Make Your Valves Safe

Did You Know

Merriman can make your plant safer & reduce maintenance costs?






SPINDLE GAURDS are robust PVC pipe enclosed in a shock absorbing elastomeric waterproof foam sleeve, covered with a high visibility, dirt resistant vinyl sheath. Held in place by a coated stainless steel tether, they slip over exposed valve spindles in less than 15 seconds & protect your workers & valve spindles for years to come.
A SAFER WORKPLACE Workers are protected from injuries associated with exposed valve spindles, such as cuts, gouges, broken ribs, concussions, facial trauma, impalement etc. The high visibility, bright coloured cover raises awareness of the potential hazard & encourages a more cautious worker.
REDUCE MAINTENANCE COSTS & improve operational reliability, grease is not contaminated or washed off the threads, reducing lubrication costs. Spindles are protected from thread damage due to corrosion from the elements or fluid leakages. Sand, fly-ash or other gritty debris cannot collect in the spindle threads, ensuring your valve will operate easily when the time comes.





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Tapered Sockets for Solvent Cementing


Schedule 80 sockets are tapered!

This means there is an interference fit between pipe & socket over 50% of the length of the socket. This interference creates a penetration zone during the solvent welding process which contributes 80% of the joint strength. The tapered socket is one of the defining elements of an industrial piping system. It provides significant additional mechanical strength compared to the parallel design of the European PN16 socket. This is particularly important on the larger pipe diameters where the inertia of the moving fluid can cause large forces & stress in fittings such as elbows due to the change of direction of the moving fluid.
This tapered design should be considered during the installation process. Care should taken to allow for the effect of interference when determining lengths during a dry fit. During the solvent welding procedure a push back will be experienced & the joint should be physically restrained until the solvent cement has attained sufficient strength to resist this motion. It is important to use solvent cements that have been designed for use on schedule 80 pipe systems. These primers & cements are designed to adequately soften the PVC materials to ensure proper penetration and bonding of the components.
These web site links will take you to more detail on socket design & solvent cementing procedures.


Extreme Environments


Temperatures in unshaded bunds can easily exceed the safe working limits for PVC pipes, valves & fittings. PVC-U piping systems are generally considered to have a maximum pressure of 15 Bar at a temperature of 23°C but this drops to 3.3 bar at 60°C.

In this photograph, taken in NSW  summer 2016, the temperature of the valve was 74°C!

These high temperatures are a result of direct sunlight plus reflected heat from the white concrete bund & floor.
Repeated exposure to excessive temperature will ultimately reduce significantly the working life of the entire system. To operate so far in excess of the design parameters risks sudden catastrophic failure due to excessive expansion imposing undue stress at fittings. Leakage at threaded joints & “O” ring seals. Even normal system operating pressures will exceed permissible levels at elevated temperature & pressure surges due to dosing pump and valve operation can easily cause significant damage.
PVC is selected for pipe systems often because of its ability to handle aggressive chemicals & the consequences of significant failure to the safety of personnel and environmental contamination are very serious indeed.
These are not brand specific issues we have seen failures of installations using fittings from all the well known manufacturers, it is a fundamental principle that systems must be designed to operate within the manufacturer’s published pressure/temperature limitations.
Roofing to provide effective shading of the PVC installation is an obvious solution or using CPVC piping systems if shading is not cost effective. Double containment can also be considered for difficult applications.
These web links will take you to our data sheets for a more detailed explanation of temperature/pressure effects and provision for thermal expansion.