ASME PTC-6 Nozzle

Throat-Tap Nozzle

Long Radius Throat-Tap Nozzles acc. ASME PTC-6 are available for performance testing of steam turbines in power generation plants.

Extreme care must be taken to obtain the high order of accuracy necessary in primary water-flow measurement. There is always a need of a calibration.

The SEIKO Throat-Tap nozzles are manufactured with strict accordance to the ASME power test code and furnished with four throat taps as standard. The beta-ratio is limited to the range of 0,25 to 0,5 and the inlet/outlet sections are at least 20xD / 10xD. Also a Flow Straightner is compulsory 2-4xD outset of meterrun by ASME code.

Flanged assemblies are normally used with relatively low pressures such as when the flow element is in the condensate line upstream of the main feed pump.

Welded assemblies are often used at high pressure levels. To meet the requirement of inspection the nozzle both before and after a test, a welded flow section shall include a plugged inspection port immediately upstream of the nozzle.

In applications where the residual pressure loss has a high importance to be as low as possible, there would be the opportunity to upgrade the Throat-Tap Nozzle with a sheet metal outlet cone.

There are 4 pairs of taps located 1xD before the Nozzle and at the throat.

As mentioned above the calibration is required for 20 points/ tapping pair. Means a calibration with overall 80 points. This points have to be in a default range, called "slope".

Depending on customer requirements, the typical 1/2 in. or 3/4 in. tappings have a but or socket weld, screw thread or flange connection. Tappings maybe equiped with shut-off valves.

Available in wide variety of materials, but usually out of SS316.

The flow calculation is performed according to the ASME PTC 6.

Due to the calibration the typically uncertainty of a ASME PTC 6 Throat Tap Nozzle is ~0,1 - 0,3%

The pressure loss is similar to the Long Radius Nozzle depending on the design of the flow straightner.

SEIKO recommends a Throat-Tap Nozzle out of stainless steel or hardfaced to ensure a long-life-highly accurate measuring.

We use cookies to provide you with our website. By clicking on 'Accept', you agree to allow the use of cookies on our website. Accept