Gauge movement: the pinion-and-segment mechanism that turns Bourdon-tube travel into pointer rotation in a dial gauge

01

Copper-alloy or 300-series stainless movement, matched to the tube and the service

WIKA's two 2½ and 4 in (63 and 100 mm) Bourdon-tube gauge lines, both built to ASME B40.100 and EN 837-1, show the split. The 212.54 has a copper-alloy movement with copper-alloy C-shape or helical tubes in the 2½ in size, while the 232.54, intended for adverse service where pulsation or vibration exists, has a 300-series stainless steel movement with a 316L stainless steel Bourdon tube and connection. [1] [2]

On the 232.54 the tube is C-type up to 1,000 psi and helical at 1,500 psi in the 2 and 2½ in sizes, and C-type to 1,500 psi and helical at 2,000 psi in the 4 in size; the case can be filled with 99.7 % glycerine (type 233.54), which WIKA lists as giving vibration and shock resistance. Accuracy is ±2/1/2 % of span (ASME B40.100 Grade A) for 2½ in and ±1 % of span (Grade 1A) for 4 in. [2]

Both data sheets give an additional temperature error of ±0.4 % of span for every 10 °C (18 °F) away from the 20 °C reference, and an ambient range of −40 to +60 °C dry. [1] [2] Editorial calculation: in a 60 °C enclosure the temperature term alone is (60 − 20) ÷ 10 × 0.4 = 1.6 % of span, more than the ±1 % accuracy class of the 4 in gauge; on a 0–1,000 psi dial that is 16 psi. The two terms are shown side by side here, not combined by any rule from the data sheets.

For a replacement or OEM movement, give the gauge size and dial sweep, Bourdon tube type (C-shape or helical) and its tip travel, the movement material, pointer shaft diameter and length, and whether the case will be liquid filled.

02

Why pinion and segment teeth wear under pulsation, and what that does to accuracy

A 1941 patent by Manning, Maxwell & Moore describes the usual gauge movement as "commonly comprising a pinion meshing with a gear segment" and explains its weakness in service with "constant and often violent vibration" or rapidly pulsating pressure: the constant relative motion wears the meshing teeth of pinion and segment and their staffs and bearings, so "the accuracy of the gauge is quickly destroyed". [3]

The same patent notes that a pinion-and-segment movement is expensive to make even from the cheapest materials, and that making it from wear-resistant materials to a high precision raises the cost further; its own answer was to replace the gearing with a crank and connecting rod while keeping provision for calibration adjustment. [3] Current makers instead use stainless movements and liquid filling for vibration service, as in WIKA's 232.54/233.54. [2]

For an order this means asking how the supplier protects the tooth mesh: the movement material, whether the case is to be filled, and whether a restrictor is fitted at the connection, which WIKA lists as a 316 stainless steel option. [2]

Ask for the movement material, any coating on pinion and segment, the case fill, and the accuracy class the movement is calibrated to in the finished gauge.

03

Pointer, zero adjustment and the parts that set the reading

WIKA lists the 232.54 pointer as black aluminium, friction adjustable, and the 212.54 pointer as adjustable; the 2½ in stainless dial carries a stop pin. [2] [1]

04

Movement details to agree with the supplier

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Gauge: [size; dial sweep; accuracy class]
Bourdon tube: [C-shape or helical; material; tip travel]
Movement: [material; coating; pointer shaft size]
Service: [vibration; pulsation; case fill; restrictor]
Quantity: [spare parts or OEM volume]

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