Masoneilan 78-80H High-Capacity Set Pressure Transfer Valve

Overview

The Masoneilan 78-80H is a high-capacity, three-way transfer valve of the set-pressure regulating type. Like the standard-capacity 78-80S, it combines a floating-ball pilot valve and a three-port valve in a single unit, but its larger passages give it more than three times the flow coefficient, which allows it to charge or vent bigger actuator chambers without a noticeable delay. The associated 08-80H is the same valve without the pilot, and the two are designed to work as a set, so that one pilot valve can sequence several transfer bodies.

Seven Star LLC, a trusted supplier of Masoneilan products, supplies the Masoneilan 78-80H to refineries, gas plants, power stations and water facilities in Oman and the GCC. Maintenance planners often need to match this valve to an existing model plate with the correct housing and temperature suffix, and our instrumentation division in Muscat does that check before a quotation is issued.

Set-Pressure Transfer Principle

The pilot part of the Masoneilan 78-80H compares the signal pressure at its SIG port with a set pressure fixed by a spring and adjust knob. While the signal exceeds the set pressure, the valve passes air from IN to OUT. When the signal drops below the set pressure or to zero, it cuts off IN and connects OUT to EXH, venting the connected equipment. The valve is normally factory set, and the manual describes a short procedure to reset it with a gauge and a regulator on the signal port: relieve the spring, tighten it one or two turns, set the signal to the specified pressure, and then turn the adjust knob until air no longer leaks from OUT.

The large air capacity of the Masoneilan 78-80H has a practical consequence. Taking the signal from near the IN side of the body makes the signal and supply pressures fluctuate and can cause hunting, so the signal should be fed from a separate point. The Masoneilan 78-80H also provides a SIG OUT port that sends the pilot signal to any number of 08-80H bodies, and the valve may be used as a lock-up valve by blind-plugging both EXH ports.

Engineering Design of the Masoneilan 78-80H

The numbering system of the Masoneilan 78-80H defines the product by four elements: the base number 78-80 for the set-pressure regulating three-way transfer valve or 08-80 for the plain three-way valve, the letter H for high capacity, suffix A for the temperature range, and suffix B for housing material. Suffix A blank gives minus 30 to plus 83 degrees Celsius, and the suffix H gives 0 to 100 degrees Celsius. Suffix B blank gives an aluminium alloy housing, and the suffix 316L gives a 316L stainless steel housing with NPT connections.

The parts list of the Masoneilan 78-80H shows a chromated aluminium body and housing, a SUS303 stainless steel plug with nitrile seal, a piston, a SUS440C stainless steel pilot ball, a fabric-reinforced nitrile diaphragm, stainless filters and screws, spring steel springs and Valox 420 plastic for the adjust knob and spacer. As on the 78-80S, rubber parts should be replaced every five years, and repairs are made at the factory through the agent or sales office. The signal may not exceed 1.03 MPa (10.5 kgf/cm2). The valve is certified in several jurisdictions, including CU-TR Ex for the Russian Federation, China Ex and Kazakhstan, and is ATEX compliant.

Key Features

The following features, taken from the Baker Hughes instruction manual, show why the Masoneilan 78-80H is chosen where actuator volume is large:

• The Masoneilan 78-80H has a Cv of 4.5 from IN to OUT and 5.0 from OUT to EXH gives high air capacity for large actuator chambers and volume boosters.
• Rc 1/2 main ports and an Rc 1/4 signal port are standard, with NPT 1/2 and NPT 1/4 alternatives.
• A 316L stainless steel housing option gives better resistance to corrosive atmospheres than the standard aluminium alloy.
• Two exhaust ports provide a choice of vent position and can both be plugged when the valve works as a lock-up valve.
• A set pressure range of 100 kPa to 700 kPa with hysteresis of 34 kPa or less defines a repeatable changeover point.
• The SIG OUT port lets one 78-80H sequence several 08-80H valves for simultaneous transfer with minimal tubing.
• Maximum operating pressure is 1.72 MPa at the body and 1.03 MPa at the signal connection.
• A temperature suffix extends the operating range from minus 30 to plus 83 degrees Celsius up to 0 to 100 degrees Celsius.

Industrial Applications

The Masoneilan 78-80H is selected when a transfer valve has to move a large volume of instrument air quickly, for example on large diaphragm or piston actuators on big butterfly, ball or globe valves. In Oman such valves are found in cooling water systems at power and desalination plants, in refinery and gas processing units, and in pipeline stations, where an air failure must leave the valve in a defined state. The stainless steel housing option suits coastal sites such as Sohar and Salalah, where salt-laden air attacks aluminium fittings.

Seven Star LLC supplies the Masoneilan 78-80H with the actuators and accessories around it. Engineers can combine it with the Masoneilan Type 51/52/53 piston actuators or the Masoneilan Type 87/88 spring-diaphragm actuators, add a Masoneilan BR200 volume booster relay, and compare the smaller 78-80S for actuators that do not need this capacity.

Technical Specifications

The table lists the data published for the Masoneilan 78-80H in the Baker Hughes instruction manual for the 78-80H and 08-80H transfer valves (Rev. B).

Related Masoneilan pneumatic accessories include the Masoneilan 78-80S transfer valve, Masoneilan 77-80H air valve, Masoneilan BR400 high capacity volume booster relay and Masoneilan 78 air filter regulator.

Request a Quote for Masoneilan 78-80H

To request a quotation for the Masoneilan 78-80H, send Seven Star LLC the full model number from the nameplate, including the temperature and housing suffixes, together with the actuator volume, the required set pressure and the port thread type. We confirm the configuration, check availability and lead time and supply the Baker Hughes instruction manual for download from this page. As trusted supplier for Masoneilan in Oman and the GCC, we deliver genuine products with manufacturer documentation and local support.