HYDROCARBON
ENGINEERING
58
alone is not enough to ensure accurate measurement. Other
factors play a part in the level of accuracy, for example:
n
Installation effects.
n
Flow meter specification.
n
Accuracy of secondary measurements such as
temperature and pressure.
n
Compliance with measurement procedures.
n
Levels of staff training.
To address this issue, it is necessary to ensure
compliance with the relevant standards and legislation and
to regularly check that best practice is being adhered to. The
process through which this is applied is called auditing.
What is auditing?
Auditing, when applied to a flow measurement system, can
be defined as ‘a technical review of a measurement system
by an independent authority against agreed criteria to
ascertain if acceptable equipment, processes, procedures,
management and personnel competency levels are in place
and are being implemented’.
In recent years, the relative importance of auditing has
increased given the proposed shift in recommended practice
from ‘time-based’ meter calibrations to ‘risk-based’ or
‘condition-based’ scheduling. With these approaches, flow
meter calibration schedules are defined by a range of
factors, including the likely rate of deterioration or drift of
the flow meter, rather than a simple time-based schedule, as
has traditionally been the case.
This has the potential benefits of optimising the
frequency with which flow calibrations should be carried
out; however, it also means that effective and frequent
auditing has become even more important in maintaining an
accurate measurement system.
Audits can fall into three main categories:
1.
First party audit ('us on ourselves'): an internal audit
carried out in-house by company personnel in order to
assess the implementation and effectiveness of the
quality management system.
2.
Second party audit ('us on them'): an external audit by a
purchaser (or customer) of a vendor or potential vendor,
i.e. of one party to a contract on the other for the
supply of goods/services.
3.
Third party audit ('them on us’): an audit for the
purposes of independent system approval. There may
be special cases such as calibration laboratories where
the basis of the audit is specified by the approval body.
As part of a measurement system, it is recommended
that internal (first party) audits be conducted on a regular
basis. However, first party audits can lack impartiality due to
the conflicts of interest that arise, particularly where fiscal
measurements are concerned.
It is for this reason that third party audits are the mode
of choice and should be conducted to ensure that the
measurement system is verified objectively by an
independent and impartial body. This is desirable as it is the
only way to fundamentally avoid issues arising from
self-interest, such as a desire to evade taxation,
increase/mask profit or overlook fundamental problems in
the measurement process.
The issue of impartiality should be taken extremely
seriously and should be one of the primary requirements of
any body conducting a third party audit. Likewise,
independent bodies engaging in third party auditing should
implement company policies, operating procedures and staff
training in an effort to safeguard against threats to
impartiality that may have a bearing on the outcome of the
audit.
Particular threats to impartiality can come from a
number of sources, such as personal relationships between
auditors and those being audited, personal intimidation or
coercion, bribery, competition for audit contracts or
advocacy issues arising from the auditor already being in the
employ of the company being audited. It is therefore
important that auditing bodies take steps to prevent any
potential threats to impartiality.
What happens in an audit?
In order for an audit to be effective, it must be performed in
a methodical and systematic manner. As such, incorporating
a well defined structure to any audit is critical. Technical
audits therefore consist of two main stages:
Desktop audit
The objective of the desktop audit is to review the
documented elements of the system. Firstly, the auditor
must establish whether the written policies and
instructions comply with the standards, then, secondly,
assess whether the instructions are complete, unambiguous
and workable.
This stage often takes place several weeks ahead of the
implementation audit, and is often carried out in the
premises of the auditor rather than the company being
audited. In addition, given time constraints, it is common for
the audit not to be completely exhaustive. Instead, the
auditor will sample a range of documentation in order to
gain a representative overview of the state of the clients
system. It is typical for an auditor to have limited time
available for an audit. A trade-off must therefore be found,
which allows them to allocate resources between each
stage of the audit.
Implementation audit
The objective of the implementation audit is to review
current practices and recent records to assess whether
working practices accurately match the document system
and that the staff responsible for implementing the
measurement practice understand the system.
Preparation
One of the keys to effective auditing is preparation. This
applies to both the assessor, and the company being
audited. As part of this preparation, the auditor and client
should have agreed key details such as the standards against
which the audit will be conducted, the timescale and scope
of the audit. The assessor should request or collect as much
information and documentation as is required in order to
complete the audit well in advance to allow procedures,
policies, training manuals, records, etc., to be reviewed
ahead of the audit taking place.
