Blaw Knox K5735

Contents

• Overview
  • General data
• Lines
• Tower forms
• Tower details

Overview

Blaw Knox K5735 is a UK electricity pylon (steel lattice transmission tower) series designed for contract NWE PL7, a line delivering power from Penwortham to ICI Hillhouse in Thorton-Cleveleys, constructed around 1940 and demolished around 1976.

Drawings for the double circuit towers were filed by National Grid under “PL7” alongside Watshams SEE PL7, under the assumption that they were related types. The towers can be seen in aerial photography from 1946, locating the line in the NWE region of the CEB and suggesting a contract of NWE PL7. Subsequently, the National Grid drawing schedule for NWE PL7 has been recovered and gives the design contract as “Flyde - Hillhouse NWE PL7” [sic], confirming the earlier suggestion.

NWE PL7 was superseded by a 400 kV L6 line and subsequently demolished. No other lines are known to have used this tower type; the decision to design all new towers during World War II for this line was a curious one, especially with the Wartime Grid Reinforcements and other wartime 132 kV lines using the very similar PL4 type. The design itself represents a midpoint between PL4 (1936) and PL16 (1944–45).

At ICI Hillhouse the double-circuit line split into two single-circuit spans, terminating on an undentified single-circuit terminal (SST) type. The same type of SST tower can still be found near Middleton, south west of Lancaster; this is the only tower of its type on the short line from Heysham substation to Middleton, suggesting it is the last remnant of the now demolished PL4/WGR Quernmore–Heysham line.

The DD2 type is virtually identical to SWE PL16 D2. Aside from draughting discrepancies, the only change appears to be the modification to accommodate double earthwires, specifically the addition of an earthwire crossarm along with a height increase of the top phase crossarm to match the change in tower height. Likewise, the DD30 tower is virtually identical to PL16 D30.

In keeping with tradition, the DD60 and DD90 towers share the same design as DD30 and are simply wider at the base. This practice was not continued with PL16, whose D60/DD60 and D90/DD90 towers each had its own design of tower body.

General data

Designed for	Central Electricity Board (CEB) (presumed)
Design contractor	Blaw Knox, Milliken Brothers branch
Found
Status	Demolished
Height (straight line tower)	89′–9″ (27.4 m) (DD2)
Voltage	132 kV
Dates back to	1940 (drawings)
Known conductors	Single
Drawing ranges	K5735 / XM1742
Circuit count	Double

Lines

• Penwortham–ICI Hillhouse (demolished)

Tower forms

So far only the DD2, DD30, DD60 and DD90 drawings have been recovered.

The following diagrams are shown to scale at 12 pixels per metre:

The dashed line within the peak of each angle tower represents a member that is only present on earthwire changeover towers.

Tower details

See dimensions on the site guide page for a key to the tables.

D10 and DDT are listed but no general arrangement drawings or erection diagrams are recorded. Various special towers are listed and, with the line no longer in existence, it is difficult to know which towers went where.