DA - All-Metal Sight Flow Indicators - Flap, Rotor, or Drip Indication

The KOBOLD DA series is a line of heavy-duty, all-metal sight glass flow indicators for liquids, designed for industrial piping systems. A flap, rotor, or drip tube behind the sight glass makes liquid movement visible, so operators can confirm at a glance that the line is flowing. Bodies are offered in cast iron, cast steel, or 316 stainless steel with soda-lime or borosilicate glass windows. Process connections range from 1/4" to 2" NPT and from 1/2" to 8" ANSI flange. The standard pressure rating is 230 PSIG (15.9 bar), with optional 360 PSIG (24.8 bar) and 580 PSIG (40.0 bar) versions and temperature ratings up to 530 °F (277 °C), depending on model and glass selection.

Flap, Rotor, or Drip Tube Indication

Three models cover different indication needs: the DAK indicates with a flap of 316-Ti stainless steel, the DAR with a rotor, and the DAT with a drip tube. Each shows flow directly through the glass window, with model-specific mounting positions.

• DAK (flap): mounts horizontally or vertically with flow from bottom to top.
• DAR (rotor): universal mounting position, with a rated flow speed of 8.2 ft/s (2.5 m/s). The rotor is plastic for service to 250 °F (121 °C) or PTFE (option R) for service to 500 °F (260 °C); PTFE is standard at nominal size 2" and above.
• DAT (drip): installs in any position, preferably vertical with flow from the top. Threaded sizes up to 1/2" use an inlet with a half face plate; other sizes use a drip tube.

Heavy-Duty, All-Metal Construction

Each DA pairs a metal housing and cover plates with a glass window and graphite seals, a construction engineered for the pressures, temperatures, and handling conditions of industrial liquid service. Housings come in grey cast iron, 316 stainless steel, or cast steel, and windows in soda-lime or borosilicate glass.

• Housings: grey cast iron GG 25 (EN-GJL-250), 316 stainless steel (1.4408), or cast steel GS-C 25 (1.0619). Cast iron is available on flanged versions only.
• Sight glass: soda-lime glass per DIN 8902 as standard; borosilicate glass per DIN 7080 optional for higher temperatures.
• Seals: graphite as standard; other seal materials on request.
• Screws: stainless steel on stainless bodies; zinc-plated steel on cast iron and cast steel bodies.

Pressure and Temperature Ratings

Standard DA units operate to 230 PSIG. Stainless steel and cast steel models can be supplied for 360 PSIG or 580 PSIG, both with borosilicate glass. Temperature limits run from 250 or 300 °F with soda-lime glass, depending on model, up to 530 °F with borosilicate glass.

• Option P (360 PSIG) uses ANSI Class 300 flanges on flanged models and is limited to sizes 4" and under; option Q (580 PSIG) is limited to flanged sizes 3" and under. Neither is offered on cast iron bodies.
• DAK and DAT: 300 °F (149 °C) with soda-lime glass; 530 °F (277 °C) with borosilicate glass.
• DAR: 250 °F (121 °C) with soda-lime glass; 500 °F (260 °C) with borosilicate glass and PTFE rotor.
• The lowest-rated component in the body, seal, and glass combination determines the maximum permissible pressure and temperature.

Connections, Sizes, and Weights

Threaded versions cover 1/4" to 2" NPT with stainless steel or cast steel bodies. Flanged versions cover 1/2" to 8" ANSI Class 150 in all three materials, with Class 300 flanges on the higher pressure options. Approximate weights range from 4.85 lb to 260.15 lb.

Installation and Maintenance

DA indicators install directly in the line and require no special maintenance. Observe the flow direction arrow on the body, check cover screw torques before start-up, recheck them after the first exposure to operating pressure and temperature, and treat glass plates as replaceable wear parts.

• Flanged installation: pipe flanges must be concentric and plane-parallel, with clearance equal to the overall length of the unit plus two gasket thicknesses.
• Threaded installation: hold the unit at the end being screwed in with a suitable wrench, never by the sight glass cover.
• Glass care: plates removed after operation are not reused, and glass showing fissures or a milky surface is replaced together with new gaskets.
• With demineralized condensate or steam mixtures and pH values from approximately 8, protecting the glass with mica discs is recommended.

Testing, Hazardous Areas, and Compliance

Every DA sight glass is factory tested for strength per DIN EN 12266 Part 1 at 1.5 times nominal pressure and for tightness under water with 29–87 psi (2–6 bar) compressed air. The series falls under Pressure Equipment Directive 2014/68/EU; CE marking depends on size and pressure class.

• DA indicators are purely mechanical devices without electrical components; they require no ATEX marking and can be installed in hazardous areas when bonded into the plant equipotential system.
• Conformance standards include EN 558, EN 1092, EN 12266, and EN 12516; the devices contain no substances prohibited by the RoHS Directive.

Common Questions about DA - All-Metal Sight Flow Indicators