Keystone Yarway Automatic Recirculation Control Valves

The Yarway Automatic Recirculation Control (ARC) Valve provides effective as well as economical protection for centrifugal pumps against the serious damage from overheating or instability that can result from even a few minutes of low flow. By providing recirculation flow to the suction source of the pump the ARC assures a minimum flow for stable pump operation.

Features

• Automatic recirculation control
• Intrinsically safe design
• Maintenance and operating costs reduced
• Complete recirculation system
• Valves are completely flow tested
• Installation costs reduced

Complete system solutions for performance you can depend on

Yarway valves are supplied as part of a complete solution involving the thorough analysis of the pumping and piping system. This equips Keystone with the information necessary to specify accurate, reliable pump protection.

The Yarway ARC valve – one valve, four functions

Designed as a self contained unit the Yarway ARC valve provides the functions of a check valve, flow sensing element, bypass flow control valve and multistage pressure letdown device.

The Yarway ARC System

Installed in pumping system the ARC valve automatically functions as a check valve to prevent reverse flow, a flow sensing element, a by-pass control valve and a multistage cascade valve for the dissipation of high pressure. Only three pipe connections are required to install a Yarway ARC Valve compared with the many which would be required on a multi-component system. As a self-contained system it requires no instrument signal, power source, or any of the associated maintenance.

The modulating ARC Valves create operating economies in several ways. The ARC recirculates only the flow through the pump at all times. Under full process main flow demand, recirculation flow is not required. But as process main flow demand decreases recirculation becomes necessary.

Unlike continuous recirculation the ARC responds directly to the needs of the system. This performance avoids the need to oversize the pump and driver necessary with continuous recirculation maintaining efficient operation. Oversizing a pump adds significantly to the capital cost of the system as well as to the cost of energy needed for operation.

Multi-component System

Yarway System

How it works

The ARC is a three ported valve with inlet, outlet and bypass connections. The fundamental element is a check valve disc. This disc sits in the flow path from inlet to outlet and performs the functions of a flow sensing device and non return check valve.

The disc is spring loaded and when there is zero process demand the disc is held on its seat. As the downstream regulating or isolating valve is opened there is a differential pressure created across the disc and it lifts off its seat.

As the process flow increases the disc continues to lift until it reaches its full travel position, the movement of the disc has created a variably opening orifice between itself and the seat, this means that the pressure drop across the disc remains relatively constant until it has reached its full travel position, any further increase in process flow will cause a relative increase in the pressure drop.

As the position of the disc is proportional to the process demand of the system, the ARC valve is designed whereby on decreasing demand the bypass port is opened at a predetermined position of the disc.

Conversely, on increasing process demand, the bypass port can be closed at the same disc position, this part of the valve operation is known as the ‘switch point’. The ‘switch point’ occurs when the pump is running at or slightly above its minimum continuous stable flow.

Back pressure considerations

Many system problems can occur in the return piping to the receiving vessel. Typically these are flashing og liquid into its vapour phase and choked flow which can also generate noise and pipe vibration.

The solution is to increase the bypass line pressure to prevent flashing flow. This is achieved by installing a restriction device sized to establish the required back pressure for a given flow rate. A simple orifice plate is suitable for on/off applications but for a modulating valve a modulating orifice or back pressure regulator (BPR) will be required.

The BPR is designed with a spring loaded plunger set to maintain the liquid pressure in the line at, or above, the level required to prevent caviation or two phase flow, in the bypass valve and piping between the valve and regulator. The BPR provides an effective solution for handling the complete bypass flow range.

Flow tested for your peace of mind

A certified test curve is supplied with every Yarway ARC valve, just as you would insist is supplied with a pump. The performance characteristics of the valves are extensively evaluated using the comprehensive testing facilities of the Yarway laboratory.

Yarway ARC valves are tested over the complete flow range, providing you with the assurance that each valve satisfies every necessary performance requirement.

Analysis includes:

• Total flow through the pump
• Disc position
• Pressure drop
• Response to sudden changes in flow
• Bypass capacity

All Yarway products are backed by the stringent quality standards of ISO 9001.

ARC valve applications

ARC valves are suitable for any liquid applications handled by conventional centrifugal pumps. Some of the industries which use ARC valves and their applications are listed below.

Industries

• Utility and Industrial power plant
• Refineries
• Ethylene plant
• Fertiliser plant
• Tank and storage farms
• Gas treatment plant
• Petrochemical industry
• Pulp and paper industry
• Steel industry
• Offshore industry

Applications

• Boiler feedwater
• Kerosene
• Propane/Butane
• Benzene
• Naphtha
• Ethylene
• Ammonia
• Firewater
• Seawater
• Crude oil

Six reasons for specifing Yarway ARC valves

Automatic recirculation control

By automatic control of the minimum flow, energy and heat costs are reduced. Pump capacity can be selected according to process requirements eliminating the need to “oversize” for continuous recirculation.

Intrinsically safe design

Intrinsically safe design with all static seals, packless design (no stuffing boxes), no leak path to atmosphere and no electrical wiring. ARC valves are ideal for pumping application in the hydrocarbon industry.

Maintenance and operating costs reduced

The simple design and construction of Yarway ARC valves enable routine inspection and maintenance to be easily carried out. With few moving parts the ARC valves design ensures greater reliability throughout its working life.

Complete recirculation system

The Yarway ARC valve is a complete and self contained recirculation system. This eliminates the need for multi-vendor specification and responsibility of the recirculation system.

Valves are completely flow tested

In our Hydraulic Performance Test Laboratory, state-of-the-art data acquisition and computer graphics techniques are called upon to test every valve over its complete flow range.

Installation costs reduced

The self-contained ARC has only three pipe connections and does not require any power source or instrument signal. It replaces a multi-component system with its requirements for numerous connections, additional instrumentation and extra cost.

The ARC valve range

SERIES 9100
Ratings: ANSI Class 150–600
Sizes: 1” to 8”
Connections: Flanged
SERIES 7100
Ratings: ANSI Class 900–1500
Sizes: 3” to 8”
Connections: Flanged or Buttweld
ARC valves are available in larger sizes and rated to ANSI class 2500 for certain applications

How to order

To assist you in ordering Yarway ARC valves please use the data form below as a guide to providing the necessary information for selection and sizing of a valve to meet the protection requirements as specified by the pump manufacturer. Each valve is selected to meet the specific application requirements. Please note selection is not based on line size.