Switchboards for a biological wastewater treatment plant: level, alarms and drives

The task

A treatment plant runs around the clock, and its pumps start by liquid level rather than by schedule. Hence the requirements for the switchboards:

• level control at many points at once — tanks and sumps differ in depth;
• alarm signalling brought together in one place, with an audible warning;
• smooth flow control, so that direct-on-line starting does not hit the plant network or the pumps themselves;
• IP54 construction — treatment plant rooms are damp: splashes and condensation.

The solution

Six identical ShchN-1…ShchN-6 terminal cabinets (400×400×350 mm, 15 kg, IP54, 2 A) — local connection points: a DIN rail with terminal blocks and earthing inside, an indicator lamp in a protective bracket on the side wall, and the works nameplate, a hazard sign and a lock on the front.

The ShchSN-2 control cabinet (1000×650×300 mm, 40 kg) — all the apparatus is on the door: four panel-mounted digital signal setters cut into the sheet, three rows of indicator lamps above them, and start/stop buttons and manual–off–auto selectors below, one set per each of the four mechanisms; the terminal blocks are on the mounting plate inside the body.

The ShchSN-3 central signalling cabinet (1000×650×300 mm, 40 kg) — a central signalling unit, six three-channel liquid level switches (relays) (up to eighteen level monitoring channels) and an audible siren: every plant alarm is brought into one cabinet.

Four ShchSN-4/1…4/4 cabinets (80 kg, IP54) — each with a 100 A circuit breaker, a variable-frequency drive and a motor choke. The choke sits between the drive and the motor: it damps voltage spikes on the long cable to the pump and protects the winding insulation.

We select components to the customer's specification — the same cabinet can be built on any equipment the customer prefers.

Every cabinet carries its own works passport; the ShchN/ShchSN designations follow the customer's diagram. We build such switchboards as a standard line: pump control cabinets ShchUN and cabinets with a variable-frequency drive and soft starter.

Figures (from the passports and nameplates)

Photo report: from the row of cabinets to the wiring inside

We will build to your diagram

Switchboards for treatment plants and pumping stations — level control, alarm signalling, variable-frequency drives — from the single-line diagram to works testing. A similar job for the pump stations of a fuel site — the fire and sewage pump station case. Send a request and an engineer will match a solution to your equipment.