The problem:

The existing hotwell located outside the boiler house was leaking due to wear and tear and needed replacing. Furthermore, the cold makeup water pipework required upgrading.

The Solution:

The new hotwell was situated inside the boilerhouse, making it convenient for the installation which could be carried out with the boiler plant in operation.

The size of the hotwell needed to be sufficient enough to provide one hour’s boiler running if the cold makeup water supply is interrupted for any reason. However, the system we were using was stated as being 100% makeup, meaning the hotwell should never require cold makeup water as all the condensate returns back to the hotwell and is not wasted.

However, there is a requirement to store the condensate returns without the hotwell overflowing. The hotwell was made to match the boiler steam output of 4.5tons and the level controls were adjusted to suit. This way the amount of hot water storage is kept to a minimum with reduced heat loss and steam usage through the heating injector.

Hotwell Specification

The hotwell was manufactured from 6mm thick 304L stainless steel, welded construction and externally braced with a mild steel channel. It also had the following features:

  • Sealed access door
  • Vent, overflow and drain connections
  • Thermostatically controlled steam injection heating system
  • Electronic level control system including a low-level alarm feature
  • Digital temperature indication
  • Contents gauge
  • Flanged connections to boiler feed pumps
  • Condensate return sparge
  • Cold makeup water inlet and control valve
  • Heavy duty support stand, designed to allow access to relocated water treatment equipment
  • Access ladder and platform system

The hotwell was supplied and delivered to the site and positioned inside the boilerhouse.  Platforms and access ladders were erected, vents, overflow pipes to the atmosphere and feed water supply pipes were installed and the cold makeup water supply pipework from and to the existing softener plant was modified and upgraded in stainless steel pipe.

Furthermore, an electrical installation to the hotwell level control system and control panel was carried out and wiring to the chemical dosing system was modified as necessary. Following this, the hotwell was filled with water and checked for operation of level controls and the existing hotwell was removed and a controlled boiler shutdown was performed.

The condensate returns and steam injection supply was changed over and the existing steam supply was blanked off whilst the existing boiler feed pump water supply pipework was removed and changed over to the new supply pipe.

The hotwells were changed over prior to firing the boiler and adjusting the level controls over a period of time before finally insulating the hotwell and condensate return pipes and metal cladding them with aluminum stucco cladding / covering before removing redundant pipework.