Intelligent control for safety curtains at sea

A HID product story

Edited by the Engineeringtalk editorial team Oct 12, 2001

The latest safety curtain installation from specialist Blackout Triple E, on The Golden Princess, a 109,000 ton luxury cruise liner, relies on Hitachi control equipment

Theatrical equipment has to be reliable - after all, the show must go on.

When the theatre is on board a cruise liner, the need for reliability increases since it is impossible to get a service engineer to call when a ship is at sea.

Scenery and curtain equipment specialist Blackout Triple E has unparalleled experience in such installations and relies on Hitachi control equipment from HID Limited for its systems.

The latest Blackout Triple E installation is on The Golden Princess, a 109,000 ton luxury cruise liner, which boasts 710 cabins, a nightclub, wedding chapel, two speciality restaurants and three separate show lounges.

The vessel is the latest member of the P and O Princess Cruises fleet and set off on her maiden voyage from Southampton on 16 May this year.

In the main lounge, aboard The Golden Princess, is a new design of safety curtain again sees the need for reliability as being of paramount importance.

The curtain has a number of control features that are unusual, not least of which is the ability for the curtain to be operated from the bridge of the ship as well as locally within the lounge.

The safety curtain uses Hitachi SJ100 AC inverters to provide a variable speed drive for the curtain's motor.

This is linked via an Hitachi micro PLC to provide a "teach" facility to enable the curtain to be programmed using a simple pushbutton control.

This straightforward control is duplicated at the ship's bridge where similar pushbuttons are connected by hard wiring to the main control panel.

The control panels were designed and constructed by HID in collaboration with engineers from Blackout Triple E.

The variable speed drive is provided by a 0.75kW Hitachi SJ100, which easily handles constant torque loads where high torque is needed at low speeds.

The SJ100 has a high starting torque of 200%, or more, and is equipped with regenerative braking as standard.

This makes it ideal for raising and lowering the heavy steel safety curtain since it offers the high degree of control required by Blackout Triple E's specification.

To enable a simple pushbutton control for raising, lowering and stopping the curtain, HID's engineering design team developed a remarkably inexpensive solution.

This used a pulse encoder fitted to the safety curtain's electric motor, which provides feedback to an Hitachi EH-28 Micro PLC.

The PLC is used to enable a teach facility for the operator.

It is important that the heavy curtain does not drop with a bang to the floor of the stage and equally, that it rises to an accurate stop position at the height of its travel.

It was also required to have a central "home" position programmed into the curtain.

The EH-28 Micro PLC is a small but powerful unit that enables a start and stop position for the three commands to be memorized so that, once set up, all the shipboard curtain operator has to do is press the relevant button.

Indeed, such is the in-built power of the EH Micro range, that the resultant PLC program, for all its apparent sophistication, requires only 30 to 40 lines of code.

The safety curtain also has a Category 4 E-stop system that allows the curtain to complete its closing cycle in the event of, say, a fire, even if the emergency stop button is erroneously depressed during the fire alarm period.

Blackout Triple E has become a leader in many fields of theatrical staging, including shipboard installations.

The builder of the Golden Princess, HMS Italia, is already working with Blackout Triple E on two further ships for P and O Princess Cruises.

Blackout Triple E has worked with HID Limited for many years on a variety of installations both afloat and on shore in top theatres.