pwr_october-2023 - 14

O&M
The Added Value of Corrosion
Protection for Pump and
Valve Maintenance
Power plants depend on hundreds of
valves and many different pumps to
carry out operations 24/7. Good maintenance
procedures-including routine
tasks and predictive maintenance-are
critical to keeping these assets online
and functioning as smoothly as possible.
Incorporating corrosion mitigation
adds value to the process by targeting
a significant risk factor before and after
maintenance begins.
Good maintenance starts with proper
preservation. In a very real way, good
pump and valve maintenance starts at the
manufacturing plant. What the manufacturer
does or does not do to the valve can
affect its performance and integrity down
the road. For instance, if the manufacturer
does not effectively preserve the valve,
pockets of moisture can lead to corrosion
weeks or years later, potentially reducing
the valve's useful life dramatically. On the
other hand, good preservation at the outset
can lead to pumps or valves that are
still in good condition when maintenance
goes to install them as spares two or
three years later.
To ensure good protection, manufacturers
should
include
anticorrosion
measures
at the time of hydrostatic testing,
when high-pressure water surges
through the system to check for leaks.
When the water is drained, it unavoidably
leaves behind pockets of residual
moisture that can incite corrosion at any
time. Adding a corrosion inhibitor (an
example is Cortec's VpCI-649) to the hydrotest
water, protects against corrosion
both during hydrotesting and (depending
on the dosage of inhibitor used) for
months or years after. Fogging the pump
casing or valve port with a vapor phase
corrosion inhibitor thereafter adds additional
protection within the intricate void
space as long as openings are capped.
On the outside of the pump or valve,
highly sensitive flange faces must be
kept in prime condition for safety and
effectiveness at installation. These surfaces
are highly vulnerable to physical
damage during shipping and handling.
Unfortunately, a common mistake is to
cover the flanges with plywood (Figure
1), which can actually cause corrosion
by absorbing and holding moisture right
14
1. This image provides an example of what
should NOT be done to protect valve and
pump flanges during storage and transit. Plywood
covers can trap moisture and encourage
corrosion on sensitive flange surfaces.
Courtesy: Precision Piping Products
next to the metal surface. Best practices,
therefore, typically include protecting
the clean flange face with a removable
corrosion inhibitor coating (VpCI-389 and
VpCI-391 are examples) and capping
with a rigid plastic flange protector (Figure
2) to prevent physical damage and
keep vapor phase corrosion inhibitors inside
the valve. The pump or valve bodies
can also be protected with a temporary
coating if desired.
Once onsite, pumps and valves should
be inspected before further processing.
Precision Piping Products, a manufacturer
of flange protectors, offers recommendations
such as the following on its
pump inspection form:
■ Make sure pump is stored on a flat,
sound surface six inches above the
ground and out of standing water (if
outdoors).
■ Check for signs of damage on the
equipment or crates.
■ Make sure covers and connections are
properly sealed with protective products
and fastened with at least 50%
of the bolts or multi-nuts required.
■ Make sure shaft and coupling are
painted with a product such as VpCI368
or equivalent.
■ Apply CorrLube grease to grease fittings
before shaft rotation.
www.powermag.com
3. Storing clean valves in VpCI-126 film helps
ensure they stay rust-free, ready to use at any
time maintenance may need a replacement.
Courtesy: Cortec
POWER | October 2023
2. An example of proper flange protection.
A rigid, non-wood flange BUMPER from Precision
Piping Products protects this sensitive
surface against physical damage, which
could compromise the integrity of the valve.
The flange cover can also be used to help trap
vapor phase corrosion inhibitor fogging fluid
inside the void space for interim corrosion protection
during storage and shipping. Courtesy:
Precision Piping Products
■ Add vapor phase corrosion inhibitor
additive to oil if pump is lubricated.
■ Make sure seal tabs are not in locking
position.
■ pump shaft (this helps lubricate bearings,
detect damage, and prevent bearing
brinelling and shaft deflection).
After inspection, components can either
be installed immediately or wrapped
in a film such as VpCI-126 film to ensure
maintenance can find ready-to-use
spares when a replacement is needed
(Figure 3).
http://www.powermag.com
PWR_ October-2023

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