B3 Pressure, flow direction and valve position
When the knife gate valve is open, P1=P2, the pipe line pressure may not
exceed maximum allowable working pressure body according to each valve.
When the valve is closed, the differential pressure ∆P, is the difference
between P1 and P2 (∆P = ± (P1-P2).
The differential pressure ∆P may not exceed maximum allowable differential
pressure according to each valve. Maximum allowable differential pressure
for closed valve is available in data sheets.
•Valves types XV, HL, HG, HP, HX, BV, WB, D2G , SLV, SLF, SLH and SLX are bi-directional and can therefore be
installed independent of the pressure ratio in any direction in the pipe line.
•Valid for MP only:
This valve type is bi-directional but have a preferred pressure direction. The preferred direction is achieved when the
SEAT SIDE is installed as the valve outlet (towards P2) provided that P1>P2.
•Valid for MV only:
This valve type has different differential pressure ∆P capacities in the flow directions. The maximum ∆P capacity of
the valve is achieved when the SEAT SIDE is installed as the valve outlet (towards P2) provided that P1 > P2. When
the valve is closed, the pressure ratio shall be P1>P2. Some sizes of MV equipped with specific seats are capable to
handle certain differential pressure in reversed pressure direction. For further information, see data sheets on
www.stafsjo.com.
•Valid for RKO and RKS only: These valve types have different differential pressure ∆P capacities in the flow
direction. The maximum ∆P capacity of the valve is achieved when the seat side is installed as the valve inlet
(towards P1) provided that P1>P2. When the valve is closed, the pressure ratio shall be P1>P2.
•Valid for TV only:
This valve shall be installed with the seat side to the tank. The removable retainer ring shall be mounted towards the
tank which implies that changing of the seat can only be done when the tank is empty.
•All valve types, except for valves D2G, JTV, RKO and RKS are preferred to be installed in a horizontal pipe
(system) with the actuator in a vertical upright position.
Valid for D2G, RKO, JTV and RKS only:
These valve types are designed to be installed in a vertical pipe.
B4 Necessary support for special cases
The dead weight of a valve in large dimension together with its actuator may cause tensions/deformations in the valve
that could affect the valve’s function, specifically when it is installed at inclined positions or in a vertical pipe. In these
cases, the valve and/or actuator shall be supported to avoid functional failure.
Valves that are exposed to vibrations or other mechanical stresses can be subject to forces that will affect valves
tightness and ability to operate. In these cases, the valves and actuators shall be supported to avoid function failure.
Support details are the responsibility of the customer. Stafsjö will assist on request.
B5 Steps to install
On handwheel operated valves, when the handwheel is not assembled at delivery, follow the steps below to assemble
the handwheel to the valve.
