Dry-seal Wiggins gasholder


A dry-seal Wiggins gasholder is a device designed to hold gas. Designed by John Wiggins in 1936, it was first manufactured in 1940 and achieved widespread use across the USA.

Dry-seal Wiggins type gasholder

A dry-seal gasholder can be designed to have a gross volume ranging from, whilst having a working pressure range between. The dry-seal gasholder is finished with an anti-corrosive treatment to counteract local climatic conditions and also any chemical attack from the stored medium. This anti-corrosive treatment is fully compatible with the sealing membrane and also the environment.

Foundation

A concrete and hardcore base designed to withstand the weight of the steel gasholder structure constructed upon it and to withstand dynamic climatic conditions acting upon the gasholder etc.

Main tank

The main tank is designed to accommodate the design requirements laid down by the customer and climatic conditions. There are three main sub-elements to the tank:
; Tank bottom
; Piston support structure
; Tank shell
; Staircase tower
; Shell access doors
; Shell vents
; Inlet nozzle
; Outlet nozzle
; Shell drains
; Shell manways
; Earthing bosses
; Volume relief pipes
; Volume relief limit switches
; Level weight system
; Level weight limit switches
; Contents scale
; Seal angle
; Tank roof
; Centre vent
; Roof vents
; Roof manways
; Circumferential handrailing
; Radial walkway
; Volume relief valve actuators
; Level weight pulley structures
; Load cell nozzles
; Radar nozzles
; Roof interior lighting nozzles

Piston

The gasholder piston moves up and down the inside of the shell as gas enters and exits the gasholder.
The weight of the piston produces the pressure at which the gasholder will operate. The piston is designed to apply an equally distributed weight to ensure that the piston remains level at all times. The piston made up of the following sub-elements:
; Piston deck
; Piston manway
; Load cell chain receptacle
; Piston seal angle
; Level weight rope anchors
; Piston fender
; Piston walkway
; Piston ladders
; Radar reflector plates
; Abutment plates
; Piston torsion ring

Sealing membrane

The seal of the gasholder is designed to operate in the conditions specified by the client and to suit the stored medium. The seal rolls from the shell to the abutment surface of the piston and vice versa providing the piston with a frictionless self-centering facility. During depressurisation the seal also provides a gas tight facility that protects the holder from vacuum damage by blocking the gas outlet nozzle. During commissioning of the gasholder the sealing membrane is set into an operating condition. This setting must be carried out every time the gasholder is depressurised, otherwise known as "popping" the seal.