryer. These tools are used to acquire information to be used for
predicting the next maintenance cycle and recommending improvements to equipment.
Monitoring of dryers in this way during routine maintenance and using this
information in a computerized maintenance program results in predictive
maintenance. Other tools required, but often overlooked, are manufacturer’s
manuals and specifications, factory training and periodic upgrading and
manufacturer’s technical expertise, i.e. consultations or technical
help desk.

One of the most important tools is the maintenance checklist. This list or
inspection sheet should be specific for the type of equipment and information
required. It should not have check boxes for these are not specific. The
technician must be directed by the inspection sheet, i.e. instead of a check
box for ‘ Flow check ‘ the mechanic should have to write in the
actual readings and conditions. It should also have a list of all the tests
required to ascertain the condition of the dryer so the technician can record
these for later input into the database. From this information recommendations
can be made for further savings. This information will tell us whether the
dryer is sized properly for the air flow required and recommendations can
be made. This information also gives us the monitoring ability for predictive

For ease of maintenance and time saving all equipment should be standardized.
This not only saves on information required, but also saves immensely on
time and tools that are required due a great variety of equipment. It is
much easier and less time consuming to maintain equipment that is similar
and has not been altered (except upgrade modifications) from a standard.
Another benefit of standardizing is that parts are more common and therefore
inventory levels are lower. The initial cost of purchasing replacement equipment
for old or non standard equipment is quickly paid back by the savings in
maintenance and breakdown costs.

Accurate record keeping is a must for a proactive maintenance program. Ideally
a computerized database should be maintained daily. Information should be
input at least after every routine inspection on a timely basis. The database
should be integrated with a maintenance management program that forecasts
maintenance based upon input of information (from inspection sheets) received
from the maintenance technicians. The maintenance program will then predict
routine maintenance based upon actual indications of each dryer and routine
maintenance can be performed when required. This predictive maintenance program
will greatly reduce unforeseen failures. Recommendations can be easily made
for equipment upgrade or replacement and the condition of equipment is easily

The maintenance program can also be allocated to an outside contractor. This
can be a more cost effective way of implementing a proactive maintenance
program. Of course the contractor must have trained personnel, the proper
tools and be familiar with proactive maintenance, including maintaining a
computerized predictive maintenance program.

4. Summary 

A good proactive maintenance program is a combination of the latest technology,
educated personnel, and management support. 

Achieving a very successful proactive maintenance program requires planning,
training and a good information system. Adequate implementation planning
and training will ensure the highest use and best value of the air dryers.
The savings after implementation of the system will come from many sources.
They include improved personnel utilization, reduced overtime, improved plant
performance, reduced downtime, increased plant reliability and reduced
emergencies. The major savings come from reduced loss of revenue when the
plant is shutdown (cable loss) and equipment replacement cost due to failure
caused by ineffective maintenance.

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