WIKA 990.10 Threaded Diaphragm Seal for Pressure Gauges

Overview

The WIKA 990.10 is a diaphragm seal with threaded process connection in a threaded design, used to protect pressure measuring instruments from difficult media. In a diaphragm seal system the diaphragm separates the instrument from the process, and the pressure is transmitted to the gauge, switch or transmitter through a system fill fluid sealed inside the assembly. WIKA designed the WIKA 990.10 for aggressive, hot, corrosive, environmentally hazardous or toxic media in the process industry, and it covers pressure ranges up to 250 bar.

Seven Star LLC supplies the WIKA 990.10 as a separate component or as a complete factory-filled system with a WIKA pressure gauge, to customers in Oman and across the GCC, with engineering support in Muscat. Many buyers searching for a diaphragm seal gauge actually need this combination, and we coordinate the gauge, seal, fill fluid and certificates as one tagged item.

Operating Principle

When process pressure acts on the flexible diaphragm of the WIKA 990.10, the diaphragm displaces a small volume of fill fluid, which transmits the pressure hydraulically to the measuring element of the attached instrument. As general engineering background, this keeps corrosive, crystallising, polymerising or very hot media away from the Bourdon tube, prevents clogging of narrow instrument bores and allows the instrument to be installed in a cleaner, cooler location.

The seal can be mounted to the instrument in three ways: direct mounting, a cooling element for high process temperatures, or a flexible capillary for remote mounting. In the WIKA 990.10 the diaphragm is welded to the upper body, and the lower body is screwed on and sealed, so the lower body can be replaced without modifying the filled diaphragm seal system. The maximum process temperature of the complete system is limited by the joining method, the fill fluid and the instrument, which is why WIKA engineers each system for its duty.

Engineering Design of the WIKA 990.10

As standard the instrument connection is an axial adapter for direct mounting, with optional G ½, G ¼, ½ NPT or ¼ NPT female adapters, capillaries or cooling elements. The standard sealing between upper and lower body is PTFE up to 260 °C, with metal C-spring seals in silver-plated stainless steel or Inconel for up to 400 °C. Single or dual flushing connections in G ¼, G ⅛, ¼ NPT or ⅛ NPT allow the lower chamber to be cleaned, and plug screws are available to close them.

Process connections of the WIKA 990.10 cover male threads G ½ A as standard with G ¼ A to G 1½ A options, ½ NPT with ¼ NPT to 1½ NPT options, M20 x 1.5, and R ½ with R ¼, R ⅜ and R ¾, plus equivalent female threads. Wetted parts are cleaned oil and grease free per ASTM G93-03 level F as standard, with level D and ISO 15001 cleaning available. Design per NACE MR0175 or MR0103 can be specified, and vacuum service is offered in basic, premium and advanced levels.

Key Features

These are the main reasons engineers specify the WIKA 990.10 for gauge protection.

• Pressure ranges up to 0–250 bar, including vacuum and combined pressure and vacuum ranges.
• Threaded design with screwed upper and lower body allows replacement of the lower body without disturbing the filled system.
• Wetted materials include 316L, 904L, 321, 316Ti, duplex 2205, super duplex 2507, Hastelloy C22 and C276, Inconel 600 and 625, Incoloy 825, Monel 400, nickel 200, titanium and tantalum.
• Coatings such as ECTFE, PFA, gold plating and Wikaramic® extend use to highly corrosive media.
• Maximum process temperature reaches 400 °C for many metal combinations, depending on seal, fill fluid and joining method.
• Optional flushing connections let operators clean the process chamber without removing the instrument.
• NACE MR0175 and MR0103 designs support sour oil and gas and refinery service.
• Direct, cooling element or capillary mounting gives flexibility in where the gauge is placed.

Industrial Applications

In Oman the WIKA 990.10 is used on sour crude and produced water lines, chemical injection skids for corrosion inhibitor and scale inhibitor, hypochlorite and acid dosing at desalination plants on the Batinah coast and in Sur, caustic and amine service in gas plants, and hot oil or steam lines in refineries at Sohar and Duqm. Wastewater plants also use threaded seals on sludge lines, where the flushing connection prevents build-up.

For flanged process connections, the related WIKA 990.27 Diaphragm Seal offers a different body style, and a stainless gauge such as the WIKA 232.50 Stainless Steel Bourdon Tube Pressure Gauge or its liquid-filled sibling WIKA 233.50 Bourdon Tube Pressure Gauge is the usual instrument mounted on top. Seven Star LLC supplies the WIKA 990.10 with engineering support, and our team in Muscat will help you select materials and fill fluid for each tag in Oman or elsewhere in the GCC.

Technical Specifications

The WIKA 990.10 data below comes from WIKA data sheet DS 99.01.

Ordering a Complete System

As general advice, a diaphragm seal should be ordered as a filled system together with the instrument rather than assembled on site, because the fill and evacuation determine accuracy and temperature behaviour. When you request a WIKA 990.10 system, state the process medium, pressure and temperature, the gauge model and range, the mounting type and any NACE or cleaning requirement, and WIKA will define the fill fluid accordingly.

How to Order

Contact Seven Star LLC with your process data and preferred gauge to obtain a quotation for the WIKA 990.10 seal or a complete seal and gauge assembly. Our Muscat engineers will check availability and lead time, attach the WIKA data sheet DS 99.01 and support installation and spares for sites in Oman and across the GCC.