The pH control system shall be of the one-way type. That is, it shall be capable of adjusting pH that always varies in the same direction from the required value. It shall be a single, integrated process unit which samples, measures and controls the pH of liquid in a treatment tank by circulating a stream of liquid from that tank past a pH sensor and by metering and mixing a pH adjustment chemical into the circulating liquid by means of a venturi injector.
The process unit shall be configured to control pH by injecting ______ (Specify either acid or base) as required to satisfy the control settings.
The pH control system shall consist of three sub-systems:
The liquid sampling/circulation sub-system shall consist of a centrifugal pump plus its suction pipework and its discharge pipework.
The suction pipework shall include a strainer to protect sampling/circulation clearances against blockage.
The discharge pipework shall include one venturi and shall provide for pH sensor mounting. Materials of construction in contact with the injectate in the discharge pipework shall be suitable for use with common pH adjustment chemicals.
The pipework in the liquid sampling/circulation sub-system shall be fully assembled and shall include all necessary intermediate fittings and supports. The pipework shall terminate at NPT pipe fittings which permit extension of the inlet and outlet pipework to the treatment tank which __________ (Specify one: shall be provided as part of this contract OR shall be provided by the owner).
The injection sub-system shall include the following elements:
Materials of construction in contact with injectate shall be suitable for use with common pH adjustment chemicals.
The instrumentation/control sub-system shall include industrial grade in-line pH sensing, display and control devices. In addition, a means shall be provided so that operators can select between periodic and continuous pH control modes. Independently-settable alarm/interlock contacts shall be available for use by the owner to alert personnel or to interlock other process equipment.
The system shall provide operator-accessible switches, push-buttons, set point and alarm contact adjustments and timer settings. All control and instrumentation devices shall be mounted in a NEMA 4X enclosure. Any required control circuit fusing shall be included.
Capacity and usage
The nominal maximum continuous injection rate shall be ______ (Specify one: 15gph, 60gph, 160gph, 400gph). The injector shall be configured for an injectate which (Select one: raises, lowers) pH.
By adjusting the controls, it shall be possible to reduce the effective injection rate by a factor of at least 1000 from the nominal maximum continuous injection rate.
The pH control system shall include a contactor and an overload relay for the centrifugal pump motor. The owner will provide one properly sized and fused branch circuit as the power source for the pump. The electrical characteristics of the circuit will be: __________ (Specify one: single phase OR three phase) at ____ Vac (Specify voltage). The owner will also provide a properly sized and fused 120Vac circuit to power the control system.
All components shall be assembled on a protective frame. The frame shall be constructed of 304 stainless steel.
Chemical feed tank
(Specify one of the following three alternatives)
(Specify one of the following two alternatives)
This specification covers the requirement for ______ units (Specify quantity) pH control systems.
The pH control system shall be a ChemIndustrial pH Control System, model ______________ as manufactured by:
ChemIndustrial Systems, Inc.
PO Box 500
Cedarburg, WI 53012