JFD WHE - 3, Operation And Maintenance Manual

KI-OM-0591 Rev 3

3

Introduction

which configuration should be used. The higher capacity configuration is usually
used to allow for better control.

2 If the bypass dump valve remains fully open during normal operation, indicating

heating over-capacity then the lower kW heater configuration should be used to
improve control and unit performance.

3 If the bypass valve remains fully closed during normal operation, indicating

heating under-capacity or a possible heater bank fault then a higher kW
configuration should be used to improve control.

1.3.2

Fluid System

The WHE-3 may function with either salt water or fresh water as the heating medium. The unit
is provided with two inlets for fluid, one for fresh water and one for seawater. The fresh water
line is typically used for flushing the system after use. The freshwater line is fitted with a check
valve to prevent salt water contamination of the fresh water supply. The unit uses small
immersion heater elements mounted in the flange plates at either end of the stainless steel
heater tank to heat the fluid. The flow rate of the fluid through the heating tank is governed by
the action of the bypass valve.

Note

Fluid supply to the unit by the vessel must be maintained above 45 litres/min at
3 bar for correct operation.

The flow rate of fluid from the heater tank to the divers is determined by the motor speed and
the ratio of the pulley set used to couple the motor to the pump. The pump is a positive
displacement pump and is supplied with a pulley arrangement to provide a flow rate of
45 litres/min.

The fluid to be heated enters the unit at the chosen inlet and flows through a manifold and a
quarter-turn hand valve. The manifold is equipped with analogue temperature and pressure
gauges to provide operator feedback on the fluid supply. The fluid is then piped to the fresh
water inlet tee and distributed to two separate inlet filters. The filters may be isolated using
hand valves on the inlet and outlet of each filter. These filters clean input water of particulate
matter down to 50 µm in order to protect the piston pump and umbilical coupling from being
damaged and prevent clogging of the heating water tubes in the diver suits. The inlet filters
are each fitted with pressure gauges in order to monitor pressure drop across the filter and
indicate the condition of the filter cartridge. A pressure regulating valve fitted after each filter
outlet ensures that fluid is supplied from filters to heater tank at a consistent and safe
pressure, (Factory setting is 2 bar).

The fluid flows through the heater tank which houses immersion heater elements where fluid
is heated. The heater tank is fitted with a pressure relief valve (PRV), set to 2.5 bar. A float
switch housed in the level control tank mounted on top of the heater tank is used to ensure
the heater elements and pump are not run without sufficient supply. If the level in the tank
drops the level switch shuts down the system. From the level control tank, the fluid is
distributed to the temperature control valve, manual temperature control valve and pump. The
manual control valve controls the process in the same way as automatic control valve and is
provided to control the outlet temperature if automatic control is inactive. The pump supply is
directly coupled to the level control tank.

The pump is a positive displacement pump and provides consistent supply flow rate. An
accumulator is fitted to reduce the effect of pulsation caused by the pump. The fluid from the
pump flows through a flexible reinforced hose to a pressure relief valve which may be set
between 7 - 70 bar and is sufficiently sized to allow full flow bypass if a downstream blockage
occurs. During normal operation, the fluid flows to the outlet via the outlet manifold. The outlet
manifold is fitted with both pressure and temperature gauges to provide operator feedback.