MFM for Bunkering; EU MID and Singapore TR48: The Facts

by Aart Pruysen, Approval Director Europe - Emerson
Wednesday February 8, 2017

A response to the article in Ship & Bunker of 6 September 2016, called "MFM Accuracy: Understanding Why Singapore's TR 48 is Superior to EU MID" by Douglas Raitt of Lloyd's Register - Asia.

Emerson was heavily involved from the beginning (2008) with the introduction of MFM [1] in bunkering applications in Europe and later in Singapore and is therefore well positioned to give a comparison of MID certification in Europe and TR48 certification in Singapore.

MID certification process:

The MID certification process is a certification process driven by national legislation within EU for measuring equipment, when used in custody transfer. Each country within EU has implemented the Measuring Instruments Directive (MID), as issued by the European Commission, into national legislation to harmonize the requirements between EU countries so that trade barriers are avoided.

The MID has adopted the technical requirements out of OIML [2] recommendations. OIML R117, "Dynamic measuring systems for liquids other than water", is used for the MID certification of bunkering applications with a 0.5% class (maximum permissible error is 0.5%). A measuring system consists of a flow meter, ancillary/additional devices and the installation between meter and transfer point.

The MID certification process recognizes two stages, type examination testing and initial verification of each MFM, both performed by an authorized and competent organization.

Type examination testing (called "module B") is performed by a MID Notified Body, assigned by national government after showing competency. Initial verification of each MFM is performed by either a MID Notified Body (called "module F") or the manufacturer (called "module "D"). The manufacturer may only perform the initial verification acc. module D after an accreditation process by a MID Notified body, which takes place on regular basis by auditing/interviewing all involved persons and reviewing manufacturer's procedures. The integrity of these persons (Field Verification officers) is therefore of same level as the integrity of the Verification Officers from a Notified Body.

From a legal perspective, module D has same status as module F.

MID type examination testing of a measuring system:

The components of a measuring system, affecting the metrological characteristics have undergone general type examination tests in most cases, resulting in a MID component certificate, called Evaluation Certificate (or Parts certificate).

E.g. the flow meter of a bunkering measuring system was subjected to general testing acc. OIML R117 such as multiple liquids (one phase); range of liquid temperatures and pressures; electro-magnetic compatibility of electronics; ambient temperature variations; voltage variations; software testing including resistance against fraudulent use; presence of diagnostics of failing electronics of the meter etc.

Critical diagnostics under MID should lead to an alarm, to be presented both on display and printer-out, if available. These alarms may not be deleted during the transaction. When a critical alarm is present at the end of a transaction, the transaction fails under MID (likely to exceed 0.5% uncertainty).

Other components of a measuring system could be flow computer; pressure and temperature measurements.

In the case of bunkering applications, the involved meters were calibrated on water in forward and reverse direction with same settings and then calibrated in single phase on heavy fuel at SPSE in France with same settings as during water calibration plus correction settings for boundary layer effect.

This MID type examination testing has led to an accuracy statement of 0.2% for single phase heavy fuel in forward and reverse flow direction on top of the water accuracy of 0.1% and was issued by the MID Notified body, NMi – the Netherlands.

Additional testing was necessary for the two phase measurement (emptying tanks).

The two phase measurement for Emerson has been performed by emptying traceable tanks of barges in the harbors of Antwerp and Rotterdam, resulting in quantifying the effect of the two phase measurement and completing the development of special diagnostics to detect the additional uncertainty due to the two phase measurement (stripping) when in operation. The result of this testing is the Emerson aeration diagnostic [3] tool, and forms an obliged part of the MID certification to use when in operation [4].

If additional system uncertainty, caused by aeration in the process, exceeds 0.2% of total quantity of transaction, the indication and printer will state "Fail for MID"; if within 0.2%, then "Pass for MID".

By keeping the additional uncertainty in the system, caused by aeration, less than 0.2%, the ending result will be a bunkering operation that is within the industry standard of 0.5%.

The Pass/Fail aeration status on the display/ticket is acting as one the obliged validators of the transaction to comply with MID.

During these type tests for aeration, also bunkering procedures have been developed as integral part of the MID certification, to be used during operation.

Quote from Mr. Wim Volmer, business development manager at NMi - the Netherlands: "The article in Ship & Bunker assumes that MID does not include bunkering procedures, which is not correct."

Not only changing parameters within the electronics but also the piping installation between meter and transfer point is subject of assessment to comply with the integrity out of MID. The integrity assessment of the installation between meter and transfer point (how to deal with blind flanges; valves; by-passes etc) during MID type examination testing has resulted in the development of general integrity requirements, applicable for all barges/vessels.

The final result of MID type examination testing is the release of the MID EU Type Examination certificate for bunkering measuring systems, on board of barges and vessels, including conformity assessment documentation and bunkering procedures.

MID type examination testing is meant to shorten the initial MID verification process without compromising on accuracy; integrity; transparency and reliability in an efficient way.

MID initial verification of a measuring system

The involved measuring system should be in compliance with the issued documentation and includes:

  • meter to be calibrated on water via MID procedures
  • meter to be installed on a spot so that integrity requirements can be met (survey of current installation is needed prior to the mounting of the meter)
  • verification on correct functioning of all components during one complete bunkering
  • zero adjustment and zero verification during the bunkering (two stops without air entrainment in the meter)
  • attachment of all necessary sealings (electronics and installation), including making photo's
  • attachment of MID nameplate with the measurement boundaries and the responsible entity
  • issuing of EU declaration of conformity
  • issuing of a MID compliance document, containing a P&ID (Process and Instrumentation Diagram); a sealing document, identifying the equipment which has been sealed included photo's of the sealing and an audit trail to record status of commissioning and to record future changes/events.

The compliance document gives therefore an overview of status and is very transparent for stakeholders to verify the status e.g. by a surveillance company.

Quote from Mr. Niels Groenewold, CEO of VT, barge operator, Rotterdam, the Netherlands: "MID initial verification of the barges affected minor our operations; only two stops during one bunkering were necessary for zero adjustment and zero verification, all other MID activities could be performed when barge was in operation as usual".

TR 48 certification process

TR48 standard is initiated by the Singapore Marine Port Authority for the requirements of MFM, on board of barges, operating in the harbor of Singapore. This standard becomes mandatory per 1 January 2017 and is part of the license for a barge.

Accuracy of MFM for bunkering according TR48:

The accuracy of a MFM for bunker fuel according TR48 can be divided in three main steps:

  • Level  1   water calibration against a traceable reference
  • Level  2   transferability from water (approximately 20 °C) to bunker fuel (30 till 70 °C)
  • Level  3   extra uncertainty due to two phase liquid measurement when tanks are emptied

TR 48 has adopted the OIML R117 or the MID certification process for the meter, single phase and prescribes field tests for the two phase application.

Accuracy level 1 and level 2, applicable to TR48

Level 1 and level 2 are based on the deliverables from OIML R117 or the MID certification process, resulting in a Singapore W&M type certificate for the meter only, single phase, issued by WMO, the Singapore authority for issuing custody transfer approvals.

Level 1 includes a water calibration for each meter within 0.1%; level 2 includes an accuracy statement of 0.2% for single phase heavy fuel due to lack of traceable calibration facility with high flowrates on heavy fuel oil in Singapore.

It can therefore be concluded that there is no difference in accuracy between MID and TR48 level 1 and level 2 for single phase heavy fuel.

Accuracy level 3 according TR 48

An alternative method for aeration tests was developed in Singapore to obtain certification.

During commissioning of each installation, at least three receiving/delivering bunkerings with quantities corresponding to the maximum capacity of involved barge are performed at which the difference between receiving and delivering should typically lie within 0.2%.

The purpose of this method is to determine the repeatability and the aeration effect to be able to calculate the overall uncertainty to be within 0.5%. Uncertainty of this method (receiving/delivering) is hard to quantify and therefore it is justifiable to perform more than 3 bunkerings during commissioning before criteria is met.

This method, applied for every meter to be installed, is very time consuming and costly as compared to MID certification of bunkering system.
The barge crew is trained for MFM bunkering procedures during these tests.

The Pass/Fail aeration status of a transaction, as a validator of the transaction, is not presented on the bunkering ticket in Singapore under TR48; it is left to the manufacturer to present on the local display.

TR48 recommends strongly to limit the aerated part of a bunkering (<= 2%) and therefore does not require the explicit use of the aeration diagnostic in the operation of a bunkering whereas MID does.

TR48 recognizes that the transfer of fuel between two parties is based on a buyer and seller agreement and has opted to remove the aeration requirement.

Other critical alarms (i.e. failing meter; power reset) are not presented on the ticket but are required to appear on the local display (under MID required on display and ticket);

Please note that TR48 does not require the involvement of a bunker surveyor.

It should be clear to the reader that critical alarms are handled differently within MID/OIML versus TR48.

TR48 includes also integrity requirements for electronics and installation between meter and transfer point, similar as to MID (see section above).

Procedures out of MID and TR48 are leading to similar compliance documents.

The EU MID and Singapore TR48 requirements are summarized in table below:

It can be concluded that EU MID and TR48 have many similarities and some differences.

Quote from Mr. Dax van Diepen, Head of Bunker Control & Claims Recovery at Maersk: "Maersk appreciates very much all efforts performed within OIML and MPA/Spring to issue requirements for MFM bunkering applications. Both methods are well defined and properly anchored in a solid legal framework. We encourage the authorities to continue this and develop one standard, acceptable in all global harbors, for barges and vessels, to support the continuity for buyers and sellers of marine fuels basis MFM measurements"

The author welcomes any feedback. 

[1] MFM-Mass Flow Meter

[2] Note: OIML (international organization for legal metrology) issues recommendations with the purpose that Member States implement these recommendations into national legislation; OIML is a global organization; Singapore is Corresponding Member

[3] The MID limit is the maximum cumulative uncertainty that can be tolerated in a bunker transfer. The MID limit is defined by the Organization of Legal Metrology (OIML) in OIML R117-1 and Measuring Instruments Directive 2004/22/EC Annex MI-005 (since April 2016, MID reference has become 2014/32/EU). MID certified measurement addresses both measurement accuracy and security issues, and provides an independent, trustworthy measurement that can be used by all parties in a transaction.

[4] Note: The new revision of OIML recommendation R117 (measuring systems for liquids, other than water) will also mention the aeration diagnostics as an obliged part of the MFM certification for bunkering.