Anderson Greenwood Series 200 Pop Action Pilot Operated Safety Valve

Overview

The Anderson Greenwood Series 200 is a pop action pilot operated safety valve with a non-flowing pilot, built by Emerson for overpressure protection of gas, vapor and many mixed phase systems. According to the Emerson technical datasheet, the Anderson Greenwood Series 200 protects systems from 25 to over 6170 psig (1.72 to over 425.5 barg), and higher pressures up to 10,500 psig (724 barg) are available on request. Introduced in 1966 and refined continuously since then, the design is described by Emerson as the standard against which other pilot operated valves are compared. Because the main valve is held closed by system pressure rather than a heavy spring, the valve stays tight to at least 95% of set pressure, letting plants run closer to their design limits without seat leakage.

Seven Star LLC supplies the Anderson Greenwood Series 200 to gas processing plants, pipeline compressor stations, refineries, offshore facilities and power plants in the Sultanate of Oman and across the GCC. Our Muscat engineering team helps buyers turn a relief case into a complete model number, check materials and soft goods against the service, and organise documentation for the plant file, from our office in Muscat.

Operating Principle of the Anderson Greenwood Series 200

In the normal closed position of the Anderson Greenwood Series 200, full system pressure is sensed at the pressure pick-up in the main valve inlet. That pressure passes through the pilot into the dome, the volume above the main valve piston. Because the piston seal area is larger than the main seat sealing area, the net force on the piston is downward and the valve stays tightly closed. The higher the system pressure, the greater the closing force, which is exactly the opposite of a direct spring operated valve, where seat loading falls as pressure approaches set.

When the pilot senses set pressure, its relief seat snaps open and the blowdown seat snaps closed at the same moment, venting dome pressure through the pilot to atmosphere. The main valve then opens fully at set pressure, so no overpressure is needed to reach full capacity. The blowdown seat stays closed until the chosen system blowdown has been reached; it then snaps open while the relief seat snaps closed, re-pressurising the dome and closing the main valve. Blowdown depends on spindle lift off the relief seat and is adjusted externally by raising or lowering the blowdown assembly, with a minimum blowdown of 3% shown in the datasheet.

Engineering Design

The Anderson Greenwood Series 200 uses a vertically mounted, non-flowing pilot fixed to the main valve with a rugged bracket that protects it against vibration and careless handling. A non-flowing pilot only passes fluid during the relief cycle, which limits the entry of dirt and the formation of hydrates; low velocities let most particles drop out upstream of the pilot inlet screen, making the valve suitable for dirty and wet gas. The replaceable main valve seat sits on the piston, the main valve nozzle can be replaced in the field, and lettered orifice valves meet API Standard 526 dimensional requirements. API 526 direct spring center-to-face dimensions are also offered, so an existing spring valve can be replaced without piping modifications.

The balanced design of the Anderson Greenwood Series 200 means that main valve lift is not affected by back pressure, so no metal bellows is needed. Main valve bodies are offered in carbon steel with stainless steel trim (/S1), stainless steel body and trim (/S), low temperature carbon steel (/L1), duplex (/D) and super duplex (/P), with NACE MR0175 compliant versions of several combinations. Soft seats and seals on the Anderson Greenwood Series 200 are renewable quickly without lapping.

Key Features

The Emerson datasheet lists the following features for the Anderson Greenwood Series 200 pilot operated safety valve:

• Total valve tightness to at least 95% of set pressure, allowing operation nearer set pressure without leakage and with less product loss.
• Balanced piston design that keeps lift unaffected by back pressure, eliminating costly and fragile bellows.
• Field test capability that verifies set pressure with the valve in service, without an isolation block valve.
• Soft seats that extend service life, reduce maintenance and avoid expensive metal seat lapping.
• Pop action with full lift at set pressure, which also helps prevent freeze-ups in cryogenic or refrigerant service.
• External, independent blowdown adjustment that gives repeatable settings without removing the valve.
• ASME Section VIII and Section XIII (UV designator) code stamp for gas service, CE mark to PED 2014/68/EU, and DOT (49 CFR 192.199) and CSA Z662 compliance.
• Remote pressure sense connection available, and an optional cartridge pilot filter for extremely dirty service.

Industrial Applications

Gas transmission and processing is the natural home of the Anderson Greenwood Series 200. In Oman, typical installations include inlet separators and slug catchers, gas dehydration and compression trains, fuel gas skids, pig launchers and receivers, and high pressure gas injection systems, where the ability to operate close to set pressure directly increases throughput. The very wide pressure range lets one valve type cover low pressure vessels as well as Class 2500 piping, and the reduced height and weight of a pilot operated valve compared with a large spring valve is valuable on offshore platforms and crowded skids.

Emerson’s -423 to +600°F (-253 to +315°C) temperature range also brings the Anderson Greenwood Series 200 into LNG, cryogenic and refrigerant service, where pop action prevents freezing during relief. Seven Star LLC supplies valves and spare soft goods kits for these duties to operators and EPC contractors in Muscat, Sohar, Duqm and Salalah and throughout the GCC.

Accessories and Options

Options listed for the Anderson Greenwood Series 200 include a field test connection, backflow preventer, pilot supply filter, pressure spike snubber for gas, remote pressure sense connection, remote valve lift indicator, manual unloader, pilot lift lever, remote unloader and NACE trim to MR0175/ISO 15156:2015. A full nozzle main valve is available as an option. On an Anderson Greenwood Series 200, a backflow preventer is recommended where the outlet can see pressure above the inlet, for example when several valves discharge into a common flare header.

Selection Guidance (General)

The following points are general engineering practice rather than manufacturer data. Size the required orifice area for the governing relief case with the formulas in the datasheet or Emerson’s sizing software, then choose the inlet rating, materials and soft goods for the fluid and temperature. Check whether pop action suits the service: for liquids or where minimal product loss is required, a modulating pilot such as the Series 400 may be preferable. The Anderson Greenwood Series 200 model number is built from pilot series, main valve lift type, piston type, inlet flange rating, orifice letter, inlet and outlet size and material code, for example a Series 200 valve with soft seats, Class 600 inlet and CS body with SS trim.

Technical Specifications

Key data for the Anderson Greenwood Series 200 from datasheet VCTDS-00543:

How to Order

To request a quotation for the Anderson Greenwood Series 200, send Seven Star LLC the fluid, required relieving capacity, set pressure, back pressure, inlet and outlet ratings, temperature and material requirements. Our Muscat team will review the selection against the Emerson datasheet, which you can download from this page, and prepare a formal offer. Engineers comparing pressure relief options may also review the Anderson Greenwood Series 90/9000 pressure relief valve, the LESER Type 811 pilot-operated safety valve and the Crosby JOS-E conventional pressure relief valve. Seven Star LLC provides model selection support from Muscat for customers throughout Oman and the GCC.