FR0264

March 1992

To investigate and assess internal leakage in various meter/manifold combinations and to investigate and develop a preferred new connector design.

In January 1992, the report on Evaluation of Manifold Meter Connector Designs FR 0156(1) was produced. The report identified three problems in relation to o-rings or meter/manifold dimensions.

• The critical dimensions of manifold connectors vary between both meter and manifold manufacturers since they are not built to a common standard. This will lead to internal leakage in some instances.
• The connectors use o-rings which seal by screw down compression. This is not one of the recommended methods for using o-rings.
• The o-rings may easily become dislodged or misplaced during installation, causing internal leakage. Further work was recommended to quantify the leakage in various meter/manifold combinations, particularly with regard to the possibility of internal by-passing of the meter.

Internal leakage can occur in various meter/manifold combinations with the internal o-ring in place in the meter, which will in some cases take the meter outside of its in-service accuracy tolerances. Internal leakage is more frequent and the quantity of leakage is greater when the internal o-ring is removed. This is particularly relevant since in many meters, the o-ring can easily become dislodged during installation. Certain meter/manifold combinations appear to be more prone to internal leakage. A preferred new connector design should locate o-rings properly, not_ rely on tight manufacturing tolerances and should be readily compatible between this design and existing manifolds already installed. It is considered that option 3 given in this report fully meets these requirements.

A way forward should be sought with manufacturers and the water industry to enable a standard meter/manifold connector design to be prepared. A preferred design is presented, but a consultation phase should be implemented to assess the suitability of this and the other options considered. The final approved design should be included in the relevant meter and boundary box standards.

The extent and conditions for internal leakage in various meter/manifold combinations is quantified. Based on the findings of this and the previous report FR0156 a range of optional designs are presented and discussed. A preferred design is identified but a consultation stage is recommended before finally selecting the suitable connector design.

Copies of the Report are available from FWR, price £15.00 less 20% to FWR Members