On start-up and with the adjustment spring relaxed, upstream pressure, aided by a return spring, holds the valve head against the seat in the closed position. Rotating the handwheel in a clockwise direction causes a downward movement, which compresses the control spring and extends the bellows to set the downstream pressure.
This downward movement is transmitted via a pushrod, which causes the main valve to open. Steam then passes through the open valve into the downstream pipework and surrounds the bellows.
As downstream pressure increases, it acts through the bellows to counteract the adjustment spring force, and closes the main valve when the set pressure is reached. The valve plug modulates in an attempt to achieve constant pressure.
In order to close the valve, there must be a build-up of pressure around the bellows. This requires an increase in downstream pressure above the set pressure in proportion to the steam flow.
The downstream pressure will increase as the load falls and will be highest when the valve is closed. This change in pressure relative to a change in load means that the downstream pressure will only equal the set pressure at one load. The actual downstream pressure compared to the set point is the proportional offset; It will increase relative to the load, and this is sometimes referred to as 'droop'.
The total pressure available to close the valve consists of the downstream pressure acting on the underside of the bellows plus the inlet pressure acting on the underside of the main valve itself and the small force produced by the return spring. The control spring force must therefore be larger than the reduced pressure and inlet pressure and return spring for the downstream pressure to be set.
Any variation in the inlet pressure will alter the force it produces on the main valve and so affect the downstream pressure.
Shanghai ThinkTank Process Management Co., Ltd. is the sole production and R&D institute of Taiwan STONE Company in Mainland China. ThinkTank entered Chinese market in 2002 and moved from Hangzhou to Shanghai headquarter in 2012. Based on over 30 years experience in researching and manufacturing automatic instruments, brining in overseas advanced technology and combining domestic users real working situation, ThinkTank is specialized in producing new typed self-regulating valves, control valves and various kinds of automatic instruments. ThinkTank's business includes engineering projects such as electricity, metallurgy, petrochemical processing, light industry and building materials, municipal water service and natural gas.
Enterprise history
1985.08 Taiwan STONE company was established in Taipei city.
1990.02 Sales network covered Southeast Asia.
2002.06 Branch office was fund in Hangzhou, Zhejiang, handling all business in China
2012.10 Mainland head office was moved to Pudong, Shanghai
Shanghai ThinkTank Process Management Co., Ltd. Has a professional team works for control valves design and engineering application. ThinkTank develops a series of hi-tech products after absorbing overseas advanced technology and innovating.
*New self-regulating, micro pressure, differential pressure, flow, temperature control valve
*New pneumatic (electric) linear actuator (low dB, high pressure) control valve
*Pneumatic (electric) rotary actuator (O/V ball, butterfly) control valve
*Pneumatic (electric) special corrosion resisting control valve
Shanghai ThinkTank Process Management Co., Ltd sticks to the policy of "client oriented, quality comes first, and faith is root". Depending on many years experience on engineering application in various industries, ThinkTank provide clients with good, reliable full service, focusing on maximizing the rate of return on investment for clients.
