Page 109 - Industrial Plants

API 676 Compliance of Progressive

Cavity Pumps

Owing to their operating principle and their roots in waste water treatment,
Progressive Cavity Pumps (PCP) come with typical deviations against
petrochemical standard API 676. Some of these deviations are inevitable, others
can be healed. It is often headache and topic of discussion for project engineers
to understand and identify which of these deviations are relevant, critical or
acceptable for their project

rogressive cavity pumps also known
as Eccentric screw pumps are positive
displacement pumps that handle fluids
gently and with minimal shear or
agitation/turbulence/emulsifying. They
Pmanage fluids of highest viscosity and
highest solids content, even abrasive or large particles.
They can generate high pressure, 48 bar and more.
They are suitable for high vapor pressure (low NPSH) as
well as multiphase fluids. Due to linear performance
curve and low pulsation they are suitable for dosing
applications.
Flow direction can be reversed simply by reversing the 676 and petrochemical applications on the one hand,
motor rotation. and typical waste water applications on the other hand.
In the oil & gas industry PCP are often applied to This demonstrates that a design optimized for waste
convey sludge or oily water, or in situations where light water is unable to satisfy petrochemical requirements.
hydrocarbons raise the vapor pressure to a level where Manufacturers of PCP regularly have to customize their
other pump types would cavitate. A forte of PC pumps basic designs in order to upgrade them for use in oil &
is vertical semi-submersed installation on a drum gas, which dramatically increases cost and lead time.
(closed drain, image below). Let us look at the two critical issues that give rise to
Open/closed drain drums or flare knock-out drums are most discussion and customization.
a frequent application.
Historically PCP are rooted in municipal or industrial
waste water treatment plants (WWTP) and
manufacturers of PCP continue to supply the lion’s
share of their products into such applications. Naturally
the design as well as production process of typical PCP
are optimized for this market.
However, the requirements of petrochemical
applications are quite different from waste water
treatment and generally on a higher level. Furthermore,
the petrochemical industry is largely based on US
American standards while most PCP manufacturers are
based in Europe.
The table compares some basic requirements of API

IndustrIal Plants - May 2017
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