The Directive ("PED") will have significant implications on sealing technology, which is of course used extensively for the reliable and safe containment of fluids under high pressure. In response, the Mechanical Seals Division of the ESA has developed a statement of guidance about the legislation and its relevance to sealing systems.
The Directive was formally adopted by the European Parliament and
the Council on 1997 May 29, the essentials of which are outlined below. For full details,
please refer to the Official Journal of the European Communities No. L181 of 1997 July 9
(ISBN 011 916 0927). The Directive will enter into force on 1999 November 29, but
compliance with its requirements will be optional until 2002 May 29.
| Essentials of the PED relating to sealing systems | |||||
HAZARDOUS FLUID |
NON-HAZARDOUS FLUID |
CE CATEGORY |
|||
Group 1 |
Group 2 |
||||
| Less than 25 | bar litres | Less than 50 | bar litres | = | N/A |
| 25 to 50 | -- " -- | 50 to 200 | -- " -- | = | Category i |
| 50 to 200 | -- " -- | 200 to 1000 | -- " -- | = | Category ii |
| 200 to 1000 | -- " -- | 1000 to 3000 | -- " -- | = | Category iii |
| Over 1000 | -- " -- | Over 3000 | -- " -- | = | Category iv |
Actions required |
|
Below Category i |
Risk assessment to determine Category classification. Sound engineering practice. No CE mark may be applied |
Category i |
As above, plus technical documentation and conformity assessment covering design, manufacture and operation. Affix CE mark with Notified Body identification number, provide a declaration of conformity, retain records for 10 years |
Category ii |
As Category i, plus manufacture controlled within ISO 9002 or 9003. Quality system and final test monitored by a Notified Body |
Category iii |
As Category ii, plus design verified as conforming by a Notified Body, or design type approval certificate is valid. |
Category iv |
As Category iii, plus Notified Body verification of conformity and release |
Implications for mechanical
seals
In order to clarify the legal and technical requirements of the Pressure Equipment
Directive, the ESA has sought advice from sources across Europe, including the Verein
Deutscher Maschinenbau-Anstalten e.V. (VDMA, Germany) and the Department of Trade and
Industry (dti, United Kingdom).
Although in the majority of cases seal manufacturers may not be
advised of the ultimate destination of the product, the Pressure Equipment Directive
applies to equipment destined for use only in EU Member States.
It is accepted that pumps and the majority of equipment with rotating shaft seals are
exempt from the Pressure Equipment Directive.
Further to earlier statements on the EU Machinery Directive
(98/37/EC), it is apparent that mechanical seals do not fall within the
definition of machinery, but optionally, ESA Members may comply within the scope of the
Machinery Directive by:
issuing a
Declaration of Incorporation
supplying the
mechanical seal without a CE mark
supplying
appropriate Instruction Manuals
maintaining
systems for the compilation of Technical Files as appropriate
Basic scope of the PED
with respect to mechanical seal systems
All devices shown within the Pressure Equipment Directive circuit (such as vessels,
valves, pressure relief devices, coolers,
etc.) must comply with the requirements of the Pressure Equipment Directive.
Course of action by Members of
the ESA Mechanical Seals Division
1. Unless advised to the contrary by the
purchaser, it is assumed that European Directives are not appropriate to mechanical seals
and systems.
2. Pump gland plates, sleeves and seal chambers are assumed to be part of the pump casing and will comply with the requirements of the Pump Safety Standard, EN 809.
3. Single mechanical seals may comply optionally with the Machinery Directive (as indicated above).
4. In multiple seal arrangements, with a risk assessment based upon failure of the primary (inboard) seal, both the primary and secondary (outboard) seals will comply with the Machinery Directive (as indicated above).
5. The equipment which
will fall within the scope of the Pressure Equipment Directive is indicated in the diagram
above. In general, this will commence at the point of attachment (normally threaded union)
of the system pipework to the gland or seal plate. When supplied as fully assembled
devices by Member Companies of the Mechanical Seals Division of the ESA, and where
appropriate (based upon the group category, pressure and volume classifications of the
Directive) :
a Declaration
of Conformity will be issued
the CE mark
will be applied
systems will
be maintained for the compilation of Technical Files as appropriate
6. When Member Companies supply components or sub-assemblies which will eventually be incorporated into a system within the scope of the Pressure Equipment Directive, the above procedure 5. will be followed where appropriate for those components or sub-assemblies, based upon the group category, pressure and volume classifications of the Directive.
7. In all cases when Member Companies supply components or sub-assemblies which will eventually be incorporated into a system within the scope of the Pressure Equipment Directive, the organisation responsible for final assembly of the complete system will be responsible for meeting the requirements of the Directive for that complete system.
8. Risk assessment will be based upon failure of the primary (inboard) seal, as follows:
8.1. Seal buffer liquid (unpressurised) systems; presumes the buffer liquid may be contaminated with process fluid, and the outboard seal and seal system are containing the buffer / process fluid under the conditions normally applied to the primary seal. Hence, the criteria used for establishing the category within the Pressure Equipment Directive will be based upon the most arduous fluid (buffer or process fluid) at the process operating pressure.
8.2.Seal buffer gas or non-buffer containment (unpressurised) systems; presumes the containment space may be contaminated with process fluid, and the outboard seal and seal condition monitoring system are containing the buffer / process fluid under the conditions normally applied to the primary seal. Hence the criteria used for establishing the category within the Pressure Equipment Directive will be based upon the process fluid at the process operating pressure. In general, however, the seal condition monitoring system will have a system pressure/volume multiple below that covered by the Pressure Equipment Directive and is an assembly rarely supplied by the seal industry.
8.3. Seal barrier (pressure higher than process fluid) systems; two possible levels of assessment:
(a) fast shut-off in the event of primary seal deterioration or failure. In this case, the outboard seal and seal system are containing the barrier fluid under conditions identical to normal operation. Hence, the criteria used for establishing the category within the Pressure Equipment Directive will be based upon the barrier fluid at the barrier system pressure.
(b) slow shut-off in the event of primary seal deterioration or failure. In this instance, the outboard seal and seal system are containing the process fluid under the conditions normally applied to the primary seal. Hence, the criteria used for establishing the category within the Pressure Equipment Directive will be based upon the most arduous fluid (barrier or process fluid) at the barrier system pressure.
9. Connecting pipework which is within the scope of the Pressure Equipment Directive (as indicated above), will be normally the responsibility of the purchaser. All system volume assumptions made by the Members of the Mechanical Seals Division of the ESA will generally exclude connecting pipework, unless supplied as part of an assembled system.
10. Products supplied by Member Companies of the Mechanical Seals Division of the ESA prior to 2002 May 29 will continue to comply with existing national legislation. Products supplied from that date will comply with the Community regime of the Pressure Equipment Directive.
11. In order that Member Companies may comply with existing national legislation and the requirements of the Pressure Equipment Directive, information required from the purchaser is indicated below.
12. Member Companies will be responsible for providing their own operating instructions for their own specific equipment, and will be responsible for maintaining technical files as appropriate.
13. Individual Member Companies may modify all or part of the above procedures as appropriate for specific local conditions.
| Information required from the purchaser | |
| 1. Process fluid | (N1, N2 ...see Notes, below) |
| 2. Total seal chamber heat generation | (N3) |
| 3. Shaft diameter | (N4) |
| 4. Process temperature and pressure | (N4) |
| 5. Electrical power supply | (N5) |
| 6. Electrical hazard rating | (N5) |
| 7. Is cooling water available, and at what temperature ? | |
| 8. Local ambient temperature | |
| 9. Customer name / end user | (N6) |
| 10. Location | (N7) |
| 11. Specifications | (N8) |
| 12. Certification requirements | (N9) |
| 13. Delivery / commercial requirements | (N10) |
| Notes |
|
| N1 | Needed to allow selection of barrier fluid. If not available, discuss fluids which would be acceptable |
| N2 | Ensure correct chemical name is obtained |
| N3 | Includes all heat generated in seal chamber from mechanical seals and any internal pumping device but not heat soak |
| N4 | Allows calculation of heat soak and barrier pressure |
| N5 | May not be necessary if there are no electrics on system |
| N6 | End user name may indicate type of system favoured or imply highly specified equipment |
| N7 | Some locations (offshore, desert, tropical, arctic) imply special materials or considerations |
| N8 | Specifications may be very complex, covering design, materials, build, testing, storage, etc. |
| N9 | Certification levels may include NDE, PMI, QP, stage witness etc. |
| N10 | Delivery dates, shipping, site storage, can all affect quotation |
Information provided for guidance only. The ESA does not warrant, either expressly or by implication, the accuracy or completeness of the information, nor does the ESA assume any liability resulting from the reliance upon any detail contained herein. The information does not attempt to address compliance requirements of regulations specific to a particular industrial facility. Please consult your appropriate local, regional, state, national or federal authorities for precise compliance issues.
