Translation of pressure gauge specifications; I appreciate any corrections from everyone (especially the highlighted parts)

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7.0 PRESSURE INSTRUMENTS 7.1 Application Practices for Pressure Instruments 7.1.1 All process connections for pressure instruments shall be at least 20 mm (3/4”) in diameter. The use of reducing bushings to connect pressure or temperature instruments to process lines is not permitted. The diameter of all process connection parts for pressure instruments must be at least 3/4”. Elbow fittings (reduce-bore sleeves) are not permitted for the process connections of pressure or temperature instruments. 7.1.2 The primary valves for pressure transmitters, pressure gauges, and local pressure controllers shall be of commercially available type, specifically manufactured for this service. The primary valve shall have a block and bleed arrangement built into the valve. The primary valves used in pressure transmitters, pressure gauges, and local pressure controllers should be of the type that is commercially available and designed specifically for such applications. The one-way valve should be equipped with a blockage relief device. 7.1.3 Independent pressure gauges shall be provided on process lines near a blind pressure transmitter or controller unless specifically deleted by the OWNER. Independent pressure gauges should be installed next to pressure transmitters or controllers that do not display pressure, unless the OWNER orders that they be removed. 7.1.4 Diaphragm seals shall be used where the pressure measuring element may be damaged or otherwise adversely affected by the medium being measured. If the measuring element is at risk of damage or erosion by the medium being measured, a diaphragm seal should be used. 7.2 Pressure Instruments Hardware Specification 7.2.1 All pressure gauges shall have at least 316 SS bourdon tubes and moving parts; however, each process pressure gauge must be evaluated individually to ensure that the materials used are suitable from a corrosion resistance perspective. Tubes and sockets that are not made of 316 SS must be clearly and permanently marked on the gauge body, indicating the type of material used. All pressure gauges must have at least 316SS bourdon tubes and moving components. In any case, each process pressure gauge should be independently inspected to ensure that the material used is suitable for monitoring at corrosion points (under pressure). If the tubes and sockets are not made of 316SS, it must be clearly indicated that they are part of the housing, with the type of material specified. 7.2.2 Overrange protection shall be provided for a maximum operating pressure plus 30 percent overrange. Overpressure protection equivalent to 30% above the maximum operating pressure is required. 7.2.3 Filled systems or chemical seal attachments shall be used on all pressure instruments where the process fluid would freeze, congeal, corrode or otherwise render the pressure sensing element ineffective. When the process fluid in pressure instruments could cause freezing, condensation, corrosion, or render the pressure sensing element ineffective, filled systems or chemical seals should be employed. 7.2.4 Siphons or “pig tail” condensate seals shall be provided in piping to isolate connected pressure instruments in steam or other hot condensing vapor services. Such instruments must be properly supported. Siphons or trap devices should be used to prevent steam or other condensed substances from coming into contact with the pressure instruments. Such instruments require good support. 7.2.5 Pressure instruments shall be capable of withstanding over-pressure up to the design pressure or releasing pressure of the equipment without damage. When this requirement cannot be fulfilled, gauge protection devices can be employed. Differential pressure instruments shall also be considered in this application. Pressure instruments should be able to withstand pressures that exceed the design pressure or to release such pressures without being damaged. When this requirement cannot be met, a meter protection device should be used. Differential pressure instruments also need to take this situation into account. 7.2.6 The range of locally mounted pressure gauges shall be 125% of that of the protection relief valves (except for thermal expansion relief). The pressure range of instruments installed locally should be 125% of that of the protection relief valves (excluding those for thermal expansion). 7.2.7 All pressure instruments shall have direct reading indication scales. All pressure instruments need to have scales that allow for direct reading of the values. 7.2.8 Pressure gauges shall have an accuracy of ±0.5% of the full scale for which they are calibrated. Pressure gauges shall comply with BS-1780, while differential pressure transmitters shall comply with BS-6174. Pressure gauges should have a calibration accuracy of ±0.5% of their full scale range. Gauge pressure meters shall comply with the BS-1780 standard, while differential pressure transmitters shall comply with the BS-6174 standard. 7.2.9 All pressure gauges, except instrument receiver gauges, shall have 1/2” MNPT connections. Receiver gauge connections shall be 1/4” MNPT. The nominal sizes of the dial faces shall be as follows: • 100 mm for mounting on process lines (bottom mount). • 100 mm for mounting on vessels (bottom mount). • 150 mm for mounting on panels (flush mount, back connection). • 150 mm for pressure differential. Local pressure gauges shall normally have a weather-proof phenol case with a solid front and a rubber blow-out disc with a diameter of at least 25 mm (1”). The lens shall be glass. All pressure gauges, except for instrument receiver gauges, should use 1/2” MNPT male threads for their connections, while receiver gauges should use 1/4” MNPT male threads. The nominal dimensions of the dial are as follows: l * Instruments installed on process pipelines (mounted at the bottom) have a diameter of 100mm. l * Instruments installed on containers (mounted at the bottom) also have a diameter of 100mm. l * Panel-mounted instruments (mounted directly, with back connection) have a diameter of 150mm. l * Differential pressure gauges have a diameter of 150mm. Local pressure gauges usually come with a rainproof phenolic enclosure that includes a liquid reservoir and a rubber discharge disk with a diameter of at least 25mm; the lens should be made of glass. Pressure gauges shall be equipped with a full scale pressure range that includes a “0” pressure reading. The pressure gauges must have a dial with a “0” marking on it, indicating the full scale of pressure. The gauge pointers should be balanced and equipped with a micrometer adjustment, so that zero drift can be corrected without having to adjust the moving parts. The indicator needles must be balanced and allow for fine tuning, enabling zero-point drift to be corrected without altering the movable components. The identifying tag number shall be neatly and clearly marked on the back of each gauge. The identification tag number should be neatly and clearly written on the back of each gauge. Pressure gauges used in environments subject to pulsation or vibration, as well as those installed at the outlet of all pumps, must be filled with silicone fluid. The entire face of the gauge should be covered by this fluid, and the filling plug should serve as a pressure relief mechanism when the internal pressure reaches 10 psig or more. Flush-mounted, fluid-filled pressure gauges are typically used in local equipment panels, such as compressors, pumps, boilers, heaters, etc. In situations involving pulsation and vibration, as well as at the outlets of all pumps, pressure gauges must be filled with silicone oil; their surfaces must be covered by the fluid, and the rubber plug should allow pressure to be released when the internal pressure reaches 10 psig or higher. Gauge filled with flowing liquid is generally used for on-site installation (i.e., compressors, pumps, boilers, heaters, etc.). 7.2.10 Where applicable, pressure switches shall have an adjustable set point with a calibrated scale reference. The switches shall have SPDT contacts, with a rating of 2 amps at 24 VDC minimum. The snap-acting switch shall be hermetically sealed or have gold-plated contacts, and shall not be activated prematurely due to vibration. Where feasible, pressure switches should have an adjustable set point along with appropriate calibration markings. The pressure switch must have SPDT contacts of at least 2A, 24VDC rating. Action-type switches should have metal-sealed or gold-plated contacts to prevent premature activation due to vibration.