Data Sheet Pressure switch Type RT For industrial and marine applications RT pressure switches incorporate a pressure controlled, single-pole change over swich where the contact position depends on the pressure in the connection port and the set value. The RT series consists of pressure switches, differential pressure switches and pressure switches for neutral zone regulation, all for general use within the industrial and marine segments. The series also covers safety pressure switches dedicated for steam boiler plants. For installations in which operation is particularly critical from safety and economic points of view, the use of fail-safe pressure switches is recommended. The use of gold-plated contacts is also recommended in such installations, provided operation involves only a few switching cycles or signal currents and voltages. Features: • Simple design • High accuracy • High repeatability • Long operation life time • Available with all major marine approvals • Safety Integrity Level: SIL 2 according to IEC 61508

Pressure switch, Type RT Portfolio overview Overview / Survey Figure 1: Overview / Survey 0 Standard pressure switches Pressure switches for steam plant approved by TÜV Pressure switches with adjustable neutral zone Differential pressure switches Table 1: Examples of RT types RT 113 For manual setting; cover with windows For tamper proof; cap and blank cover

Pressure switch, Type RT Function RT 19, RT 30 and pressure switches with max. reset When the pressure exceeds the set range value, contacts 1-4 make and contact 1-2 brake. The contacts changeover to their initial position when the pressure falls to the range value minus the differential (see Figure 3: Contact function, setting for rising pressure.). Figure 2: Contact function, setting for rising pressure. Scale setting Mechanical differential Contact function: I. Alarm for rising pressure given at the set range value. II. Alarm for falling pressure given at the set range value minus the differential....

Pressure switch, Type RT The start pressure of 6 bar must be set on the range scale. The differential must be set as the difference between the stop pressure (7 bar) and the start pressure (6 bar) = 1 bar. According to Figure 25, the differential setting disc must be set on 8. Example 2: The burner on a steam boiler must cut out when the pressure exceeds 17 bar. Automatic restart must not occur. Choose an RT 19B with external reset. If extra safety is demanded, an RT 19S with internal max. reset can be used. The range is 5 – 25 bar and the differential is fixed at approx. 1 bar. The range scale...

Pressure switch, Type RT Figure 5 shows a cross-section through a bellows element for the RT 30W with fail-safe for rising pressure. On rising pressure the contact arm is actuated to break the connection between terminals 1 and 2. If a defect occurs in the inner bellows the pressure is led to the outer bellows. The outer bellows has an area three times as large as the inner bellows. The connection between terminals 1 and 2 becomes broken. If a defect occurs in the outer bellows, there will be atmospheric pressure in the gap between the two bellows. This actuates the contact system to break the...

Pressure switch, Type RT Figure 8: Contact function, setting of falling differential pressure Scale setting Mechanical differential Contact function: I. Contacts make when differential pressure falls below the range scale setting. II. Contacts make when pressure rises above the range scale setting plus the fixed mechanical differential. Units with adjustable neutral zone (SPDTNP) If the differential pressure rises above the set value plus the differential, contacts 1-4 make.If the pressure falls by the amount of the differential (which is fixed in this unit), contacts 1-4 break. If the pressure...

Pressure switch, Type RT Application RT-L pressure switches are fitted with a switch with an adjustable neutral zone. This enables the units to be used for floating control. The terminology involved is explained below. Figure 10: Application Setting knob Range scale Neutral zone disc Floating control A form of discontinuous control where the correcting element (e.g. valve, damper, or similar) moves towards one extreme position at a rate independent of the magnitude of the error when the error exceeds a definit positive value, and towards the opposite extreme position when the error exceeds a...

Pressure switch, Type RT The neutral zone, 35 - 32 = 3 m wg, corresponding to 0.3 bar, must be set on the neutral zone disc (40), see Figure 10. According to the diagram, see Figure 14, the disc setting is 1 or just over. A more accurate setting can be obtained by using the test setup shown in Figure 16. Figure 16: Test setup for setting the pressure switch Pressure guage Compressed air Signal lamp for falling and rising pressure Control and monitoring of pressure differentials A differential pressure switch is a pressure controlled switch that cuts in and cuts out the current dependent on the...

Pressure switch, Type RT Figure 17: Differential pressure switch Setting disc Range scale When installing, the low pressure connection (LP) must always be upwards. Table 3: Neutral zone setting Diff. range © Danfoss | Climate Solutions | 2021.02 NZ = Natural zone / Dead zone Diff. range Position NZ = Natural zone / Dead zone Diff. range Position Diff. range NZ = Natural zone / Dead zone NZ = Natural zone / Dead zone

Pressure switch, Type RT Product specification Technical data Table 4: Technical data Designation Ambient temperature In general -50 – 70 °C Diaphragm version -10 – 70 °C TÜV approved -40 – 70 °C Media temperature In general -50 – 100 °C Diaphragm version -10 – 90 °C TÜV appr. -40 – 150 °C Contact system Single-pole changeover switch (SPDT), see Figure 22 Contact load Contact material: AgCdO Direct current: DC-13: 12 W, 220 V (see Figure 23) Special contact system See Spare parts and accessories Cable entry Solid / stranded Flexible, without ferrules Flexible, with ferrules Tightening torque...