MAIN PRINCIPLES FOR ASSEMBLY OF METER ORIFICE PLATES MATTECH
Not only keeping production technology of primary elements but their assembly to piping system has decisive influence on the accuracy of flow measurement. The piping has to be fully filled in by measured homogenous fluid.

General principles:
Centric orifice plates are placed between flanges. Flanges have to be welded co-axially and perpendicularly to longitudinal axis of the piping. Welds can not protrude in the inside diameter of the piping. During assembly of individual orifice plates which are not supplied with locks, it is necessary to pay special attention to correct centring into piping. Meter tube (orifice plate) has to be assembled co-axially with piping in front of as well as behind the tube so that deviation does not exceed ISO5167 standard limits. Before assembly of meter tube (orifice plate) the piping has to be deprived of solid as well as fluid impurities. When installing tube (orifice plate) these have to be separated from all constructions so that stop valves could be assembled or condensing vessels to outlets. We recommend to support the meter tube (orifice plate) by suitable supports or to attach it to hangers so that flange connections and sealings were not excessively stressed. We strongly recommend to support the piping near connection with orifice plate for easier assembly and disassembly.

Keeping of straight lengths in front of and behind primary element:
Primary element (orifice plate, nozzle etc.) has to be built into two sections of direct cylindrical piping of constant section in which there are no obstacles or branching off than those permitted by ISO5167 standard. Straight lengths depend on kind of pipe fittings in front of and behind primary element and diameter ratio d/D. Special requirements are on two and more elbows, 90°in various planes - these make helical movement of measured fluid. Lengths are stated in table 2 of ISO 5167 standard. Straight lengths in the table are min. values and it is always recommended to use longer ones. The most often mistake is not to keep straight lengths.

Welded-on pieces for thermometers:
Welded-on piece should be placed behind primary element in distance of 5D from primary element. (D-inside diameter of piping). Bore for welded-on pieces should be drilled, in case of autogenous burnt there are scales in the piping which cause lesser accuracy of measurement.

Placement of outlets:
Outlets are installed during production in accordance with piping dimensions and number of bolts event. according to customer‘ s requirements.

Direction of flow:
Direction of media flow in piping has to be in accordance with the direction of arrow on taping chamber or on orifice plate flange. During disassembly of orifice plate you have to pay attention to assembly so that bevelling inside orifice would be on minus side.

Sealing: When sealing is replaced, its edge or burrs can not interfere into inner part of piping or into chamber (chamber orifice plates).

Tightening of nuts on screws:
During transport of meter tube or assembled orifice plates with counter flanges to the customer, nuts can be loosened and have to be tightened when placed into piping. To prevent distortion of flanges and insufficient tightening of sealings, the screws have to be tightened in the alternating way – in a cross. Approx. a week after putting into operation we recommend tightening of screws again.

Seals
Meter tube is sealed by the producer. In case of damage of metrology seal, you have to contact producer. The damaged seal has to be replaced and new one can be placed on meter tube only by assembly organisation registered by ČMI.

During measurement piping has to be fully filled with the measured fluid.