The pH control system shall be of the two-way type. That is, it shall be capable of adjusting pH that may vary either above or below 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 pH adjustment chemicals into the circulating liquid by means of venturi injectors.
The process unit shall be configured to inject both acid and base. The unit shall automatically determine which of the two materials is the appropriate pH adjustment agent under any particular set of process conditions and shall control pH by injecting that agent as required to satisfy the control settings.
The pH control system shall consist of four 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 two venturis 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).
Injection sub-systems #1 and #2 shall each include the following elements (2 sets of each):
Materials of construction in contact with the 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
Injection sub-system #1: The nominal maximum continuous injection rate shall be ______ (Specify one: 15gph, 60gph, 160gph, 400gph). Sub-system #1 shall be configured for an injectate which raises pH.
Injection sub-system #2: The nominal maximum continuous injection rate shall be ______ (Specify one: 15gph, 60gph, 160gph, 400gph). Sub-system #2 shall be configured for an injectate which 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 Tanks
(Specify one of the following three alternatives)
The pH control system shall include two 45 US gallon chemical feed tanks, one for each neutralizing chemical. The tanks shall be made from rotomolded UV resistant high density polyethylene (HDPE). The tanks shall be integrated with the system frame. The outlet of each tank shall be piped to the inlet of the injectate sub-system. Shut-off valves shall be provided.
The pH control system shall include 2 free standing chemical feed tanks. The tanks shall be made from UV resistant rotomolded HDPE. The first chemical feed tank shall be a ChemIndustrial™ Model # _____ having a capacity of _____gallons (Specify appropriate tank model and capacity from ChemIndustrial’s tank brochure BR500). The second chemical feed tank shall be a ChemIndustrial™ Model # _____ having a capacity of _____gallons (Specify appropriate tank model and capacity from ChemIndustrial’s tank brochure BR500). The outlet of each tank shall be provided with a shut-off valve and 10 feet of resistant hose for connection to the pH control system..
The chemical feed tanks will be provided by others.
(Specify one of the following two alternatives)
The pH control system shall include a free standing treatment tank. The tank shall be made from UV resistant HDPE. The tank shall be a ____________________ (Specify one from: Vertical dome top tank OR Horizontal free-standing leg tank OR Cone bottom tank). The neutralizing tank shall be a ChemIndustrial™ Model # _____ having a capacity of _____gallons (Specify appropriate tank model and capacity from ChemIndustrial’s tank brochure BR500). Tank connections and other fixtures shall be in accord with the attached schedule and drawing(s).
The treatment tank will be provided by others.
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