Slide plates / guillotines and blanking plates are essentially two names for the same piece of equipment – a blade which slides across the cross-sectional area of a duct shutting it off. There are two distinct types of slide plate/guillotine, slot-entry and fully enclosed (sometimes known as fully bonneted).
In a slot-entry guillotine the blade enters through a slot in the top of the duct and proceeds down side guides until coming to rest on the bottom of the duct. A gasketed slot cover is secured across the entry slot when the blade is in either the raised or lowered position, only being removed when the blade is in transit.
In a fully enclosed guillotine the blade is housed in an enclosure which forms a sealed annex to the duct. There is no need for a slot cover meaning there is never a break in the duct, no matter whether the blade is at rest or in transit.
Often the most cost-effective way to lower a guillotine blade is by gravity and then to raise it using a manual or electric winch. Other methods, such as pneumatic or hydraulic rams or screw jacks, can also be used.
Generally the only reason to use a guillotine instead of a damper is when there is very limited upstream to downstream room in the duct. If the process gas contains dust or particulates, then a guillotine is not ordinarily recommended as the long sliding guides can become chocked with dust and the blade can jam. The isolated rotary bearing surfaces of a damper do not suffer from this problem.
In a blanking pate an entire duct flange is de-coupled and the two duct section are jacked apart slightly by jacking points provided on the blanking plate frame. A plate is then lowered into the gap created between the flanges, usually using a manual winch, and the flanges jacked back together sandwiching the plate between them. The flange fastenings are then replaced and the duct is isolated.
A blanking plate is the only true way to isolate a duct completely, such that operatives can safely work downstream.
Flowrite has supplied several damper / blanking plate combination units where an upstream damper is used to shut-off >99% of the duct’s cross-sectional area so that a flanged connection, immediately downstream of the damper, can be unbolted and jacked apart. The blanking plate is then lowered to isolate the ducts.